icuSources/common/unicode/utf8.h

   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