1 <html> 2 <head> 3 <title>pcre2api specification</title> 4 </head> 5 <body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> 6 <h1>pcre2api man page</h1> 7 <p> 8 Return to the <a href="index.html">PCRE2 index page</a>. 9 </p> 10 <p> 11 This page is part of the PCRE2 HTML documentation. It was generated 12 automatically from the original man page. If there is any nonsense in it, 13 please consult the man page, in case the conversion went wrong. 14 <br> 15 <ul> 16 <li><a name="TOC1" href="#SEC1">PCRE2 NATIVE API BASIC FUNCTIONS</a> 17 <li><a name="TOC2" href="#SEC2">PCRE2 NATIVE API AUXILIARY MATCH FUNCTIONS</a> 18 <li><a name="TOC3" href="#SEC3">PCRE2 NATIVE API GENERAL CONTEXT FUNCTIONS</a> 19 <li><a name="TOC4" href="#SEC4">PCRE2 NATIVE API COMPILE CONTEXT FUNCTIONS</a> 20 <li><a name="TOC5" href="#SEC5">PCRE2 NATIVE API MATCH CONTEXT FUNCTIONS</a> 21 <li><a name="TOC6" href="#SEC6">PCRE2 NATIVE API STRING EXTRACTION FUNCTIONS</a> 22 <li><a name="TOC7" href="#SEC7">PCRE2 NATIVE API STRING SUBSTITUTION FUNCTION</a> 23 <li><a name="TOC8" href="#SEC8">PCRE2 NATIVE API JIT FUNCTIONS</a> 24 <li><a name="TOC9" href="#SEC9">PCRE2 NATIVE API SERIALIZATION FUNCTIONS</a> 25 <li><a name="TOC10" href="#SEC10">PCRE2 NATIVE API AUXILIARY FUNCTIONS</a> 26 <li><a name="TOC11" href="#SEC11">PCRE2 NATIVE API OBSOLETE FUNCTIONS</a> 27 <li><a name="TOC12" href="#SEC12">PCRE2 EXPERIMENTAL PATTERN CONVERSION FUNCTIONS</a> 28 <li><a name="TOC13" href="#SEC13">PCRE2 8-BIT, 16-BIT, AND 32-BIT LIBRARIES</a> 29 <li><a name="TOC14" href="#SEC14">PCRE2 API OVERVIEW</a> 30 <li><a name="TOC15" href="#SEC15">STRING LENGTHS AND OFFSETS</a> 31 <li><a name="TOC16" href="#SEC16">NEWLINES</a> 32 <li><a name="TOC17" href="#SEC17">MULTITHREADING</a> 33 <li><a name="TOC18" href="#SEC18">PCRE2 CONTEXTS</a> 34 <li><a name="TOC19" href="#SEC19">CHECKING BUILD-TIME OPTIONS</a> 35 <li><a name="TOC20" href="#SEC20">COMPILING A PATTERN</a> 36 <li><a name="TOC21" href="#SEC21">JUST-IN-TIME (JIT) COMPILATION</a> 37 <li><a name="TOC22" href="#SEC22">LOCALE SUPPORT</a> 38 <li><a name="TOC23" href="#SEC23">INFORMATION ABOUT A COMPILED PATTERN</a> 39 <li><a name="TOC24" href="#SEC24">INFORMATION ABOUT A PATTERN'S CALLOUTS</a> 40 <li><a name="TOC25" href="#SEC25">SERIALIZATION AND PRECOMPILING</a> 41 <li><a name="TOC26" href="#SEC26">THE MATCH DATA BLOCK</a> 42 <li><a name="TOC27" href="#SEC27">MATCHING A PATTERN: THE TRADITIONAL FUNCTION</a> 43 <li><a name="TOC28" href="#SEC28">NEWLINE HANDLING WHEN MATCHING</a> 44 <li><a name="TOC29" href="#SEC29">HOW PCRE2_MATCH() RETURNS A STRING AND CAPTURED SUBSTRINGS</a> 45 <li><a name="TOC30" href="#SEC30">OTHER INFORMATION ABOUT A MATCH</a> 46 <li><a name="TOC31" href="#SEC31">ERROR RETURNS FROM <b>pcre2_match()</b></a> 47 <li><a name="TOC32" href="#SEC32">OBTAINING A TEXTUAL ERROR MESSAGE</a> 48 <li><a name="TOC33" href="#SEC33">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a> 49 <li><a name="TOC34" href="#SEC34">EXTRACTING A LIST OF ALL CAPTURED SUBSTRINGS</a> 50 <li><a name="TOC35" href="#SEC35">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a> 51 <li><a name="TOC36" href="#SEC36">CREATING A NEW STRING WITH SUBSTITUTIONS</a> 52 <li><a name="TOC37" href="#SEC37">DUPLICATE SUBPATTERN NAMES</a> 53 <li><a name="TOC38" href="#SEC38">FINDING ALL POSSIBLE MATCHES AT ONE POSITION</a> 54 <li><a name="TOC39" href="#SEC39">MATCHING A PATTERN: THE ALTERNATIVE FUNCTION</a> 55 <li><a name="TOC40" href="#SEC40">SEE ALSO</a> 56 <li><a name="TOC41" href="#SEC41">AUTHOR</a> 57 <li><a name="TOC42" href="#SEC42">REVISION</a> 58 </ul> 59 <P> 60 <b>#include <pcre2.h></b> 61 <br> 62 <br> 63 PCRE2 is a new API for PCRE, starting at release 10.0. This document contains a 64 description of all its native functions. See the 65 <a href="pcre2.html"><b>pcre2</b></a> 66 document for an overview of all the PCRE2 documentation. 67 </P> 68 <br><a name="SEC1" href="#TOC1">PCRE2 NATIVE API BASIC FUNCTIONS</a><br> 69 <P> 70 <b>pcre2_code *pcre2_compile(PCRE2_SPTR <i>pattern</i>, PCRE2_SIZE <i>length</i>,</b> 71 <b> uint32_t <i>options</i>, int *<i>errorcode</i>, PCRE2_SIZE *<i>erroroffset,</i></b> 72 <b> pcre2_compile_context *<i>ccontext</i>);</b> 73 <br> 74 <br> 75 <b>void pcre2_code_free(pcre2_code *<i>code</i>);</b> 76 <br> 77 <br> 78 <b>pcre2_match_data *pcre2_match_data_create(uint32_t <i>ovecsize</i>,</b> 79 <b> pcre2_general_context *<i>gcontext</i>);</b> 80 <br> 81 <br> 82 <b>pcre2_match_data *pcre2_match_data_create_from_pattern(</b> 83 <b> const pcre2_code *<i>code</i>, pcre2_general_context *<i>gcontext</i>);</b> 84 <br> 85 <br> 86 <b>int pcre2_match(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 87 <b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 88 <b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 89 <b> pcre2_match_context *<i>mcontext</i>);</b> 90 <br> 91 <br> 92 <b>int pcre2_dfa_match(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 93 <b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 94 <b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 95 <b> pcre2_match_context *<i>mcontext</i>,</b> 96 <b> int *<i>workspace</i>, PCRE2_SIZE <i>wscount</i>);</b> 97 <br> 98 <br> 99 <b>void pcre2_match_data_free(pcre2_match_data *<i>match_data</i>);</b> 100 </P> 101 <br><a name="SEC2" href="#TOC1">PCRE2 NATIVE API AUXILIARY MATCH FUNCTIONS</a><br> 102 <P> 103 <b>PCRE2_SPTR pcre2_get_mark(pcre2_match_data *<i>match_data</i>);</b> 104 <br> 105 <br> 106 <b>uint32_t pcre2_get_ovector_count(pcre2_match_data *<i>match_data</i>);</b> 107 <br> 108 <br> 109 <b>PCRE2_SIZE *pcre2_get_ovector_pointer(pcre2_match_data *<i>match_data</i>);</b> 110 <br> 111 <br> 112 <b>PCRE2_SIZE pcre2_get_startchar(pcre2_match_data *<i>match_data</i>);</b> 113 </P> 114 <br><a name="SEC3" href="#TOC1">PCRE2 NATIVE API GENERAL CONTEXT FUNCTIONS</a><br> 115 <P> 116 <b>pcre2_general_context *pcre2_general_context_create(</b> 117 <b> void *(*<i>private_malloc</i>)(PCRE2_SIZE, void *),</b> 118 <b> void (*<i>private_free</i>)(void *, void *), void *<i>memory_data</i>);</b> 119 <br> 120 <br> 121 <b>pcre2_general_context *pcre2_general_context_copy(</b> 122 <b> pcre2_general_context *<i>gcontext</i>);</b> 123 <br> 124 <br> 125 <b>void pcre2_general_context_free(pcre2_general_context *<i>gcontext</i>);</b> 126 </P> 127 <br><a name="SEC4" href="#TOC1">PCRE2 NATIVE API COMPILE CONTEXT FUNCTIONS</a><br> 128 <P> 129 <b>pcre2_compile_context *pcre2_compile_context_create(</b> 130 <b> pcre2_general_context *<i>gcontext</i>);</b> 131 <br> 132 <br> 133 <b>pcre2_compile_context *pcre2_compile_context_copy(</b> 134 <b> pcre2_compile_context *<i>ccontext</i>);</b> 135 <br> 136 <br> 137 <b>void pcre2_compile_context_free(pcre2_compile_context *<i>ccontext</i>);</b> 138 <br> 139 <br> 140 <b>int pcre2_set_bsr(pcre2_compile_context *<i>ccontext</i>,</b> 141 <b> uint32_t <i>value</i>);</b> 142 <br> 143 <br> 144 <b>int pcre2_set_character_tables(pcre2_compile_context *<i>ccontext</i>,</b> 145 <b> const unsigned char *<i>tables</i>);</b> 146 <br> 147 <br> 148 <b>int pcre2_set_compile_extra_options(pcre2_compile_context *<i>ccontext</i>,</b> 149 <b> uint32_t <i>extra_options</i>);</b> 150 <br> 151 <br> 152 <b>int pcre2_set_max_pattern_length(pcre2_compile_context *<i>ccontext</i>,</b> 153 <b> PCRE2_SIZE <i>value</i>);</b> 154 <br> 155 <br> 156 <b>int pcre2_set_newline(pcre2_compile_context *<i>ccontext</i>,</b> 157 <b> uint32_t <i>value</i>);</b> 158 <br> 159 <br> 160 <b>int pcre2_set_parens_nest_limit(pcre2_compile_context *<i>ccontext</i>,</b> 161 <b> uint32_t <i>value</i>);</b> 162 <br> 163 <br> 164 <b>int pcre2_set_compile_recursion_guard(pcre2_compile_context *<i>ccontext</i>,</b> 165 <b> int (*<i>guard_function</i>)(uint32_t, void *), void *<i>user_data</i>);</b> 166 </P> 167 <br><a name="SEC5" href="#TOC1">PCRE2 NATIVE API MATCH CONTEXT FUNCTIONS</a><br> 168 <P> 169 <b>pcre2_match_context *pcre2_match_context_create(</b> 170 <b> pcre2_general_context *<i>gcontext</i>);</b> 171 <br> 172 <br> 173 <b>pcre2_match_context *pcre2_match_context_copy(</b> 174 <b> pcre2_match_context *<i>mcontext</i>);</b> 175 <br> 176 <br> 177 <b>void pcre2_match_context_free(pcre2_match_context *<i>mcontext</i>);</b> 178 <br> 179 <br> 180 <b>int pcre2_set_callout(pcre2_match_context *<i>mcontext</i>,</b> 181 <b> int (*<i>callout_function</i>)(pcre2_callout_block *, void *),</b> 182 <b> void *<i>callout_data</i>);</b> 183 <br> 184 <br> 185 <b>int pcre2_set_offset_limit(pcre2_match_context *<i>mcontext</i>,</b> 186 <b> PCRE2_SIZE <i>value</i>);</b> 187 <br> 188 <br> 189 <b>int pcre2_set_heap_limit(pcre2_match_context *<i>mcontext</i>,</b> 190 <b> uint32_t <i>value</i>);</b> 191 <br> 192 <br> 193 <b>int pcre2_set_match_limit(pcre2_match_context *<i>mcontext</i>,</b> 194 <b> uint32_t <i>value</i>);</b> 195 <br> 196 <br> 197 <b>int pcre2_set_depth_limit(pcre2_match_context *<i>mcontext</i>,</b> 198 <b> uint32_t <i>value</i>);</b> 199 </P> 200 <br><a name="SEC6" href="#TOC1">PCRE2 NATIVE API STRING EXTRACTION FUNCTIONS</a><br> 201 <P> 202 <b>int pcre2_substring_copy_byname(pcre2_match_data *<i>match_data</i>,</b> 203 <b> PCRE2_SPTR <i>name</i>, PCRE2_UCHAR *<i>buffer</i>, PCRE2_SIZE *<i>bufflen</i>);</b> 204 <br> 205 <br> 206 <b>int pcre2_substring_copy_bynumber(pcre2_match_data *<i>match_data</i>,</b> 207 <b> uint32_t <i>number</i>, PCRE2_UCHAR *<i>buffer</i>,</b> 208 <b> PCRE2_SIZE *<i>bufflen</i>);</b> 209 <br> 210 <br> 211 <b>void pcre2_substring_free(PCRE2_UCHAR *<i>buffer</i>);</b> 212 <br> 213 <br> 214 <b>int pcre2_substring_get_byname(pcre2_match_data *<i>match_data</i>,</b> 215 <b> PCRE2_SPTR <i>name</i>, PCRE2_UCHAR **<i>bufferptr</i>, PCRE2_SIZE *<i>bufflen</i>);</b> 216 <br> 217 <br> 218 <b>int pcre2_substring_get_bynumber(pcre2_match_data *<i>match_data</i>,</b> 219 <b> uint32_t <i>number</i>, PCRE2_UCHAR **<i>bufferptr</i>,</b> 220 <b> PCRE2_SIZE *<i>bufflen</i>);</b> 221 <br> 222 <br> 223 <b>int pcre2_substring_length_byname(pcre2_match_data *<i>match_data</i>,</b> 224 <b> PCRE2_SPTR <i>name</i>, PCRE2_SIZE *<i>length</i>);</b> 225 <br> 226 <br> 227 <b>int pcre2_substring_length_bynumber(pcre2_match_data *<i>match_data</i>,</b> 228 <b> uint32_t <i>number</i>, PCRE2_SIZE *<i>length</i>);</b> 229 <br> 230 <br> 231 <b>int pcre2_substring_nametable_scan(const pcre2_code *<i>code</i>,</b> 232 <b> PCRE2_SPTR <i>name</i>, PCRE2_SPTR *<i>first</i>, PCRE2_SPTR *<i>last</i>);</b> 233 <br> 234 <br> 235 <b>int pcre2_substring_number_from_name(const pcre2_code *<i>code</i>,</b> 236 <b> PCRE2_SPTR <i>name</i>);</b> 237 <br> 238 <br> 239 <b>void pcre2_substring_list_free(PCRE2_SPTR *<i>list</i>);</b> 240 <br> 241 <br> 242 <b>int pcre2_substring_list_get(pcre2_match_data *<i>match_data</i>,</b> 243 <b>" PCRE2_UCHAR ***<i>listptr</i>, PCRE2_SIZE **<i>lengthsptr</i>);</b> 244 </P> 245 <br><a name="SEC7" href="#TOC1">PCRE2 NATIVE API STRING SUBSTITUTION FUNCTION</a><br> 246 <P> 247 <b>int pcre2_substitute(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 248 <b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 249 <b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 250 <b> pcre2_match_context *<i>mcontext</i>, PCRE2_SPTR \fIreplacementzfP,</b> 251 <b> PCRE2_SIZE <i>rlength</i>, PCRE2_UCHAR *<i>outputbuffer</i>,</b> 252 <b> PCRE2_SIZE *<i>outlengthptr</i>);</b> 253 </P> 254 <br><a name="SEC8" href="#TOC1">PCRE2 NATIVE API JIT FUNCTIONS</a><br> 255 <P> 256 <b>int pcre2_jit_compile(pcre2_code *<i>code</i>, uint32_t <i>options</i>);</b> 257 <br> 258 <br> 259 <b>int pcre2_jit_match(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 260 <b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 261 <b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 262 <b> pcre2_match_context *<i>mcontext</i>);</b> 263 <br> 264 <br> 265 <b>void pcre2_jit_free_unused_memory(pcre2_general_context *<i>gcontext</i>);</b> 266 <br> 267 <br> 268 <b>pcre2_jit_stack *pcre2_jit_stack_create(PCRE2_SIZE <i>startsize</i>,</b> 269 <b> PCRE2_SIZE <i>maxsize</i>, pcre2_general_context *<i>gcontext</i>);</b> 270 <br> 271 <br> 272 <b>void pcre2_jit_stack_assign(pcre2_match_context *<i>mcontext</i>,</b> 273 <b> pcre2_jit_callback <i>callback_function</i>, void *<i>callback_data</i>);</b> 274 <br> 275 <br> 276 <b>void pcre2_jit_stack_free(pcre2_jit_stack *<i>jit_stack</i>);</b> 277 </P> 278 <br><a name="SEC9" href="#TOC1">PCRE2 NATIVE API SERIALIZATION FUNCTIONS</a><br> 279 <P> 280 <b>int32_t pcre2_serialize_decode(pcre2_code **<i>codes</i>,</b> 281 <b> int32_t <i>number_of_codes</i>, const uint8_t *<i>bytes</i>,</b> 282 <b> pcre2_general_context *<i>gcontext</i>);</b> 283 <br> 284 <br> 285 <b>int32_t pcre2_serialize_encode(const pcre2_code **<i>codes</i>,</b> 286 <b> int32_t <i>number_of_codes</i>, uint8_t **<i>serialized_bytes</i>,</b> 287 <b> PCRE2_SIZE *<i>serialized_size</i>, pcre2_general_context *<i>gcontext</i>);</b> 288 <br> 289 <br> 290 <b>void pcre2_serialize_free(uint8_t *<i>bytes</i>);</b> 291 <br> 292 <br> 293 <b>int32_t pcre2_serialize_get_number_of_codes(const uint8_t *<i>bytes</i>);</b> 294 </P> 295 <br><a name="SEC10" href="#TOC1">PCRE2 NATIVE API AUXILIARY FUNCTIONS</a><br> 296 <P> 297 <b>pcre2_code *pcre2_code_copy(const pcre2_code *<i>code</i>);</b> 298 <br> 299 <br> 300 <b>pcre2_code *pcre2_code_copy_with_tables(const pcre2_code *<i>code</i>);</b> 301 <br> 302 <br> 303 <b>int pcre2_get_error_message(int <i>errorcode</i>, PCRE2_UCHAR *<i>buffer</i>,</b> 304 <b> PCRE2_SIZE <i>bufflen</i>);</b> 305 <br> 306 <br> 307 <b>const unsigned char *pcre2_maketables(pcre2_general_context *<i>gcontext</i>);</b> 308 <br> 309 <br> 310 <b>int pcre2_pattern_info(const pcre2 *<i>code</i>, uint32_t <i>what</i>, void *<i>where</i>);</b> 311 <br> 312 <br> 313 <b>int pcre2_callout_enumerate(const pcre2_code *<i>code</i>,</b> 314 <b> int (*<i>callback</i>)(pcre2_callout_enumerate_block *, void *),</b> 315 <b> void *<i>user_data</i>);</b> 316 <br> 317 <br> 318 <b>int pcre2_config(uint32_t <i>what</i>, void *<i>where</i>);</b> 319 </P> 320 <br><a name="SEC11" href="#TOC1">PCRE2 NATIVE API OBSOLETE FUNCTIONS</a><br> 321 <P> 322 <b>int pcre2_set_recursion_limit(pcre2_match_context *<i>mcontext</i>,</b> 323 <b> uint32_t <i>value</i>);</b> 324 <br> 325 <br> 326 <b>int pcre2_set_recursion_memory_management(</b> 327 <b> pcre2_match_context *<i>mcontext</i>,</b> 328 <b> void *(*<i>private_malloc</i>)(PCRE2_SIZE, void *),</b> 329 <b> void (*<i>private_free</i>)(void *, void *), void *<i>memory_data</i>);</b> 330 <br> 331 <br> 332 These functions became obsolete at release 10.30 and are retained only for 333 backward compatibility. They should not be used in new code. The first is 334 replaced by <b>pcre2_set_depth_limit()</b>; the second is no longer needed and 335 has no effect (it always returns zero). 336 </P> 337 <br><a name="SEC12" href="#TOC1">PCRE2 EXPERIMENTAL PATTERN CONVERSION FUNCTIONS</a><br> 338 <P> 339 <b>pcre2_convert_context *pcre2_convert_context_create(</b> 340 <b> pcre2_general_context *<i>gcontext</i>);</b> 341 <br> 342 <br> 343 <b>pcre2_convert_context *pcre2_convert_context_copy(</b> 344 <b> pcre2_convert_context *<i>cvcontext</i>);</b> 345 <br> 346 <br> 347 <b>void pcre2_convert_context_free(pcre2_convert_context *<i>cvcontext</i>);</b> 348 <br> 349 <br> 350 <b>int pcre2_set_glob_escape(pcre2_convert_context *<i>cvcontext</i>,</b> 351 <b> uint32_t <i>escape_char</i>);</b> 352 <br> 353 <br> 354 <b>int pcre2_set_glob_separator(pcre2_convert_context *<i>cvcontext</i>,</b> 355 <b> uint32_t <i>separator_char</i>);</b> 356 <br> 357 <br> 358 <b>int pcre2_pattern_convert(PCRE2_SPTR <i>pattern</i>, PCRE2_SIZE <i>length</i>,</b> 359 <b> uint32_t <i>options</i>, PCRE2_UCHAR **<i>buffer</i>,</b> 360 <b> PCRE2_SIZE *<i>blength</i>, pcre2_convert_context *<i>cvcontext</i>);</b> 361 <br> 362 <br> 363 <b>void pcre2_converted_pattern_free(PCRE2_UCHAR *<i>converted_pattern</i>);</b> 364 <br> 365 <br> 366 These functions provide a way of converting non-PCRE2 patterns into 367 patterns that can be processed by <b>pcre2_compile()</b>. This facility is 368 experimental and may be changed in future releases. At present, "globs" and 369 POSIX basic and extended patterns can be converted. Details are given in the 370 <a href="pcre2convert.html"><b>pcre2convert</b></a> 371 documentation. 372 </P> 373 <br><a name="SEC13" href="#TOC1">PCRE2 8-BIT, 16-BIT, AND 32-BIT LIBRARIES</a><br> 374 <P> 375 There are three PCRE2 libraries, supporting 8-bit, 16-bit, and 32-bit code 376 units, respectively. However, there is just one header file, <b>pcre2.h</b>. 377 This contains the function prototypes and other definitions for all three 378 libraries. One, two, or all three can be installed simultaneously. On Unix-like 379 systems the libraries are called <b>libpcre2-8</b>, <b>libpcre2-16</b>, and 380 <b>libpcre2-32</b>, and they can also co-exist with the original PCRE libraries. 381 </P> 382 <P> 383 Character strings are passed to and from a PCRE2 library as a sequence of 384 unsigned integers in code units of the appropriate width. Every PCRE2 function 385 comes in three different forms, one for each library, for example: 386 <pre> 387 <b>pcre2_compile_8()</b> 388 <b>pcre2_compile_16()</b> 389 <b>pcre2_compile_32()</b> 390 </pre> 391 There are also three different sets of data types: 392 <pre> 393 <b>PCRE2_UCHAR8, PCRE2_UCHAR16, PCRE2_UCHAR32</b> 394 <b>PCRE2_SPTR8, PCRE2_SPTR16, PCRE2_SPTR32</b> 395 </pre> 396 The UCHAR types define unsigned code units of the appropriate widths. For 397 example, PCRE2_UCHAR16 is usually defined as `uint16_t'. The SPTR types are 398 constant pointers to the equivalent UCHAR types, that is, they are pointers to 399 vectors of unsigned code units. 400 </P> 401 <P> 402 Many applications use only one code unit width. For their convenience, macros 403 are defined whose names are the generic forms such as <b>pcre2_compile()</b> and 404 PCRE2_SPTR. These macros use the value of the macro PCRE2_CODE_UNIT_WIDTH to 405 generate the appropriate width-specific function and macro names. 406 PCRE2_CODE_UNIT_WIDTH is not defined by default. An application must define it 407 to be 8, 16, or 32 before including <b>pcre2.h</b> in order to make use of the 408 generic names. 409 </P> 410 <P> 411 Applications that use more than one code unit width can be linked with more 412 than one PCRE2 library, but must define PCRE2_CODE_UNIT_WIDTH to be 0 before 413 including <b>pcre2.h</b>, and then use the real function names. Any code that is 414 to be included in an environment where the value of PCRE2_CODE_UNIT_WIDTH is 415 unknown should also use the real function names. (Unfortunately, it is not 416 possible in C code to save and restore the value of a macro.) 417 </P> 418 <P> 419 If PCRE2_CODE_UNIT_WIDTH is not defined before including <b>pcre2.h</b>, a 420 compiler error occurs. 421 </P> 422 <P> 423 When using multiple libraries in an application, you must take care when 424 processing any particular pattern to use only functions from a single library. 425 For example, if you want to run a match using a pattern that was compiled with 426 <b>pcre2_compile_16()</b>, you must do so with <b>pcre2_match_16()</b>, not 427 <b>pcre2_match_8()</b> or <b>pcre2_match_32()</b>. 428 </P> 429 <P> 430 In the function summaries above, and in the rest of this document and other 431 PCRE2 documents, functions and data types are described using their generic 432 names, without the _8, _16, or _32 suffix. 433 </P> 434 <br><a name="SEC14" href="#TOC1">PCRE2 API OVERVIEW</a><br> 435 <P> 436 PCRE2 has its own native API, which is described in this document. There are 437 also some wrapper functions for the 8-bit library that correspond to the 438 POSIX regular expression API, but they do not give access to all the 439 functionality of PCRE2. They are described in the 440 <a href="pcre2posix.html"><b>pcre2posix</b></a> 441 documentation. Both these APIs define a set of C function calls. 442 </P> 443 <P> 444 The native API C data types, function prototypes, option values, and error 445 codes are defined in the header file <b>pcre2.h</b>, which also contains 446 definitions of PCRE2_MAJOR and PCRE2_MINOR, the major and minor release numbers 447 for the library. Applications can use these to include support for different 448 releases of PCRE2. 449 </P> 450 <P> 451 In a Windows environment, if you want to statically link an application program 452 against a non-dll PCRE2 library, you must define PCRE2_STATIC before including 453 <b>pcre2.h</b>. 454 </P> 455 <P> 456 The functions <b>pcre2_compile()</b> and <b>pcre2_match()</b> are used for 457 compiling and matching regular expressions in a Perl-compatible manner. A 458 sample program that demonstrates the simplest way of using them is provided in 459 the file called <i>pcre2demo.c</i> in the PCRE2 source distribution. A listing 460 of this program is given in the 461 <a href="pcre2demo.html"><b>pcre2demo</b></a> 462 documentation, and the 463 <a href="pcre2sample.html"><b>pcre2sample</b></a> 464 documentation describes how to compile and run it. 465 </P> 466 <P> 467 The compiling and matching functions recognize various options that are passed 468 as bits in an options argument. There are also some more complicated parameters 469 such as custom memory management functions and resource limits that are passed 470 in "contexts" (which are just memory blocks, described below). Simple 471 applications do not need to make use of contexts. 472 </P> 473 <P> 474 Just-in-time (JIT) compiler support is an optional feature of PCRE2 that can be 475 built in appropriate hardware environments. It greatly speeds up the matching 476 performance of many patterns. Programs can request that it be used if 477 available by calling <b>pcre2_jit_compile()</b> after a pattern has been 478 successfully compiled by <b>pcre2_compile()</b>. This does nothing if JIT 479 support is not available. 480 </P> 481 <P> 482 More complicated programs might need to make use of the specialist functions 483 <b>pcre2_jit_stack_create()</b>, <b>pcre2_jit_stack_free()</b>, and 484 <b>pcre2_jit_stack_assign()</b> in order to control the JIT code's memory usage. 485 </P> 486 <P> 487 JIT matching is automatically used by <b>pcre2_match()</b> if it is available, 488 unless the PCRE2_NO_JIT option is set. There is also a direct interface for JIT 489 matching, which gives improved performance at the expense of less sanity 490 checking. The JIT-specific functions are discussed in the 491 <a href="pcre2jit.html"><b>pcre2jit</b></a> 492 documentation. 493 </P> 494 <P> 495 A second matching function, <b>pcre2_dfa_match()</b>, which is not 496 Perl-compatible, is also provided. This uses a different algorithm for the 497 matching. The alternative algorithm finds all possible matches (at a given 498 point in the subject), and scans the subject just once (unless there are 499 lookaround assertions). However, this algorithm does not return captured 500 substrings. A description of the two matching algorithms and their advantages 501 and disadvantages is given in the 502 <a href="pcre2matching.html"><b>pcre2matching</b></a> 503 documentation. There is no JIT support for <b>pcre2_dfa_match()</b>. 504 </P> 505 <P> 506 In addition to the main compiling and matching functions, there are convenience 507 functions for extracting captured substrings from a subject string that has 508 been matched by <b>pcre2_match()</b>. They are: 509 <pre> 510 <b>pcre2_substring_copy_byname()</b> 511 <b>pcre2_substring_copy_bynumber()</b> 512 <b>pcre2_substring_get_byname()</b> 513 <b>pcre2_substring_get_bynumber()</b> 514 <b>pcre2_substring_list_get()</b> 515 <b>pcre2_substring_length_byname()</b> 516 <b>pcre2_substring_length_bynumber()</b> 517 <b>pcre2_substring_nametable_scan()</b> 518 <b>pcre2_substring_number_from_name()</b> 519 </pre> 520 <b>pcre2_substring_free()</b> and <b>pcre2_substring_list_free()</b> are also 521 provided, to free memory used for extracted strings. If either of these 522 functions is called with a NULL argument, the function returns immediately 523 without doing anything. 524 </P> 525 <P> 526 The function <b>pcre2_substitute()</b> can be called to match a pattern and 527 return a copy of the subject string with substitutions for parts that were 528 matched. 529 </P> 530 <P> 531 Functions whose names begin with <b>pcre2_serialize_</b> are used for saving 532 compiled patterns on disc or elsewhere, and reloading them later. 533 </P> 534 <P> 535 Finally, there are functions for finding out information about a compiled 536 pattern (<b>pcre2_pattern_info()</b>) and about the configuration with which 537 PCRE2 was built (<b>pcre2_config()</b>). 538 </P> 539 <P> 540 Functions with names ending with <b>_free()</b> are used for freeing memory 541 blocks of various sorts. In all cases, if one of these functions is called with 542 a NULL argument, it does nothing. 543 </P> 544 <br><a name="SEC15" href="#TOC1">STRING LENGTHS AND OFFSETS</a><br> 545 <P> 546 The PCRE2 API uses string lengths and offsets into strings of code units in 547 several places. These values are always of type PCRE2_SIZE, which is an 548 unsigned integer type, currently always defined as <i>size_t</i>. The largest 549 value that can be stored in such a type (that is ~(PCRE2_SIZE)0) is reserved 550 as a special indicator for zero-terminated strings and unset offsets. 551 Therefore, the longest string that can be handled is one less than this 552 maximum. 553 <a name="newlines"></a></P> 554 <br><a name="SEC16" href="#TOC1">NEWLINES</a><br> 555 <P> 556 PCRE2 supports five different conventions for indicating line breaks in 557 strings: a single CR (carriage return) character, a single LF (linefeed) 558 character, the two-character sequence CRLF, any of the three preceding, or any 559 Unicode newline sequence. The Unicode newline sequences are the three just 560 mentioned, plus the single characters VT (vertical tab, U+000B), FF (form feed, 561 U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS 562 (paragraph separator, U+2029). 563 </P> 564 <P> 565 Each of the first three conventions is used by at least one operating system as 566 its standard newline sequence. When PCRE2 is built, a default can be specified. 567 If it is not, the default is set to LF, which is the Unix standard. However, 568 the newline convention can be changed by an application when calling 569 <b>pcre2_compile()</b>, or it can be specified by special text at the start of 570 the pattern itself; this overrides any other settings. See the 571 <a href="pcre2pattern.html"><b>pcre2pattern</b></a> 572 page for details of the special character sequences. 573 </P> 574 <P> 575 In the PCRE2 documentation the word "newline" is used to mean "the character or 576 pair of characters that indicate a line break". The choice of newline 577 convention affects the handling of the dot, circumflex, and dollar 578 metacharacters, the handling of #-comments in /x mode, and, when CRLF is a 579 recognized line ending sequence, the match position advancement for a 580 non-anchored pattern. There is more detail about this in the 581 <a href="#matchoptions">section on <b>pcre2_match()</b> options</a> 582 below. 583 </P> 584 <P> 585 The choice of newline convention does not affect the interpretation of 586 the \n or \r escape sequences, nor does it affect what \R matches; this has 587 its own separate convention. 588 </P> 589 <br><a name="SEC17" href="#TOC1">MULTITHREADING</a><br> 590 <P> 591 In a multithreaded application it is important to keep thread-specific data 592 separate from data that can be shared between threads. The PCRE2 library code 593 itself is thread-safe: it contains no static or global variables. The API is 594 designed to be fairly simple for non-threaded applications while at the same 595 time ensuring that multithreaded applications can use it. 596 </P> 597 <P> 598 There are several different blocks of data that are used to pass information 599 between the application and the PCRE2 libraries. 600 </P> 601 <br><b> 602 The compiled pattern 603 </b><br> 604 <P> 605 A pointer to the compiled form of a pattern is returned to the user when 606 <b>pcre2_compile()</b> is successful. The data in the compiled pattern is fixed, 607 and does not change when the pattern is matched. Therefore, it is thread-safe, 608 that is, the same compiled pattern can be used by more than one thread 609 simultaneously. For example, an application can compile all its patterns at the 610 start, before forking off multiple threads that use them. However, if the 611 just-in-time (JIT) optimization feature is being used, it needs separate memory 612 stack areas for each thread. See the 613 <a href="pcre2jit.html"><b>pcre2jit</b></a> 614 documentation for more details. 615 </P> 616 <P> 617 In a more complicated situation, where patterns are compiled only when they are 618 first needed, but are still shared between threads, pointers to compiled 619 patterns must be protected from simultaneous writing by multiple threads, at 620 least until a pattern has been compiled. The logic can be something like this: 621 <pre> 622 Get a read-only (shared) lock (mutex) for pointer 623 if (pointer == NULL) 624 { 625 Get a write (unique) lock for pointer 626 pointer = pcre2_compile(... 627 } 628 Release the lock 629 Use pointer in pcre2_match() 630 </pre> 631 Of course, testing for compilation errors should also be included in the code. 632 </P> 633 <P> 634 If JIT is being used, but the JIT compilation is not being done immediately, 635 (perhaps waiting to see if the pattern is used often enough) similar logic is 636 required. JIT compilation updates a pointer within the compiled code block, so 637 a thread must gain unique write access to the pointer before calling 638 <b>pcre2_jit_compile()</b>. Alternatively, <b>pcre2_code_copy()</b> or 639 <b>pcre2_code_copy_with_tables()</b> can be used to obtain a private copy of the 640 compiled code before calling the JIT compiler. 641 </P> 642 <br><b> 643 Context blocks 644 </b><br> 645 <P> 646 The next main section below introduces the idea of "contexts" in which PCRE2 647 functions are called. A context is nothing more than a collection of parameters 648 that control the way PCRE2 operates. Grouping a number of parameters together 649 in a context is a convenient way of passing them to a PCRE2 function without 650 using lots of arguments. The parameters that are stored in contexts are in some 651 sense "advanced features" of the API. Many straightforward applications will 652 not need to use contexts. 653 </P> 654 <P> 655 In a multithreaded application, if the parameters in a context are values that 656 are never changed, the same context can be used by all the threads. However, if 657 any thread needs to change any value in a context, it must make its own 658 thread-specific copy. 659 </P> 660 <br><b> 661 Match blocks 662 </b><br> 663 <P> 664 The matching functions need a block of memory for storing the results of a 665 match. This includes details of what was matched, as well as additional 666 information such as the name of a (*MARK) setting. Each thread must provide its 667 own copy of this memory. 668 </P> 669 <br><a name="SEC18" href="#TOC1">PCRE2 CONTEXTS</a><br> 670 <P> 671 Some PCRE2 functions have a lot of parameters, many of which are used only by 672 specialist applications, for example, those that use custom memory management 673 or non-standard character tables. To keep function argument lists at a 674 reasonable size, and at the same time to keep the API extensible, "uncommon" 675 parameters are passed to certain functions in a <b>context</b> instead of 676 directly. A context is just a block of memory that holds the parameter values. 677 Applications that do not need to adjust any of the context parameters can pass 678 NULL when a context pointer is required. 679 </P> 680 <P> 681 There are three different types of context: a general context that is relevant 682 for several PCRE2 operations, a compile-time context, and a match-time context. 683 </P> 684 <br><b> 685 The general context 686 </b><br> 687 <P> 688 At present, this context just contains pointers to (and data for) external 689 memory management functions that are called from several places in the PCRE2 690 library. The context is named `general' rather than specifically `memory' 691 because in future other fields may be added. If you do not want to supply your 692 own custom memory management functions, you do not need to bother with a 693 general context. A general context is created by: 694 <br> 695 <br> 696 <b>pcre2_general_context *pcre2_general_context_create(</b> 697 <b> void *(*<i>private_malloc</i>)(PCRE2_SIZE, void *),</b> 698 <b> void (*<i>private_free</i>)(void *, void *), void *<i>memory_data</i>);</b> 699 <br> 700 <br> 701 The two function pointers specify custom memory management functions, whose 702 prototypes are: 703 <pre> 704 <b>void *private_malloc(PCRE2_SIZE, void *);</b> 705 <b>void private_free(void *, void *);</b> 706 </pre> 707 Whenever code in PCRE2 calls these functions, the final argument is the value 708 of <i>memory_data</i>. Either of the first two arguments of the creation 709 function may be NULL, in which case the system memory management functions 710 <i>malloc()</i> and <i>free()</i> are used. (This is not currently useful, as 711 there are no other fields in a general context, but in future there might be.) 712 The <i>private_malloc()</i> function is used (if supplied) to obtain memory for 713 storing the context, and all three values are saved as part of the context. 714 </P> 715 <P> 716 Whenever PCRE2 creates a data block of any kind, the block contains a pointer 717 to the <i>free()</i> function that matches the <i>malloc()</i> function that was 718 used. When the time comes to free the block, this function is called. 719 </P> 720 <P> 721 A general context can be copied by calling: 722 <br> 723 <br> 724 <b>pcre2_general_context *pcre2_general_context_copy(</b> 725 <b> pcre2_general_context *<i>gcontext</i>);</b> 726 <br> 727 <br> 728 The memory used for a general context should be freed by calling: 729 <br> 730 <br> 731 <b>void pcre2_general_context_free(pcre2_general_context *<i>gcontext</i>);</b> 732 <br> 733 <br> 734 If this function is passed a NULL argument, it returns immediately without 735 doing anything. 736 <a name="compilecontext"></a></P> 737 <br><b> 738 The compile context 739 </b><br> 740 <P> 741 A compile context is required if you want to provide an external function for 742 stack checking during compilation or to change the default values of any of the 743 following compile-time parameters: 744 <pre> 745 What \R matches (Unicode newlines or CR, LF, CRLF only) 746 PCRE2's character tables 747 The newline character sequence 748 The compile time nested parentheses limit 749 The maximum length of the pattern string 750 The extra options bits (none set by default) 751 </pre> 752 A compile context is also required if you are using custom memory management. 753 If none of these apply, just pass NULL as the context argument of 754 <i>pcre2_compile()</i>. 755 </P> 756 <P> 757 A compile context is created, copied, and freed by the following functions: 758 <br> 759 <br> 760 <b>pcre2_compile_context *pcre2_compile_context_create(</b> 761 <b> pcre2_general_context *<i>gcontext</i>);</b> 762 <br> 763 <br> 764 <b>pcre2_compile_context *pcre2_compile_context_copy(</b> 765 <b> pcre2_compile_context *<i>ccontext</i>);</b> 766 <br> 767 <br> 768 <b>void pcre2_compile_context_free(pcre2_compile_context *<i>ccontext</i>);</b> 769 <br> 770 <br> 771 A compile context is created with default values for its parameters. These can 772 be changed by calling the following functions, which return 0 on success, or 773 PCRE2_ERROR_BADDATA if invalid data is detected. 774 <br> 775 <br> 776 <b>int pcre2_set_bsr(pcre2_compile_context *<i>ccontext</i>,</b> 777 <b> uint32_t <i>value</i>);</b> 778 <br> 779 <br> 780 The value must be PCRE2_BSR_ANYCRLF, to specify that \R matches only CR, LF, 781 or CRLF, or PCRE2_BSR_UNICODE, to specify that \R matches any Unicode line 782 ending sequence. The value is used by the JIT compiler and by the two 783 interpreted matching functions, <i>pcre2_match()</i> and 784 <i>pcre2_dfa_match()</i>. 785 <br> 786 <br> 787 <b>int pcre2_set_character_tables(pcre2_compile_context *<i>ccontext</i>,</b> 788 <b> const unsigned char *<i>tables</i>);</b> 789 <br> 790 <br> 791 The value must be the result of a call to <i>pcre2_maketables()</i>, whose only 792 argument is a general context. This function builds a set of character tables 793 in the current locale. 794 <br> 795 <br> 796 <b>int pcre2_set_compile_extra_options(pcre2_compile_context *<i>ccontext</i>,</b> 797 <b> uint32_t <i>extra_options</i>);</b> 798 <br> 799 <br> 800 As PCRE2 has developed, almost all the 32 option bits that are available in 801 the <i>options</i> argument of <b>pcre2_compile()</b> have been used up. To avoid 802 running out, the compile context contains a set of extra option bits which are 803 used for some newer, assumed rarer, options. This function sets those bits. It 804 always sets all the bits (either on or off). It does not modify any existing 805 setting. The available options are defined in the section entitled "Extra 806 compile options" 807 <a href="#extracompileoptions">below.</a> 808 <br> 809 <br> 810 <b>int pcre2_set_max_pattern_length(pcre2_compile_context *<i>ccontext</i>,</b> 811 <b> PCRE2_SIZE <i>value</i>);</b> 812 <br> 813 <br> 814 This sets a maximum length, in code units, for any pattern string that is 815 compiled with this context. If the pattern is longer, an error is generated. 816 This facility is provided so that applications that accept patterns from 817 external sources can limit their size. The default is the largest number that a 818 PCRE2_SIZE variable can hold, which is effectively unlimited. 819 <br> 820 <br> 821 <b>int pcre2_set_newline(pcre2_compile_context *<i>ccontext</i>,</b> 822 <b> uint32_t <i>value</i>);</b> 823 <br> 824 <br> 825 This specifies which characters or character sequences are to be recognized as 826 newlines. The value must be one of PCRE2_NEWLINE_CR (carriage return only), 827 PCRE2_NEWLINE_LF (linefeed only), PCRE2_NEWLINE_CRLF (the two-character 828 sequence CR followed by LF), PCRE2_NEWLINE_ANYCRLF (any of the above), 829 PCRE2_NEWLINE_ANY (any Unicode newline sequence), or PCRE2_NEWLINE_NUL (the 830 NUL character, that is a binary zero). 831 </P> 832 <P> 833 A pattern can override the value set in the compile context by starting with a 834 sequence such as (*CRLF). See the 835 <a href="pcre2pattern.html"><b>pcre2pattern</b></a> 836 page for details. 837 </P> 838 <P> 839 When a pattern is compiled with the PCRE2_EXTENDED or PCRE2_EXTENDED_MORE 840 option, the newline convention affects the recognition of the end of internal 841 comments starting with #. The value is saved with the compiled pattern for 842 subsequent use by the JIT compiler and by the two interpreted matching 843 functions, <i>pcre2_match()</i> and <i>pcre2_dfa_match()</i>. 844 <br> 845 <br> 846 <b>int pcre2_set_parens_nest_limit(pcre2_compile_context *<i>ccontext</i>,</b> 847 <b> uint32_t <i>value</i>);</b> 848 <br> 849 <br> 850 This parameter ajusts the limit, set when PCRE2 is built (default 250), on the 851 depth of parenthesis nesting in a pattern. This limit stops rogue patterns 852 using up too much system stack when being compiled. The limit applies to 853 parentheses of all kinds, not just capturing parentheses. 854 <br> 855 <br> 856 <b>int pcre2_set_compile_recursion_guard(pcre2_compile_context *<i>ccontext</i>,</b> 857 <b> int (*<i>guard_function</i>)(uint32_t, void *), void *<i>user_data</i>);</b> 858 <br> 859 <br> 860 There is at least one application that runs PCRE2 in threads with very limited 861 system stack, where running out of stack is to be avoided at all costs. The 862 parenthesis limit above cannot take account of how much stack is actually 863 available during compilation. For a finer control, you can supply a function 864 that is called whenever <b>pcre2_compile()</b> starts to compile a parenthesized 865 part of a pattern. This function can check the actual stack size (or anything 866 else that it wants to, of course). 867 </P> 868 <P> 869 The first argument to the callout function gives the current depth of 870 nesting, and the second is user data that is set up by the last argument of 871 <b>pcre2_set_compile_recursion_guard()</b>. The callout function should return 872 zero if all is well, or non-zero to force an error. 873 <a name="matchcontext"></a></P> 874 <br><b> 875 The match context 876 </b><br> 877 <P> 878 A match context is required if you want to: 879 <pre> 880 Set up a callout function 881 Set an offset limit for matching an unanchored pattern 882 Change the limit on the amount of heap used when matching 883 Change the backtracking match limit 884 Change the backtracking depth limit 885 Set custom memory management specifically for the match 886 </pre> 887 If none of these apply, just pass NULL as the context argument of 888 <b>pcre2_match()</b>, <b>pcre2_dfa_match()</b>, or <b>pcre2_jit_match()</b>. 889 </P> 890 <P> 891 A match context is created, copied, and freed by the following functions: 892 <br> 893 <br> 894 <b>pcre2_match_context *pcre2_match_context_create(</b> 895 <b> pcre2_general_context *<i>gcontext</i>);</b> 896 <br> 897 <br> 898 <b>pcre2_match_context *pcre2_match_context_copy(</b> 899 <b> pcre2_match_context *<i>mcontext</i>);</b> 900 <br> 901 <br> 902 <b>void pcre2_match_context_free(pcre2_match_context *<i>mcontext</i>);</b> 903 <br> 904 <br> 905 A match context is created with default values for its parameters. These can 906 be changed by calling the following functions, which return 0 on success, or 907 PCRE2_ERROR_BADDATA if invalid data is detected. 908 <br> 909 <br> 910 <b>int pcre2_set_callout(pcre2_match_context *<i>mcontext</i>,</b> 911 <b> int (*<i>callout_function</i>)(pcre2_callout_block *, void *),</b> 912 <b> void *<i>callout_data</i>);</b> 913 <br> 914 <br> 915 This sets up a "callout" function for PCRE2 to call at specified points 916 during a matching operation. Details are given in the 917 <a href="pcre2callout.html"><b>pcre2callout</b></a> 918 documentation. 919 <br> 920 <br> 921 <b>int pcre2_set_offset_limit(pcre2_match_context *<i>mcontext</i>,</b> 922 <b> PCRE2_SIZE <i>value</i>);</b> 923 <br> 924 <br> 925 The <i>offset_limit</i> parameter limits how far an unanchored search can 926 advance in the subject string. The default value is PCRE2_UNSET. The 927 <b>pcre2_match()</b> and <b>pcre2_dfa_match()</b> functions return 928 PCRE2_ERROR_NOMATCH if a match with a starting point before or at the given 929 offset is not found. The <b>pcre2_substitute()</b> function makes no more 930 substitutions. 931 </P> 932 <P> 933 For example, if the pattern /abc/ is matched against "123abc" with an offset 934 limit less than 3, the result is PCRE2_ERROR_NO_MATCH. A match can never be 935 found if the <i>startoffset</i> argument of <b>pcre2_match()</b>, 936 <b>pcre2_dfa_match()</b>, or <b>pcre2_substitute()</b> is greater than the offset 937 limit set in the match context. 938 </P> 939 <P> 940 When using this facility, you must set the PCRE2_USE_OFFSET_LIMIT option when 941 calling <b>pcre2_compile()</b> so that when JIT is in use, different code can be 942 compiled. If a match is started with a non-default match limit when 943 PCRE2_USE_OFFSET_LIMIT is not set, an error is generated. 944 </P> 945 <P> 946 The offset limit facility can be used to track progress when searching large 947 subject strings or to limit the extent of global substitutions. See also the 948 PCRE2_FIRSTLINE option, which requires a match to start before or at the first 949 newline that follows the start of matching in the subject. If this is set with 950 an offset limit, a match must occur in the first line and also within the 951 offset limit. In other words, whichever limit comes first is used. 952 <br> 953 <br> 954 <b>int pcre2_set_heap_limit(pcre2_match_context *<i>mcontext</i>,</b> 955 <b> uint32_t <i>value</i>);</b> 956 <br> 957 <br> 958 The <i>heap_limit</i> parameter specifies, in units of kibibytes (1024 bytes), 959 the maximum amount of heap memory that <b>pcre2_match()</b> may use to hold 960 backtracking information when running an interpretive match. This limit also 961 applies to <b>pcre2_dfa_match()</b>, which may use the heap when processing 962 patterns with a lot of nested pattern recursion or lookarounds or atomic 963 groups. This limit does not apply to matching with the JIT optimization, which 964 has its own memory control arrangements (see the 965 <a href="pcre2jit.html"><b>pcre2jit</b></a> 966 documentation for more details). If the limit is reached, the negative error 967 code PCRE2_ERROR_HEAPLIMIT is returned. The default limit can be set when PCRE2 968 is built; if it is not, the default is set very large and is essentially 969 "unlimited". 970 </P> 971 <P> 972 A value for the heap limit may also be supplied by an item at the start of a 973 pattern of the form 974 <pre> 975 (*LIMIT_HEAP=ddd) 976 </pre> 977 where ddd is a decimal number. However, such a setting is ignored unless ddd is 978 less than the limit set by the caller of <b>pcre2_match()</b> or, if no such 979 limit is set, less than the default. 980 </P> 981 <P> 982 The <b>pcre2_match()</b> function starts out using a 20KiB vector on the system 983 stack for recording backtracking points. The more nested backtracking points 984 there are (that is, the deeper the search tree), the more memory is needed. 985 Heap memory is used only if the initial vector is too small. If the heap limit 986 is set to a value less than 21 (in particular, zero) no heap memory will be 987 used. In this case, only patterns that do not have a lot of nested backtracking 988 can be successfully processed. 989 </P> 990 <P> 991 Similarly, for <b>pcre2_dfa_match()</b>, a vector on the system stack is used 992 when processing pattern recursions, lookarounds, or atomic groups, and only if 993 this is not big enough is heap memory used. In this case, too, setting a value 994 of zero disables the use of the heap. 995 <br> 996 <br> 997 <b>int pcre2_set_match_limit(pcre2_match_context *<i>mcontext</i>,</b> 998 <b> uint32_t <i>value</i>);</b> 999 <br> 1000 <br> 1001 The <i>match_limit</i> parameter provides a means of preventing PCRE2 from using 1002 up too many computing resources when processing patterns that are not going to 1003 match, but which have a very large number of possibilities in their search 1004 trees. The classic example is a pattern that uses nested unlimited repeats. 1005 </P> 1006 <P> 1007 There is an internal counter in <b>pcre2_match()</b> that is incremented each 1008 time round its main matching loop. If this value reaches the match limit, 1009 <b>pcre2_match()</b> returns the negative value PCRE2_ERROR_MATCHLIMIT. This has 1010 the effect of limiting the amount of backtracking that can take place. For 1011 patterns that are not anchored, the count restarts from zero for each position 1012 in the subject string. This limit also applies to <b>pcre2_dfa_match()</b>, 1013 though the counting is done in a different way. 1014 </P> 1015 <P> 1016 When <b>pcre2_match()</b> is called with a pattern that was successfully 1017 processed by <b>pcre2_jit_compile()</b>, the way in which matching is executed 1018 is entirely different. However, there is still the possibility of runaway 1019 matching that goes on for a very long time, and so the <i>match_limit</i> value 1020 is also used in this case (but in a different way) to limit how long the 1021 matching can continue. 1022 </P> 1023 <P> 1024 The default value for the limit can be set when PCRE2 is built; the default 1025 default is 10 million, which handles all but the most extreme cases. A value 1026 for the match limit may also be supplied by an item at the start of a pattern 1027 of the form 1028 <pre> 1029 (*LIMIT_MATCH=ddd) 1030 </pre> 1031 where ddd is a decimal number. However, such a setting is ignored unless ddd is 1032 less than the limit set by the caller of <b>pcre2_match()</b> or 1033 <b>pcre2_dfa_match()</b> or, if no such limit is set, less than the default. 1034 <br> 1035 <br> 1036 <b>int pcre2_set_depth_limit(pcre2_match_context *<i>mcontext</i>,</b> 1037 <b> uint32_t <i>value</i>);</b> 1038 <br> 1039 <br> 1040 This parameter limits the depth of nested backtracking in <b>pcre2_match()</b>. 1041 Each time a nested backtracking point is passed, a new memory "frame" is used 1042 to remember the state of matching at that point. Thus, this parameter 1043 indirectly limits the amount of memory that is used in a match. However, 1044 because the size of each memory "frame" depends on the number of capturing 1045 parentheses, the actual memory limit varies from pattern to pattern. This limit 1046 was more useful in versions before 10.30, where function recursion was used for 1047 backtracking. 1048 </P> 1049 <P> 1050 The depth limit is not relevant, and is ignored, when matching is done using 1051 JIT compiled code. However, it is supported by <b>pcre2_dfa_match()</b>, which 1052 uses it to limit the depth of nested internal recursive function calls that 1053 implement atomic groups, lookaround assertions, and pattern recursions. This 1054 limits, indirectly, the amount of system stack that is used. It was more useful 1055 in versions before 10.32, when stack memory was used for local workspace 1056 vectors for recursive function calls. From version 10.32, only local variables 1057 are allocated on the stack and as each call uses only a few hundred bytes, even 1058 a small stack can support quite a lot of recursion. 1059 </P> 1060 <P> 1061 If the depth of internal recursive function calls is great enough, local 1062 workspace vectors are allocated on the heap from version 10.32 onwards, so the 1063 depth limit also indirectly limits the amount of heap memory that is used. A 1064 recursive pattern such as /(.(?2))((?1)|)/, when matched to a very long string 1065 using <b>pcre2_dfa_match()</b>, can use a great deal of memory. However, it is 1066 probably better to limit heap usage directly by calling 1067 <b>pcre2_set_heap_limit()</b>. 1068 </P> 1069 <P> 1070 The default value for the depth limit can be set when PCRE2 is built; if it is 1071 not, the default is set to the same value as the default for the match limit. 1072 If the limit is exceeded, <b>pcre2_match()</b> or <b>pcre2_dfa_match()</b> 1073 returns PCRE2_ERROR_DEPTHLIMIT. A value for the depth limit may also be 1074 supplied by an item at the start of a pattern of the form 1075 <pre> 1076 (*LIMIT_DEPTH=ddd) 1077 </pre> 1078 where ddd is a decimal number. However, such a setting is ignored unless ddd is 1079 less than the limit set by the caller of <b>pcre2_match()</b> or 1080 <b>pcre2_dfa_match()</b> or, if no such limit is set, less than the default. 1081 </P> 1082 <br><a name="SEC19" href="#TOC1">CHECKING BUILD-TIME OPTIONS</a><br> 1083 <P> 1084 <b>int pcre2_config(uint32_t <i>what</i>, void *<i>where</i>);</b> 1085 </P> 1086 <P> 1087 The function <b>pcre2_config()</b> makes it possible for a PCRE2 client to 1088 discover which optional features have been compiled into the PCRE2 library. The 1089 <a href="pcre2build.html"><b>pcre2build</b></a> 1090 documentation has more details about these optional features. 1091 </P> 1092 <P> 1093 The first argument for <b>pcre2_config()</b> specifies which information is 1094 required. The second argument is a pointer to memory into which the information 1095 is placed. If NULL is passed, the function returns the amount of memory that is 1096 needed for the requested information. For calls that return numerical values, 1097 the value is in bytes; when requesting these values, <i>where</i> should point 1098 to appropriately aligned memory. For calls that return strings, the required 1099 length is given in code units, not counting the terminating zero. 1100 </P> 1101 <P> 1102 When requesting information, the returned value from <b>pcre2_config()</b> is 1103 non-negative on success, or the negative error code PCRE2_ERROR_BADOPTION if 1104 the value in the first argument is not recognized. The following information is 1105 available: 1106 <pre> 1107 PCRE2_CONFIG_BSR 1108 </pre> 1109 The output is a uint32_t integer whose value indicates what character 1110 sequences the \R escape sequence matches by default. A value of 1111 PCRE2_BSR_UNICODE means that \R matches any Unicode line ending sequence; a 1112 value of PCRE2_BSR_ANYCRLF means that \R matches only CR, LF, or CRLF. The 1113 default can be overridden when a pattern is compiled. 1114 <pre> 1115 PCRE2_CONFIG_COMPILED_WIDTHS 1116 </pre> 1117 The output is a uint32_t integer whose lower bits indicate which code unit 1118 widths were selected when PCRE2 was built. The 1-bit indicates 8-bit support, 1119 and the 2-bit and 4-bit indicate 16-bit and 32-bit support, respectively. 1120 <pre> 1121 PCRE2_CONFIG_DEPTHLIMIT 1122 </pre> 1123 The output is a uint32_t integer that gives the default limit for the depth of 1124 nested backtracking in <b>pcre2_match()</b> or the depth of nested recursions, 1125 lookarounds, and atomic groups in <b>pcre2_dfa_match()</b>. Further details are 1126 given with <b>pcre2_set_depth_limit()</b> above. 1127 <pre> 1128 PCRE2_CONFIG_HEAPLIMIT 1129 </pre> 1130 The output is a uint32_t integer that gives, in kibibytes, the default limit 1131 for the amount of heap memory used by <b>pcre2_match()</b> or 1132 <b>pcre2_dfa_match()</b>. Further details are given with 1133 <b>pcre2_set_heap_limit()</b> above. 1134 <pre> 1135 PCRE2_CONFIG_JIT 1136 </pre> 1137 The output is a uint32_t integer that is set to one if support for just-in-time 1138 compiling is available; otherwise it is set to zero. 1139 <pre> 1140 PCRE2_CONFIG_JITTARGET 1141 </pre> 1142 The <i>where</i> argument should point to a buffer that is at least 48 code 1143 units long. (The exact length required can be found by calling 1144 <b>pcre2_config()</b> with <b>where</b> set to NULL.) The buffer is filled with a 1145 string that contains the name of the architecture for which the JIT compiler is 1146 configured, for example "x86 32bit (little endian + unaligned)". If JIT support 1147 is not available, PCRE2_ERROR_BADOPTION is returned, otherwise the number of 1148 code units used is returned. This is the length of the string, plus one unit 1149 for the terminating zero. 1150 <pre> 1151 PCRE2_CONFIG_LINKSIZE 1152 </pre> 1153 The output is a uint32_t integer that contains the number of bytes used for 1154 internal linkage in compiled regular expressions. When PCRE2 is configured, the 1155 value can be set to 2, 3, or 4, with the default being 2. This is the value 1156 that is returned by <b>pcre2_config()</b>. However, when the 16-bit library is 1157 compiled, a value of 3 is rounded up to 4, and when the 32-bit library is 1158 compiled, internal linkages always use 4 bytes, so the configured value is not 1159 relevant. 1160 </P> 1161 <P> 1162 The default value of 2 for the 8-bit and 16-bit libraries is sufficient for all 1163 but the most massive patterns, since it allows the size of the compiled pattern 1164 to be up to 65535 code units. Larger values allow larger regular expressions to 1165 be compiled by those two libraries, but at the expense of slower matching. 1166 <pre> 1167 PCRE2_CONFIG_MATCHLIMIT 1168 </pre> 1169 The output is a uint32_t integer that gives the default match limit for 1170 <b>pcre2_match()</b>. Further details are given with 1171 <b>pcre2_set_match_limit()</b> above. 1172 <pre> 1173 PCRE2_CONFIG_NEWLINE 1174 </pre> 1175 The output is a uint32_t integer whose value specifies the default character 1176 sequence that is recognized as meaning "newline". The values are: 1177 <pre> 1178 PCRE2_NEWLINE_CR Carriage return (CR) 1179 PCRE2_NEWLINE_LF Linefeed (LF) 1180 PCRE2_NEWLINE_CRLF Carriage return, linefeed (CRLF) 1181 PCRE2_NEWLINE_ANY Any Unicode line ending 1182 PCRE2_NEWLINE_ANYCRLF Any of CR, LF, or CRLF 1183 PCRE2_NEWLINE_NUL The NUL character (binary zero) 1184 </pre> 1185 The default should normally correspond to the standard sequence for your 1186 operating system. 1187 <pre> 1188 PCRE2_CONFIG_NEVER_BACKSLASH_C 1189 </pre> 1190 The output is a uint32_t integer that is set to one if the use of \C was 1191 permanently disabled when PCRE2 was built; otherwise it is set to zero. 1192 <pre> 1193 PCRE2_CONFIG_PARENSLIMIT 1194 </pre> 1195 The output is a uint32_t integer that gives the maximum depth of nesting 1196 of parentheses (of any kind) in a pattern. This limit is imposed to cap the 1197 amount of system stack used when a pattern is compiled. It is specified when 1198 PCRE2 is built; the default is 250. This limit does not take into account the 1199 stack that may already be used by the calling application. For finer control 1200 over compilation stack usage, see <b>pcre2_set_compile_recursion_guard()</b>. 1201 <pre> 1202 PCRE2_CONFIG_STACKRECURSE 1203 </pre> 1204 This parameter is obsolete and should not be used in new code. The output is a 1205 uint32_t integer that is always set to zero. 1206 <pre> 1207 PCRE2_CONFIG_UNICODE_VERSION 1208 </pre> 1209 The <i>where</i> argument should point to a buffer that is at least 24 code 1210 units long. (The exact length required can be found by calling 1211 <b>pcre2_config()</b> with <b>where</b> set to NULL.) If PCRE2 has been compiled 1212 without Unicode support, the buffer is filled with the text "Unicode not 1213 supported". Otherwise, the Unicode version string (for example, "8.0.0") is 1214 inserted. The number of code units used is returned. This is the length of the 1215 string plus one unit for the terminating zero. 1216 <pre> 1217 PCRE2_CONFIG_UNICODE 1218 </pre> 1219 The output is a uint32_t integer that is set to one if Unicode support is 1220 available; otherwise it is set to zero. Unicode support implies UTF support. 1221 <pre> 1222 PCRE2_CONFIG_VERSION 1223 </pre> 1224 The <i>where</i> argument should point to a buffer that is at least 24 code 1225 units long. (The exact length required can be found by calling 1226 <b>pcre2_config()</b> with <b>where</b> set to NULL.) The buffer is filled with 1227 the PCRE2 version string, zero-terminated. The number of code units used is 1228 returned. This is the length of the string plus one unit for the terminating 1229 zero. 1230 <a name="compiling"></a></P> 1231 <br><a name="SEC20" href="#TOC1">COMPILING A PATTERN</a><br> 1232 <P> 1233 <b>pcre2_code *pcre2_compile(PCRE2_SPTR <i>pattern</i>, PCRE2_SIZE <i>length</i>,</b> 1234 <b> uint32_t <i>options</i>, int *<i>errorcode</i>, PCRE2_SIZE *<i>erroroffset,</i></b> 1235 <b> pcre2_compile_context *<i>ccontext</i>);</b> 1236 <br> 1237 <br> 1238 <b>void pcre2_code_free(pcre2_code *<i>code</i>);</b> 1239 <br> 1240 <br> 1241 <b>pcre2_code *pcre2_code_copy(const pcre2_code *<i>code</i>);</b> 1242 <br> 1243 <br> 1244 <b>pcre2_code *pcre2_code_copy_with_tables(const pcre2_code *<i>code</i>);</b> 1245 </P> 1246 <P> 1247 The <b>pcre2_compile()</b> function compiles a pattern into an internal form. 1248 The pattern is defined by a pointer to a string of code units and a length (in 1249 code units). If the pattern is zero-terminated, the length can be specified as 1250 PCRE2_ZERO_TERMINATED. The function returns a pointer to a block of memory that 1251 contains the compiled pattern and related data, or NULL if an error occurred. 1252 </P> 1253 <P> 1254 If the compile context argument <i>ccontext</i> is NULL, memory for the compiled 1255 pattern is obtained by calling <b>malloc()</b>. Otherwise, it is obtained from 1256 the same memory function that was used for the compile context. The caller must 1257 free the memory by calling <b>pcre2_code_free()</b> when it is no longer needed. 1258 If <b>pcre2_code_free()</b> is called with a NULL argument, it returns 1259 immediately, without doing anything. 1260 </P> 1261 <P> 1262 The function <b>pcre2_code_copy()</b> makes a copy of the compiled code in new 1263 memory, using the same memory allocator as was used for the original. However, 1264 if the code has been processed by the JIT compiler (see 1265 <a href="#jitcompiling">below),</a> 1266 the JIT information cannot be copied (because it is position-dependent). 1267 The new copy can initially be used only for non-JIT matching, though it can be 1268 passed to <b>pcre2_jit_compile()</b> if required. If <b>pcre2_code_copy()</b> is 1269 called with a NULL argument, it returns NULL. 1270 </P> 1271 <P> 1272 The <b>pcre2_code_copy()</b> function provides a way for individual threads in a 1273 multithreaded application to acquire a private copy of shared compiled code. 1274 However, it does not make a copy of the character tables used by the compiled 1275 pattern; the new pattern code points to the same tables as the original code. 1276 (See 1277 <a href="#jitcompiling">"Locale Support"</a> 1278 below for details of these character tables.) In many applications the same 1279 tables are used throughout, so this behaviour is appropriate. Nevertheless, 1280 there are occasions when a copy of a compiled pattern and the relevant tables 1281 are needed. The <b>pcre2_code_copy_with_tables()</b> provides this facility. 1282 Copies of both the code and the tables are made, with the new code pointing to 1283 the new tables. The memory for the new tables is automatically freed when 1284 <b>pcre2_code_free()</b> is called for the new copy of the compiled code. If 1285 <b>pcre2_code_copy_withy_tables()</b> is called with a NULL argument, it returns 1286 NULL. 1287 </P> 1288 <P> 1289 NOTE: When one of the matching functions is called, pointers to the compiled 1290 pattern and the subject string are set in the match data block so that they can 1291 be referenced by the substring extraction functions. After running a match, you 1292 must not free a compiled pattern (or a subject string) until after all 1293 operations on the 1294 <a href="#matchdatablock">match data block</a> 1295 have taken place. 1296 </P> 1297 <P> 1298 The <i>options</i> argument for <b>pcre2_compile()</b> contains various bit 1299 settings that affect the compilation. It should be zero if no options are 1300 required. The available options are described below. Some of them (in 1301 particular, those that are compatible with Perl, but some others as well) can 1302 also be set and unset from within the pattern (see the detailed description in 1303 the 1304 <a href="pcre2pattern.html"><b>pcre2pattern</b></a> 1305 documentation). 1306 </P> 1307 <P> 1308 For those options that can be different in different parts of the pattern, the 1309 contents of the <i>options</i> argument specifies their settings at the start of 1310 compilation. The PCRE2_ANCHORED, PCRE2_ENDANCHORED, and PCRE2_NO_UTF_CHECK 1311 options can be set at the time of matching as well as at compile time. 1312 </P> 1313 <P> 1314 Other, less frequently required compile-time parameters (for example, the 1315 newline setting) can be provided in a compile context (as described 1316 <a href="#compilecontext">above).</a> 1317 </P> 1318 <P> 1319 If <i>errorcode</i> or <i>erroroffset</i> is NULL, <b>pcre2_compile()</b> returns 1320 NULL immediately. Otherwise, the variables to which these point are set to an 1321 error code and an offset (number of code units) within the pattern, 1322 respectively, when <b>pcre2_compile()</b> returns NULL because a compilation 1323 error has occurred. The values are not defined when compilation is successful 1324 and <b>pcre2_compile()</b> returns a non-NULL value. 1325 </P> 1326 <P> 1327 There are nearly 100 positive error codes that <b>pcre2_compile()</b> may return 1328 if it finds an error in the pattern. There are also some negative error codes 1329 that are used for invalid UTF strings. These are the same as given by 1330 <b>pcre2_match()</b> and <b>pcre2_dfa_match()</b>, and are described in the 1331 <a href="pcre2unicode.html"><b>pcre2unicode</b></a> 1332 page. There is no separate documentation for the positive error codes, because 1333 the textual error messages that are obtained by calling the 1334 <b>pcre2_get_error_message()</b> function (see "Obtaining a textual error 1335 message" 1336 <a href="#geterrormessage">below)</a> 1337 should be self-explanatory. Macro names starting with PCRE2_ERROR_ are defined 1338 for both positive and negative error codes in <b>pcre2.h</b>. 1339 </P> 1340 <P> 1341 The value returned in <i>erroroffset</i> is an indication of where in the 1342 pattern the error occurred. It is not necessarily the furthest point in the 1343 pattern that was read. For example, after the error "lookbehind assertion is 1344 not fixed length", the error offset points to the start of the failing 1345 assertion. For an invalid UTF-8 or UTF-16 string, the offset is that of the 1346 first code unit of the failing character. 1347 </P> 1348 <P> 1349 Some errors are not detected until the whole pattern has been scanned; in these 1350 cases, the offset passed back is the length of the pattern. Note that the 1351 offset is in code units, not characters, even in a UTF mode. It may sometimes 1352 point into the middle of a UTF-8 or UTF-16 character. 1353 </P> 1354 <P> 1355 This code fragment shows a typical straightforward call to 1356 <b>pcre2_compile()</b>: 1357 <pre> 1358 pcre2_code *re; 1359 PCRE2_SIZE erroffset; 1360 int errorcode; 1361 re = pcre2_compile( 1362 "^A.*Z", /* the pattern */ 1363 PCRE2_ZERO_TERMINATED, /* the pattern is zero-terminated */ 1364 0, /* default options */ 1365 &errorcode, /* for error code */ 1366 &erroffset, /* for error offset */ 1367 NULL); /* no compile context */ 1368 </pre> 1369 The following names for option bits are defined in the <b>pcre2.h</b> header 1370 file: 1371 <pre> 1372 PCRE2_ANCHORED 1373 </pre> 1374 If this bit is set, the pattern is forced to be "anchored", that is, it is 1375 constrained to match only at the first matching point in the string that is 1376 being searched (the "subject string"). This effect can also be achieved by 1377 appropriate constructs in the pattern itself, which is the only way to do it in 1378 Perl. 1379 <pre> 1380 PCRE2_ALLOW_EMPTY_CLASS 1381 </pre> 1382 By default, for compatibility with Perl, a closing square bracket that 1383 immediately follows an opening one is treated as a data character for the 1384 class. When PCRE2_ALLOW_EMPTY_CLASS is set, it terminates the class, which 1385 therefore contains no characters and so can never match. 1386 <pre> 1387 PCRE2_ALT_BSUX 1388 </pre> 1389 This option request alternative handling of three escape sequences, which 1390 makes PCRE2's behaviour more like ECMAscript (aka JavaScript). When it is set: 1391 </P> 1392 <P> 1393 (1) \U matches an upper case "U" character; by default \U causes a compile 1394 time error (Perl uses \U to upper case subsequent characters). 1395 </P> 1396 <P> 1397 (2) \u matches a lower case "u" character unless it is followed by four 1398 hexadecimal digits, in which case the hexadecimal number defines the code point 1399 to match. By default, \u causes a compile time error (Perl uses it to upper 1400 case the following character). 1401 </P> 1402 <P> 1403 (3) \x matches a lower case "x" character unless it is followed by two 1404 hexadecimal digits, in which case the hexadecimal number defines the code point 1405 to match. By default, as in Perl, a hexadecimal number is always expected after 1406 \x, but it may have zero, one, or two digits (so, for example, \xz matches a 1407 binary zero character followed by z). 1408 <pre> 1409 PCRE2_ALT_CIRCUMFLEX 1410 </pre> 1411 In multiline mode (when PCRE2_MULTILINE is set), the circumflex metacharacter 1412 matches at the start of the subject (unless PCRE2_NOTBOL is set), and also 1413 after any internal newline. However, it does not match after a newline at the 1414 end of the subject, for compatibility with Perl. If you want a multiline 1415 circumflex also to match after a terminating newline, you must set 1416 PCRE2_ALT_CIRCUMFLEX. 1417 <pre> 1418 PCRE2_ALT_VERBNAMES 1419 </pre> 1420 By default, for compatibility with Perl, the name in any verb sequence such as 1421 (*MARK:NAME) is any sequence of characters that does not include a closing 1422 parenthesis. The name is not processed in any way, and it is not possible to 1423 include a closing parenthesis in the name. However, if the PCRE2_ALT_VERBNAMES 1424 option is set, normal backslash processing is applied to verb names and only an 1425 unescaped closing parenthesis terminates the name. A closing parenthesis can be 1426 included in a name either as \) or between \Q and \E. If the PCRE2_EXTENDED 1427 or PCRE2_EXTENDED_MORE option is set with PCRE2_ALT_VERBNAMES, unescaped 1428 whitespace in verb names is skipped and #-comments are recognized, exactly as 1429 in the rest of the pattern. 1430 <pre> 1431 PCRE2_AUTO_CALLOUT 1432 </pre> 1433 If this bit is set, <b>pcre2_compile()</b> automatically inserts callout items, 1434 all with number 255, before each pattern item, except immediately before or 1435 after an explicit callout in the pattern. For discussion of the callout 1436 facility, see the 1437 <a href="pcre2callout.html"><b>pcre2callout</b></a> 1438 documentation. 1439 <pre> 1440 PCRE2_CASELESS 1441 </pre> 1442 If this bit is set, letters in the pattern match both upper and lower case 1443 letters in the subject. It is equivalent to Perl's /i option, and it can be 1444 changed within a pattern by a (?i) option setting. If PCRE2_UTF is set, Unicode 1445 properties are used for all characters with more than one other case, and for 1446 all characters whose code points are greater than U+007F. For lower valued 1447 characters with only one other case, a lookup table is used for speed. When 1448 PCRE2_UTF is not set, a lookup table is used for all code points less than 256, 1449 and higher code points (available only in 16-bit or 32-bit mode) are treated as 1450 not having another case. 1451 <pre> 1452 PCRE2_DOLLAR_ENDONLY 1453 </pre> 1454 If this bit is set, a dollar metacharacter in the pattern matches only at the 1455 end of the subject string. Without this option, a dollar also matches 1456 immediately before a newline at the end of the string (but not before any other 1457 newlines). The PCRE2_DOLLAR_ENDONLY option is ignored if PCRE2_MULTILINE is 1458 set. There is no equivalent to this option in Perl, and no way to set it within 1459 a pattern. 1460 <pre> 1461 PCRE2_DOTALL 1462 </pre> 1463 If this bit is set, a dot metacharacter in the pattern matches any character, 1464 including one that indicates a newline. However, it only ever matches one 1465 character, even if newlines are coded as CRLF. Without this option, a dot does 1466 not match when the current position in the subject is at a newline. This option 1467 is equivalent to Perl's /s option, and it can be changed within a pattern by a 1468 (?s) option setting. A negative class such as [^a] always matches newline 1469 characters, and the \N escape sequence always matches a non-newline character, 1470 independent of the setting of PCRE2_DOTALL. 1471 <pre> 1472 PCRE2_DUPNAMES 1473 </pre> 1474 If this bit is set, names used to identify capturing subpatterns need not be 1475 unique. This can be helpful for certain types of pattern when it is known that 1476 only one instance of the named subpattern can ever be matched. There are more 1477 details of named subpatterns below; see also the 1478 <a href="pcre2pattern.html"><b>pcre2pattern</b></a> 1479 documentation. 1480 <pre> 1481 PCRE2_ENDANCHORED 1482 </pre> 1483 If this bit is set, the end of any pattern match must be right at the end of 1484 the string being searched (the "subject string"). If the pattern match 1485 succeeds by reaching (*ACCEPT), but does not reach the end of the subject, the 1486 match fails at the current starting point. For unanchored patterns, a new match 1487 is then tried at the next starting point. However, if the match succeeds by 1488 reaching the end of the pattern, but not the end of the subject, backtracking 1489 occurs and an alternative match may be found. Consider these two patterns: 1490 <pre> 1491 .(*ACCEPT)|.. 1492 .|.. 1493 </pre> 1494 If matched against "abc" with PCRE2_ENDANCHORED set, the first matches "c" 1495 whereas the second matches "bc". The effect of PCRE2_ENDANCHORED can also be 1496 achieved by appropriate constructs in the pattern itself, which is the only way 1497 to do it in Perl. 1498 </P> 1499 <P> 1500 For DFA matching with <b>pcre2_dfa_match()</b>, PCRE2_ENDANCHORED applies only 1501 to the first (that is, the longest) matched string. Other parallel matches, 1502 which are necessarily substrings of the first one, must obviously end before 1503 the end of the subject. 1504 <pre> 1505 PCRE2_EXTENDED 1506 </pre> 1507 If this bit is set, most white space characters in the pattern are totally 1508 ignored except when escaped or inside a character class. However, white space 1509 is not allowed within sequences such as (?> that introduce various 1510 parenthesized subpatterns, nor within numerical quantifiers such as {1,3}. 1511 Ignorable white space is permitted between an item and a following quantifier 1512 and between a quantifier and a following + that indicates possessiveness. 1513 PCRE2_EXTENDED is equivalent to Perl's /x option, and it can be changed within 1514 a pattern by a (?x) option setting. 1515 </P> 1516 <P> 1517 When PCRE2 is compiled without Unicode support, PCRE2_EXTENDED recognizes as 1518 white space only those characters with code points less than 256 that are 1519 flagged as white space in its low-character table. The table is normally 1520 created by 1521 <a href="pcre2_maketables.html"><b>pcre2_maketables()</b>,</a> 1522 which uses the <b>isspace()</b> function to identify space characters. In most 1523 ASCII environments, the relevant characters are those with code points 0x0009 1524 (tab), 0x000A (linefeed), 0x000B (vertical tab), 0x000C (formfeed), 0x000D 1525 (carriage return), and 0x0020 (space). 1526 </P> 1527 <P> 1528 When PCRE2 is compiled with Unicode support, in addition to these characters, 1529 five more Unicode "Pattern White Space" characters are recognized by 1530 PCRE2_EXTENDED. These are U+0085 (next line), U+200E (left-to-right mark), 1531 U+200F (right-to-left mark), U+2028 (line separator), and U+2029 (paragraph 1532 separator). This set of characters is the same as recognized by Perl's /x 1533 option. Note that the horizontal and vertical space characters that are matched 1534 by the \h and \v escapes in patterns are a much bigger set. 1535 </P> 1536 <P> 1537 As well as ignoring most white space, PCRE2_EXTENDED also causes characters 1538 between an unescaped # outside a character class and the next newline, 1539 inclusive, to be ignored, which makes it possible to include comments inside 1540 complicated patterns. Note that the end of this type of comment is a literal 1541 newline sequence in the pattern; escape sequences that happen to represent a 1542 newline do not count. 1543 </P> 1544 <P> 1545 Which characters are interpreted as newlines can be specified by a setting in 1546 the compile context that is passed to <b>pcre2_compile()</b> or by a special 1547 sequence at the start of the pattern, as described in the section entitled 1548 <a href="pcre2pattern.html#newlines">"Newline conventions"</a> 1549 in the <b>pcre2pattern</b> documentation. A default is defined when PCRE2 is 1550 built. 1551 <pre> 1552 PCRE2_EXTENDED_MORE 1553 </pre> 1554 This option has the effect of PCRE2_EXTENDED, but, in addition, unescaped space 1555 and horizontal tab characters are ignored inside a character class. Note: only 1556 these two characters are ignored, not the full set of pattern white space 1557 characters that are ignored outside a character class. PCRE2_EXTENDED_MORE is 1558 equivalent to Perl's /xx option, and it can be changed within a pattern by a 1559 (?xx) option setting. 1560 <pre> 1561 PCRE2_FIRSTLINE 1562 </pre> 1563 If this option is set, the start of an unanchored pattern match must be before 1564 or at the first newline in the subject string following the start of matching, 1565 though the matched text may continue over the newline. If <i>startoffset</i> is 1566 non-zero, the limiting newline is not necessarily the first newline in the 1567 subject. For example, if the subject string is "abc\nxyz" (where \n 1568 represents a single-character newline) a pattern match for "yz" succeeds with 1569 PCRE2_FIRSTLINE if <i>startoffset</i> is greater than 3. See also 1570 PCRE2_USE_OFFSET_LIMIT, which provides a more general limiting facility. If 1571 PCRE2_FIRSTLINE is set with an offset limit, a match must occur in the first 1572 line and also within the offset limit. In other words, whichever limit comes 1573 first is used. 1574 <pre> 1575 PCRE2_LITERAL 1576 </pre> 1577 If this option is set, all meta-characters in the pattern are disabled, and it 1578 is treated as a literal string. Matching literal strings with a regular 1579 expression engine is not the most efficient way of doing it. If you are doing a 1580 lot of literal matching and are worried about efficiency, you should consider 1581 using other approaches. The only other main options that are allowed with 1582 PCRE2_LITERAL are: PCRE2_ANCHORED, PCRE2_ENDANCHORED, PCRE2_AUTO_CALLOUT, 1583 PCRE2_CASELESS, PCRE2_FIRSTLINE, PCRE2_NO_START_OPTIMIZE, PCRE2_NO_UTF_CHECK, 1584 PCRE2_UTF, and PCRE2_USE_OFFSET_LIMIT. The extra options PCRE2_EXTRA_MATCH_LINE 1585 and PCRE2_EXTRA_MATCH_WORD are also supported. Any other options cause an 1586 error. 1587 <pre> 1588 PCRE2_MATCH_UNSET_BACKREF 1589 </pre> 1590 If this option is set, a backreference to an unset subpattern group matches an 1591 empty string (by default this causes the current matching alternative to fail). 1592 A pattern such as (\1)(a) succeeds when this option is set (assuming it can 1593 find an "a" in the subject), whereas it fails by default, for Perl 1594 compatibility. Setting this option makes PCRE2 behave more like ECMAscript (aka 1595 JavaScript). 1596 <pre> 1597 PCRE2_MULTILINE 1598 </pre> 1599 By default, for the purposes of matching "start of line" and "end of line", 1600 PCRE2 treats the subject string as consisting of a single line of characters, 1601 even if it actually contains newlines. The "start of line" metacharacter (^) 1602 matches only at the start of the string, and the "end of line" metacharacter 1603 ($) matches only at the end of the string, or before a terminating newline 1604 (except when PCRE2_DOLLAR_ENDONLY is set). Note, however, that unless 1605 PCRE2_DOTALL is set, the "any character" metacharacter (.) does not match at a 1606 newline. This behaviour (for ^, $, and dot) is the same as Perl. 1607 </P> 1608 <P> 1609 When PCRE2_MULTILINE it is set, the "start of line" and "end of line" 1610 constructs match immediately following or immediately before internal newlines 1611 in the subject string, respectively, as well as at the very start and end. This 1612 is equivalent to Perl's /m option, and it can be changed within a pattern by a 1613 (?m) option setting. Note that the "start of line" metacharacter does not match 1614 after a newline at the end of the subject, for compatibility with Perl. 1615 However, you can change this by setting the PCRE2_ALT_CIRCUMFLEX option. If 1616 there are no newlines in a subject string, or no occurrences of ^ or $ in a 1617 pattern, setting PCRE2_MULTILINE has no effect. 1618 <pre> 1619 PCRE2_NEVER_BACKSLASH_C 1620 </pre> 1621 This option locks out the use of \C in the pattern that is being compiled. 1622 This escape can cause unpredictable behaviour in UTF-8 or UTF-16 modes, because 1623 it may leave the current matching point in the middle of a multi-code-unit 1624 character. This option may be useful in applications that process patterns from 1625 external sources. Note that there is also a build-time option that permanently 1626 locks out the use of \C. 1627 <pre> 1628 PCRE2_NEVER_UCP 1629 </pre> 1630 This option locks out the use of Unicode properties for handling \B, \b, \D, 1631 \d, \S, \s, \W, \w, and some of the POSIX character classes, as described 1632 for the PCRE2_UCP option below. In particular, it prevents the creator of the 1633 pattern from enabling this facility by starting the pattern with (*UCP). This 1634 option may be useful in applications that process patterns from external 1635 sources. The option combination PCRE_UCP and PCRE_NEVER_UCP causes an error. 1636 <pre> 1637 PCRE2_NEVER_UTF 1638 </pre> 1639 This option locks out interpretation of the pattern as UTF-8, UTF-16, or 1640 UTF-32, depending on which library is in use. In particular, it prevents the 1641 creator of the pattern from switching to UTF interpretation by starting the 1642 pattern with (*UTF). This option may be useful in applications that process 1643 patterns from external sources. The combination of PCRE2_UTF and 1644 PCRE2_NEVER_UTF causes an error. 1645 <pre> 1646 PCRE2_NO_AUTO_CAPTURE 1647 </pre> 1648 If this option is set, it disables the use of numbered capturing parentheses in 1649 the pattern. Any opening parenthesis that is not followed by ? behaves as if it 1650 were followed by ?: but named parentheses can still be used for capturing (and 1651 they acquire numbers in the usual way). This is the same as Perl's /n option. 1652 Note that, when this option is set, references to capturing groups 1653 (backreferences or recursion/subroutine calls) may only refer to named groups, 1654 though the reference can be by name or by number. 1655 <pre> 1656 PCRE2_NO_AUTO_POSSESS 1657 </pre> 1658 If this option is set, it disables "auto-possessification", which is an 1659 optimization that, for example, turns a+b into a++b in order to avoid 1660 backtracks into a+ that can never be successful. However, if callouts are in 1661 use, auto-possessification means that some callouts are never taken. You can 1662 set this option if you want the matching functions to do a full unoptimized 1663 search and run all the callouts, but it is mainly provided for testing 1664 purposes. 1665 <pre> 1666 PCRE2_NO_DOTSTAR_ANCHOR 1667 </pre> 1668 If this option is set, it disables an optimization that is applied when .* is 1669 the first significant item in a top-level branch of a pattern, and all the 1670 other branches also start with .* or with \A or \G or ^. The optimization is 1671 automatically disabled for .* if it is inside an atomic group or a capturing 1672 group that is the subject of a backreference, or if the pattern contains 1673 (*PRUNE) or (*SKIP). When the optimization is not disabled, such a pattern is 1674 automatically anchored if PCRE2_DOTALL is set for all the .* items and 1675 PCRE2_MULTILINE is not set for any ^ items. Otherwise, the fact that any match 1676 must start either at the start of the subject or following a newline is 1677 remembered. Like other optimizations, this can cause callouts to be skipped. 1678 <pre> 1679 PCRE2_NO_START_OPTIMIZE 1680 </pre> 1681 This is an option whose main effect is at matching time. It does not change 1682 what <b>pcre2_compile()</b> generates, but it does affect the output of the JIT 1683 compiler. 1684 </P> 1685 <P> 1686 There are a number of optimizations that may occur at the start of a match, in 1687 order to speed up the process. For example, if it is known that an unanchored 1688 match must start with a specific code unit value, the matching code searches 1689 the subject for that value, and fails immediately if it cannot find it, without 1690 actually running the main matching function. This means that a special item 1691 such as (*COMMIT) at the start of a pattern is not considered until after a 1692 suitable starting point for the match has been found. Also, when callouts or 1693 (*MARK) items are in use, these "start-up" optimizations can cause them to be 1694 skipped if the pattern is never actually used. The start-up optimizations are 1695 in effect a pre-scan of the subject that takes place before the pattern is run. 1696 </P> 1697 <P> 1698 The PCRE2_NO_START_OPTIMIZE option disables the start-up optimizations, 1699 possibly causing performance to suffer, but ensuring that in cases where the 1700 result is "no match", the callouts do occur, and that items such as (*COMMIT) 1701 and (*MARK) are considered at every possible starting position in the subject 1702 string. 1703 </P> 1704 <P> 1705 Setting PCRE2_NO_START_OPTIMIZE may change the outcome of a matching operation. 1706 Consider the pattern 1707 <pre> 1708 (*COMMIT)ABC 1709 </pre> 1710 When this is compiled, PCRE2 records the fact that a match must start with the 1711 character "A". Suppose the subject string is "DEFABC". The start-up 1712 optimization scans along the subject, finds "A" and runs the first match 1713 attempt from there. The (*COMMIT) item means that the pattern must match the 1714 current starting position, which in this case, it does. However, if the same 1715 match is run with PCRE2_NO_START_OPTIMIZE set, the initial scan along the 1716 subject string does not happen. The first match attempt is run starting from 1717 "D" and when this fails, (*COMMIT) prevents any further matches being tried, so 1718 the overall result is "no match". 1719 </P> 1720 <P> 1721 There are also other start-up optimizations. For example, a minimum length for 1722 the subject may be recorded. Consider the pattern 1723 <pre> 1724 (*MARK:A)(X|Y) 1725 </pre> 1726 The minimum length for a match is one character. If the subject is "ABC", there 1727 will be attempts to match "ABC", "BC", and "C". An attempt to match an empty 1728 string at the end of the subject does not take place, because PCRE2 knows that 1729 the subject is now too short, and so the (*MARK) is never encountered. In this 1730 case, the optimization does not affect the overall match result, which is still 1731 "no match", but it does affect the auxiliary information that is returned. 1732 <pre> 1733 PCRE2_NO_UTF_CHECK 1734 </pre> 1735 When PCRE2_UTF is set, the validity of the pattern as a UTF string is 1736 automatically checked. There are discussions about the validity of 1737 <a href="pcre2unicode.html#utf8strings">UTF-8 strings,</a> 1738 <a href="pcre2unicode.html#utf16strings">UTF-16 strings,</a> 1739 and 1740 <a href="pcre2unicode.html#utf32strings">UTF-32 strings</a> 1741 in the 1742 <a href="pcre2unicode.html"><b>pcre2unicode</b></a> 1743 document. If an invalid UTF sequence is found, <b>pcre2_compile()</b> returns a 1744 negative error code. 1745 </P> 1746 <P> 1747 If you know that your pattern is a valid UTF string, and you want to skip this 1748 check for performance reasons, you can set the PCRE2_NO_UTF_CHECK option. When 1749 it is set, the effect of passing an invalid UTF string as a pattern is 1750 undefined. It may cause your program to crash or loop. 1751 </P> 1752 <P> 1753 Note that this option can also be passed to <b>pcre2_match()</b> and 1754 <b>pcre_dfa_match()</b>, to suppress UTF validity checking of the subject 1755 string. 1756 </P> 1757 <P> 1758 Note also that setting PCRE2_NO_UTF_CHECK at compile time does not disable the 1759 error that is given if an escape sequence for an invalid Unicode code point is 1760 encountered in the pattern. In particular, the so-called "surrogate" code 1761 points (0xd800 to 0xdfff) are invalid. If you want to allow escape sequences 1762 such as \x{d800} you can set the PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES extra 1763 option, as described in the section entitled "Extra compile options" 1764 <a href="#extracompileoptions">below.</a> 1765 However, this is possible only in UTF-8 and UTF-32 modes, because these values 1766 are not representable in UTF-16. 1767 <pre> 1768 PCRE2_UCP 1769 </pre> 1770 This option changes the way PCRE2 processes \B, \b, \D, \d, \S, \s, \W, 1771 \w, and some of the POSIX character classes. By default, only ASCII characters 1772 are recognized, but if PCRE2_UCP is set, Unicode properties are used instead to 1773 classify characters. More details are given in the section on 1774 <a href="pcre2pattern.html#genericchartypes">generic character types</a> 1775 in the 1776 <a href="pcre2pattern.html"><b>pcre2pattern</b></a> 1777 page. If you set PCRE2_UCP, matching one of the items it affects takes much 1778 longer. The option is available only if PCRE2 has been compiled with Unicode 1779 support (which is the default). 1780 <pre> 1781 PCRE2_UNGREEDY 1782 </pre> 1783 This option inverts the "greediness" of the quantifiers so that they are not 1784 greedy by default, but become greedy if followed by "?". It is not compatible 1785 with Perl. It can also be set by a (?U) option setting within the pattern. 1786 <pre> 1787 PCRE2_USE_OFFSET_LIMIT 1788 </pre> 1789 This option must be set for <b>pcre2_compile()</b> if 1790 <b>pcre2_set_offset_limit()</b> is going to be used to set a non-default offset 1791 limit in a match context for matches that use this pattern. An error is 1792 generated if an offset limit is set without this option. For more details, see 1793 the description of <b>pcre2_set_offset_limit()</b> in the 1794 <a href="#matchcontext">section</a> 1795 that describes match contexts. See also the PCRE2_FIRSTLINE 1796 option above. 1797 <pre> 1798 PCRE2_UTF 1799 </pre> 1800 This option causes PCRE2 to regard both the pattern and the subject strings 1801 that are subsequently processed as strings of UTF characters instead of 1802 single-code-unit strings. It is available when PCRE2 is built to include 1803 Unicode support (which is the default). If Unicode support is not available, 1804 the use of this option provokes an error. Details of how PCRE2_UTF changes the 1805 behaviour of PCRE2 are given in the 1806 <a href="pcre2unicode.html"><b>pcre2unicode</b></a> 1807 page. In particular, note that it changes the way PCRE2_CASELESS handles 1808 characters with code points greater than 127. 1809 <a name="extracompileoptions"></a></P> 1810 <br><b> 1811 Extra compile options 1812 </b><br> 1813 <P> 1814 Unlike the main compile-time options, the extra options are not saved with the 1815 compiled pattern. The option bits that can be set in a compile context by 1816 calling the <b>pcre2_set_compile_extra_options()</b> function are as follows: 1817 <pre> 1818 PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES 1819 </pre> 1820 This option applies when compiling a pattern in UTF-8 or UTF-32 mode. It is 1821 forbidden in UTF-16 mode, and ignored in non-UTF modes. Unicode "surrogate" 1822 code points in the range 0xd800 to 0xdfff are used in pairs in UTF-16 to encode 1823 code points with values in the range 0x10000 to 0x10ffff. The surrogates cannot 1824 therefore be represented in UTF-16. They can be represented in UTF-8 and 1825 UTF-32, but are defined as invalid code points, and cause errors if encountered 1826 in a UTF-8 or UTF-32 string that is being checked for validity by PCRE2. 1827 </P> 1828 <P> 1829 These values also cause errors if encountered in escape sequences such as 1830 \x{d912} within a pattern. However, it seems that some applications, when 1831 using PCRE2 to check for unwanted characters in UTF-8 strings, explicitly test 1832 for the surrogates using escape sequences. The PCRE2_NO_UTF_CHECK option does 1833 not disable the error that occurs, because it applies only to the testing of 1834 input strings for UTF validity. 1835 </P> 1836 <P> 1837 If the extra option PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES is set, surrogate code 1838 point values in UTF-8 and UTF-32 patterns no longer provoke errors and are 1839 incorporated in the compiled pattern. However, they can only match subject 1840 characters if the matching function is called with PCRE2_NO_UTF_CHECK set. 1841 <pre> 1842 PCRE2_EXTRA_BAD_ESCAPE_IS_LITERAL 1843 </pre> 1844 This is a dangerous option. Use with care. By default, an unrecognized escape 1845 such as \j or a malformed one such as \x{2z} causes a compile-time error when 1846 detected by <b>pcre2_compile()</b>. Perl is somewhat inconsistent in handling 1847 such items: for example, \j is treated as a literal "j", and non-hexadecimal 1848 digits in \x{} are just ignored, though warnings are given in both cases if 1849 Perl's warning switch is enabled. However, a malformed octal number after \o{ 1850 always causes an error in Perl. 1851 </P> 1852 <P> 1853 If the PCRE2_EXTRA_BAD_ESCAPE_IS_LITERAL extra option is passed to 1854 <b>pcre2_compile()</b>, all unrecognized or erroneous escape sequences are 1855 treated as single-character escapes. For example, \j is a literal "j" and 1856 \x{2z} is treated as the literal string "x{2z}". Setting this option means 1857 that typos in patterns may go undetected and have unexpected results. This is a 1858 dangerous option. Use with care. 1859 <pre> 1860 PCRE2_EXTRA_MATCH_LINE 1861 </pre> 1862 This option is provided for use by the <b>-x</b> option of <b>pcre2grep</b>. It 1863 causes the pattern only to match complete lines. This is achieved by 1864 automatically inserting the code for "^(?:" at the start of the compiled 1865 pattern and ")$" at the end. Thus, when PCRE2_MULTILINE is set, the matched 1866 line may be in the middle of the subject string. This option can be used with 1867 PCRE2_LITERAL. 1868 <pre> 1869 PCRE2_EXTRA_MATCH_WORD 1870 </pre> 1871 This option is provided for use by the <b>-w</b> option of <b>pcre2grep</b>. It 1872 causes the pattern only to match strings that have a word boundary at the start 1873 and the end. This is achieved by automatically inserting the code for "\b(?:" 1874 at the start of the compiled pattern and ")\b" at the end. The option may be 1875 used with PCRE2_LITERAL. However, it is ignored if PCRE2_EXTRA_MATCH_LINE is 1876 also set. 1877 <a name="jitcompiling"></a></P> 1878 <br><a name="SEC21" href="#TOC1">JUST-IN-TIME (JIT) COMPILATION</a><br> 1879 <P> 1880 <b>int pcre2_jit_compile(pcre2_code *<i>code</i>, uint32_t <i>options</i>);</b> 1881 <br> 1882 <br> 1883 <b>int pcre2_jit_match(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 1884 <b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 1885 <b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 1886 <b> pcre2_match_context *<i>mcontext</i>);</b> 1887 <br> 1888 <br> 1889 <b>void pcre2_jit_free_unused_memory(pcre2_general_context *<i>gcontext</i>);</b> 1890 <br> 1891 <br> 1892 <b>pcre2_jit_stack *pcre2_jit_stack_create(PCRE2_SIZE <i>startsize</i>,</b> 1893 <b> PCRE2_SIZE <i>maxsize</i>, pcre2_general_context *<i>gcontext</i>);</b> 1894 <br> 1895 <br> 1896 <b>void pcre2_jit_stack_assign(pcre2_match_context *<i>mcontext</i>,</b> 1897 <b> pcre2_jit_callback <i>callback_function</i>, void *<i>callback_data</i>);</b> 1898 <br> 1899 <br> 1900 <b>void pcre2_jit_stack_free(pcre2_jit_stack *<i>jit_stack</i>);</b> 1901 </P> 1902 <P> 1903 These functions provide support for JIT compilation, which, if the just-in-time 1904 compiler is available, further processes a compiled pattern into machine code 1905 that executes much faster than the <b>pcre2_match()</b> interpretive matching 1906 function. Full details are given in the 1907 <a href="pcre2jit.html"><b>pcre2jit</b></a> 1908 documentation. 1909 </P> 1910 <P> 1911 JIT compilation is a heavyweight optimization. It can take some time for 1912 patterns to be analyzed, and for one-off matches and simple patterns the 1913 benefit of faster execution might be offset by a much slower compilation time. 1914 Most (but not all) patterns can be optimized by the JIT compiler. 1915 <a name="localesupport"></a></P> 1916 <br><a name="SEC22" href="#TOC1">LOCALE SUPPORT</a><br> 1917 <P> 1918 PCRE2 handles caseless matching, and determines whether characters are letters, 1919 digits, or whatever, by reference to a set of tables, indexed by character code 1920 point. This applies only to characters whose code points are less than 256. By 1921 default, higher-valued code points never match escapes such as \w or \d. 1922 However, if PCRE2 is built with Unicode support, all characters can be tested 1923 with \p and \P, or, alternatively, the PCRE2_UCP option can be set when a 1924 pattern is compiled; this causes \w and friends to use Unicode property 1925 support instead of the built-in tables. 1926 </P> 1927 <P> 1928 The use of locales with Unicode is discouraged. If you are handling characters 1929 with code points greater than 128, you should either use Unicode support, or 1930 use locales, but not try to mix the two. 1931 </P> 1932 <P> 1933 PCRE2 contains an internal set of character tables that are used by default. 1934 These are sufficient for many applications. Normally, the internal tables 1935 recognize only ASCII characters. However, when PCRE2 is built, it is possible 1936 to cause the internal tables to be rebuilt in the default "C" locale of the 1937 local system, which may cause them to be different. 1938 </P> 1939 <P> 1940 The internal tables can be overridden by tables supplied by the application 1941 that calls PCRE2. These may be created in a different locale from the default. 1942 As more and more applications change to using Unicode, the need for this locale 1943 support is expected to die away. 1944 </P> 1945 <P> 1946 External tables are built by calling the <b>pcre2_maketables()</b> function, in 1947 the relevant locale. The result can be passed to <b>pcre2_compile()</b> as often 1948 as necessary, by creating a compile context and calling 1949 <b>pcre2_set_character_tables()</b> to set the tables pointer therein. For 1950 example, to build and use tables that are appropriate for the French locale 1951 (where accented characters with values greater than 128 are treated as 1952 letters), the following code could be used: 1953 <pre> 1954 setlocale(LC_CTYPE, "fr_FR"); 1955 tables = pcre2_maketables(NULL); 1956 ccontext = pcre2_compile_context_create(NULL); 1957 pcre2_set_character_tables(ccontext, tables); 1958 re = pcre2_compile(..., ccontext); 1959 </pre> 1960 The locale name "fr_FR" is used on Linux and other Unix-like systems; if you 1961 are using Windows, the name for the French locale is "french". It is the 1962 caller's responsibility to ensure that the memory containing the tables remains 1963 available for as long as it is needed. 1964 </P> 1965 <P> 1966 The pointer that is passed (via the compile context) to <b>pcre2_compile()</b> 1967 is saved with the compiled pattern, and the same tables are used by 1968 <b>pcre2_match()</b> and <b>pcre_dfa_match()</b>. Thus, for any single pattern, 1969 compilation and matching both happen in the same locale, but different patterns 1970 can be processed in different locales. 1971 <a name="infoaboutpattern"></a></P> 1972 <br><a name="SEC23" href="#TOC1">INFORMATION ABOUT A COMPILED PATTERN</a><br> 1973 <P> 1974 <b>int pcre2_pattern_info(const pcre2 *<i>code</i>, uint32_t <i>what</i>, void *<i>where</i>);</b> 1975 </P> 1976 <P> 1977 The <b>pcre2_pattern_info()</b> function returns general information about a 1978 compiled pattern. For information about callouts, see the 1979 <a href="pcre2pattern.html#infoaboutcallouts">next section.</a> 1980 The first argument for <b>pcre2_pattern_info()</b> is a pointer to the compiled 1981 pattern. The second argument specifies which piece of information is required, 1982 and the third argument is a pointer to a variable to receive the data. If the 1983 third argument is NULL, the first argument is ignored, and the function returns 1984 the size in bytes of the variable that is required for the information 1985 requested. Otherwise, the yield of the function is zero for success, or one of 1986 the following negative numbers: 1987 <pre> 1988 PCRE2_ERROR_NULL the argument <i>code</i> was NULL 1989 PCRE2_ERROR_BADMAGIC the "magic number" was not found 1990 PCRE2_ERROR_BADOPTION the value of <i>what</i> was invalid 1991 PCRE2_ERROR_UNSET the requested field is not set 1992 </pre> 1993 The "magic number" is placed at the start of each compiled pattern as an simple 1994 check against passing an arbitrary memory pointer. Here is a typical call of 1995 <b>pcre2_pattern_info()</b>, to obtain the length of the compiled pattern: 1996 <pre> 1997 int rc; 1998 size_t length; 1999 rc = pcre2_pattern_info( 2000 re, /* result of pcre2_compile() */ 2001 PCRE2_INFO_SIZE, /* what is required */ 2002 &length); /* where to put the data */ 2003 </pre> 2004 The possible values for the second argument are defined in <b>pcre2.h</b>, and 2005 are as follows: 2006 <pre> 2007 PCRE2_INFO_ALLOPTIONS 2008 PCRE2_INFO_ARGOPTIONS 2009 PCRE2_INFO_EXTRAOPTIONS 2010 </pre> 2011 Return copies of the pattern's options. The third argument should point to a 2012 <b>uint32_t</b> variable. PCRE2_INFO_ARGOPTIONS returns exactly the options that 2013 were passed to <b>pcre2_compile()</b>, whereas PCRE2_INFO_ALLOPTIONS returns 2014 the compile options as modified by any top-level (*XXX) option settings such as 2015 (*UTF) at the start of the pattern itself. PCRE2_INFO_EXTRAOPTIONS returns the 2016 extra options that were set in the compile context by calling the 2017 pcre2_set_compile_extra_options() function. 2018 </P> 2019 <P> 2020 For example, if the pattern /(*UTF)abc/ is compiled with the PCRE2_EXTENDED 2021 option, the result for PCRE2_INFO_ALLOPTIONS is PCRE2_EXTENDED and PCRE2_UTF. 2022 Option settings such as (?i) that can change within a pattern do not affect the 2023 result of PCRE2_INFO_ALLOPTIONS, even if they appear right at the start of the 2024 pattern. (This was different in some earlier releases.) 2025 </P> 2026 <P> 2027 A pattern compiled without PCRE2_ANCHORED is automatically anchored by PCRE2 if 2028 the first significant item in every top-level branch is one of the following: 2029 <pre> 2030 ^ unless PCRE2_MULTILINE is set 2031 \A always 2032 \G always 2033 .* sometimes - see below 2034 </pre> 2035 When .* is the first significant item, anchoring is possible only when all the 2036 following are true: 2037 <pre> 2038 .* is not in an atomic group 2039 .* is not in a capturing group that is the subject of a backreference 2040 PCRE2_DOTALL is in force for .* 2041 Neither (*PRUNE) nor (*SKIP) appears in the pattern 2042 PCRE2_NO_DOTSTAR_ANCHOR is not set 2043 </pre> 2044 For patterns that are auto-anchored, the PCRE2_ANCHORED bit is set in the 2045 options returned for PCRE2_INFO_ALLOPTIONS. 2046 <pre> 2047 PCRE2_INFO_BACKREFMAX 2048 </pre> 2049 Return the number of the highest backreference in the pattern. The third 2050 argument should point to an <b>uint32_t</b> variable. Named subpatterns acquire 2051 numbers as well as names, and these count towards the highest backreference. 2052 Backreferences such as \4 or \g{12} match the captured characters of the 2053 given group, but in addition, the check that a capturing group is set in a 2054 conditional subpattern such as (?(3)a|b) is also a backreference. Zero is 2055 returned if there are no backreferences. 2056 <pre> 2057 PCRE2_INFO_BSR 2058 </pre> 2059 The output is a uint32_t integer whose value indicates what character sequences 2060 the \R escape sequence matches. A value of PCRE2_BSR_UNICODE means that \R 2061 matches any Unicode line ending sequence; a value of PCRE2_BSR_ANYCRLF means 2062 that \R matches only CR, LF, or CRLF. 2063 <pre> 2064 PCRE2_INFO_CAPTURECOUNT 2065 </pre> 2066 Return the highest capturing subpattern number in the pattern. In patterns 2067 where (?| is not used, this is also the total number of capturing subpatterns. 2068 The third argument should point to an <b>uint32_t</b> variable. 2069 <pre> 2070 PCRE2_INFO_DEPTHLIMIT 2071 </pre> 2072 If the pattern set a backtracking depth limit by including an item of the form 2073 (*LIMIT_DEPTH=nnnn) at the start, the value is returned. The third argument 2074 should point to a uint32_t integer. If no such value has been set, the call to 2075 <b>pcre2_pattern_info()</b> returns the error PCRE2_ERROR_UNSET. Note that this 2076 limit will only be used during matching if it is less than the limit set or 2077 defaulted by the caller of the match function. 2078 <pre> 2079 PCRE2_INFO_FIRSTBITMAP 2080 </pre> 2081 In the absence of a single first code unit for a non-anchored pattern, 2082 <b>pcre2_compile()</b> may construct a 256-bit table that defines a fixed set of 2083 values for the first code unit in any match. For example, a pattern that starts 2084 with [abc] results in a table with three bits set. When code unit values 2085 greater than 255 are supported, the flag bit for 255 means "any code unit of 2086 value 255 or above". If such a table was constructed, a pointer to it is 2087 returned. Otherwise NULL is returned. The third argument should point to a 2088 <b>const uint8_t *</b> variable. 2089 <pre> 2090 PCRE2_INFO_FIRSTCODETYPE 2091 </pre> 2092 Return information about the first code unit of any matched string, for a 2093 non-anchored pattern. The third argument should point to an <b>uint32_t</b> 2094 variable. If there is a fixed first value, for example, the letter "c" from a 2095 pattern such as (cat|cow|coyote), 1 is returned, and the value can be retrieved 2096 using PCRE2_INFO_FIRSTCODEUNIT. If there is no fixed first value, but it is 2097 known that a match can occur only at the start of the subject or following a 2098 newline in the subject, 2 is returned. Otherwise, and for anchored patterns, 0 2099 is returned. 2100 <pre> 2101 PCRE2_INFO_FIRSTCODEUNIT 2102 </pre> 2103 Return the value of the first code unit of any matched string for a pattern 2104 where PCRE2_INFO_FIRSTCODETYPE returns 1; otherwise return 0. The third 2105 argument should point to an <b>uint32_t</b> variable. In the 8-bit library, the 2106 value is always less than 256. In the 16-bit library the value can be up to 2107 0xffff. In the 32-bit library in UTF-32 mode the value can be up to 0x10ffff, 2108 and up to 0xffffffff when not using UTF-32 mode. 2109 <pre> 2110 PCRE2_INFO_FRAMESIZE 2111 </pre> 2112 Return the size (in bytes) of the data frames that are used to remember 2113 backtracking positions when the pattern is processed by <b>pcre2_match()</b> 2114 without the use of JIT. The third argument should point to a <b>size_t</b> 2115 variable. The frame size depends on the number of capturing parentheses in the 2116 pattern. Each additional capturing group adds two PCRE2_SIZE variables. 2117 <pre> 2118 PCRE2_INFO_HASBACKSLASHC 2119 </pre> 2120 Return 1 if the pattern contains any instances of \C, otherwise 0. The third 2121 argument should point to an <b>uint32_t</b> variable. 2122 <pre> 2123 PCRE2_INFO_HASCRORLF 2124 </pre> 2125 Return 1 if the pattern contains any explicit matches for CR or LF characters, 2126 otherwise 0. The third argument should point to an <b>uint32_t</b> variable. An 2127 explicit match is either a literal CR or LF character, or \r or \n or one of 2128 the equivalent hexadecimal or octal escape sequences. 2129 <pre> 2130 PCRE2_INFO_HEAPLIMIT 2131 </pre> 2132 If the pattern set a heap memory limit by including an item of the form 2133 (*LIMIT_HEAP=nnnn) at the start, the value is returned. The third argument 2134 should point to a uint32_t integer. If no such value has been set, the call to 2135 <b>pcre2_pattern_info()</b> returns the error PCRE2_ERROR_UNSET. Note that this 2136 limit will only be used during matching if it is less than the limit set or 2137 defaulted by the caller of the match function. 2138 <pre> 2139 PCRE2_INFO_JCHANGED 2140 </pre> 2141 Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise 2142 0. The third argument should point to an <b>uint32_t</b> variable. (?J) and 2143 (?-J) set and unset the local PCRE2_DUPNAMES option, respectively. 2144 <pre> 2145 PCRE2_INFO_JITSIZE 2146 </pre> 2147 If the compiled pattern was successfully processed by 2148 <b>pcre2_jit_compile()</b>, return the size of the JIT compiled code, otherwise 2149 return zero. The third argument should point to a <b>size_t</b> variable. 2150 <pre> 2151 PCRE2_INFO_LASTCODETYPE 2152 </pre> 2153 Returns 1 if there is a rightmost literal code unit that must exist in any 2154 matched string, other than at its start. The third argument should point to an 2155 <b>uint32_t</b> variable. If there is no such value, 0 is returned. When 1 is 2156 returned, the code unit value itself can be retrieved using 2157 PCRE2_INFO_LASTCODEUNIT. For anchored patterns, a last literal value is 2158 recorded only if it follows something of variable length. For example, for the 2159 pattern /^a\d+z\d+/ the returned value is 1 (with "z" returned from 2160 PCRE2_INFO_LASTCODEUNIT), but for /^a\dz\d/ the returned value is 0. 2161 <pre> 2162 PCRE2_INFO_LASTCODEUNIT 2163 </pre> 2164 Return the value of the rightmost literal code unit that must exist in any 2165 matched string, other than at its start, for a pattern where 2166 PCRE2_INFO_LASTCODETYPE returns 1. Otherwise, return 0. The third argument 2167 should point to an <b>uint32_t</b> variable. 2168 <pre> 2169 PCRE2_INFO_MATCHEMPTY 2170 </pre> 2171 Return 1 if the pattern might match an empty string, otherwise 0. The third 2172 argument should point to an <b>uint32_t</b> variable. When a pattern contains 2173 recursive subroutine calls it is not always possible to determine whether or 2174 not it can match an empty string. PCRE2 takes a cautious approach and returns 1 2175 in such cases. 2176 <pre> 2177 PCRE2_INFO_MATCHLIMIT 2178 </pre> 2179 If the pattern set a match limit by including an item of the form 2180 (*LIMIT_MATCH=nnnn) at the start, the value is returned. The third argument 2181 should point to a uint32_t integer. If no such value has been set, the call to 2182 <b>pcre2_pattern_info()</b> returns the error PCRE2_ERROR_UNSET. Note that this 2183 limit will only be used during matching if it is less than the limit set or 2184 defaulted by the caller of the match function. 2185 <pre> 2186 PCRE2_INFO_MAXLOOKBEHIND 2187 </pre> 2188 Return the number of characters (not code units) in the longest lookbehind 2189 assertion in the pattern. The third argument should point to a uint32_t 2190 integer. This information is useful when doing multi-segment matching using the 2191 partial matching facilities. Note that the simple assertions \b and \B 2192 require a one-character lookbehind. \A also registers a one-character 2193 lookbehind, though it does not actually inspect the previous character. This is 2194 to ensure that at least one character from the old segment is retained when a 2195 new segment is processed. Otherwise, if there are no lookbehinds in the 2196 pattern, \A might match incorrectly at the start of a second or subsequent 2197 segment. 2198 <pre> 2199 PCRE2_INFO_MINLENGTH 2200 </pre> 2201 If a minimum length for matching subject strings was computed, its value is 2202 returned. Otherwise the returned value is 0. The value is a number of 2203 characters, which in UTF mode may be different from the number of code units. 2204 The third argument should point to an <b>uint32_t</b> variable. The value is a 2205 lower bound to the length of any matching string. There may not be any strings 2206 of that length that do actually match, but every string that does match is at 2207 least that long. 2208 <pre> 2209 PCRE2_INFO_NAMECOUNT 2210 PCRE2_INFO_NAMEENTRYSIZE 2211 PCRE2_INFO_NAMETABLE 2212 </pre> 2213 PCRE2 supports the use of named as well as numbered capturing parentheses. The 2214 names are just an additional way of identifying the parentheses, which still 2215 acquire numbers. Several convenience functions such as 2216 <b>pcre2_substring_get_byname()</b> are provided for extracting captured 2217 substrings by name. It is also possible to extract the data directly, by first 2218 converting the name to a number in order to access the correct pointers in the 2219 output vector (described with <b>pcre2_match()</b> below). To do the conversion, 2220 you need to use the name-to-number map, which is described by these three 2221 values. 2222 </P> 2223 <P> 2224 The map consists of a number of fixed-size entries. PCRE2_INFO_NAMECOUNT gives 2225 the number of entries, and PCRE2_INFO_NAMEENTRYSIZE gives the size of each 2226 entry in code units; both of these return a <b>uint32_t</b> value. The entry 2227 size depends on the length of the longest name. 2228 </P> 2229 <P> 2230 PCRE2_INFO_NAMETABLE returns a pointer to the first entry of the table. This is 2231 a PCRE2_SPTR pointer to a block of code units. In the 8-bit library, the first 2232 two bytes of each entry are the number of the capturing parenthesis, most 2233 significant byte first. In the 16-bit library, the pointer points to 16-bit 2234 code units, the first of which contains the parenthesis number. In the 32-bit 2235 library, the pointer points to 32-bit code units, the first of which contains 2236 the parenthesis number. The rest of the entry is the corresponding name, zero 2237 terminated. 2238 </P> 2239 <P> 2240 The names are in alphabetical order. If (?| is used to create multiple groups 2241 with the same number, as described in the 2242 <a href="pcre2pattern.html#dupsubpatternnumber">section on duplicate subpattern numbers</a> 2243 in the 2244 <a href="pcre2pattern.html"><b>pcre2pattern</b></a> 2245 page, the groups may be given the same name, but there is only one entry in the 2246 table. Different names for groups of the same number are not permitted. 2247 </P> 2248 <P> 2249 Duplicate names for subpatterns with different numbers are permitted, but only 2250 if PCRE2_DUPNAMES is set. They appear in the table in the order in which they 2251 were found in the pattern. In the absence of (?| this is the order of 2252 increasing number; when (?| is used this is not necessarily the case because 2253 later subpatterns may have lower numbers. 2254 </P> 2255 <P> 2256 As a simple example of the name/number table, consider the following pattern 2257 after compilation by the 8-bit library (assume PCRE2_EXTENDED is set, so white 2258 space - including newlines - is ignored): 2259 <pre> 2260 (?<date> (?<year>(\d\d)?\d\d) - (?<month>\d\d) - (?<day>\d\d) ) 2261 </pre> 2262 There are four named subpatterns, so the table has four entries, and each entry 2263 in the table is eight bytes long. The table is as follows, with non-printing 2264 bytes shows in hexadecimal, and undefined bytes shown as ??: 2265 <pre> 2266 00 01 d a t e 00 ?? 2267 00 05 d a y 00 ?? ?? 2268 00 04 m o n t h 00 2269 00 02 y e a r 00 ?? 2270 </pre> 2271 When writing code to extract data from named subpatterns using the 2272 name-to-number map, remember that the length of the entries is likely to be 2273 different for each compiled pattern. 2274 <pre> 2275 PCRE2_INFO_NEWLINE 2276 </pre> 2277 The output is one of the following <b>uint32_t</b> values: 2278 <pre> 2279 PCRE2_NEWLINE_CR Carriage return (CR) 2280 PCRE2_NEWLINE_LF Linefeed (LF) 2281 PCRE2_NEWLINE_CRLF Carriage return, linefeed (CRLF) 2282 PCRE2_NEWLINE_ANY Any Unicode line ending 2283 PCRE2_NEWLINE_ANYCRLF Any of CR, LF, or CRLF 2284 PCRE2_NEWLINE_NUL The NUL character (binary zero) 2285 </pre> 2286 This identifies the character sequence that will be recognized as meaning 2287 "newline" while matching. 2288 <pre> 2289 PCRE2_INFO_SIZE 2290 </pre> 2291 Return the size of the compiled pattern in bytes (for all three libraries). The 2292 third argument should point to a <b>size_t</b> variable. This value includes the 2293 size of the general data block that precedes the code units of the compiled 2294 pattern itself. The value that is used when <b>pcre2_compile()</b> is getting 2295 memory in which to place the compiled pattern may be slightly larger than the 2296 value returned by this option, because there are cases where the code that 2297 calculates the size has to over-estimate. Processing a pattern with the JIT 2298 compiler does not alter the value returned by this option. 2299 <a name="infoaboutcallouts"></a></P> 2300 <br><a name="SEC24" href="#TOC1">INFORMATION ABOUT A PATTERN'S CALLOUTS</a><br> 2301 <P> 2302 <b>int pcre2_callout_enumerate(const pcre2_code *<i>code</i>,</b> 2303 <b> int (*<i>callback</i>)(pcre2_callout_enumerate_block *, void *),</b> 2304 <b> void *<i>user_data</i>);</b> 2305 <br> 2306 <br> 2307 A script language that supports the use of string arguments in callouts might 2308 like to scan all the callouts in a pattern before running the match. This can 2309 be done by calling <b>pcre2_callout_enumerate()</b>. The first argument is a 2310 pointer to a compiled pattern, the second points to a callback function, and 2311 the third is arbitrary user data. The callback function is called for every 2312 callout in the pattern in the order in which they appear. Its first argument is 2313 a pointer to a callout enumeration block, and its second argument is the 2314 <i>user_data</i> value that was passed to <b>pcre2_callout_enumerate()</b>. The 2315 contents of the callout enumeration block are described in the 2316 <a href="pcre2callout.html"><b>pcre2callout</b></a> 2317 documentation, which also gives further details about callouts. 2318 </P> 2319 <br><a name="SEC25" href="#TOC1">SERIALIZATION AND PRECOMPILING</a><br> 2320 <P> 2321 It is possible to save compiled patterns on disc or elsewhere, and reload them 2322 later, subject to a number of restrictions. The host on which the patterns are 2323 reloaded must be running the same version of PCRE2, with the same code unit 2324 width, and must also have the same endianness, pointer width, and PCRE2_SIZE 2325 type. Before compiled patterns can be saved, they must be converted to a 2326 "serialized" form, which in the case of PCRE2 is really just a bytecode dump. 2327 The functions whose names begin with <b>pcre2_serialize_</b> are used for 2328 converting to and from the serialized form. They are described in the 2329 <a href="pcre2serialize.html"><b>pcre2serialize</b></a> 2330 documentation. Note that PCRE2 serialization does not convert compiled patterns 2331 to an abstract format like Java or .NET serialization. 2332 <a name="matchdatablock"></a></P> 2333 <br><a name="SEC26" href="#TOC1">THE MATCH DATA BLOCK</a><br> 2334 <P> 2335 <b>pcre2_match_data *pcre2_match_data_create(uint32_t <i>ovecsize</i>,</b> 2336 <b> pcre2_general_context *<i>gcontext</i>);</b> 2337 <br> 2338 <br> 2339 <b>pcre2_match_data *pcre2_match_data_create_from_pattern(</b> 2340 <b> const pcre2_code *<i>code</i>, pcre2_general_context *<i>gcontext</i>);</b> 2341 <br> 2342 <br> 2343 <b>void pcre2_match_data_free(pcre2_match_data *<i>match_data</i>);</b> 2344 </P> 2345 <P> 2346 Information about a successful or unsuccessful match is placed in a match 2347 data block, which is an opaque structure that is accessed by function calls. In 2348 particular, the match data block contains a vector of offsets into the subject 2349 string that define the matched part of the subject and any substrings that were 2350 captured. This is known as the <i>ovector</i>. 2351 </P> 2352 <P> 2353 Before calling <b>pcre2_match()</b>, <b>pcre2_dfa_match()</b>, or 2354 <b>pcre2_jit_match()</b> you must create a match data block by calling one of 2355 the creation functions above. For <b>pcre2_match_data_create()</b>, the first 2356 argument is the number of pairs of offsets in the <i>ovector</i>. One pair of 2357 offsets is required to identify the string that matched the whole pattern, with 2358 an additional pair for each captured substring. For example, a value of 4 2359 creates enough space to record the matched portion of the subject plus three 2360 captured substrings. A minimum of at least 1 pair is imposed by 2361 <b>pcre2_match_data_create()</b>, so it is always possible to return the overall 2362 matched string. 2363 </P> 2364 <P> 2365 The second argument of <b>pcre2_match_data_create()</b> is a pointer to a 2366 general context, which can specify custom memory management for obtaining the 2367 memory for the match data block. If you are not using custom memory management, 2368 pass NULL, which causes <b>malloc()</b> to be used. 2369 </P> 2370 <P> 2371 For <b>pcre2_match_data_create_from_pattern()</b>, the first argument is a 2372 pointer to a compiled pattern. The ovector is created to be exactly the right 2373 size to hold all the substrings a pattern might capture. The second argument is 2374 again a pointer to a general context, but in this case if NULL is passed, the 2375 memory is obtained using the same allocator that was used for the compiled 2376 pattern (custom or default). 2377 </P> 2378 <P> 2379 A match data block can be used many times, with the same or different compiled 2380 patterns. You can extract information from a match data block after a match 2381 operation has finished, using functions that are described in the sections on 2382 <a href="#matchedstrings">matched strings</a> 2383 and 2384 <a href="#matchotherdata">other match data</a> 2385 below. 2386 </P> 2387 <P> 2388 When a call of <b>pcre2_match()</b> fails, valid data is available in the match 2389 block only when the error is PCRE2_ERROR_NOMATCH, PCRE2_ERROR_PARTIAL, or one 2390 of the error codes for an invalid UTF string. Exactly what is available depends 2391 on the error, and is detailed below. 2392 </P> 2393 <P> 2394 When one of the matching functions is called, pointers to the compiled pattern 2395 and the subject string are set in the match data block so that they can be 2396 referenced by the extraction functions. After running a match, you must not 2397 free a compiled pattern or a subject string until after all operations on the 2398 match data block (for that match) have taken place. 2399 </P> 2400 <P> 2401 When a match data block itself is no longer needed, it should be freed by 2402 calling <b>pcre2_match_data_free()</b>. If this function is called with a NULL 2403 argument, it returns immediately, without doing anything. 2404 </P> 2405 <br><a name="SEC27" href="#TOC1">MATCHING A PATTERN: THE TRADITIONAL FUNCTION</a><br> 2406 <P> 2407 <b>int pcre2_match(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 2408 <b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 2409 <b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 2410 <b> pcre2_match_context *<i>mcontext</i>);</b> 2411 </P> 2412 <P> 2413 The function <b>pcre2_match()</b> is called to match a subject string against a 2414 compiled pattern, which is passed in the <i>code</i> argument. You can call 2415 <b>pcre2_match()</b> with the same <i>code</i> argument as many times as you 2416 like, in order to find multiple matches in the subject string or to match 2417 different subject strings with the same pattern. 2418 </P> 2419 <P> 2420 This function is the main matching facility of the library, and it operates in 2421 a Perl-like manner. For specialist use there is also an alternative matching 2422 function, which is described 2423 <a href="#dfamatch">below</a> 2424 in the section about the <b>pcre2_dfa_match()</b> function. 2425 </P> 2426 <P> 2427 Here is an example of a simple call to <b>pcre2_match()</b>: 2428 <pre> 2429 pcre2_match_data *md = pcre2_match_data_create(4, NULL); 2430 int rc = pcre2_match( 2431 re, /* result of pcre2_compile() */ 2432 "some string", /* the subject string */ 2433 11, /* the length of the subject string */ 2434 0, /* start at offset 0 in the subject */ 2435 0, /* default options */ 2436 md, /* the match data block */ 2437 NULL); /* a match context; NULL means use defaults */ 2438 </pre> 2439 If the subject string is zero-terminated, the length can be given as 2440 PCRE2_ZERO_TERMINATED. A match context must be provided if certain less common 2441 matching parameters are to be changed. For details, see the section on 2442 <a href="#matchcontext">the match context</a> 2443 above. 2444 </P> 2445 <br><b> 2446 The string to be matched by <b>pcre2_match()</b> 2447 </b><br> 2448 <P> 2449 The subject string is passed to <b>pcre2_match()</b> as a pointer in 2450 <i>subject</i>, a length in <i>length</i>, and a starting offset in 2451 <i>startoffset</i>. The length and offset are in code units, not characters. 2452 That is, they are in bytes for the 8-bit library, 16-bit code units for the 2453 16-bit library, and 32-bit code units for the 32-bit library, whether or not 2454 UTF processing is enabled. 2455 </P> 2456 <P> 2457 If <i>startoffset</i> is greater than the length of the subject, 2458 <b>pcre2_match()</b> returns PCRE2_ERROR_BADOFFSET. When the starting offset is 2459 zero, the search for a match starts at the beginning of the subject, and this 2460 is by far the most common case. In UTF-8 or UTF-16 mode, the starting offset 2461 must point to the start of a character, or to the end of the subject (in UTF-32 2462 mode, one code unit equals one character, so all offsets are valid). Like the 2463 pattern string, the subject may contain binary zeros. 2464 </P> 2465 <P> 2466 A non-zero starting offset is useful when searching for another match in the 2467 same subject by calling <b>pcre2_match()</b> again after a previous success. 2468 Setting <i>startoffset</i> differs from passing over a shortened string and 2469 setting PCRE2_NOTBOL in the case of a pattern that begins with any kind of 2470 lookbehind. For example, consider the pattern 2471 <pre> 2472 \Biss\B 2473 </pre> 2474 which finds occurrences of "iss" in the middle of words. (\B matches only if 2475 the current position in the subject is not a word boundary.) When applied to 2476 the string "Mississipi" the first call to <b>pcre2_match()</b> finds the first 2477 occurrence. If <b>pcre2_match()</b> is called again with just the remainder of 2478 the subject, namely "issipi", it does not match, because \B is always false at 2479 the start of the subject, which is deemed to be a word boundary. However, if 2480 <b>pcre2_match()</b> is passed the entire string again, but with 2481 <i>startoffset</i> set to 4, it finds the second occurrence of "iss" because it 2482 is able to look behind the starting point to discover that it is preceded by a 2483 letter. 2484 </P> 2485 <P> 2486 Finding all the matches in a subject is tricky when the pattern can match an 2487 empty string. It is possible to emulate Perl's /g behaviour by first trying the 2488 match again at the same offset, with the PCRE2_NOTEMPTY_ATSTART and 2489 PCRE2_ANCHORED options, and then if that fails, advancing the starting offset 2490 and trying an ordinary match again. There is some code that demonstrates how to 2491 do this in the 2492 <a href="pcre2demo.html"><b>pcre2demo</b></a> 2493 sample program. In the most general case, you have to check to see if the 2494 newline convention recognizes CRLF as a newline, and if so, and the current 2495 character is CR followed by LF, advance the starting offset by two characters 2496 instead of one. 2497 </P> 2498 <P> 2499 If a non-zero starting offset is passed when the pattern is anchored, a single 2500 attempt to match at the given offset is made. This can only succeed if the 2501 pattern does not require the match to be at the start of the subject. In other 2502 words, the anchoring must be the result of setting the PCRE2_ANCHORED option or 2503 the use of .* with PCRE2_DOTALL, not by starting the pattern with ^ or \A. 2504 <a name="matchoptions"></a></P> 2505 <br><b> 2506 Option bits for <b>pcre2_match()</b> 2507 </b><br> 2508 <P> 2509 The unused bits of the <i>options</i> argument for <b>pcre2_match()</b> must be 2510 zero. The only bits that may be set are PCRE2_ANCHORED, PCRE2_ENDANCHORED, 2511 PCRE2_NOTBOL, PCRE2_NOTEOL, PCRE2_NOTEMPTY, PCRE2_NOTEMPTY_ATSTART, 2512 PCRE2_NO_JIT, PCRE2_NO_UTF_CHECK, PCRE2_PARTIAL_HARD, and PCRE2_PARTIAL_SOFT. 2513 Their action is described below. 2514 </P> 2515 <P> 2516 Setting PCRE2_ANCHORED or PCRE2_ENDANCHORED at match time is not supported by 2517 the just-in-time (JIT) compiler. If it is set, JIT matching is disabled and the 2518 interpretive code in <b>pcre2_match()</b> is run. Apart from PCRE2_NO_JIT 2519 (obviously), the remaining options are supported for JIT matching. 2520 <pre> 2521 PCRE2_ANCHORED 2522 </pre> 2523 The PCRE2_ANCHORED option limits <b>pcre2_match()</b> to matching at the first 2524 matching position. If a pattern was compiled with PCRE2_ANCHORED, or turned out 2525 to be anchored by virtue of its contents, it cannot be made unachored at 2526 matching time. Note that setting the option at match time disables JIT 2527 matching. 2528 <pre> 2529 PCRE2_ENDANCHORED 2530 </pre> 2531 If the PCRE2_ENDANCHORED option is set, any string that <b>pcre2_match()</b> 2532 matches must be right at the end of the subject string. Note that setting the 2533 option at match time disables JIT matching. 2534 <pre> 2535 PCRE2_NOTBOL 2536 </pre> 2537 This option specifies that first character of the subject string is not the 2538 beginning of a line, so the circumflex metacharacter should not match before 2539 it. Setting this without having set PCRE2_MULTILINE at compile time causes 2540 circumflex never to match. This option affects only the behaviour of the 2541 circumflex metacharacter. It does not affect \A. 2542 <pre> 2543 PCRE2_NOTEOL 2544 </pre> 2545 This option specifies that the end of the subject string is not the end of a 2546 line, so the dollar metacharacter should not match it nor (except in multiline 2547 mode) a newline immediately before it. Setting this without having set 2548 PCRE2_MULTILINE at compile time causes dollar never to match. This option 2549 affects only the behaviour of the dollar metacharacter. It does not affect \Z 2550 or \z. 2551 <pre> 2552 PCRE2_NOTEMPTY 2553 </pre> 2554 An empty string is not considered to be a valid match if this option is set. If 2555 there are alternatives in the pattern, they are tried. If all the alternatives 2556 match the empty string, the entire match fails. For example, if the pattern 2557 <pre> 2558 a?b? 2559 </pre> 2560 is applied to a string not beginning with "a" or "b", it matches an empty 2561 string at the start of the subject. With PCRE2_NOTEMPTY set, this match is not 2562 valid, so <b>pcre2_match()</b> searches further into the string for occurrences 2563 of "a" or "b". 2564 <pre> 2565 PCRE2_NOTEMPTY_ATSTART 2566 </pre> 2567 This is like PCRE2_NOTEMPTY, except that it locks out an empty string match 2568 only at the first matching position, that is, at the start of the subject plus 2569 the starting offset. An empty string match later in the subject is permitted. 2570 If the pattern is anchored, such a match can occur only if the pattern contains 2571 \K. 2572 <pre> 2573 PCRE2_NO_JIT 2574 </pre> 2575 By default, if a pattern has been successfully processed by 2576 <b>pcre2_jit_compile()</b>, JIT is automatically used when <b>pcre2_match()</b> 2577 is called with options that JIT supports. Setting PCRE2_NO_JIT disables the use 2578 of JIT; it forces matching to be done by the interpreter. 2579 <pre> 2580 PCRE2_NO_UTF_CHECK 2581 </pre> 2582 When PCRE2_UTF is set at compile time, the validity of the subject as a UTF 2583 string is checked by default when <b>pcre2_match()</b> is subsequently called. 2584 If a non-zero starting offset is given, the check is applied only to that part 2585 of the subject that could be inspected during matching, and there is a check 2586 that the starting offset points to the first code unit of a character or to the 2587 end of the subject. If there are no lookbehind assertions in the pattern, the 2588 check starts at the starting offset. Otherwise, it starts at the length of the 2589 longest lookbehind before the starting offset, or at the start of the subject 2590 if there are not that many characters before the starting offset. Note that the 2591 sequences \b and \B are one-character lookbehinds. 2592 </P> 2593 <P> 2594 The check is carried out before any other processing takes place, and a 2595 negative error code is returned if the check fails. There are several UTF error 2596 codes for each code unit width, corresponding to different problems with the 2597 code unit sequence. There are discussions about the validity of 2598 <a href="pcre2unicode.html#utf8strings">UTF-8 strings,</a> 2599 <a href="pcre2unicode.html#utf16strings">UTF-16 strings,</a> 2600 and 2601 <a href="pcre2unicode.html#utf32strings">UTF-32 strings</a> 2602 in the 2603 <a href="pcre2unicode.html"><b>pcre2unicode</b></a> 2604 page. 2605 </P> 2606 <P> 2607 If you know that your subject is valid, and you want to skip these checks for 2608 performance reasons, you can set the PCRE2_NO_UTF_CHECK option when calling 2609 <b>pcre2_match()</b>. You might want to do this for the second and subsequent 2610 calls to <b>pcre2_match()</b> if you are making repeated calls to find other 2611 matches in the same subject string. 2612 </P> 2613 <P> 2614 <b>Warning:</b> When PCRE2_NO_UTF_CHECK is set, the effect of passing an invalid 2615 string as a subject, or an invalid value of <i>startoffset</i>, is undefined. 2616 Your program may crash or loop indefinitely. 2617 <pre> 2618 PCRE2_PARTIAL_HARD 2619 PCRE2_PARTIAL_SOFT 2620 </pre> 2621 These options turn on the partial matching feature. A partial match occurs if 2622 the end of the subject string is reached successfully, but there are not enough 2623 subject characters to complete the match. If this happens when 2624 PCRE2_PARTIAL_SOFT (but not PCRE2_PARTIAL_HARD) is set, matching continues by 2625 testing any remaining alternatives. Only if no complete match can be found is 2626 PCRE2_ERROR_PARTIAL returned instead of PCRE2_ERROR_NOMATCH. In other words, 2627 PCRE2_PARTIAL_SOFT specifies that the caller is prepared to handle a partial 2628 match, but only if no complete match can be found. 2629 </P> 2630 <P> 2631 If PCRE2_PARTIAL_HARD is set, it overrides PCRE2_PARTIAL_SOFT. In this case, if 2632 a partial match is found, <b>pcre2_match()</b> immediately returns 2633 PCRE2_ERROR_PARTIAL, without considering any other alternatives. In other 2634 words, when PCRE2_PARTIAL_HARD is set, a partial match is considered to be more 2635 important that an alternative complete match. 2636 </P> 2637 <P> 2638 There is a more detailed discussion of partial and multi-segment matching, with 2639 examples, in the 2640 <a href="pcre2partial.html"><b>pcre2partial</b></a> 2641 documentation. 2642 </P> 2643 <br><a name="SEC28" href="#TOC1">NEWLINE HANDLING WHEN MATCHING</a><br> 2644 <P> 2645 When PCRE2 is built, a default newline convention is set; this is usually the 2646 standard convention for the operating system. The default can be overridden in 2647 a 2648 <a href="#compilecontext">compile context</a> 2649 by calling <b>pcre2_set_newline()</b>. It can also be overridden by starting a 2650 pattern string with, for example, (*CRLF), as described in the 2651 <a href="pcre2pattern.html#newlines">section on newline conventions</a> 2652 in the 2653 <a href="pcre2pattern.html"><b>pcre2pattern</b></a> 2654 page. During matching, the newline choice affects the behaviour of the dot, 2655 circumflex, and dollar metacharacters. It may also alter the way the match 2656 starting position is advanced after a match failure for an unanchored pattern. 2657 </P> 2658 <P> 2659 When PCRE2_NEWLINE_CRLF, PCRE2_NEWLINE_ANYCRLF, or PCRE2_NEWLINE_ANY is set as 2660 the newline convention, and a match attempt for an unanchored pattern fails 2661 when the current starting position is at a CRLF sequence, and the pattern 2662 contains no explicit matches for CR or LF characters, the match position is 2663 advanced by two characters instead of one, in other words, to after the CRLF. 2664 </P> 2665 <P> 2666 The above rule is a compromise that makes the most common cases work as 2667 expected. For example, if the pattern is .+A (and the PCRE2_DOTALL option is 2668 not set), it does not match the string "\r\nA" because, after failing at the 2669 start, it skips both the CR and the LF before retrying. However, the pattern 2670 [\r\n]A does match that string, because it contains an explicit CR or LF 2671 reference, and so advances only by one character after the first failure. 2672 </P> 2673 <P> 2674 An explicit match for CR of LF is either a literal appearance of one of those 2675 characters in the pattern, or one of the \r or \n or equivalent octal or 2676 hexadecimal escape sequences. Implicit matches such as [^X] do not count, nor 2677 does \s, even though it includes CR and LF in the characters that it matches. 2678 </P> 2679 <P> 2680 Notwithstanding the above, anomalous effects may still occur when CRLF is a 2681 valid newline sequence and explicit \r or \n escapes appear in the pattern. 2682 <a name="matchedstrings"></a></P> 2683 <br><a name="SEC29" href="#TOC1">HOW PCRE2_MATCH() RETURNS A STRING AND CAPTURED SUBSTRINGS</a><br> 2684 <P> 2685 <b>uint32_t pcre2_get_ovector_count(pcre2_match_data *<i>match_data</i>);</b> 2686 <br> 2687 <br> 2688 <b>PCRE2_SIZE *pcre2_get_ovector_pointer(pcre2_match_data *<i>match_data</i>);</b> 2689 </P> 2690 <P> 2691 In general, a pattern matches a certain portion of the subject, and in 2692 addition, further substrings from the subject may be picked out by 2693 parenthesized parts of the pattern. Following the usage in Jeffrey Friedl's 2694 book, this is called "capturing" in what follows, and the phrase "capturing 2695 subpattern" or "capturing group" is used for a fragment of a pattern that picks 2696 out a substring. PCRE2 supports several other kinds of parenthesized subpattern 2697 that do not cause substrings to be captured. The <b>pcre2_pattern_info()</b> 2698 function can be used to find out how many capturing subpatterns there are in a 2699 compiled pattern. 2700 </P> 2701 <P> 2702 You can use auxiliary functions for accessing captured substrings 2703 <a href="#extractbynumber">by number</a> 2704 or 2705 <a href="#extractbyname">by name,</a> 2706 as described in sections below. 2707 </P> 2708 <P> 2709 Alternatively, you can make direct use of the vector of PCRE2_SIZE values, 2710 called the <b>ovector</b>, which contains the offsets of captured strings. It is 2711 part of the 2712 <a href="#matchdatablock">match data block.</a> 2713 The function <b>pcre2_get_ovector_pointer()</b> returns the address of the 2714 ovector, and <b>pcre2_get_ovector_count()</b> returns the number of pairs of 2715 values it contains. 2716 </P> 2717 <P> 2718 Within the ovector, the first in each pair of values is set to the offset of 2719 the first code unit of a substring, and the second is set to the offset of the 2720 first code unit after the end of a substring. These values are always code unit 2721 offsets, not character offsets. That is, they are byte offsets in the 8-bit 2722 library, 16-bit offsets in the 16-bit library, and 32-bit offsets in the 32-bit 2723 library. 2724 </P> 2725 <P> 2726 After a partial match (error return PCRE2_ERROR_PARTIAL), only the first pair 2727 of offsets (that is, <i>ovector[0]</i> and <i>ovector[1]</i>) are set. They 2728 identify the part of the subject that was partially matched. See the 2729 <a href="pcre2partial.html"><b>pcre2partial</b></a> 2730 documentation for details of partial matching. 2731 </P> 2732 <P> 2733 After a fully successful match, the first pair of offsets identifies the 2734 portion of the subject string that was matched by the entire pattern. The next 2735 pair is used for the first captured substring, and so on. The value returned by 2736 <b>pcre2_match()</b> is one more than the highest numbered pair that has been 2737 set. For example, if two substrings have been captured, the returned value is 2738 3. If there are no captured substrings, the return value from a successful 2739 match is 1, indicating that just the first pair of offsets has been set. 2740 </P> 2741 <P> 2742 If a pattern uses the \K escape sequence within a positive assertion, the 2743 reported start of a successful match can be greater than the end of the match. 2744 For example, if the pattern (?=ab\K) is matched against "ab", the start and 2745 end offset values for the match are 2 and 0. 2746 </P> 2747 <P> 2748 If a capturing subpattern group is matched repeatedly within a single match 2749 operation, it is the last portion of the subject that it matched that is 2750 returned. 2751 </P> 2752 <P> 2753 If the ovector is too small to hold all the captured substring offsets, as much 2754 as possible is filled in, and the function returns a value of zero. If captured 2755 substrings are not of interest, <b>pcre2_match()</b> may be called with a match 2756 data block whose ovector is of minimum length (that is, one pair). 2757 </P> 2758 <P> 2759 It is possible for capturing subpattern number <i>n+1</i> to match some part of 2760 the subject when subpattern <i>n</i> has not been used at all. For example, if 2761 the string "abc" is matched against the pattern (a|(z))(bc) the return from the 2762 function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this 2763 happens, both values in the offset pairs corresponding to unused subpatterns 2764 are set to PCRE2_UNSET. 2765 </P> 2766 <P> 2767 Offset values that correspond to unused subpatterns at the end of the 2768 expression are also set to PCRE2_UNSET. For example, if the string "abc" is 2769 matched against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. 2770 The return from the function is 2, because the highest used capturing 2771 subpattern number is 1. The offsets for for the second and third capturing 2772 subpatterns (assuming the vector is large enough, of course) are set to 2773 PCRE2_UNSET. 2774 </P> 2775 <P> 2776 Elements in the ovector that do not correspond to capturing parentheses in the 2777 pattern are never changed. That is, if a pattern contains <i>n</i> capturing 2778 parentheses, no more than <i>ovector[0]</i> to <i>ovector[2n+1]</i> are set by 2779 <b>pcre2_match()</b>. The other elements retain whatever values they previously 2780 had. After a failed match attempt, the contents of the ovector are unchanged. 2781 <a name="matchotherdata"></a></P> 2782 <br><a name="SEC30" href="#TOC1">OTHER INFORMATION ABOUT A MATCH</a><br> 2783 <P> 2784 <b>PCRE2_SPTR pcre2_get_mark(pcre2_match_data *<i>match_data</i>);</b> 2785 <br> 2786 <br> 2787 <b>PCRE2_SIZE pcre2_get_startchar(pcre2_match_data *<i>match_data</i>);</b> 2788 </P> 2789 <P> 2790 As well as the offsets in the ovector, other information about a match is 2791 retained in the match data block and can be retrieved by the above functions in 2792 appropriate circumstances. If they are called at other times, the result is 2793 undefined. 2794 </P> 2795 <P> 2796 After a successful match, a partial match (PCRE2_ERROR_PARTIAL), or a failure 2797 to match (PCRE2_ERROR_NOMATCH), a (*MARK), (*PRUNE), or (*THEN) name may be 2798 available. The function <b>pcre2_get_mark()</b> can be called to access this 2799 name. The same function applies to all three verbs. It returns a pointer to the 2800 zero-terminated name, which is within the compiled pattern. If no name is 2801 available, NULL is returned. The length of the name (excluding the terminating 2802 zero) is stored in the code unit that precedes the name. You should use this 2803 length instead of relying on the terminating zero if the name might contain a 2804 binary zero. 2805 </P> 2806 <P> 2807 After a successful match, the name that is returned is the last (*MARK), 2808 (*PRUNE), or (*THEN) name encountered on the matching path through the pattern. 2809 Instances of (*PRUNE) and (*THEN) without names are ignored. Thus, for example, 2810 if the matching path contains (*MARK:A)(*PRUNE), the name "A" is returned. 2811 After a "no match" or a partial match, the last encountered name is returned. 2812 For example, consider this pattern: 2813 <pre> 2814 ^(*MARK:A)((*MARK:B)a|b)c 2815 </pre> 2816 When it matches "bc", the returned name is A. The B mark is "seen" in the first 2817 branch of the group, but it is not on the matching path. On the other hand, 2818 when this pattern fails to match "bx", the returned name is B. 2819 </P> 2820 <P> 2821 <b>Warning:</b> By default, certain start-of-match optimizations are used to 2822 give a fast "no match" result in some situations. For example, if the anchoring 2823 is removed from the pattern above, there is an initial check for the presence 2824 of "c" in the subject before running the matching engine. This check fails for 2825 "bx", causing a match failure without seeing any marks. You can disable the 2826 start-of-match optimizations by setting the PCRE2_NO_START_OPTIMIZE option for 2827 <b>pcre2_compile()</b> or starting the pattern with (*NO_START_OPT). 2828 </P> 2829 <P> 2830 After a successful match, a partial match, or one of the invalid UTF errors 2831 (for example, PCRE2_ERROR_UTF8_ERR5), <b>pcre2_get_startchar()</b> can be 2832 called. After a successful or partial match it returns the code unit offset of 2833 the character at which the match started. For a non-partial match, this can be 2834 different to the value of <i>ovector[0]</i> if the pattern contains the \K 2835 escape sequence. After a partial match, however, this value is always the same 2836 as <i>ovector[0]</i> because \K does not affect the result of a partial match. 2837 </P> 2838 <P> 2839 After a UTF check failure, <b>pcre2_get_startchar()</b> can be used to obtain 2840 the code unit offset of the invalid UTF character. Details are given in the 2841 <a href="pcre2unicode.html"><b>pcre2unicode</b></a> 2842 page. 2843 <a name="errorlist"></a></P> 2844 <br><a name="SEC31" href="#TOC1">ERROR RETURNS FROM <b>pcre2_match()</b></a><br> 2845 <P> 2846 If <b>pcre2_match()</b> fails, it returns a negative number. This can be 2847 converted to a text string by calling the <b>pcre2_get_error_message()</b> 2848 function (see "Obtaining a textual error message" 2849 <a href="#geterrormessage">below).</a> 2850 Negative error codes are also returned by other functions, and are documented 2851 with them. The codes are given names in the header file. If UTF checking is in 2852 force and an invalid UTF subject string is detected, one of a number of 2853 UTF-specific negative error codes is returned. Details are given in the 2854 <a href="pcre2unicode.html"><b>pcre2unicode</b></a> 2855 page. The following are the other errors that may be returned by 2856 <b>pcre2_match()</b>: 2857 <pre> 2858 PCRE2_ERROR_NOMATCH 2859 </pre> 2860 The subject string did not match the pattern. 2861 <pre> 2862 PCRE2_ERROR_PARTIAL 2863 </pre> 2864 The subject string did not match, but it did match partially. See the 2865 <a href="pcre2partial.html"><b>pcre2partial</b></a> 2866 documentation for details of partial matching. 2867 <pre> 2868 PCRE2_ERROR_BADMAGIC 2869 </pre> 2870 PCRE2 stores a 4-byte "magic number" at the start of the compiled code, to 2871 catch the case when it is passed a junk pointer. This is the error that is 2872 returned when the magic number is not present. 2873 <pre> 2874 PCRE2_ERROR_BADMODE 2875 </pre> 2876 This error is given when a compiled pattern is passed to a function in a 2877 library of a different code unit width, for example, a pattern compiled by 2878 the 8-bit library is passed to a 16-bit or 32-bit library function. 2879 <pre> 2880 PCRE2_ERROR_BADOFFSET 2881 </pre> 2882 The value of <i>startoffset</i> was greater than the length of the subject. 2883 <pre> 2884 PCRE2_ERROR_BADOPTION 2885 </pre> 2886 An unrecognized bit was set in the <i>options</i> argument. 2887 <pre> 2888 PCRE2_ERROR_BADUTFOFFSET 2889 </pre> 2890 The UTF code unit sequence that was passed as a subject was checked and found 2891 to be valid (the PCRE2_NO_UTF_CHECK option was not set), but the value of 2892 <i>startoffset</i> did not point to the beginning of a UTF character or the end 2893 of the subject. 2894 <pre> 2895 PCRE2_ERROR_CALLOUT 2896 </pre> 2897 This error is never generated by <b>pcre2_match()</b> itself. It is provided for 2898 use by callout functions that want to cause <b>pcre2_match()</b> or 2899 <b>pcre2_callout_enumerate()</b> to return a distinctive error code. See the 2900 <a href="pcre2callout.html"><b>pcre2callout</b></a> 2901 documentation for details. 2902 <pre> 2903 PCRE2_ERROR_DEPTHLIMIT 2904 </pre> 2905 The nested backtracking depth limit was reached. 2906 <pre> 2907 PCRE2_ERROR_HEAPLIMIT 2908 </pre> 2909 The heap limit was reached. 2910 <pre> 2911 PCRE2_ERROR_INTERNAL 2912 </pre> 2913 An unexpected internal error has occurred. This error could be caused by a bug 2914 in PCRE2 or by overwriting of the compiled pattern. 2915 <pre> 2916 PCRE2_ERROR_JIT_STACKLIMIT 2917 </pre> 2918 This error is returned when a pattern that was successfully studied using JIT 2919 is being matched, but the memory available for the just-in-time processing 2920 stack is not large enough. See the 2921 <a href="pcre2jit.html"><b>pcre2jit</b></a> 2922 documentation for more details. 2923 <pre> 2924 PCRE2_ERROR_MATCHLIMIT 2925 </pre> 2926 The backtracking match limit was reached. 2927 <pre> 2928 PCRE2_ERROR_NOMEMORY 2929 </pre> 2930 If a pattern contains many nested backtracking points, heap memory is used to 2931 remember them. This error is given when the memory allocation function (default 2932 or custom) fails. Note that a different error, PCRE2_ERROR_HEAPLIMIT, is given 2933 if the amount of memory needed exceeds the heap limit. 2934 <pre> 2935 PCRE2_ERROR_NULL 2936 </pre> 2937 Either the <i>code</i>, <i>subject</i>, or <i>match_data</i> argument was passed 2938 as NULL. 2939 <pre> 2940 PCRE2_ERROR_RECURSELOOP 2941 </pre> 2942 This error is returned when <b>pcre2_match()</b> detects a recursion loop within 2943 the pattern. Specifically, it means that either the whole pattern or a 2944 subpattern has been called recursively for the second time at the same position 2945 in the subject string. Some simple patterns that might do this are detected and 2946 faulted at compile time, but more complicated cases, in particular mutual 2947 recursions between two different subpatterns, cannot be detected until matching 2948 is attempted. 2949 <a name="geterrormessage"></a></P> 2950 <br><a name="SEC32" href="#TOC1">OBTAINING A TEXTUAL ERROR MESSAGE</a><br> 2951 <P> 2952 <b>int pcre2_get_error_message(int <i>errorcode</i>, PCRE2_UCHAR *<i>buffer</i>,</b> 2953 <b> PCRE2_SIZE <i>bufflen</i>);</b> 2954 </P> 2955 <P> 2956 A text message for an error code from any PCRE2 function (compile, match, or 2957 auxiliary) can be obtained by calling <b>pcre2_get_error_message()</b>. The code 2958 is passed as the first argument, with the remaining two arguments specifying a 2959 code unit buffer and its length in code units, into which the text message is 2960 placed. The message is returned in code units of the appropriate width for the 2961 library that is being used. 2962 </P> 2963 <P> 2964 The returned message is terminated with a trailing zero, and the function 2965 returns the number of code units used, excluding the trailing zero. If the 2966 error number is unknown, the negative error code PCRE2_ERROR_BADDATA is 2967 returned. If the buffer is too small, the message is truncated (but still with 2968 a trailing zero), and the negative error code PCRE2_ERROR_NOMEMORY is returned. 2969 None of the messages are very long; a buffer size of 120 code units is ample. 2970 <a name="extractbynumber"></a></P> 2971 <br><a name="SEC33" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NUMBER</a><br> 2972 <P> 2973 <b>int pcre2_substring_length_bynumber(pcre2_match_data *<i>match_data</i>,</b> 2974 <b> uint32_t <i>number</i>, PCRE2_SIZE *<i>length</i>);</b> 2975 <br> 2976 <br> 2977 <b>int pcre2_substring_copy_bynumber(pcre2_match_data *<i>match_data</i>,</b> 2978 <b> uint32_t <i>number</i>, PCRE2_UCHAR *<i>buffer</i>,</b> 2979 <b> PCRE2_SIZE *<i>bufflen</i>);</b> 2980 <br> 2981 <br> 2982 <b>int pcre2_substring_get_bynumber(pcre2_match_data *<i>match_data</i>,</b> 2983 <b> uint32_t <i>number</i>, PCRE2_UCHAR **<i>bufferptr</i>,</b> 2984 <b> PCRE2_SIZE *<i>bufflen</i>);</b> 2985 <br> 2986 <br> 2987 <b>void pcre2_substring_free(PCRE2_UCHAR *<i>buffer</i>);</b> 2988 </P> 2989 <P> 2990 Captured substrings can be accessed directly by using the ovector as described 2991 <a href="#matchedstrings">above.</a> 2992 For convenience, auxiliary functions are provided for extracting captured 2993 substrings as new, separate, zero-terminated strings. A substring that contains 2994 a binary zero is correctly extracted and has a further zero added on the end, 2995 but the result is not, of course, a C string. 2996 </P> 2997 <P> 2998 The functions in this section identify substrings by number. The number zero 2999 refers to the entire matched substring, with higher numbers referring to 3000 substrings captured by parenthesized groups. After a partial match, only 3001 substring zero is available. An attempt to extract any other substring gives 3002 the error PCRE2_ERROR_PARTIAL. The next section describes similar functions for 3003 extracting captured substrings by name. 3004 </P> 3005 <P> 3006 If a pattern uses the \K escape sequence within a positive assertion, the 3007 reported start of a successful match can be greater than the end of the match. 3008 For example, if the pattern (?=ab\K) is matched against "ab", the start and 3009 end offset values for the match are 2 and 0. In this situation, calling these 3010 functions with a zero substring number extracts a zero-length empty string. 3011 </P> 3012 <P> 3013 You can find the length in code units of a captured substring without 3014 extracting it by calling <b>pcre2_substring_length_bynumber()</b>. The first 3015 argument is a pointer to the match data block, the second is the group number, 3016 and the third is a pointer to a variable into which the length is placed. If 3017 you just want to know whether or not the substring has been captured, you can 3018 pass the third argument as NULL. 3019 </P> 3020 <P> 3021 The <b>pcre2_substring_copy_bynumber()</b> function copies a captured substring 3022 into a supplied buffer, whereas <b>pcre2_substring_get_bynumber()</b> copies it 3023 into new memory, obtained using the same memory allocation function that was 3024 used for the match data block. The first two arguments of these functions are a 3025 pointer to the match data block and a capturing group number. 3026 </P> 3027 <P> 3028 The final arguments of <b>pcre2_substring_copy_bynumber()</b> are a pointer to 3029 the buffer and a pointer to a variable that contains its length in code units. 3030 This is updated to contain the actual number of code units used for the 3031 extracted substring, excluding the terminating zero. 3032 </P> 3033 <P> 3034 For <b>pcre2_substring_get_bynumber()</b> the third and fourth arguments point 3035 to variables that are updated with a pointer to the new memory and the number 3036 of code units that comprise the substring, again excluding the terminating 3037 zero. When the substring is no longer needed, the memory should be freed by 3038 calling <b>pcre2_substring_free()</b>. 3039 </P> 3040 <P> 3041 The return value from all these functions is zero for success, or a negative 3042 error code. If the pattern match failed, the match failure code is returned. 3043 If a substring number greater than zero is used after a partial match, 3044 PCRE2_ERROR_PARTIAL is returned. Other possible error codes are: 3045 <pre> 3046 PCRE2_ERROR_NOMEMORY 3047 </pre> 3048 The buffer was too small for <b>pcre2_substring_copy_bynumber()</b>, or the 3049 attempt to get memory failed for <b>pcre2_substring_get_bynumber()</b>. 3050 <pre> 3051 PCRE2_ERROR_NOSUBSTRING 3052 </pre> 3053 There is no substring with that number in the pattern, that is, the number is 3054 greater than the number of capturing parentheses. 3055 <pre> 3056 PCRE2_ERROR_UNAVAILABLE 3057 </pre> 3058 The substring number, though not greater than the number of captures in the 3059 pattern, is greater than the number of slots in the ovector, so the substring 3060 could not be captured. 3061 <pre> 3062 PCRE2_ERROR_UNSET 3063 </pre> 3064 The substring did not participate in the match. For example, if the pattern is 3065 (abc)|(def) and the subject is "def", and the ovector contains at least two 3066 capturing slots, substring number 1 is unset. 3067 </P> 3068 <br><a name="SEC34" href="#TOC1">EXTRACTING A LIST OF ALL CAPTURED SUBSTRINGS</a><br> 3069 <P> 3070 <b>int pcre2_substring_list_get(pcre2_match_data *<i>match_data</i>,</b> 3071 <b>" PCRE2_UCHAR ***<i>listptr</i>, PCRE2_SIZE **<i>lengthsptr</i>);</b> 3072 <br> 3073 <br> 3074 <b>void pcre2_substring_list_free(PCRE2_SPTR *<i>list</i>);</b> 3075 </P> 3076 <P> 3077 The <b>pcre2_substring_list_get()</b> function extracts all available substrings 3078 and builds a list of pointers to them. It also (optionally) builds a second 3079 list that contains their lengths (in code units), excluding a terminating zero 3080 that is added to each of them. All this is done in a single block of memory 3081 that is obtained using the same memory allocation function that was used to get 3082 the match data block. 3083 </P> 3084 <P> 3085 This function must be called only after a successful match. If called after a 3086 partial match, the error code PCRE2_ERROR_PARTIAL is returned. 3087 </P> 3088 <P> 3089 The address of the memory block is returned via <i>listptr</i>, which is also 3090 the start of the list of string pointers. The end of the list is marked by a 3091 NULL pointer. The address of the list of lengths is returned via 3092 <i>lengthsptr</i>. If your strings do not contain binary zeros and you do not 3093 therefore need the lengths, you may supply NULL as the <b>lengthsptr</b> 3094 argument to disable the creation of a list of lengths. The yield of the 3095 function is zero if all went well, or PCRE2_ERROR_NOMEMORY if the memory block 3096 could not be obtained. When the list is no longer needed, it should be freed by 3097 calling <b>pcre2_substring_list_free()</b>. 3098 </P> 3099 <P> 3100 If this function encounters a substring that is unset, which can happen when 3101 capturing subpattern number <i>n+1</i> matches some part of the subject, but 3102 subpattern <i>n</i> has not been used at all, it returns an empty string. This 3103 can be distinguished from a genuine zero-length substring by inspecting the 3104 appropriate offset in the ovector, which contain PCRE2_UNSET for unset 3105 substrings, or by calling <b>pcre2_substring_length_bynumber()</b>. 3106 <a name="extractbyname"></a></P> 3107 <br><a name="SEC35" href="#TOC1">EXTRACTING CAPTURED SUBSTRINGS BY NAME</a><br> 3108 <P> 3109 <b>int pcre2_substring_number_from_name(const pcre2_code *<i>code</i>,</b> 3110 <b> PCRE2_SPTR <i>name</i>);</b> 3111 <br> 3112 <br> 3113 <b>int pcre2_substring_length_byname(pcre2_match_data *<i>match_data</i>,</b> 3114 <b> PCRE2_SPTR <i>name</i>, PCRE2_SIZE *<i>length</i>);</b> 3115 <br> 3116 <br> 3117 <b>int pcre2_substring_copy_byname(pcre2_match_data *<i>match_data</i>,</b> 3118 <b> PCRE2_SPTR <i>name</i>, PCRE2_UCHAR *<i>buffer</i>, PCRE2_SIZE *<i>bufflen</i>);</b> 3119 <br> 3120 <br> 3121 <b>int pcre2_substring_get_byname(pcre2_match_data *<i>match_data</i>,</b> 3122 <b> PCRE2_SPTR <i>name</i>, PCRE2_UCHAR **<i>bufferptr</i>, PCRE2_SIZE *<i>bufflen</i>);</b> 3123 <br> 3124 <br> 3125 <b>void pcre2_substring_free(PCRE2_UCHAR *<i>buffer</i>);</b> 3126 </P> 3127 <P> 3128 To extract a substring by name, you first have to find associated number. 3129 For example, for this pattern: 3130 <pre> 3131 (a+)b(?<xxx>\d+)... 3132 </pre> 3133 the number of the subpattern called "xxx" is 2. If the name is known to be 3134 unique (PCRE2_DUPNAMES was not set), you can find the number from the name by 3135 calling <b>pcre2_substring_number_from_name()</b>. The first argument is the 3136 compiled pattern, and the second is the name. The yield of the function is the 3137 subpattern number, PCRE2_ERROR_NOSUBSTRING if there is no subpattern of that 3138 name, or PCRE2_ERROR_NOUNIQUESUBSTRING if there is more than one subpattern of 3139 that name. Given the number, you can extract the substring directly from the 3140 ovector, or use one of the "bynumber" functions described above. 3141 </P> 3142 <P> 3143 For convenience, there are also "byname" functions that correspond to the 3144 "bynumber" functions, the only difference being that the second argument is a 3145 name instead of a number. If PCRE2_DUPNAMES is set and there are duplicate 3146 names, these functions scan all the groups with the given name, and return the 3147 first named string that is set. 3148 </P> 3149 <P> 3150 If there are no groups with the given name, PCRE2_ERROR_NOSUBSTRING is 3151 returned. If all groups with the name have numbers that are greater than the 3152 number of slots in the ovector, PCRE2_ERROR_UNAVAILABLE is returned. If there 3153 is at least one group with a slot in the ovector, but no group is found to be 3154 set, PCRE2_ERROR_UNSET is returned. 3155 </P> 3156 <P> 3157 <b>Warning:</b> If the pattern uses the (?| feature to set up multiple 3158 subpatterns with the same number, as described in the 3159 <a href="pcre2pattern.html#dupsubpatternnumber">section on duplicate subpattern numbers</a> 3160 in the 3161 <a href="pcre2pattern.html"><b>pcre2pattern</b></a> 3162 page, you cannot use names to distinguish the different subpatterns, because 3163 names are not included in the compiled code. The matching process uses only 3164 numbers. For this reason, the use of different names for subpatterns of the 3165 same number causes an error at compile time. 3166 </P> 3167 <br><a name="SEC36" href="#TOC1">CREATING A NEW STRING WITH SUBSTITUTIONS</a><br> 3168 <P> 3169 <b>int pcre2_substitute(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 3170 <b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 3171 <b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 3172 <b> pcre2_match_context *<i>mcontext</i>, PCRE2_SPTR <i>replacement</i>,</b> 3173 <b> PCRE2_SIZE <i>rlength</i>, PCRE2_UCHAR *\fIoutputbuffer\zfP,</b> 3174 <b> PCRE2_SIZE *<i>outlengthptr</i>);</b> 3175 </P> 3176 <P> 3177 This function calls <b>pcre2_match()</b> and then makes a copy of the subject 3178 string in <i>outputbuffer</i>, replacing the part that was matched with the 3179 <i>replacement</i> string, whose length is supplied in <b>rlength</b>. This can 3180 be given as PCRE2_ZERO_TERMINATED for a zero-terminated string. Matches in 3181 which a \K item in a lookahead in the pattern causes the match to end before 3182 it starts are not supported, and give rise to an error return. For global 3183 replacements, matches in which \K in a lookbehind causes the match to start 3184 earlier than the point that was reached in the previous iteration are also not 3185 supported. 3186 </P> 3187 <P> 3188 The first seven arguments of <b>pcre2_substitute()</b> are the same as for 3189 <b>pcre2_match()</b>, except that the partial matching options are not 3190 permitted, and <i>match_data</i> may be passed as NULL, in which case a match 3191 data block is obtained and freed within this function, using memory management 3192 functions from the match context, if provided, or else those that were used to 3193 allocate memory for the compiled code. 3194 </P> 3195 <P> 3196 If an external <i>match_data</i> block is provided, its contents afterwards 3197 are those set by the final call to <b>pcre2_match()</b>, which will have 3198 ended in a matching error. The contents of the ovector within the match data 3199 block may or may not have been changed. 3200 </P> 3201 <P> 3202 The <i>outlengthptr</i> argument must point to a variable that contains the 3203 length, in code units, of the output buffer. If the function is successful, the 3204 value is updated to contain the length of the new string, excluding the 3205 trailing zero that is automatically added. 3206 </P> 3207 <P> 3208 If the function is not successful, the value set via <i>outlengthptr</i> depends 3209 on the type of error. For syntax errors in the replacement string, the value is 3210 the offset in the replacement string where the error was detected. For other 3211 errors, the value is PCRE2_UNSET by default. This includes the case of the 3212 output buffer being too small, unless PCRE2_SUBSTITUTE_OVERFLOW_LENGTH is set 3213 (see below), in which case the value is the minimum length needed, including 3214 space for the trailing zero. Note that in order to compute the required length, 3215 <b>pcre2_substitute()</b> has to simulate all the matching and copying, instead 3216 of giving an error return as soon as the buffer overflows. Note also that the 3217 length is in code units, not bytes. 3218 </P> 3219 <P> 3220 In the replacement string, which is interpreted as a UTF string in UTF mode, 3221 and is checked for UTF validity unless the PCRE2_NO_UTF_CHECK option is set, a 3222 dollar character is an escape character that can specify the insertion of 3223 characters from capturing groups or (*MARK), (*PRUNE), or (*THEN) items in the 3224 pattern. The following forms are always recognized: 3225 <pre> 3226 $$ insert a dollar character 3227 $<n> or ${<n>} insert the contents of group <n> 3228 $*MARK or ${*MARK} insert a (*MARK), (*PRUNE), or (*THEN) name 3229 </pre> 3230 Either a group number or a group name can be given for <n>. Curly brackets are 3231 required only if the following character would be interpreted as part of the 3232 number or name. The number may be zero to include the entire matched string. 3233 For example, if the pattern a(b)c is matched with "=abc=" and the replacement 3234 string "+$1$0$1+", the result is "=+babcb+=". 3235 </P> 3236 <P> 3237 $*MARK inserts the name from the last encountered (*MARK), (*PRUNE), or (*THEN) 3238 on the matching path that has a name. (*MARK) must always include a name, but 3239 (*PRUNE) and (*THEN) need not. For example, in the case of (*MARK:A)(*PRUNE) 3240 the name inserted is "A", but for (*MARK:A)(*PRUNE:B) the relevant name is "B". 3241 This facility can be used to perform simple simultaneous substitutions, as this 3242 <b>pcre2test</b> example shows: 3243 <pre> 3244 /(*MARK:pear)apple|(*MARK:orange)lemon/g,replace=${*MARK} 3245 apple lemon 3246 2: pear orange 3247 </pre> 3248 As well as the usual options for <b>pcre2_match()</b>, a number of additional 3249 options can be set in the <i>options</i> argument of <b>pcre2_substitute()</b>. 3250 </P> 3251 <P> 3252 PCRE2_SUBSTITUTE_GLOBAL causes the function to iterate over the subject string, 3253 replacing every matching substring. If this option is not set, only the first 3254 matching substring is replaced. The search for matches takes place in the 3255 original subject string (that is, previous replacements do not affect it). 3256 Iteration is implemented by advancing the <i>startoffset</i> value for each 3257 search, which is always passed the entire subject string. If an offset limit is 3258 set in the match context, searching stops when that limit is reached. 3259 </P> 3260 <P> 3261 You can restrict the effect of a global substitution to a portion of the 3262 subject string by setting either or both of <i>startoffset</i> and an offset 3263 limit. Here is a \fPpcre2test\fP example: 3264 <pre> 3265 /B/g,replace=!,use_offset_limit 3266 ABC ABC ABC ABC\=offset=3,offset_limit=12 3267 2: ABC A!C A!C ABC 3268 </pre> 3269 When continuing with global substitutions after matching a substring with zero 3270 length, an attempt to find a non-empty match at the same offset is performed. 3271 If this is not successful, the offset is advanced by one character except when 3272 CRLF is a valid newline sequence and the next two characters are CR, LF. In 3273 this case, the offset is advanced by two characters. 3274 </P> 3275 <P> 3276 PCRE2_SUBSTITUTE_OVERFLOW_LENGTH changes what happens when the output buffer is 3277 too small. The default action is to return PCRE2_ERROR_NOMEMORY immediately. If 3278 this option is set, however, <b>pcre2_substitute()</b> continues to go through 3279 the motions of matching and substituting (without, of course, writing anything) 3280 in order to compute the size of buffer that is needed. This value is passed 3281 back via the <i>outlengthptr</i> variable, with the result of the function still 3282 being PCRE2_ERROR_NOMEMORY. 3283 </P> 3284 <P> 3285 Passing a buffer size of zero is a permitted way of finding out how much memory 3286 is needed for given substitution. However, this does mean that the entire 3287 operation is carried out twice. Depending on the application, it may be more 3288 efficient to allocate a large buffer and free the excess afterwards, instead of 3289 using PCRE2_SUBSTITUTE_OVERFLOW_LENGTH. 3290 </P> 3291 <P> 3292 PCRE2_SUBSTITUTE_UNKNOWN_UNSET causes references to capturing groups that do 3293 not appear in the pattern to be treated as unset groups. This option should be 3294 used with care, because it means that a typo in a group name or number no 3295 longer causes the PCRE2_ERROR_NOSUBSTRING error. 3296 </P> 3297 <P> 3298 PCRE2_SUBSTITUTE_UNSET_EMPTY causes unset capturing groups (including unknown 3299 groups when PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set) to be treated as empty 3300 strings when inserted as described above. If this option is not set, an attempt 3301 to insert an unset group causes the PCRE2_ERROR_UNSET error. This option does 3302 not influence the extended substitution syntax described below. 3303 </P> 3304 <P> 3305 PCRE2_SUBSTITUTE_EXTENDED causes extra processing to be applied to the 3306 replacement string. Without this option, only the dollar character is special, 3307 and only the group insertion forms listed above are valid. When 3308 PCRE2_SUBSTITUTE_EXTENDED is set, two things change: 3309 </P> 3310 <P> 3311 Firstly, backslash in a replacement string is interpreted as an escape 3312 character. The usual forms such as \n or \x{ddd} can be used to specify 3313 particular character codes, and backslash followed by any non-alphanumeric 3314 character quotes that character. Extended quoting can be coded using \Q...\E, 3315 exactly as in pattern strings. 3316 </P> 3317 <P> 3318 There are also four escape sequences for forcing the case of inserted letters. 3319 The insertion mechanism has three states: no case forcing, force upper case, 3320 and force lower case. The escape sequences change the current state: \U and 3321 \L change to upper or lower case forcing, respectively, and \E (when not 3322 terminating a \Q quoted sequence) reverts to no case forcing. The sequences 3323 \u and \l force the next character (if it is a letter) to upper or lower 3324 case, respectively, and then the state automatically reverts to no case 3325 forcing. Case forcing applies to all inserted characters, including those from 3326 captured groups and letters within \Q...\E quoted sequences. 3327 </P> 3328 <P> 3329 Note that case forcing sequences such as \U...\E do not nest. For example, 3330 the result of processing "\Uaa\LBB\Ecc\E" is "AAbbcc"; the final \E has no 3331 effect. 3332 </P> 3333 <P> 3334 The second effect of setting PCRE2_SUBSTITUTE_EXTENDED is to add more 3335 flexibility to group substitution. The syntax is similar to that used by Bash: 3336 <pre> 3337 ${<n>:-<string>} 3338 ${<n>:+<string1>:<string2>} 3339 </pre> 3340 As before, <n> may be a group number or a name. The first form specifies a 3341 default value. If group <n> is set, its value is inserted; if not, <string> is 3342 expanded and the result inserted. The second form specifies strings that are 3343 expanded and inserted when group <n> is set or unset, respectively. The first 3344 form is just a convenient shorthand for 3345 <pre> 3346 ${<n>:+${<n>}:<string>} 3347 </pre> 3348 Backslash can be used to escape colons and closing curly brackets in the 3349 replacement strings. A change of the case forcing state within a replacement 3350 string remains in force afterwards, as shown in this <b>pcre2test</b> example: 3351 <pre> 3352 /(some)?(body)/substitute_extended,replace=${1:+\U:\L}HeLLo 3353 body 3354 1: hello 3355 somebody 3356 1: HELLO 3357 </pre> 3358 The PCRE2_SUBSTITUTE_UNSET_EMPTY option does not affect these extended 3359 substitutions. However, PCRE2_SUBSTITUTE_UNKNOWN_UNSET does cause unknown 3360 groups in the extended syntax forms to be treated as unset. 3361 </P> 3362 <P> 3363 If successful, <b>pcre2_substitute()</b> returns the number of replacements that 3364 were made. This may be zero if no matches were found, and is never greater than 3365 1 unless PCRE2_SUBSTITUTE_GLOBAL is set. 3366 </P> 3367 <P> 3368 In the event of an error, a negative error code is returned. Except for 3369 PCRE2_ERROR_NOMATCH (which is never returned), errors from <b>pcre2_match()</b> 3370 are passed straight back. 3371 </P> 3372 <P> 3373 PCRE2_ERROR_NOSUBSTRING is returned for a non-existent substring insertion, 3374 unless PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set. 3375 </P> 3376 <P> 3377 PCRE2_ERROR_UNSET is returned for an unset substring insertion (including an 3378 unknown substring when PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set) when the simple 3379 (non-extended) syntax is used and PCRE2_SUBSTITUTE_UNSET_EMPTY is not set. 3380 </P> 3381 <P> 3382 PCRE2_ERROR_NOMEMORY is returned if the output buffer is not big enough. If the 3383 PCRE2_SUBSTITUTE_OVERFLOW_LENGTH option is set, the size of buffer that is 3384 needed is returned via <i>outlengthptr</i>. Note that this does not happen by 3385 default. 3386 </P> 3387 <P> 3388 PCRE2_ERROR_BADREPLACEMENT is used for miscellaneous syntax errors in the 3389 replacement string, with more particular errors being PCRE2_ERROR_BADREPESCAPE 3390 (invalid escape sequence), PCRE2_ERROR_REPMISSINGBRACE (closing curly bracket 3391 not found), PCRE2_ERROR_BADSUBSTITUTION (syntax error in extended group 3392 substitution), and PCRE2_ERROR_BADSUBSPATTERN (the pattern match ended before 3393 it started or the match started earlier than the current position in the 3394 subject, which can happen if \K is used in an assertion). 3395 </P> 3396 <P> 3397 As for all PCRE2 errors, a text message that describes the error can be 3398 obtained by calling the <b>pcre2_get_error_message()</b> function (see 3399 "Obtaining a textual error message" 3400 <a href="#geterrormessage">above).</a> 3401 </P> 3402 <br><a name="SEC37" href="#TOC1">DUPLICATE SUBPATTERN NAMES</a><br> 3403 <P> 3404 <b>int pcre2_substring_nametable_scan(const pcre2_code *<i>code</i>,</b> 3405 <b> PCRE2_SPTR <i>name</i>, PCRE2_SPTR *<i>first</i>, PCRE2_SPTR *<i>last</i>);</b> 3406 </P> 3407 <P> 3408 When a pattern is compiled with the PCRE2_DUPNAMES option, names for 3409 subpatterns are not required to be unique. Duplicate names are always allowed 3410 for subpatterns with the same number, created by using the (?| feature. Indeed, 3411 if such subpatterns are named, they are required to use the same names. 3412 </P> 3413 <P> 3414 Normally, patterns with duplicate names are such that in any one match, only 3415 one of the named subpatterns participates. An example is shown in the 3416 <a href="pcre2pattern.html"><b>pcre2pattern</b></a> 3417 documentation. 3418 </P> 3419 <P> 3420 When duplicates are present, <b>pcre2_substring_copy_byname()</b> and 3421 <b>pcre2_substring_get_byname()</b> return the first substring corresponding to 3422 the given name that is set. Only if none are set is PCRE2_ERROR_UNSET is 3423 returned. The <b>pcre2_substring_number_from_name()</b> function returns the 3424 error PCRE2_ERROR_NOUNIQUESUBSTRING when there are duplicate names. 3425 </P> 3426 <P> 3427 If you want to get full details of all captured substrings for a given name, 3428 you must use the <b>pcre2_substring_nametable_scan()</b> function. The first 3429 argument is the compiled pattern, and the second is the name. If the third and 3430 fourth arguments are NULL, the function returns a group number for a unique 3431 name, or PCRE2_ERROR_NOUNIQUESUBSTRING otherwise. 3432 </P> 3433 <P> 3434 When the third and fourth arguments are not NULL, they must be pointers to 3435 variables that are updated by the function. After it has run, they point to the 3436 first and last entries in the name-to-number table for the given name, and the 3437 function returns the length of each entry in code units. In both cases, 3438 PCRE2_ERROR_NOSUBSTRING is returned if there are no entries for the given name. 3439 </P> 3440 <P> 3441 The format of the name table is described 3442 <a href="#infoaboutpattern">above</a> 3443 in the section entitled <i>Information about a pattern</i>. Given all the 3444 relevant entries for the name, you can extract each of their numbers, and hence 3445 the captured data. 3446 </P> 3447 <br><a name="SEC38" href="#TOC1">FINDING ALL POSSIBLE MATCHES AT ONE POSITION</a><br> 3448 <P> 3449 The traditional matching function uses a similar algorithm to Perl, which stops 3450 when it finds the first match at a given point in the subject. If you want to 3451 find all possible matches, or the longest possible match at a given position, 3452 consider using the alternative matching function (see below) instead. If you 3453 cannot use the alternative function, you can kludge it up by making use of the 3454 callout facility, which is described in the 3455 <a href="pcre2callout.html"><b>pcre2callout</b></a> 3456 documentation. 3457 </P> 3458 <P> 3459 What you have to do is to insert a callout right at the end of the pattern. 3460 When your callout function is called, extract and save the current matched 3461 substring. Then return 1, which forces <b>pcre2_match()</b> to backtrack and try 3462 other alternatives. Ultimately, when it runs out of matches, 3463 <b>pcre2_match()</b> will yield PCRE2_ERROR_NOMATCH. 3464 <a name="dfamatch"></a></P> 3465 <br><a name="SEC39" href="#TOC1">MATCHING A PATTERN: THE ALTERNATIVE FUNCTION</a><br> 3466 <P> 3467 <b>int pcre2_dfa_match(const pcre2_code *<i>code</i>, PCRE2_SPTR <i>subject</i>,</b> 3468 <b> PCRE2_SIZE <i>length</i>, PCRE2_SIZE <i>startoffset</i>,</b> 3469 <b> uint32_t <i>options</i>, pcre2_match_data *<i>match_data</i>,</b> 3470 <b> pcre2_match_context *<i>mcontext</i>,</b> 3471 <b> int *<i>workspace</i>, PCRE2_SIZE <i>wscount</i>);</b> 3472 </P> 3473 <P> 3474 The function <b>pcre2_dfa_match()</b> is called to match a subject string 3475 against a compiled pattern, using a matching algorithm that scans the subject 3476 string just once (not counting lookaround assertions), and does not backtrack. 3477 This has different characteristics to the normal algorithm, and is not 3478 compatible with Perl. Some of the features of PCRE2 patterns are not supported. 3479 Nevertheless, there are times when this kind of matching can be useful. For a 3480 discussion of the two matching algorithms, and a list of features that 3481 <b>pcre2_dfa_match()</b> does not support, see the 3482 <a href="pcre2matching.html"><b>pcre2matching</b></a> 3483 documentation. 3484 </P> 3485 <P> 3486 The arguments for the <b>pcre2_dfa_match()</b> function are the same as for 3487 <b>pcre2_match()</b>, plus two extras. The ovector within the match data block 3488 is used in a different way, and this is described below. The other common 3489 arguments are used in the same way as for <b>pcre2_match()</b>, so their 3490 description is not repeated here. 3491 </P> 3492 <P> 3493 The two additional arguments provide workspace for the function. The workspace 3494 vector should contain at least 20 elements. It is used for keeping track of 3495 multiple paths through the pattern tree. More workspace is needed for patterns 3496 and subjects where there are a lot of potential matches. 3497 </P> 3498 <P> 3499 Here is an example of a simple call to <b>pcre2_dfa_match()</b>: 3500 <pre> 3501 int wspace[20]; 3502 pcre2_match_data *md = pcre2_match_data_create(4, NULL); 3503 int rc = pcre2_dfa_match( 3504 re, /* result of pcre2_compile() */ 3505 "some string", /* the subject string */ 3506 11, /* the length of the subject string */ 3507 0, /* start at offset 0 in the subject */ 3508 0, /* default options */ 3509 md, /* the match data block */ 3510 NULL, /* a match context; NULL means use defaults */ 3511 wspace, /* working space vector */ 3512 20); /* number of elements (NOT size in bytes) */ 3513 </PRE> 3514 </P> 3515 <br><b> 3516 Option bits for <b>pcre_dfa_match()</b> 3517 </b><br> 3518 <P> 3519 The unused bits of the <i>options</i> argument for <b>pcre2_dfa_match()</b> must 3520 be zero. The only bits that may be set are PCRE2_ANCHORED, PCRE2_ENDANCHORED, 3521 PCRE2_NOTBOL, PCRE2_NOTEOL, PCRE2_NOTEMPTY, PCRE2_NOTEMPTY_ATSTART, 3522 PCRE2_NO_UTF_CHECK, PCRE2_PARTIAL_HARD, PCRE2_PARTIAL_SOFT, PCRE2_DFA_SHORTEST, 3523 and PCRE2_DFA_RESTART. All but the last four of these are exactly the same as 3524 for <b>pcre2_match()</b>, so their description is not repeated here. 3525 <pre> 3526 PCRE2_PARTIAL_HARD 3527 PCRE2_PARTIAL_SOFT 3528 </pre> 3529 These have the same general effect as they do for <b>pcre2_match()</b>, but the 3530 details are slightly different. When PCRE2_PARTIAL_HARD is set for 3531 <b>pcre2_dfa_match()</b>, it returns PCRE2_ERROR_PARTIAL if the end of the 3532 subject is reached and there is still at least one matching possibility that 3533 requires additional characters. This happens even if some complete matches have 3534 already been found. When PCRE2_PARTIAL_SOFT is set, the return code 3535 PCRE2_ERROR_NOMATCH is converted into PCRE2_ERROR_PARTIAL if the end of the 3536 subject is reached, there have been no complete matches, but there is still at 3537 least one matching possibility. The portion of the string that was inspected 3538 when the longest partial match was found is set as the first matching string in 3539 both cases. There is a more detailed discussion of partial and multi-segment 3540 matching, with examples, in the 3541 <a href="pcre2partial.html"><b>pcre2partial</b></a> 3542 documentation. 3543 <pre> 3544 PCRE2_DFA_SHORTEST 3545 </pre> 3546 Setting the PCRE2_DFA_SHORTEST option causes the matching algorithm to stop as 3547 soon as it has found one match. Because of the way the alternative algorithm 3548 works, this is necessarily the shortest possible match at the first possible 3549 matching point in the subject string. 3550 <pre> 3551 PCRE2_DFA_RESTART 3552 </pre> 3553 When <b>pcre2_dfa_match()</b> returns a partial match, it is possible to call it 3554 again, with additional subject characters, and have it continue with the same 3555 match. The PCRE2_DFA_RESTART option requests this action; when it is set, the 3556 <i>workspace</i> and <i>wscount</i> options must reference the same vector as 3557 before because data about the match so far is left in them after a partial 3558 match. There is more discussion of this facility in the 3559 <a href="pcre2partial.html"><b>pcre2partial</b></a> 3560 documentation. 3561 </P> 3562 <br><b> 3563 Successful returns from <b>pcre2_dfa_match()</b> 3564 </b><br> 3565 <P> 3566 When <b>pcre2_dfa_match()</b> succeeds, it may have matched more than one 3567 substring in the subject. Note, however, that all the matches from one run of 3568 the function start at the same point in the subject. The shorter matches are 3569 all initial substrings of the longer matches. For example, if the pattern 3570 <pre> 3571 <.*> 3572 </pre> 3573 is matched against the string 3574 <pre> 3575 This is <something> <something else> <something further> no more 3576 </pre> 3577 the three matched strings are 3578 <pre> 3579 <something> <something else> <something further> 3580 <something> <something else> 3581 <something> 3582 </pre> 3583 On success, the yield of the function is a number greater than zero, which is 3584 the number of matched substrings. The offsets of the substrings are returned in 3585 the ovector, and can be extracted by number in the same way as for 3586 <b>pcre2_match()</b>, but the numbers bear no relation to any capturing groups 3587 that may exist in the pattern, because DFA matching does not support group 3588 capture. 3589 </P> 3590 <P> 3591 Calls to the convenience functions that extract substrings by name 3592 return the error PCRE2_ERROR_DFA_UFUNC (unsupported function) if used after a 3593 DFA match. The convenience functions that extract substrings by number never 3594 return PCRE2_ERROR_NOSUBSTRING. 3595 </P> 3596 <P> 3597 The matched strings are stored in the ovector in reverse order of length; that 3598 is, the longest matching string is first. If there were too many matches to fit 3599 into the ovector, the yield of the function is zero, and the vector is filled 3600 with the longest matches. 3601 </P> 3602 <P> 3603 NOTE: PCRE2's "auto-possessification" optimization usually applies to character 3604 repeats at the end of a pattern (as well as internally). For example, the 3605 pattern "a\d+" is compiled as if it were "a\d++". For DFA matching, this 3606 means that only one possible match is found. If you really do want multiple 3607 matches in such cases, either use an ungreedy repeat such as "a\d+?" or set 3608 the PCRE2_NO_AUTO_POSSESS option when compiling. 3609 </P> 3610 <br><b> 3611 Error returns from <b>pcre2_dfa_match()</b> 3612 </b><br> 3613 <P> 3614 The <b>pcre2_dfa_match()</b> function returns a negative number when it fails. 3615 Many of the errors are the same as for <b>pcre2_match()</b>, as described 3616 <a href="#errorlist">above.</a> 3617 There are in addition the following errors that are specific to 3618 <b>pcre2_dfa_match()</b>: 3619 <pre> 3620 PCRE2_ERROR_DFA_UITEM 3621 </pre> 3622 This return is given if <b>pcre2_dfa_match()</b> encounters an item in the 3623 pattern that it does not support, for instance, the use of \C in a UTF mode or 3624 a backreference. 3625 <pre> 3626 PCRE2_ERROR_DFA_UCOND 3627 </pre> 3628 This return is given if <b>pcre2_dfa_match()</b> encounters a condition item 3629 that uses a backreference for the condition, or a test for recursion in a 3630 specific group. These are not supported. 3631 <pre> 3632 PCRE2_ERROR_DFA_WSSIZE 3633 </pre> 3634 This return is given if <b>pcre2_dfa_match()</b> runs out of space in the 3635 <i>workspace</i> vector. 3636 <pre> 3637 PCRE2_ERROR_DFA_RECURSE 3638 </pre> 3639 When a recursive subpattern is processed, the matching function calls itself 3640 recursively, using private memory for the ovector and <i>workspace</i>. This 3641 error is given if the internal ovector is not large enough. This should be 3642 extremely rare, as a vector of size 1000 is used. 3643 <pre> 3644 PCRE2_ERROR_DFA_BADRESTART 3645 </pre> 3646 When <b>pcre2_dfa_match()</b> is called with the <b>PCRE2_DFA_RESTART</b> option, 3647 some plausibility checks are made on the contents of the workspace, which 3648 should contain data about the previous partial match. If any of these checks 3649 fail, this error is given. 3650 </P> 3651 <br><a name="SEC40" href="#TOC1">SEE ALSO</a><br> 3652 <P> 3653 <b>pcre2build</b>(3), <b>pcre2callout</b>(3), <b>pcre2demo(3)</b>, 3654 <b>pcre2matching</b>(3), <b>pcre2partial</b>(3), <b>pcre2posix</b>(3), 3655 <b>pcre2sample</b>(3), <b>pcre2unicode</b>(3). 3656 </P> 3657 <br><a name="SEC41" href="#TOC1">AUTHOR</a><br> 3658 <P> 3659 Philip Hazel 3660 <br> 3661 University Computing Service 3662 <br> 3663 Cambridge, England. 3664 <br> 3665 </P> 3666 <br><a name="SEC42" href="#TOC1">REVISION</a><br> 3667 <P> 3668 Last updated: 07 September 2018 3669 <br> 3670 Copyright © 1997-2018 University of Cambridge. 3671 <br> 3672 <p> 3673 Return to the <a href="index.html">PCRE2 index page</a>. 3674 </p> 3675
