icuSources/common/unicode/utf8.h

   1 // © 2016 and later: Unicode, Inc. and others.
   2 // License & terms of use: http://www.unicode.org/copyright.html
   3 /*
   4 *******************************************************************************
   5 *
   6 *   Copyright (C) 1999-2015, International Business Machines
   7 *   Corporation and others.  All Rights Reserved.
   8 *
   9 *******************************************************************************
  10 *   file name:  utf8.h
  11 *   encoding:   UTF-8
  12 *   tab size:   8 (not used)
  13 *   indentation:4
  14 *
  15 *   created on: 1999sep13
  16 *   created by: Markus W. Scherer
  17 */
  18
  19 /**
  20  * \file
  21  * \brief C API: 8-bit Unicode handling macros
  22  *
  23  * This file defines macros to deal with 8-bit Unicode (UTF-8) code units (bytes) and strings.
  24  *
  25  * For more information see utf.h and the ICU User Guide Strings chapter
  26  * (http://userguide.icu-project.org/strings).
  27  *
  28  * <em>Usage:</em>
  29  * ICU coding guidelines for if() statements should be followed when using these macros.
  30  * Compound statements (curly braces {}) must be used  for if-else-while...
  31  * bodies and all macro statements should be terminated with semicolon.
  32  */
  33
  34 #ifndef __UTF8_H__
  35 #define __UTF8_H__
  36
  37 #include "unicode/umachine.h"
  38 #ifndef __UTF_H__
  39 #   include "unicode/utf.h"
  40 #endif
  41
  42 /* internal definitions ----------------------------------------------------- */
  43
  44 /**
  45  * Counts the trail bytes for a UTF-8 lead byte.
  46  * Returns 0 for 0..0xc1 as well as for 0xf5..0xff.
  47  * leadByte might be evaluated multiple times.
  48  *
  49  * This is internal since it is not meant to be called directly by external clients;
  50  * however it is called by public macros in this file and thus must remain stable.
  51  *
  52  * @param leadByte The first byte of a UTF-8 sequence. Must be 0..0xff.
  53  * @internal
  54  */
  55 #define U8_COUNT_TRAIL_BYTES(leadByte) \
  56     (U8_IS_LEAD(leadByte) ? \
  57         ((uint8_t)(leadByte)>=0xe0)+((uint8_t)(leadByte)>=0xf0)+1 : 0)
  58
  59 /**
  60  * Counts the trail bytes for a UTF-8 lead byte of a valid UTF-8 sequence.
  61  * Returns 0 for 0..0xc1. Undefined for 0xf5..0xff.
  62  * leadByte might be evaluated multiple times.
  63  *
  64  * This is internal since it is not meant to be called directly by external clients;
  65  * however it is called by public macros in this file and thus must remain stable.
  66  *
  67  * @param leadByte The first byte of a UTF-8 sequence. Must be 0..0xff.
  68  * @internal
  69  */
  70 #define U8_COUNT_TRAIL_BYTES_UNSAFE(leadByte) \
  71     (((uint8_t)(leadByte)>=0xc2)+((uint8_t)(leadByte)>=0xe0)+((uint8_t)(leadByte)>=0xf0))
  72
  73 /**
  74  * Mask a UTF-8 lead byte, leave only the lower bits that form part of the code point value.
  75  *
  76  * This is internal since it is not meant to be called directly by external clients;
  77  * however it is called by public macros in this file and thus must remain stable.
  78  * @internal
  79  */
  80 #define U8_MASK_LEAD_BYTE(leadByte, countTrailBytes) ((leadByte)&=(1<<(6-(countTrailBytes)))-1)
  81
  82 /**
  83  * Internal bit vector for 3-byte UTF-8 validity check, for use in U8_IS_VALID_LEAD3_AND_T1.
  84  * Each bit indicates whether one lead byte + first trail byte pair starts a valid sequence.
  85  * Lead byte E0..EF bits 3..0 are used as byte index,
  86  * first trail byte bits 7..5 are used as bit index into that byte.
  87  * @see U8_IS_VALID_LEAD3_AND_T1
  88  * @internal
  89  */
  90 #define U8_LEAD3_T1_BITS "\x20\x30\x30\x30\x30\x30\x30\x30\x30\x30\x30\x30\x30\x10\x30\x30"
  91
  92 /**
  93  * Internal 3-byte UTF-8 validity check.
  94  * Non-zero if lead byte E0..EF and first trail byte 00..FF start a valid sequence.
  95  * @internal
  96  */
  97 #define U8_IS_VALID_LEAD3_AND_T1(lead, t1) (U8_LEAD3_T1_BITS[(lead)&0xf]&(1<<((uint8_t)(t1)>>5)))
  98
  99 /**
 100  * Internal bit vector for 4-byte UTF-8 validity check, for use in U8_IS_VALID_LEAD4_AND_T1.
 101  * Each bit indicates whether one lead byte + first trail byte pair starts a valid sequence.
 102  * First trail byte bits 7..4 are used as byte index,
 103  * lead byte F0..F4 bits 2..0 are used as bit index into that byte.
 104  * @see U8_IS_VALID_LEAD4_AND_T1
 105  * @internal
 106  */
 107 #define U8_LEAD4_T1_BITS "\x00\x00\x00\x00\x00\x00\x00\x00\x1E\x0F\x0F\x0F\x00\x00\x00\x00"
 108
 109 /**
 110  * Internal 4-byte UTF-8 validity check.
 111  * Non-zero if lead byte F0..F4 and first trail byte 00..FF start a valid sequence.
 112  * @internal
 113  */
 114 #define U8_IS_VALID_LEAD4_AND_T1(lead, t1) (U8_LEAD4_T1_BITS[(uint8_t)(t1)>>4]&(1<<((lead)&7)))
 115
 116 /**
 117  * Function for handling "next code point" with error-checking.
 118  *
 119  * This is internal since it is not meant to be called directly by external clients;
 120  * however it is U_STABLE (not U_INTERNAL) since it is called by public macros in this
 121  * file and thus must remain stable, and should not be hidden when other internal
 122  * functions are hidden (otherwise public macros would fail to compile).
 123  * @internal
 124  */
 125 U_STABLE UChar32 U_EXPORT2
 126 utf8_nextCharSafeBody(const uint8_t *s, int32_t *pi, int32_t length, UChar32 c, UBool strict);
 127
 128 /**
 129  * Function for handling "append code point" with error-checking.
 130  *
 131  * This is internal since it is not meant to be called directly by external clients;
 132  * however it is U_STABLE (not U_INTERNAL) since it is called by public macros in this
 133  * file and thus must remain stable, and should not be hidden when other internal
 134  * functions are hidden (otherwise public macros would fail to compile).
 135  * @internal
 136  */
 137 U_STABLE int32_t U_EXPORT2
 138 utf8_appendCharSafeBody(uint8_t *s, int32_t i, int32_t length, UChar32 c, UBool *pIsError);
 139
 140 /**
 141  * Function for handling "previous code point" with error-checking.
 142  *
 143  * This is internal since it is not meant to be called directly by external clients;
 144  * however it is U_STABLE (not U_INTERNAL) since it is called by public macros in this
 145  * file and thus must remain stable, and should not be hidden when other internal
 146  * functions are hidden (otherwise public macros would fail to compile).
 147  * @internal
 148  */
 149 U_STABLE UChar32 U_EXPORT2
 150 utf8_prevCharSafeBody(const uint8_t *s, int32_t start, int32_t *pi, UChar32 c, UBool strict);
 151
 152 /**
 153  * Function for handling "skip backward one code point" with error-checking.
 154  *
 155  * This is internal since it is not meant to be called directly by external clients;
 156  * however it is U_STABLE (not U_INTERNAL) since it is called by public macros in this
 157  * file and thus must remain stable, and should not be hidden when other internal
 158  * functions are hidden (otherwise public macros would fail to compile).
 159  * @internal
 160  */
 161 U_STABLE int32_t U_EXPORT2
 162 utf8_back1SafeBody(const uint8_t *s, int32_t start, int32_t i);
 163
 164 /* single-code point definitions -------------------------------------------- */
 165
 166 /**
 167  * Does this code unit (byte) encode a code point by itself (US-ASCII 0..0x7f)?
 168  * @param c 8-bit code unit (byte)
 169  * @return TRUE or FALSE
 170  * @stable ICU 2.4
 171  */
 172 #define U8_IS_SINGLE(c) (((c)&0x80)==0)
 173
 174 /**
 175  * Is this code unit (byte) a UTF-8 lead byte? (0xC2..0xF4)
 176  * @param c 8-bit code unit (byte)
 177  * @return TRUE or FALSE
 178  * @stable ICU 2.4
 179  */
 180 #define U8_IS_LEAD(c) ((uint8_t)((c)-0xc2)<=0x32)
 181 // 0x32=0xf4-0xc2
 182
 183 /**
 184  * Is this code unit (byte) a UTF-8 trail byte? (0x80..0xBF)
 185  * @param c 8-bit code unit (byte)
 186  * @return TRUE or FALSE
 187  * @stable ICU 2.4
 188  */
 189 #define U8_IS_TRAIL(c) ((int8_t)(c)<-0x40)
 190
 191 /**
 192  * How many code units (bytes) are used for the UTF-8 encoding
 193  * of this Unicode code point?
 194  * @param c 32-bit code point
 195  * @return 1..4, or 0 if c is a surrogate or not a Unicode code point
 196  * @stable ICU 2.4
 197  */
 198 #define U8_LENGTH(c) \
 199     ((uint32_t)(c)<=0x7f ? 1 : \
 200         ((uint32_t)(c)<=0x7ff ? 2 : \
 201             ((uint32_t)(c)<=0xd7ff ? 3 : \
 202                 ((uint32_t)(c)<=0xdfff || (uint32_t)(c)>0x10ffff ? 0 : \
 203                     ((uint32_t)(c)<=0xffff ? 3 : 4)\
 204                 ) \
 205             ) \
 206         ) \
 207     )
 208
 209 /**
 210  * The maximum number of UTF-8 code units (bytes) per Unicode code point (U+0000..U+10ffff).
 211  * @return 4
 212  * @stable ICU 2.4
 213  */
 214 #define U8_MAX_LENGTH 4
 215
 216 /**
 217  * Get a code point from a string at a random-access offset,
 218  * without changing the offset.
 219  * The offset may point to either the lead byte or one of the trail bytes
 220  * for a code point, in which case the macro will read all of the bytes
 221  * for the code point.
 222  * The result is undefined if the offset points to an illegal UTF-8
 223  * byte sequence.
 224  * Iteration through a string is more efficient with U8_NEXT_UNSAFE or U8_NEXT.
 225  *
 226  * @param s const uint8_t * string
 227  * @param i string offset
 228  * @param c output UChar32 variable
 229  * @see U8_GET
 230  * @stable ICU 2.4
 231  */
 232 #define U8_GET_UNSAFE(s, i, c) { \
 233     int32_t _u8_get_unsafe_index=(int32_t)(i); \
 234     U8_SET_CP_START_UNSAFE(s, _u8_get_unsafe_index); \
 235     U8_NEXT_UNSAFE(s, _u8_get_unsafe_index, c); \
 236 }
 237
 238 /**
 239  * Get a code point from a string at a random-access offset,
 240  * without changing the offset.
 241  * The offset may point to either the lead byte or one of the trail bytes
 242  * for a code point, in which case the macro will read all of the bytes
 243  * for the code point.
 244  *
 245  * The length can be negative for a NUL-terminated string.
 246  *
 247  * If the offset points to an illegal UTF-8 byte sequence, then
 248  * c is set to a negative value.
 249  * Iteration through a string is more efficient with U8_NEXT_UNSAFE or U8_NEXT.
 250  *
 251  * @param s const uint8_t * string
 252  * @param start int32_t starting string offset
 253  * @param i int32_t string offset, must be start<=i<length
 254  * @param length int32_t string length
 255  * @param c output UChar32 variable, set to <0 in case of an error
 256  * @see U8_GET_UNSAFE
 257  * @stable ICU 2.4
 258  */
 259 #define U8_GET(s, start, i, length, c) { \
 260     int32_t _u8_get_index=(i); \
 261     U8_SET_CP_START(s, start, _u8_get_index); \
 262     U8_NEXT(s, _u8_get_index, length, c); \
 263 }
 264
 265 /**
 266  * Get a code point from a string at a random-access offset,
 267  * without changing the offset.
 268  * The offset may point to either the lead byte or one of the trail bytes
 269  * for a code point, in which case the macro will read all of the bytes
 270  * for the code point.
 271  *
 272  * The length can be negative for a NUL-terminated string.
 273  *
 274  * If the offset points to an illegal UTF-8 byte sequence, then
 275  * c is set to U+FFFD.
 276  * Iteration through a string is more efficient with U8_NEXT_UNSAFE or U8_NEXT_OR_FFFD.
 277  *
 278  * This macro does not distinguish between a real U+FFFD in the text
 279  * and U+FFFD returned for an ill-formed sequence.
 280  * Use U8_GET() if that distinction is important.
 281  *
 282  * @param s const uint8_t * string
 283  * @param start int32_t starting string offset
 284  * @param i int32_t string offset, must be start<=i<length
 285  * @param length int32_t string length
 286  * @param c output UChar32 variable, set to U+FFFD in case of an error
 287  * @see U8_GET
 288  * @stable ICU 51
 289  */
 290 #define U8_GET_OR_FFFD(s, start, i, length, c) { \
 291     int32_t _u8_get_index=(i); \
 292     U8_SET_CP_START(s, start, _u8_get_index); \
 293     U8_NEXT_OR_FFFD(s, _u8_get_index, length, c); \
 294 }
 295
 296 /* definitions with forward iteration --------------------------------------- */
 297
 298 /**
 299  * Get a code point from a string at a code point boundary offset,
 300  * and advance the offset to the next code point boundary.
 301  * (Post-incrementing forward iteration.)
 302  * "Unsafe" macro, assumes well-formed UTF-8.
 303  *
 304  * The offset may point to the lead byte of a multi-byte sequence,
 305  * in which case the macro will read the whole sequence.
 306  * The result is undefined if the offset points to a trail byte
 307  * or an illegal UTF-8 sequence.
 308  *
 309  * @param s const uint8_t * string
 310  * @param i string offset
 311  * @param c output UChar32 variable
 312  * @see U8_NEXT
 313  * @stable ICU 2.4
 314  */
 315 #define U8_NEXT_UNSAFE(s, i, c) { \
 316     (c)=(uint8_t)(s)[(i)++]; \
 317     if(!U8_IS_SINGLE(c)) { \
 318         if((c)<0xe0) { \
 319             (c)=(((c)&0x1f)<<6)|((s)[(i)++]&0x3f); \
 320         } else if((c)<0xf0) { \
 321             /* no need for (c&0xf) because the upper bits are truncated after <<12 in the cast to (UChar) */ \
 322             (c)=(UChar)(((c)<<12)|(((s)[i]&0x3f)<<6)|((s)[(i)+1]&0x3f)); \
 323             (i)+=2; \
 324         } else { \
 325             (c)=(((c)&7)<<18)|(((s)[i]&0x3f)<<12)|(((s)[(i)+1]&0x3f)<<6)|((s)[(i)+2]&0x3f); \
 326             (i)+=3; \
 327         } \
 328     } \
 329 }
 330
 331 /**
 332  * Get a code point from a string at a code point boundary offset,
 333  * and advance the offset to the next code point boundary.
 334  * (Post-incrementing forward iteration.)
 335  * "Safe" macro, checks for illegal sequences and for string boundaries.
 336  *
 337  * The length can be negative for a NUL-terminated string.
 338  *
 339  * The offset may point to the lead byte of a multi-byte sequence,
 340  * in which case the macro will read the whole sequence.
 341  * If the offset points to a trail byte or an illegal UTF-8 sequence, then
 342  * c is set to a negative value.
 343  *
 344  * @param s const uint8_t * string
 345  * @param i int32_t string offset, must be i<length
 346  * @param length int32_t string length
 347  * @param c output UChar32 variable, set to <0 in case of an error
 348  * @see U8_NEXT_UNSAFE
 349  * @stable ICU 2.4
 350  */
 351 #define U8_NEXT(s, i, length, c) U8_INTERNAL_NEXT_OR_SUB(s, i, length, c, U_SENTINEL)
 352
 353 /**
 354  * Get a code point from a string at a code point boundary offset,
 355  * and advance the offset to the next code point boundary.
 356  * (Post-incrementing forward iteration.)
 357  * "Safe" macro, checks for illegal sequences and for string boundaries.
 358  *
 359  * The length can be negative for a NUL-terminated string.
 360  *
 361  * The offset may point to the lead byte of a multi-byte sequence,
 362  * in which case the macro will read the whole sequence.
 363  * If the offset points to a trail byte or an illegal UTF-8 sequence, then
 364  * c is set to U+FFFD.
 365  *
 366  * This macro does not distinguish between a real U+FFFD in the text
 367  * and U+FFFD returned for an ill-formed sequence.
 368  * Use U8_NEXT() if that distinction is important.
 369  *
 370  * @param s const uint8_t * string
 371  * @param i int32_t string offset, must be i<length
 372  * @param length int32_t string length
 373  * @param c output UChar32 variable, set to U+FFFD in case of an error
 374  * @see U8_NEXT
 375  * @stable ICU 51
 376  */
 377 #define U8_NEXT_OR_FFFD(s, i, length, c) U8_INTERNAL_NEXT_OR_SUB(s, i, length, c, 0xfffd)
 378
 379 /** @internal */
 380 #define U8_INTERNAL_NEXT_OR_SUB(s, i, length, c, sub) { \
 381     (c)=(uint8_t)(s)[(i)++]; \
 382     if(!U8_IS_SINGLE(c)) { \
 383         uint8_t __t = 0; \
 384         if((i)!=(length) && \
 385             /* fetch/validate/assemble all but last trail byte */ \
 386             ((c)>=0xe0 ? \
 387                 ((c)<0xf0 ?  /* U+0800..U+FFFF except surrogates */ \
 388                     U8_LEAD3_T1_BITS[(c)&=0xf]&(1<<((__t=(s)[i])>>5)) && \
 389                     (__t&=0x3f, 1) \
 390                 :  /* U+10000..U+10FFFF */ \
 391                     ((c)-=0xf0)<=4 && \
 392                     U8_LEAD4_T1_BITS[(__t=(s)[i])>>4]&(1<<(c)) && \
 393                     ((c)=((c)<<6)|(__t&0x3f), ++(i)!=(length)) && \
 394                     (__t=(s)[i]-0x80)<=0x3f) && \
 395                 /* valid second-to-last trail byte */ \
 396                 ((c)=((c)<<6)|__t, ++(i)!=(length)) \
 397             :  /* U+0080..U+07FF */ \
 398                 (c)>=0xc2 && ((c)&=0x1f, 1)) && \
 399             /* last trail byte */ \
 400             (__t=(s)[i]-0x80)<=0x3f && \
 401             ((c)=((c)<<6)|__t, ++(i), 1)) { \
 402         } else { \
 403             (c)=(sub);  /* ill-formed*/ \
 404         } \
 405     } \
 406 }
 407
 408 /**
 409  * Append a code point to a string, overwriting 1 to 4 bytes.
 410  * The offset points to the current end of the string contents
 411  * and is advanced (post-increment).
 412  * "Unsafe" macro, assumes a valid code point and sufficient space in the string.
 413  * Otherwise, the result is undefined.
 414  *
 415  * @param s const uint8_t * string buffer
 416  * @param i string offset
 417  * @param c code point to append
 418  * @see U8_APPEND
 419  * @stable ICU 2.4
 420  */
 421 #define U8_APPEND_UNSAFE(s, i, c) { \
 422     uint32_t __uc=(c); \
 423     if(__uc<=0x7f) { \
 424         (s)[(i)++]=(uint8_t)__uc; \
 425     } else { \
 426         if(__uc<=0x7ff) { \
 427             (s)[(i)++]=(uint8_t)((__uc>>6)|0xc0); \
 428         } else { \
 429             if(__uc<=0xffff) { \
 430                 (s)[(i)++]=(uint8_t)((__uc>>12)|0xe0); \
 431             } else { \
 432                 (s)[(i)++]=(uint8_t)((__uc>>18)|0xf0); \
 433                 (s)[(i)++]=(uint8_t)(((__uc>>12)&0x3f)|0x80); \
 434             } \
 435             (s)[(i)++]=(uint8_t)(((__uc>>6)&0x3f)|0x80); \
 436         } \
 437         (s)[(i)++]=(uint8_t)((__uc&0x3f)|0x80); \
 438     } \
 439 }
 440
 441 /**
 442  * Append a code point to a string, overwriting 1 to 4 bytes.
 443  * The offset points to the current end of the string contents
 444  * and is advanced (post-increment).
 445  * "Safe" macro, checks for a valid code point.
 446  * If a non-ASCII code point is written, checks for sufficient space in the string.
 447  * If the code point is not valid or trail bytes do not fit,
 448  * then isError is set to TRUE.
 449  *
 450  * @param s const uint8_t * string buffer
 451  * @param i int32_t string offset, must be i<capacity
 452  * @param capacity int32_t size of the string buffer
 453  * @param c UChar32 code point to append
 454  * @param isError output UBool set to TRUE if an error occurs, otherwise not modified
 455  * @see U8_APPEND_UNSAFE
 456  * @stable ICU 2.4
 457  */
 458 #define U8_APPEND(s, i, capacity, c, isError) { \
 459     uint32_t __uc=(c); \
 460     if(__uc<=0x7f) { \
 461         (s)[(i)++]=(uint8_t)__uc; \
 462     } else if(__uc<=0x7ff && (i)+1<(capacity)) { \
 463         (s)[(i)++]=(uint8_t)((__uc>>6)|0xc0); \
 464         (s)[(i)++]=(uint8_t)((__uc&0x3f)|0x80); \
 465     } else if((__uc<=0xd7ff || (0xe000<=__uc && __uc<=0xffff)) && (i)+2<(capacity)) { \
 466         (s)[(i)++]=(uint8_t)((__uc>>12)|0xe0); \
 467         (s)[(i)++]=(uint8_t)(((__uc>>6)&0x3f)|0x80); \
 468         (s)[(i)++]=(uint8_t)((__uc&0x3f)|0x80); \
 469     } else if(0xffff<__uc && __uc<=0x10ffff && (i)+3<(capacity)) { \
 470         (s)[(i)++]=(uint8_t)((__uc>>18)|0xf0); \
 471         (s)[(i)++]=(uint8_t)(((__uc>>12)&0x3f)|0x80); \
 472         (s)[(i)++]=(uint8_t)(((__uc>>6)&0x3f)|0x80); \
 473         (s)[(i)++]=(uint8_t)((__uc&0x3f)|0x80); \
 474     } else { \
 475         (isError)=TRUE; \
 476     } \
 477 }
 478
 479 /**
 480  * Advance the string offset from one code point boundary to the next.
 481  * (Post-incrementing iteration.)
 482  * "Unsafe" macro, assumes well-formed UTF-8.
 483  *
 484  * @param s const uint8_t * string
 485  * @param i string offset
 486  * @see U8_FWD_1
 487  * @stable ICU 2.4
 488  */
 489 #define U8_FWD_1_UNSAFE(s, i) { \
 490     (i)+=1+U8_COUNT_TRAIL_BYTES_UNSAFE((s)[i]); \
 491 }
 492
 493 /**
 494  * Advance the string offset from one code point boundary to the next.
 495  * (Post-incrementing iteration.)
 496  * "Safe" macro, checks for illegal sequences and for string boundaries.
 497  *
 498  * The length can be negative for a NUL-terminated string.
 499  *
 500  * @param s const uint8_t * string
 501  * @param i int32_t string offset, must be i<length
 502  * @param length int32_t string length
 503  * @see U8_FWD_1_UNSAFE
 504  * @stable ICU 2.4
 505  */
 506 #define U8_FWD_1(s, i, length) { \
 507     uint8_t __b=(s)[(i)++]; \
 508     if(U8_IS_LEAD(__b) && (i)!=(length)) { \
 509         uint8_t __t1=(s)[i]; \
 510         if((0xe0<=__b && __b<0xf0)) { \
 511             if(U8_IS_VALID_LEAD3_AND_T1(__b, __t1) && \
 512                     ++(i)!=(length) && U8_IS_TRAIL((s)[i])) { \
 513                 ++(i); \
 514             } \
 515         } else if(__b<0xe0) { \
 516             if(U8_IS_TRAIL(__t1)) { \
 517                 ++(i); \
 518             } \
 519         } else /* c>=0xf0 */ { \
 520             if(U8_IS_VALID_LEAD4_AND_T1(__b, __t1) && \
 521                     ++(i)!=(length) && U8_IS_TRAIL((s)[i]) && \
 522                     ++(i)!=(length) && U8_IS_TRAIL((s)[i])) { \
 523                 ++(i); \
 524             } \
 525         } \
 526     } \
 527 }
 528
 529 /**
 530  * Advance the string offset from one code point boundary to the n-th next one,
 531  * i.e., move forward by n code points.
 532  * (Post-incrementing iteration.)
 533  * "Unsafe" macro, assumes well-formed UTF-8.
 534  *
 535  * @param s const uint8_t * string
 536  * @param i string offset
 537  * @param n number of code points to skip
 538  * @see U8_FWD_N
 539  * @stable ICU 2.4
 540  */
 541 #define U8_FWD_N_UNSAFE(s, i, n) { \
 542     int32_t __N=(n); \
 543     while(__N>0) { \
 544         U8_FWD_1_UNSAFE(s, i); \
 545         --__N; \
 546     } \
 547 }
 548
 549 /**
 550  * Advance the string offset from one code point boundary to the n-th next one,
 551  * i.e., move forward by n code points.
 552  * (Post-incrementing iteration.)
 553  * "Safe" macro, checks for illegal sequences and for string boundaries.
 554  *
 555  * The length can be negative for a NUL-terminated string.
 556  *
 557  * @param s const uint8_t * string
 558  * @param i int32_t string offset, must be i<length
 559  * @param length int32_t string length
 560  * @param n number of code points to skip
 561  * @see U8_FWD_N_UNSAFE
 562  * @stable ICU 2.4
 563  */
 564 #define U8_FWD_N(s, i, length, n) { \
 565     int32_t __N=(n); \
 566     while(__N>0 && ((i)<(length) || ((length)<0 && (s)[i]!=0))) { \
 567         U8_FWD_1(s, i, length); \
 568         --__N; \
 569     } \
 570 }
 571
 572 /**
 573  * Adjust a random-access offset to a code point boundary
 574  * at the start of a code point.
 575  * If the offset points to a UTF-8 trail byte,
 576  * then the offset is moved backward to the corresponding lead byte.
 577  * Otherwise, it is not modified.
 578  * "Unsafe" macro, assumes well-formed UTF-8.
 579  *
 580  * @param s const uint8_t * string
 581  * @param i string offset
 582  * @see U8_SET_CP_START
 583  * @stable ICU 2.4
 584  */
 585 #define U8_SET_CP_START_UNSAFE(s, i) { \
 586     while(U8_IS_TRAIL((s)[i])) { --(i); } \
 587 }
 588
 589 /**
 590  * Adjust a random-access offset to a code point boundary
 591  * at the start of a code point.
 592  * If the offset points to a UTF-8 trail byte,
 593  * then the offset is moved backward to the corresponding lead byte.
 594  * Otherwise, it is not modified.
 595  *
 596  * "Safe" macro, checks for illegal sequences and for string boundaries.
 597  * Unlike U8_TRUNCATE_IF_INCOMPLETE(), this macro always reads s[i].
 598  *
 599  * @param s const uint8_t * string
 600  * @param start int32_t starting string offset (usually 0)
 601  * @param i int32_t string offset, must be start<=i
 602  * @see U8_SET_CP_START_UNSAFE
 603  * @see U8_TRUNCATE_IF_INCOMPLETE
 604  * @stable ICU 2.4
 605  */
 606 #define U8_SET_CP_START(s, start, i) { \
 607     if(U8_IS_TRAIL((s)[(i)])) { \
 608         (i)=utf8_back1SafeBody(s, start, (i)); \
 609     } \
 610 }
 611
 612 /**
 613  * If the string ends with a UTF-8 byte sequence that is valid so far
 614  * but incomplete, then reduce the length of the string to end before
 615  * the lead byte of that incomplete sequence.
 616  * For example, if the string ends with E1 80, the length is reduced by 2.
 617  *
 618  * In all other cases (the string ends with a complete sequence, or it is not
 619  * possible for any further trail byte to extend the trailing sequence)
 620  * the length remains unchanged.
 621  *
 622  * Useful for processing text split across multiple buffers
 623  * (save the incomplete sequence for later)
 624  * and for optimizing iteration
 625  * (check for string length only once per character).
 626  *
 627  * "Safe" macro, checks for illegal sequences and for string boundaries.
 628  * Unlike U8_SET_CP_START(), this macro never reads s[length].
 629  *
 630  * (In UTF-16, simply check for U16_IS_LEAD(last code unit).)
 631  *
 632  * @param s const uint8_t * string
 633  * @param start int32_t starting string offset (usually 0)
 634  * @param length int32_t string length (usually start<=length)
 635  * @see U8_SET_CP_START
 636  * @stable ICU 61
 637  */
 638 #define U8_TRUNCATE_IF_INCOMPLETE(s, start, length) \
 639     if((length)>(start)) { \
 640         uint8_t __b1=s[(length)-1]; \
 641         if(U8_IS_SINGLE(__b1)) { \
 642             /* common ASCII character */ \
 643         } else if(U8_IS_LEAD(__b1)) { \
 644             --(length); \
 645         } else if(U8_IS_TRAIL(__b1) && ((length)-2)>=(start)) { \
 646             uint8_t __b2=s[(length)-2]; \
 647             if(0xe0<=__b2 && __b2<=0xf4) { \
 648                 if(__b2<0xf0 ? U8_IS_VALID_LEAD3_AND_T1(__b2, __b1) : \
 649                         U8_IS_VALID_LEAD4_AND_T1(__b2, __b1)) { \
 650                     (length)-=2; \
 651                 } \
 652             } else if(U8_IS_TRAIL(__b2) && ((length)-3)>=(start)) { \
 653                 uint8_t __b3=s[(length)-3]; \
 654                 if(0xf0<=__b3 && __b3<=0xf4 && U8_IS_VALID_LEAD4_AND_T1(__b3, __b2)) { \
 655                     (length)-=3; \
 656                 } \
 657             } \
 658         } \
 659     }
 660
 661 /* definitions with backward iteration -------------------------------------- */
 662
 663 /**
 664  * Move the string offset from one code point boundary to the previous one
 665  * and get the code point between them.
 666  * (Pre-decrementing backward iteration.)
 667  * "Unsafe" macro, assumes well-formed UTF-8.
 668  *
 669  * The input offset may be the same as the string length.
 670  * If the offset is behind a multi-byte sequence, then the macro will read
 671  * the whole sequence.
 672  * If the offset is behind a lead byte, then that itself
 673  * will be returned as the code point.
 674  * The result is undefined if the offset is behind an illegal UTF-8 sequence.
 675  *
 676  * @param s const uint8_t * string
 677  * @param i string offset
 678  * @param c output UChar32 variable
 679  * @see U8_PREV
 680  * @stable ICU 2.4
 681  */
 682 #define U8_PREV_UNSAFE(s, i, c) { \
 683     (c)=(uint8_t)(s)[--(i)]; \
 684     if(U8_IS_TRAIL(c)) { \
 685         uint8_t __b, __count=1, __shift=6; \
 686 \
 687         /* c is a trail byte */ \
 688         (c)&=0x3f; \
 689         for(;;) { \
 690             __b=(s)[--(i)]; \
 691             if(__b>=0xc0) { \
 692                 U8_MASK_LEAD_BYTE(__b, __count); \
 693                 (c)|=(UChar32)__b<<__shift; \
 694                 break; \
 695             } else { \
 696                 (c)|=(UChar32)(__b&0x3f)<<__shift; \
 697                 ++__count; \
 698                 __shift+=6; \
 699             } \
 700         } \
 701     } \
 702 }
 703
 704 /**
 705  * Move the string offset from one code point boundary to the previous one
 706  * and get the code point between them.
 707  * (Pre-decrementing backward iteration.)
 708  * "Safe" macro, checks for illegal sequences and for string boundaries.
 709  *
 710  * The input offset may be the same as the string length.
 711  * If the offset is behind a multi-byte sequence, then the macro will read
 712  * the whole sequence.
 713  * If the offset is behind a lead byte, then that itself
 714  * will be returned as the code point.
 715  * If the offset is behind an illegal UTF-8 sequence, then c is set to a negative value.
 716  *
 717  * @param s const uint8_t * string
 718  * @param start int32_t starting string offset (usually 0)
 719  * @param i int32_t string offset, must be start<i
 720  * @param c output UChar32 variable, set to <0 in case of an error
 721  * @see U8_PREV_UNSAFE
 722  * @stable ICU 2.4
 723  */
 724 #define U8_PREV(s, start, i, c) { \
 725     (c)=(uint8_t)(s)[--(i)]; \
 726     if(!U8_IS_SINGLE(c)) { \
 727         (c)=utf8_prevCharSafeBody((const uint8_t *)s, start, &(i), c, -1); \
 728     } \
 729 }
 730
 731 /**
 732  * Move the string offset from one code point boundary to the previous one
 733  * and get the code point between them.
 734  * (Pre-decrementing backward iteration.)
 735  * "Safe" macro, checks for illegal sequences and for string boundaries.
 736  *
 737  * The input offset may be the same as the string length.
 738  * If the offset is behind a multi-byte sequence, then the macro will read
 739  * the whole sequence.
 740  * If the offset is behind a lead byte, then that itself
 741  * will be returned as the code point.
 742  * If the offset is behind an illegal UTF-8 sequence, then c is set to U+FFFD.
 743  *
 744  * This macro does not distinguish between a real U+FFFD in the text
 745  * and U+FFFD returned for an ill-formed sequence.
 746  * Use U8_PREV() if that distinction is important.
 747  *
 748  * @param s const uint8_t * string
 749  * @param start int32_t starting string offset (usually 0)
 750  * @param i int32_t string offset, must be start<i
 751  * @param c output UChar32 variable, set to U+FFFD in case of an error
 752  * @see U8_PREV
 753  * @stable ICU 51
 754  */
 755 #define U8_PREV_OR_FFFD(s, start, i, c) { \
 756     (c)=(uint8_t)(s)[--(i)]; \
 757     if(!U8_IS_SINGLE(c)) { \
 758         (c)=utf8_prevCharSafeBody((const uint8_t *)s, start, &(i), c, -3); \
 759     } \
 760 }
 761
 762 /**
 763  * Move the string offset from one code point boundary to the previous one.
 764  * (Pre-decrementing backward iteration.)
 765  * The input offset may be the same as the string length.
 766  * "Unsafe" macro, assumes well-formed UTF-8.
 767  *
 768  * @param s const uint8_t * string
 769  * @param i string offset
 770  * @see U8_BACK_1
 771  * @stable ICU 2.4
 772  */
 773 #define U8_BACK_1_UNSAFE(s, i) { \
 774     while(U8_IS_TRAIL((s)[--(i)])) {} \
 775 }
 776
 777 /**
 778  * Move the string offset from one code point boundary to the previous one.
 779  * (Pre-decrementing backward iteration.)
 780  * The input offset may be the same as the string length.
 781  * "Safe" macro, checks for illegal sequences and for string boundaries.
 782  *
 783  * @param s const uint8_t * string
 784  * @param start int32_t starting string offset (usually 0)
 785  * @param i int32_t string offset, must be start<i
 786  * @see U8_BACK_1_UNSAFE
 787  * @stable ICU 2.4
 788  */
 789 #define U8_BACK_1(s, start, i) { \
 790     if(U8_IS_TRAIL((s)[--(i)])) { \
 791         (i)=utf8_back1SafeBody(s, start, (i)); \
 792     } \
 793 }
 794
 795 /**
 796  * Move the string offset from one code point boundary to the n-th one before it,
 797  * i.e., move backward by n code points.
 798  * (Pre-decrementing backward iteration.)
 799  * The input offset may be the same as the string length.
 800  * "Unsafe" macro, assumes well-formed UTF-8.
 801  *
 802  * @param s const uint8_t * string
 803  * @param i string offset
 804  * @param n number of code points to skip
 805  * @see U8_BACK_N
 806  * @stable ICU 2.4
 807  */
 808 #define U8_BACK_N_UNSAFE(s, i, n) { \
 809     int32_t __N=(n); \
 810     while(__N>0) { \
 811         U8_BACK_1_UNSAFE(s, i); \
 812         --__N; \
 813     } \
 814 }
 815
 816 /**
 817  * Move the string offset from one code point boundary to the n-th one before it,
 818  * i.e., move backward by n code points.
 819  * (Pre-decrementing backward iteration.)
 820  * The input offset may be the same as the string length.
 821  * "Safe" macro, checks for illegal sequences and for string boundaries.
 822  *
 823  * @param s const uint8_t * string
 824  * @param start int32_t index of the start of the string
 825  * @param i int32_t string offset, must be start<i
 826  * @param n number of code points to skip
 827  * @see U8_BACK_N_UNSAFE
 828  * @stable ICU 2.4
 829  */
 830 #define U8_BACK_N(s, start, i, n) { \
 831     int32_t __N=(n); \
 832     while(__N>0 && (i)>(start)) { \
 833         U8_BACK_1(s, start, i); \
 834         --__N; \
 835     } \
 836 }
 837
 838 /**
 839  * Adjust a random-access offset to a code point boundary after a code point.
 840  * If the offset is behind a partial multi-byte sequence,
 841  * then the offset is incremented to behind the whole sequence.
 842  * Otherwise, it is not modified.
 843  * The input offset may be the same as the string length.
 844  * "Unsafe" macro, assumes well-formed UTF-8.
 845  *
 846  * @param s const uint8_t * string
 847  * @param i string offset
 848  * @see U8_SET_CP_LIMIT
 849  * @stable ICU 2.4
 850  */
 851 #define U8_SET_CP_LIMIT_UNSAFE(s, i) { \
 852     U8_BACK_1_UNSAFE(s, i); \
 853     U8_FWD_1_UNSAFE(s, i); \
 854 }
 855
 856 /**
 857  * Adjust a random-access offset to a code point boundary after a code point.
 858  * If the offset is behind a partial multi-byte sequence,
 859  * then the offset is incremented to behind the whole sequence.
 860  * Otherwise, it is not modified.
 861  * The input offset may be the same as the string length.
 862  * "Safe" macro, checks for illegal sequences and for string boundaries.
 863  *
 864  * The length can be negative for a NUL-terminated string.
 865  *
 866  * @param s const uint8_t * string
 867  * @param start int32_t starting string offset (usually 0)
 868  * @param i int32_t string offset, must be start<=i<=length
 869  * @param length int32_t string length
 870  * @see U8_SET_CP_LIMIT_UNSAFE
 871  * @stable ICU 2.4
 872  */
 873 #define U8_SET_CP_LIMIT(s, start, i, length) { \
 874     if((start)<(i) && ((i)<(length) || (length)<0)) { \
 875         U8_BACK_1(s, start, i); \
 876         U8_FWD_1(s, i, length); \
 877     } \
 878 }
 879
 880 #endif