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      1 /*
      2 *******************************************************************************
      3 *
      4 *   Copyright (C) 1999-2015, International Business Machines
      5 *   Corporation and others.  All Rights Reserved.
      6 *
      7 *******************************************************************************
      8 *   file name:  utf8.h
      9 *   encoding:   US-ASCII
     10 *   tab size:   8 (not used)
     11 *   indentation:4
     12 *
     13 *   created on: 1999sep13
     14 *   created by: Markus W. Scherer
     15 */
     16 
     17 /**
     18  * \file
     19  * \brief C API: 8-bit Unicode handling macros
     20  *
     21  * This file defines macros to deal with 8-bit Unicode (UTF-8) code units (bytes) and strings.
     22  *
     23  * For more information see utf.h and the ICU User Guide Strings chapter
     24  * (http://userguide.icu-project.org/strings).
     25  *
     26  * <em>Usage:</em>
     27  * ICU coding guidelines for if() statements should be followed when using these macros.
     28  * Compound statements (curly braces {}) must be used  for if-else-while...
     29  * bodies and all macro statements should be terminated with semicolon.
     30  */
     31 
     32 #ifndef __UTF8_H__
     33 #define __UTF8_H__
     34 
     35 #include "unicode/umachine.h"
     36 #ifndef __UTF_H__
     37 #   include "unicode/utf.h"
     38 #endif
     39 
     40 /* internal definitions ----------------------------------------------------- */
     41 
     42 /**
     43  * \var utf8_countTrailBytes
     44  * Internal array with numbers of trail bytes for any given byte used in
     45  * lead byte position.
     46  *
     47  * This is internal since it is not meant to be called directly by external clients;
     48  * however it is called by public macros in this file and thus must remain stable,
     49  * and should not be hidden when other internal functions are hidden (otherwise
     50  * public macros would fail to compile).
     51  * @internal
     52  */
     53 #ifdef U_UTF8_IMPL
     54 U_EXPORT const uint8_t
     55 #elif defined(U_STATIC_IMPLEMENTATION) || defined(U_COMMON_IMPLEMENTATION)
     56 U_CFUNC const uint8_t
     57 #else
     58 U_CFUNC U_IMPORT const uint8_t /* U_IMPORT2? */ /*U_IMPORT*/
     59 #endif
     60 utf8_countTrailBytes[256];
     61 
     62 /**
     63  * Counts the trail bytes for a UTF-8 lead byte.
     64  * Returns 0 for 0..0xbf as well as for 0xfe and 0xff.
     65  *
     66  * This is internal since it is not meant to be called directly by external clients;
     67  * however it is called by public macros in this file and thus must remain stable.
     68  *
     69  * Note: Beginning with ICU 50, the implementation uses a multi-condition expression
     70  * which was shown in 2012 (on x86-64) to compile to fast, branch-free code.
     71  * leadByte is evaluated multiple times.
     72  *
     73  * The pre-ICU 50 implementation used the exported array utf8_countTrailBytes:
     74  * #define U8_COUNT_TRAIL_BYTES(leadByte) (utf8_countTrailBytes[leadByte])
     75  * leadByte was evaluated exactly once.
     76  *
     77  * @param leadByte The first byte of a UTF-8 sequence. Must be 0..0xff.
     78  * @internal
     79  */
     80 #define U8_COUNT_TRAIL_BYTES(leadByte) \
     81     ((uint8_t)(leadByte)<0xf0 ? \
     82         ((uint8_t)(leadByte)>=0xc0)+((uint8_t)(leadByte)>=0xe0) : \
     83         (uint8_t)(leadByte)<0xfe ? 3+((uint8_t)(leadByte)>=0xf8)+((uint8_t)(leadByte)>=0xfc) : 0)
     84 
     85 /**
     86  * Counts the trail bytes for a UTF-8 lead byte of a valid UTF-8 sequence.
     87  * The maximum supported lead byte is 0xf4 corresponding to U+10FFFF.
     88  * leadByte might be evaluated multiple times.
     89  *
     90  * This is internal since it is not meant to be called directly by external clients;
     91  * however it is called by public macros in this file and thus must remain stable.
     92  *
     93  * @param leadByte The first byte of a UTF-8 sequence. Must be 0..0xff.
     94  * @internal
     95  */
     96 #define U8_COUNT_TRAIL_BYTES_UNSAFE(leadByte) \
     97     (((leadByte)>=0xc0)+((leadByte)>=0xe0)+((leadByte)>=0xf0))
     98 
     99 /**
    100  * Mask a UTF-8 lead byte, leave only the lower bits that form part of the code point value.
    101  *
    102  * This is internal since it is not meant to be called directly by external clients;
    103  * however it is called by public macros in this file and thus must remain stable.
    104  * @internal
    105  */
    106 #define U8_MASK_LEAD_BYTE(leadByte, countTrailBytes) ((leadByte)&=(1<<(6-(countTrailBytes)))-1)
    107 
    108 /**
    109  * Function for handling "next code point" with error-checking.
    110  *
    111  * This is internal since it is not meant to be called directly by external clients;
    112  * however it is U_STABLE (not U_INTERNAL) since it is called by public macros in this
    113  * file and thus must remain stable, and should not be hidden when other internal
    114  * functions are hidden (otherwise public macros would fail to compile).
    115  * @internal
    116  */
    117 U_STABLE UChar32 U_EXPORT2
    118 utf8_nextCharSafeBody(const uint8_t *s, int32_t *pi, int32_t length, UChar32 c, UBool strict);
    119 
    120 /**
    121  * Function for handling "append code point" with error-checking.
    122  *
    123  * This is internal since it is not meant to be called directly by external clients;
    124  * however it is U_STABLE (not U_INTERNAL) since it is called by public macros in this
    125  * file and thus must remain stable, and should not be hidden when other internal
    126  * functions are hidden (otherwise public macros would fail to compile).
    127  * @internal
    128  */
    129 U_STABLE int32_t U_EXPORT2
    130 utf8_appendCharSafeBody(uint8_t *s, int32_t i, int32_t length, UChar32 c, UBool *pIsError);
    131 
    132 /**
    133  * Function for handling "previous code point" with error-checking.
    134  *
    135  * This is internal since it is not meant to be called directly by external clients;
    136  * however it is U_STABLE (not U_INTERNAL) since it is called by public macros in this
    137  * file and thus must remain stable, and should not be hidden when other internal
    138  * functions are hidden (otherwise public macros would fail to compile).
    139  * @internal
    140  */
    141 U_STABLE UChar32 U_EXPORT2
    142 utf8_prevCharSafeBody(const uint8_t *s, int32_t start, int32_t *pi, UChar32 c, UBool strict);
    143 
    144 /**
    145  * Function for handling "skip backward one code point" with error-checking.
    146  *
    147  * This is internal since it is not meant to be called directly by external clients;
    148  * however it is U_STABLE (not U_INTERNAL) since it is called by public macros in this
    149  * file and thus must remain stable, and should not be hidden when other internal
    150  * functions are hidden (otherwise public macros would fail to compile).
    151  * @internal
    152  */
    153 U_STABLE int32_t U_EXPORT2
    154 utf8_back1SafeBody(const uint8_t *s, int32_t start, int32_t i);
    155 
    156 /* single-code point definitions -------------------------------------------- */
    157 
    158 /**
    159  * Does this code unit (byte) encode a code point by itself (US-ASCII 0..0x7f)?
    160  * @param c 8-bit code unit (byte)
    161  * @return TRUE or FALSE
    162  * @stable ICU 2.4
    163  */
    164 #define U8_IS_SINGLE(c) (((c)&0x80)==0)
    165 
    166 /**
    167  * Is this code unit (byte) a UTF-8 lead byte?
    168  * @param c 8-bit code unit (byte)
    169  * @return TRUE or FALSE
    170  * @stable ICU 2.4
    171  */
    172 #define U8_IS_LEAD(c) ((uint8_t)((c)-0xc0)<0x3e)
    173 
    174 /**
    175  * Is this code unit (byte) a UTF-8 trail byte?
    176  * @param c 8-bit code unit (byte)
    177  * @return TRUE or FALSE
    178  * @stable ICU 2.4
    179  */
    180 #define U8_IS_TRAIL(c) (((c)&0xc0)==0x80)
    181 
    182 /**
    183  * How many code units (bytes) are used for the UTF-8 encoding
    184  * of this Unicode code point?
    185  * @param c 32-bit code point
    186  * @return 1..4, or 0 if c is a surrogate or not a Unicode code point
    187  * @stable ICU 2.4
    188  */
    189 #define U8_LENGTH(c) \
    190     ((uint32_t)(c)<=0x7f ? 1 : \
    191         ((uint32_t)(c)<=0x7ff ? 2 : \
    192             ((uint32_t)(c)<=0xd7ff ? 3 : \
    193                 ((uint32_t)(c)<=0xdfff || (uint32_t)(c)>0x10ffff ? 0 : \
    194                     ((uint32_t)(c)<=0xffff ? 3 : 4)\
    195                 ) \
    196             ) \
    197         ) \
    198     )
    199 
    200 /**
    201  * The maximum number of UTF-8 code units (bytes) per Unicode code point (U+0000..U+10ffff).
    202  * @return 4
    203  * @stable ICU 2.4
    204  */
    205 #define U8_MAX_LENGTH 4
    206 
    207 /**
    208  * Get a code point from a string at a random-access offset,
    209  * without changing the offset.
    210  * The offset may point to either the lead byte or one of the trail bytes
    211  * for a code point, in which case the macro will read all of the bytes
    212  * for the code point.
    213  * The result is undefined if the offset points to an illegal UTF-8
    214  * byte sequence.
    215  * Iteration through a string is more efficient with U8_NEXT_UNSAFE or U8_NEXT.
    216  *
    217  * @param s const uint8_t * string
    218  * @param i string offset
    219  * @param c output UChar32 variable
    220  * @see U8_GET
    221  * @stable ICU 2.4
    222  */
    223 #define U8_GET_UNSAFE(s, i, c) { \
    224     int32_t _u8_get_unsafe_index=(int32_t)(i); \
    225     U8_SET_CP_START_UNSAFE(s, _u8_get_unsafe_index); \
    226     U8_NEXT_UNSAFE(s, _u8_get_unsafe_index, c); \
    227 }
    228 
    229 /**
    230  * Get a code point from a string at a random-access offset,
    231  * without changing the offset.
    232  * The offset may point to either the lead byte or one of the trail bytes
    233  * for a code point, in which case the macro will read all of the bytes
    234  * for the code point.
    235  *
    236  * The length can be negative for a NUL-terminated string.
    237  *
    238  * If the offset points to an illegal UTF-8 byte sequence, then
    239  * c is set to a negative value.
    240  * Iteration through a string is more efficient with U8_NEXT_UNSAFE or U8_NEXT.
    241  *
    242  * @param s const uint8_t * string
    243  * @param start int32_t starting string offset
    244  * @param i int32_t string offset, must be start<=i<length
    245  * @param length int32_t string length
    246  * @param c output UChar32 variable, set to <0 in case of an error
    247  * @see U8_GET_UNSAFE
    248  * @stable ICU 2.4
    249  */
    250 #define U8_GET(s, start, i, length, c) { \
    251     int32_t _u8_get_index=(i); \
    252     U8_SET_CP_START(s, start, _u8_get_index); \
    253     U8_NEXT(s, _u8_get_index, length, c); \
    254 }
    255 
    256 /**
    257  * Get a code point from a string at a random-access offset,
    258  * without changing the offset.
    259  * The offset may point to either the lead byte or one of the trail bytes
    260  * for a code point, in which case the macro will read all of the bytes
    261  * for the code point.
    262  *
    263  * The length can be negative for a NUL-terminated string.
    264  *
    265  * If the offset points to an illegal UTF-8 byte sequence, then
    266  * c is set to U+FFFD.
    267  * Iteration through a string is more efficient with U8_NEXT_UNSAFE or U8_NEXT_OR_FFFD.
    268  *
    269  * This macro does not distinguish between a real U+FFFD in the text
    270  * and U+FFFD returned for an ill-formed sequence.
    271  * Use U8_GET() if that distinction is important.
    272  *
    273  * @param s const uint8_t * string
    274  * @param start int32_t starting string offset
    275  * @param i int32_t string offset, must be start<=i<length
    276  * @param length int32_t string length
    277  * @param c output UChar32 variable, set to U+FFFD in case of an error
    278  * @see U8_GET
    279  * @stable ICU 51
    280  */
    281 #define U8_GET_OR_FFFD(s, start, i, length, c) { \
    282     int32_t _u8_get_index=(i); \
    283     U8_SET_CP_START(s, start, _u8_get_index); \
    284     U8_NEXT_OR_FFFD(s, _u8_get_index, length, c); \
    285 }
    286 
    287 /* definitions with forward iteration --------------------------------------- */
    288 
    289 /**
    290  * Get a code point from a string at a code point boundary offset,
    291  * and advance the offset to the next code point boundary.
    292  * (Post-incrementing forward iteration.)
    293  * "Unsafe" macro, assumes well-formed UTF-8.
    294  *
    295  * The offset may point to the lead byte of a multi-byte sequence,
    296  * in which case the macro will read the whole sequence.
    297  * The result is undefined if the offset points to a trail byte
    298  * or an illegal UTF-8 sequence.
    299  *
    300  * @param s const uint8_t * string
    301  * @param i string offset
    302  * @param c output UChar32 variable
    303  * @see U8_NEXT
    304  * @stable ICU 2.4
    305  */
    306 #define U8_NEXT_UNSAFE(s, i, c) { \
    307     (c)=(uint8_t)(s)[(i)++]; \
    308     if((c)>=0x80) { \
    309         if((c)<0xe0) { \
    310             (c)=(((c)&0x1f)<<6)|((s)[(i)++]&0x3f); \
    311         } else if((c)<0xf0) { \
    312             /* no need for (c&0xf) because the upper bits are truncated after <<12 in the cast to (UChar) */ \
    313             (c)=(UChar)(((c)<<12)|(((s)[i]&0x3f)<<6)|((s)[(i)+1]&0x3f)); \
    314             (i)+=2; \
    315         } else { \
    316             (c)=(((c)&7)<<18)|(((s)[i]&0x3f)<<12)|(((s)[(i)+1]&0x3f)<<6)|((s)[(i)+2]&0x3f); \
    317             (i)+=3; \
    318         } \
    319     } \
    320 }
    321 
    322 /**
    323  * Get a code point from a string at a code point boundary offset,
    324  * and advance the offset to the next code point boundary.
    325  * (Post-incrementing forward iteration.)
    326  * "Safe" macro, checks for illegal sequences and for string boundaries.
    327  *
    328  * The length can be negative for a NUL-terminated string.
    329  *
    330  * The offset may point to the lead byte of a multi-byte sequence,
    331  * in which case the macro will read the whole sequence.
    332  * If the offset points to a trail byte or an illegal UTF-8 sequence, then
    333  * c is set to a negative value.
    334  *
    335  * @param s const uint8_t * string
    336  * @param i int32_t string offset, must be i<length
    337  * @param length int32_t string length
    338  * @param c output UChar32 variable, set to <0 in case of an error
    339  * @see U8_NEXT_UNSAFE
    340  * @stable ICU 2.4
    341  */
    342 #define U8_NEXT(s, i, length, c) { \
    343     (c)=(uint8_t)(s)[(i)++]; \
    344     if((c)>=0x80) { \
    345         uint8_t __t1, __t2; \
    346         if( /* handle U+1000..U+CFFF inline */ \
    347             (0xe0<(c) && (c)<=0xec) && \
    348             (((i)+1)<(length) || (length)<0) && \
    349             (__t1=(uint8_t)((s)[i]-0x80))<=0x3f && \
    350             (__t2=(uint8_t)((s)[(i)+1]-0x80))<= 0x3f \
    351         ) { \
    352             /* no need for (c&0xf) because the upper bits are truncated after <<12 in the cast to (UChar) */ \
    353             (c)=(UChar)(((c)<<12)|(__t1<<6)|__t2); \
    354             (i)+=2; \
    355         } else if( /* handle U+0080..U+07FF inline */ \
    356             ((c)<0xe0 && (c)>=0xc2) && \
    357             ((i)!=(length)) && \
    358             (__t1=(uint8_t)((s)[i]-0x80))<=0x3f \
    359         ) { \
    360             (c)=(((c)&0x1f)<<6)|__t1; \
    361             ++(i); \
    362         } else { \
    363             /* function call for "complicated" and error cases */ \
    364             (c)=utf8_nextCharSafeBody((const uint8_t *)s, &(i), (length), c, -1); \
    365         } \
    366     } \
    367 }
    368 
    369 /**
    370  * Get a code point from a string at a code point boundary offset,
    371  * and advance the offset to the next code point boundary.
    372  * (Post-incrementing forward iteration.)
    373  * "Safe" macro, checks for illegal sequences and for string boundaries.
    374  *
    375  * The length can be negative for a NUL-terminated string.
    376  *
    377  * The offset may point to the lead byte of a multi-byte sequence,
    378  * in which case the macro will read the whole sequence.
    379  * If the offset points to a trail byte or an illegal UTF-8 sequence, then
    380  * c is set to U+FFFD.
    381  *
    382  * This macro does not distinguish between a real U+FFFD in the text
    383  * and U+FFFD returned for an ill-formed sequence.
    384  * Use U8_NEXT() if that distinction is important.
    385  *
    386  * @param s const uint8_t * string
    387  * @param i int32_t string offset, must be i<length
    388  * @param length int32_t string length
    389  * @param c output UChar32 variable, set to U+FFFD in case of an error
    390  * @see U8_NEXT
    391  * @stable ICU 51
    392  */
    393 #define U8_NEXT_OR_FFFD(s, i, length, c) { \
    394     (c)=(uint8_t)(s)[(i)++]; \
    395     if((c)>=0x80) { \
    396         uint8_t __t1, __t2; \
    397         if( /* handle U+1000..U+CFFF inline */ \
    398             (0xe0<(c) && (c)<=0xec) && \
    399             (((i)+1)<(length) || (length)<0) && \
    400             (__t1=(uint8_t)((s)[i]-0x80))<=0x3f && \
    401             (__t2=(uint8_t)((s)[(i)+1]-0x80))<= 0x3f \
    402         ) { \
    403             /* no need for (c&0xf) because the upper bits are truncated after <<12 in the cast to (UChar) */ \
    404             (c)=(UChar)(((c)<<12)|(__t1<<6)|__t2); \
    405             (i)+=2; \
    406         } else if( /* handle U+0080..U+07FF inline */ \
    407             ((c)<0xe0 && (c)>=0xc2) && \
    408             ((i)!=(length)) && \
    409             (__t1=(uint8_t)((s)[i]-0x80))<=0x3f \
    410         ) { \
    411             (c)=(((c)&0x1f)<<6)|__t1; \
    412             ++(i); \
    413         } else { \
    414             /* function call for "complicated" and error cases */ \
    415             (c)=utf8_nextCharSafeBody((const uint8_t *)s, &(i), (length), c, -3); \
    416         } \
    417     } \
    418 }
    419 
    420 /**
    421  * Append a code point to a string, overwriting 1 to 4 bytes.
    422  * The offset points to the current end of the string contents
    423  * and is advanced (post-increment).
    424  * "Unsafe" macro, assumes a valid code point and sufficient space in the string.
    425  * Otherwise, the result is undefined.
    426  *
    427  * @param s const uint8_t * string buffer
    428  * @param i string offset
    429  * @param c code point to append
    430  * @see U8_APPEND
    431  * @stable ICU 2.4
    432  */
    433 #define U8_APPEND_UNSAFE(s, i, c) { \
    434     if((uint32_t)(c)<=0x7f) { \
    435         (s)[(i)++]=(uint8_t)(c); \
    436     } else { \
    437         if((uint32_t)(c)<=0x7ff) { \
    438             (s)[(i)++]=(uint8_t)(((c)>>6)|0xc0); \
    439         } else { \
    440             if((uint32_t)(c)<=0xffff) { \
    441                 (s)[(i)++]=(uint8_t)(((c)>>12)|0xe0); \
    442             } else { \
    443                 (s)[(i)++]=(uint8_t)(((c)>>18)|0xf0); \
    444                 (s)[(i)++]=(uint8_t)((((c)>>12)&0x3f)|0x80); \
    445             } \
    446             (s)[(i)++]=(uint8_t)((((c)>>6)&0x3f)|0x80); \
    447         } \
    448         (s)[(i)++]=(uint8_t)(((c)&0x3f)|0x80); \
    449     } \
    450 }
    451 
    452 /**
    453  * Append a code point to a string, overwriting 1 to 4 bytes.
    454  * The offset points to the current end of the string contents
    455  * and is advanced (post-increment).
    456  * "Safe" macro, checks for a valid code point.
    457  * If a non-ASCII code point is written, checks for sufficient space in the string.
    458  * If the code point is not valid or trail bytes do not fit,
    459  * then isError is set to TRUE.
    460  *
    461  * @param s const uint8_t * string buffer
    462  * @param i int32_t string offset, must be i<capacity
    463  * @param capacity int32_t size of the string buffer
    464  * @param c UChar32 code point to append
    465  * @param isError output UBool set to TRUE if an error occurs, otherwise not modified
    466  * @see U8_APPEND_UNSAFE
    467  * @stable ICU 2.4
    468  */
    469 #define U8_APPEND(s, i, capacity, c, isError) { \
    470     if((uint32_t)(c)<=0x7f) { \
    471         (s)[(i)++]=(uint8_t)(c); \
    472     } else if((uint32_t)(c)<=0x7ff && (i)+1<(capacity)) { \
    473         (s)[(i)++]=(uint8_t)(((c)>>6)|0xc0); \
    474         (s)[(i)++]=(uint8_t)(((c)&0x3f)|0x80); \
    475     } else if((uint32_t)(c)<=0xd7ff && (i)+2<(capacity)) { \
    476         (s)[(i)++]=(uint8_t)(((c)>>12)|0xe0); \
    477         (s)[(i)++]=(uint8_t)((((c)>>6)&0x3f)|0x80); \
    478         (s)[(i)++]=(uint8_t)(((c)&0x3f)|0x80); \
    479     } else { \
    480         (i)=utf8_appendCharSafeBody(s, (i), (capacity), c, &(isError)); \
    481     } \
    482 }
    483 
    484 /**
    485  * Advance the string offset from one code point boundary to the next.
    486  * (Post-incrementing iteration.)
    487  * "Unsafe" macro, assumes well-formed UTF-8.
    488  *
    489  * @param s const uint8_t * string
    490  * @param i string offset
    491  * @see U8_FWD_1
    492  * @stable ICU 2.4
    493  */
    494 #define U8_FWD_1_UNSAFE(s, i) { \
    495     (i)+=1+U8_COUNT_TRAIL_BYTES_UNSAFE((uint8_t)(s)[i]); \
    496 }
    497 
    498 /**
    499  * Advance the string offset from one code point boundary to the next.
    500  * (Post-incrementing iteration.)
    501  * "Safe" macro, checks for illegal sequences and for string boundaries.
    502  *
    503  * The length can be negative for a NUL-terminated string.
    504  *
    505  * @param s const uint8_t * string
    506  * @param i int32_t string offset, must be i<length
    507  * @param length int32_t string length
    508  * @see U8_FWD_1_UNSAFE
    509  * @stable ICU 2.4
    510  */
    511 #define U8_FWD_1(s, i, length) { \
    512     uint8_t __b=(uint8_t)(s)[(i)++]; \
    513     if(U8_IS_LEAD(__b)) { \
    514         uint8_t __count=U8_COUNT_TRAIL_BYTES(__b); \
    515         if((i)+__count>(length) && (length)>=0) { \
    516             __count=(uint8_t)((length)-(i)); \
    517         } \
    518         while(__count>0 && U8_IS_TRAIL((s)[i])) { \
    519             ++(i); \
    520             --__count; \
    521         } \
    522     } \
    523 }
    524 
    525 /**
    526  * Advance the string offset from one code point boundary to the n-th next one,
    527  * i.e., move forward by n code points.
    528  * (Post-incrementing iteration.)
    529  * "Unsafe" macro, assumes well-formed UTF-8.
    530  *
    531  * @param s const uint8_t * string
    532  * @param i string offset
    533  * @param n number of code points to skip
    534  * @see U8_FWD_N
    535  * @stable ICU 2.4
    536  */
    537 #define U8_FWD_N_UNSAFE(s, i, n) { \
    538     int32_t __N=(n); \
    539     while(__N>0) { \
    540         U8_FWD_1_UNSAFE(s, i); \
    541         --__N; \
    542     } \
    543 }
    544 
    545 /**
    546  * Advance the string offset from one code point boundary to the n-th next one,
    547  * i.e., move forward by n code points.
    548  * (Post-incrementing iteration.)
    549  * "Safe" macro, checks for illegal sequences and for string boundaries.
    550  *
    551  * The length can be negative for a NUL-terminated string.
    552  *
    553  * @param s const uint8_t * string
    554  * @param i int32_t string offset, must be i<length
    555  * @param length int32_t string length
    556  * @param n number of code points to skip
    557  * @see U8_FWD_N_UNSAFE
    558  * @stable ICU 2.4
    559  */
    560 #define U8_FWD_N(s, i, length, n) { \
    561     int32_t __N=(n); \
    562     while(__N>0 && ((i)<(length) || ((length)<0 && (s)[i]!=0))) { \
    563         U8_FWD_1(s, i, length); \
    564         --__N; \
    565     } \
    566 }
    567 
    568 /**
    569  * Adjust a random-access offset to a code point boundary
    570  * at the start of a code point.
    571  * If the offset points to a UTF-8 trail byte,
    572  * then the offset is moved backward to the corresponding lead byte.
    573  * Otherwise, it is not modified.
    574  * "Unsafe" macro, assumes well-formed UTF-8.
    575  *
    576  * @param s const uint8_t * string
    577  * @param i string offset
    578  * @see U8_SET_CP_START
    579  * @stable ICU 2.4
    580  */
    581 #define U8_SET_CP_START_UNSAFE(s, i) { \
    582     while(U8_IS_TRAIL((s)[i])) { --(i); } \
    583 }
    584 
    585 /**
    586  * Adjust a random-access offset to a code point boundary
    587  * at the start of a code point.
    588  * If the offset points to a UTF-8 trail byte,
    589  * then the offset is moved backward to the corresponding lead byte.
    590  * Otherwise, it is not modified.
    591  * "Safe" macro, checks for illegal sequences and for string boundaries.
    592  *
    593  * @param s const uint8_t * string
    594  * @param start int32_t starting string offset (usually 0)
    595  * @param i int32_t string offset, must be start<=i
    596  * @see U8_SET_CP_START_UNSAFE
    597  * @stable ICU 2.4
    598  */
    599 #define U8_SET_CP_START(s, start, i) { \
    600     if(U8_IS_TRAIL((s)[(i)])) { \
    601         (i)=utf8_back1SafeBody(s, start, (i)); \
    602     } \
    603 }
    604 
    605 /* definitions with backward iteration -------------------------------------- */
    606 
    607 /**
    608  * Move the string offset from one code point boundary to the previous one
    609  * and get the code point between them.
    610  * (Pre-decrementing backward iteration.)
    611  * "Unsafe" macro, assumes well-formed UTF-8.
    612  *
    613  * The input offset may be the same as the string length.
    614  * If the offset is behind a multi-byte sequence, then the macro will read
    615  * the whole sequence.
    616  * If the offset is behind a lead byte, then that itself
    617  * will be returned as the code point.
    618  * The result is undefined if the offset is behind an illegal UTF-8 sequence.
    619  *
    620  * @param s const uint8_t * string
    621  * @param i string offset
    622  * @param c output UChar32 variable
    623  * @see U8_PREV
    624  * @stable ICU 2.4
    625  */
    626 #define U8_PREV_UNSAFE(s, i, c) { \
    627     (c)=(uint8_t)(s)[--(i)]; \
    628     if(U8_IS_TRAIL(c)) { \
    629         uint8_t __b, __count=1, __shift=6; \
    630 \
    631         /* c is a trail byte */ \
    632         (c)&=0x3f; \
    633         for(;;) { \
    634             __b=(uint8_t)(s)[--(i)]; \
    635             if(__b>=0xc0) { \
    636                 U8_MASK_LEAD_BYTE(__b, __count); \
    637                 (c)|=(UChar32)__b<<__shift; \
    638                 break; \
    639             } else { \
    640                 (c)|=(UChar32)(__b&0x3f)<<__shift; \
    641                 ++__count; \
    642                 __shift+=6; \
    643             } \
    644         } \
    645     } \
    646 }
    647 
    648 /**
    649  * Move the string offset from one code point boundary to the previous one
    650  * and get the code point between them.
    651  * (Pre-decrementing backward iteration.)
    652  * "Safe" macro, checks for illegal sequences and for string boundaries.
    653  *
    654  * The input offset may be the same as the string length.
    655  * If the offset is behind a multi-byte sequence, then the macro will read
    656  * the whole sequence.
    657  * If the offset is behind a lead byte, then that itself
    658  * will be returned as the code point.
    659  * If the offset is behind an illegal UTF-8 sequence, then c is set to a negative value.
    660  *
    661  * @param s const uint8_t * string
    662  * @param start int32_t starting string offset (usually 0)
    663  * @param i int32_t string offset, must be start<i
    664  * @param c output UChar32 variable, set to <0 in case of an error
    665  * @see U8_PREV_UNSAFE
    666  * @stable ICU 2.4
    667  */
    668 #define U8_PREV(s, start, i, c) { \
    669     (c)=(uint8_t)(s)[--(i)]; \
    670     if((c)>=0x80) { \
    671         (c)=utf8_prevCharSafeBody((const uint8_t *)s, start, &(i), c, -1); \
    672     } \
    673 }
    674 
    675 /**
    676  * Move the string offset from one code point boundary to the previous one
    677  * and get the code point between them.
    678  * (Pre-decrementing backward iteration.)
    679  * "Safe" macro, checks for illegal sequences and for string boundaries.
    680  *
    681  * The input offset may be the same as the string length.
    682  * If the offset is behind a multi-byte sequence, then the macro will read
    683  * the whole sequence.
    684  * If the offset is behind a lead byte, then that itself
    685  * will be returned as the code point.
    686  * If the offset is behind an illegal UTF-8 sequence, then c is set to U+FFFD.
    687  *
    688  * This macro does not distinguish between a real U+FFFD in the text
    689  * and U+FFFD returned for an ill-formed sequence.
    690  * Use U8_PREV() if that distinction is important.
    691  *
    692  * @param s const uint8_t * string
    693  * @param start int32_t starting string offset (usually 0)
    694  * @param i int32_t string offset, must be start<i
    695  * @param c output UChar32 variable, set to U+FFFD in case of an error
    696  * @see U8_PREV
    697  * @stable ICU 51
    698  */
    699 #define U8_PREV_OR_FFFD(s, start, i, c) { \
    700     (c)=(uint8_t)(s)[--(i)]; \
    701     if((c)>=0x80) { \
    702         (c)=utf8_prevCharSafeBody((const uint8_t *)s, start, &(i), c, -3); \
    703     } \
    704 }
    705 
    706 /**
    707  * Move the string offset from one code point boundary to the previous one.
    708  * (Pre-decrementing backward iteration.)
    709  * The input offset may be the same as the string length.
    710  * "Unsafe" macro, assumes well-formed UTF-8.
    711  *
    712  * @param s const uint8_t * string
    713  * @param i string offset
    714  * @see U8_BACK_1
    715  * @stable ICU 2.4
    716  */
    717 #define U8_BACK_1_UNSAFE(s, i) { \
    718     while(U8_IS_TRAIL((s)[--(i)])) {} \
    719 }
    720 
    721 /**
    722  * Move the string offset from one code point boundary to the previous one.
    723  * (Pre-decrementing backward iteration.)
    724  * The input offset may be the same as the string length.
    725  * "Safe" macro, checks for illegal sequences and for string boundaries.
    726  *
    727  * @param s const uint8_t * string
    728  * @param start int32_t starting string offset (usually 0)
    729  * @param i int32_t string offset, must be start<i
    730  * @see U8_BACK_1_UNSAFE
    731  * @stable ICU 2.4
    732  */
    733 #define U8_BACK_1(s, start, i) { \
    734     if(U8_IS_TRAIL((s)[--(i)])) { \
    735         (i)=utf8_back1SafeBody(s, start, (i)); \
    736     } \
    737 }
    738 
    739 /**
    740  * Move the string offset from one code point boundary to the n-th one before it,
    741  * i.e., move backward by n code points.
    742  * (Pre-decrementing backward iteration.)
    743  * The input offset may be the same as the string length.
    744  * "Unsafe" macro, assumes well-formed UTF-8.
    745  *
    746  * @param s const uint8_t * string
    747  * @param i string offset
    748  * @param n number of code points to skip
    749  * @see U8_BACK_N
    750  * @stable ICU 2.4
    751  */
    752 #define U8_BACK_N_UNSAFE(s, i, n) { \
    753     int32_t __N=(n); \
    754     while(__N>0) { \
    755         U8_BACK_1_UNSAFE(s, i); \
    756         --__N; \
    757     } \
    758 }
    759 
    760 /**
    761  * Move the string offset from one code point boundary to the n-th one before it,
    762  * i.e., move backward by n code points.
    763  * (Pre-decrementing backward iteration.)
    764  * The input offset may be the same as the string length.
    765  * "Safe" macro, checks for illegal sequences and for string boundaries.
    766  *
    767  * @param s const uint8_t * string
    768  * @param start int32_t index of the start of the string
    769  * @param i int32_t string offset, must be start<i
    770  * @param n number of code points to skip
    771  * @see U8_BACK_N_UNSAFE
    772  * @stable ICU 2.4
    773  */
    774 #define U8_BACK_N(s, start, i, n) { \
    775     int32_t __N=(n); \
    776     while(__N>0 && (i)>(start)) { \
    777         U8_BACK_1(s, start, i); \
    778         --__N; \
    779     } \
    780 }
    781 
    782 /**
    783  * Adjust a random-access offset to a code point boundary after a code point.
    784  * If the offset is behind a partial multi-byte sequence,
    785  * then the offset is incremented to behind the whole sequence.
    786  * Otherwise, it is not modified.
    787  * The input offset may be the same as the string length.
    788  * "Unsafe" macro, assumes well-formed UTF-8.
    789  *
    790  * @param s const uint8_t * string
    791  * @param i string offset
    792  * @see U8_SET_CP_LIMIT
    793  * @stable ICU 2.4
    794  */
    795 #define U8_SET_CP_LIMIT_UNSAFE(s, i) { \
    796     U8_BACK_1_UNSAFE(s, i); \
    797     U8_FWD_1_UNSAFE(s, i); \
    798 }
    799 
    800 /**
    801  * Adjust a random-access offset to a code point boundary after a code point.
    802  * If the offset is behind a partial multi-byte sequence,
    803  * then the offset is incremented to behind the whole sequence.
    804  * Otherwise, it is not modified.
    805  * The input offset may be the same as the string length.
    806  * "Safe" macro, checks for illegal sequences and for string boundaries.
    807  *
    808  * The length can be negative for a NUL-terminated string.
    809  *
    810  * @param s const uint8_t * string
    811  * @param start int32_t starting string offset (usually 0)
    812  * @param i int32_t string offset, must be start<=i<=length
    813  * @param length int32_t string length
    814  * @see U8_SET_CP_LIMIT_UNSAFE
    815  * @stable ICU 2.4
    816  */
    817 #define U8_SET_CP_LIMIT(s, start, i, length) { \
    818     if((start)<(i) && ((i)<(length) || (length)<0)) { \
    819         U8_BACK_1(s, start, i); \
    820         U8_FWD_1(s, i, length); \
    821     } \
    822 }
    823 
    824 #endif
    825