1 <html> 2 <head> 3 <title>pcre2serialize specification</title> 4 </head> 5 <body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB"> 6 <h1>pcre2serialize 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">SAVING AND RE-USING PRECOMPILED PCRE2 PATTERNS</a> 17 <li><a name="TOC2" href="#SEC2">SECURITY CONCERNS</a> 18 <li><a name="TOC3" href="#SEC3">SAVING COMPILED PATTERNS</a> 19 <li><a name="TOC4" href="#SEC4">RE-USING PRECOMPILED PATTERNS</a> 20 <li><a name="TOC5" href="#SEC5">AUTHOR</a> 21 <li><a name="TOC6" href="#SEC6">REVISION</a> 22 </ul> 23 <br><a name="SEC1" href="#TOC1">SAVING AND RE-USING PRECOMPILED PCRE2 PATTERNS</a><br> 24 <P> 25 <b>int32_t pcre2_serialize_decode(pcre2_code **<i>codes</i>,</b> 26 <b> int32_t <i>number_of_codes</i>, const uint32_t *<i>bytes</i>,</b> 27 <b> pcre2_general_context *<i>gcontext</i>);</b> 28 <br> 29 <br> 30 <b>int32_t pcre2_serialize_encode(pcre2_code **<i>codes</i>,</b> 31 <b> int32_t <i>number_of_codes</i>, uint32_t **<i>serialized_bytes</i>,</b> 32 <b> PCRE2_SIZE *<i>serialized_size</i>, pcre2_general_context *<i>gcontext</i>);</b> 33 <br> 34 <br> 35 <b>void pcre2_serialize_free(uint8_t *<i>bytes</i>);</b> 36 <br> 37 <br> 38 <b>int32_t pcre2_serialize_get_number_of_codes(const uint8_t *<i>bytes</i>);</b> 39 <br> 40 <br> 41 If you are running an application that uses a large number of regular 42 expression patterns, it may be useful to store them in a precompiled form 43 instead of having to compile them every time the application is run. However, 44 if you are using the just-in-time optimization feature, it is not possible to 45 save and reload the JIT data, because it is position-dependent. The host on 46 which the patterns are reloaded must be running the same version of PCRE2, with 47 the same code unit width, and must also have the same endianness, pointer width 48 and PCRE2_SIZE type. For example, patterns compiled on a 32-bit system using 49 PCRE2's 16-bit library cannot be reloaded on a 64-bit system, nor can they be 50 reloaded using the 8-bit library. 51 </P> 52 <P> 53 Note that "serialization" in PCRE2 does not convert compiled patterns to an 54 abstract format like Java or .NET serialization. The serialized output is 55 really just a bytecode dump, which is why it can only be reloaded in the same 56 environment as the one that created it. Hence the restrictions mentioned above. 57 Applications that are not statically linked with a fixed version of PCRE2 must 58 be prepared to recompile patterns from their sources, in order to be immune to 59 PCRE2 upgrades. 60 </P> 61 <br><a name="SEC2" href="#TOC1">SECURITY CONCERNS</a><br> 62 <P> 63 The facility for saving and restoring compiled patterns is intended for use 64 within individual applications. As such, the data supplied to 65 <b>pcre2_serialize_decode()</b> is expected to be trusted data, not data from 66 arbitrary external sources. There is only some simple consistency checking, not 67 complete validation of what is being re-loaded. Corrupted data may cause 68 undefined results. For example, if the length field of a pattern in the 69 serialized data is corrupted, the deserializing code may read beyond the end of 70 the byte stream that is passed to it. 71 </P> 72 <br><a name="SEC3" href="#TOC1">SAVING COMPILED PATTERNS</a><br> 73 <P> 74 Before compiled patterns can be saved they must be serialized, which in PCRE2 75 means converting the pattern to a stream of bytes. A single byte stream may 76 contain any number of compiled patterns, but they must all use the same 77 character tables. A single copy of the tables is included in the byte stream 78 (its size is 1088 bytes). For more details of character tables, see the 79 <a href="pcre2api.html#localesupport">section on locale support</a> 80 in the 81 <a href="pcre2api.html"><b>pcre2api</b></a> 82 documentation. 83 </P> 84 <P> 85 The function <b>pcre2_serialize_encode()</b> creates a serialized byte stream 86 from a list of compiled patterns. Its first two arguments specify the list, 87 being a pointer to a vector of pointers to compiled patterns, and the length of 88 the vector. The third and fourth arguments point to variables which are set to 89 point to the created byte stream and its length, respectively. The final 90 argument is a pointer to a general context, which can be used to specify custom 91 memory mangagement functions. If this argument is NULL, <b>malloc()</b> is used 92 to obtain memory for the byte stream. The yield of the function is the number 93 of serialized patterns, or one of the following negative error codes: 94 <pre> 95 PCRE2_ERROR_BADDATA the number of patterns is zero or less 96 PCRE2_ERROR_BADMAGIC mismatch of id bytes in one of the patterns 97 PCRE2_ERROR_MEMORY memory allocation failed 98 PCRE2_ERROR_MIXEDTABLES the patterns do not all use the same tables 99 PCRE2_ERROR_NULL the 1st, 3rd, or 4th argument is NULL 100 </pre> 101 PCRE2_ERROR_BADMAGIC means either that a pattern's code has been corrupted, or 102 that a slot in the vector does not point to a compiled pattern. 103 </P> 104 <P> 105 Once a set of patterns has been serialized you can save the data in any 106 appropriate manner. Here is sample code that compiles two patterns and writes 107 them to a file. It assumes that the variable <i>fd</i> refers to a file that is 108 open for output. The error checking that should be present in a real 109 application has been omitted for simplicity. 110 <pre> 111 int errorcode; 112 uint8_t *bytes; 113 PCRE2_SIZE erroroffset; 114 PCRE2_SIZE bytescount; 115 pcre2_code *list_of_codes[2]; 116 list_of_codes[0] = pcre2_compile("first pattern", 117 PCRE2_ZERO_TERMINATED, 0, &errorcode, &erroroffset, NULL); 118 list_of_codes[1] = pcre2_compile("second pattern", 119 PCRE2_ZERO_TERMINATED, 0, &errorcode, &erroroffset, NULL); 120 errorcode = pcre2_serialize_encode(list_of_codes, 2, &bytes, 121 &bytescount, NULL); 122 errorcode = fwrite(bytes, 1, bytescount, fd); 123 </pre> 124 Note that the serialized data is binary data that may contain any of the 256 125 possible byte values. On systems that make a distinction between binary and 126 non-binary data, be sure that the file is opened for binary output. 127 </P> 128 <P> 129 Serializing a set of patterns leaves the original data untouched, so they can 130 still be used for matching. Their memory must eventually be freed in the usual 131 way by calling <b>pcre2_code_free()</b>. When you have finished with the byte 132 stream, it too must be freed by calling <b>pcre2_serialize_free()</b>. If this 133 function is called with a NULL argument, it returns immediately without doing 134 anything. 135 </P> 136 <br><a name="SEC4" href="#TOC1">RE-USING PRECOMPILED PATTERNS</a><br> 137 <P> 138 In order to re-use a set of saved patterns you must first make the serialized 139 byte stream available in main memory (for example, by reading from a file). The 140 management of this memory block is up to the application. You can use the 141 <b>pcre2_serialize_get_number_of_codes()</b> function to find out how many 142 compiled patterns are in the serialized data without actually decoding the 143 patterns: 144 <pre> 145 uint8_t *bytes = <serialized data>; 146 int32_t number_of_codes = pcre2_serialize_get_number_of_codes(bytes); 147 </pre> 148 The <b>pcre2_serialize_decode()</b> function reads a byte stream and recreates 149 the compiled patterns in new memory blocks, setting pointers to them in a 150 vector. The first two arguments are a pointer to a suitable vector and its 151 length, and the third argument points to a byte stream. The final argument is a 152 pointer to a general context, which can be used to specify custom memory 153 mangagement functions for the decoded patterns. If this argument is NULL, 154 <b>malloc()</b> and <b>free()</b> are used. After deserialization, the byte 155 stream is no longer needed and can be discarded. 156 <pre> 157 int32_t number_of_codes; 158 pcre2_code *list_of_codes[2]; 159 uint8_t *bytes = <serialized data>; 160 int32_t number_of_codes = 161 pcre2_serialize_decode(list_of_codes, 2, bytes, NULL); 162 </pre> 163 If the vector is not large enough for all the patterns in the byte stream, it 164 is filled with those that fit, and the remainder are ignored. The yield of the 165 function is the number of decoded patterns, or one of the following negative 166 error codes: 167 <pre> 168 PCRE2_ERROR_BADDATA second argument is zero or less 169 PCRE2_ERROR_BADMAGIC mismatch of id bytes in the data 170 PCRE2_ERROR_BADMODE mismatch of code unit size or PCRE2 version 171 PCRE2_ERROR_BADSERIALIZEDDATA other sanity check failure 172 PCRE2_ERROR_MEMORY memory allocation failed 173 PCRE2_ERROR_NULL first or third argument is NULL 174 </pre> 175 PCRE2_ERROR_BADMAGIC may mean that the data is corrupt, or that it was compiled 176 on a system with different endianness. 177 </P> 178 <P> 179 Decoded patterns can be used for matching in the usual way, and must be freed 180 by calling <b>pcre2_code_free()</b>. However, be aware that there is a potential 181 race issue if you are using multiple patterns that were decoded from a single 182 byte stream in a multithreaded application. A single copy of the character 183 tables is used by all the decoded patterns and a reference count is used to 184 arrange for its memory to be automatically freed when the last pattern is 185 freed, but there is no locking on this reference count. Therefore, if you want 186 to call <b>pcre2_code_free()</b> for these patterns in different threads, you 187 must arrange your own locking, and ensure that <b>pcre2_code_free()</b> cannot 188 be called by two threads at the same time. 189 </P> 190 <P> 191 If a pattern was processed by <b>pcre2_jit_compile()</b> before being 192 serialized, the JIT data is discarded and so is no longer available after a 193 save/restore cycle. You can, however, process a restored pattern with 194 <b>pcre2_jit_compile()</b> if you wish. 195 </P> 196 <br><a name="SEC5" href="#TOC1">AUTHOR</a><br> 197 <P> 198 Philip Hazel 199 <br> 200 University Computing Service 201 <br> 202 Cambridge, England. 203 <br> 204 </P> 205 <br><a name="SEC6" href="#TOC1">REVISION</a><br> 206 <P> 207 Last updated: 27 June 2018 208 <br> 209 Copyright © 1997-2018 University of Cambridge. 210 <br> 211 <p> 212 Return to the <a href="index.html">PCRE2 index page</a>. 213 </p> 214
