1// Copyright (C) 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:   US-ASCII
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 * \var utf8_countTrailBytes
46 * Internal array with numbers of trail bytes for any given byte used in
47 * lead byte position.
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 * and should not be hidden when other internal functions are hidden (otherwise
52 * public macros would fail to compile).
53 * @internal
54 */
55#ifdef U_UTF8_IMPL
56U_EXPORT const uint8_t
57#elif defined(U_STATIC_IMPLEMENTATION) || defined(U_COMMON_IMPLEMENTATION)
58U_CFUNC const uint8_t
59#else
60U_CFUNC U_IMPORT const uint8_t /* U_IMPORT2? */ /*U_IMPORT*/
61#endif
62utf8_countTrailBytes[256];
63
64/**
65 * Counts the trail bytes for a UTF-8 lead byte.
66 * Returns 0 for 0..0xbf as well as for 0xfe and 0xff.
67 *
68 * This is internal since it is not meant to be called directly by external clients;
69 * however it is called by public macros in this file and thus must remain stable.
70 *
71 * Note: Beginning with ICU 50, the implementation uses a multi-condition expression
72 * which was shown in 2012 (on x86-64) to compile to fast, branch-free code.
73 * leadByte is evaluated multiple times.
74 *
75 * The pre-ICU 50 implementation used the exported array utf8_countTrailBytes:
76 * #define U8_COUNT_TRAIL_BYTES(leadByte) (utf8_countTrailBytes[leadByte])
77 * leadByte was evaluated exactly once.
78 *
79 * @param leadByte The first byte of a UTF-8 sequence. Must be 0..0xff.
80 * @internal
81 */
82#define U8_COUNT_TRAIL_BYTES(leadByte) \
83    ((uint8_t)(leadByte)<0xf0 ? \
84        ((uint8_t)(leadByte)>=0xc0)+((uint8_t)(leadByte)>=0xe0) : \
85        (uint8_t)(leadByte)<0xfe ? 3+((uint8_t)(leadByte)>=0xf8)+((uint8_t)(leadByte)>=0xfc) : 0)
86
87/**
88 * Counts the trail bytes for a UTF-8 lead byte of a valid UTF-8 sequence.
89 * The maximum supported lead byte is 0xf4 corresponding to U+10FFFF.
90 * leadByte might be evaluated multiple times.
91 *
92 * This is internal since it is not meant to be called directly by external clients;
93 * however it is called by public macros in this file and thus must remain stable.
94 *
95 * @param leadByte The first byte of a UTF-8 sequence. Must be 0..0xff.
96 * @internal
97 */
98#define U8_COUNT_TRAIL_BYTES_UNSAFE(leadByte) \
99    (((leadByte)>=0xc0)+((leadByte)>=0xe0)+((leadByte)>=0xf0))
100
101/**
102 * Mask a UTF-8 lead byte, leave only the lower bits that form part of the code point value.
103 *
104 * This is internal since it is not meant to be called directly by external clients;
105 * however it is called by public macros in this file and thus must remain stable.
106 * @internal
107 */
108#define U8_MASK_LEAD_BYTE(leadByte, countTrailBytes) ((leadByte)&=(1<<(6-(countTrailBytes)))-1)
109
110/**
111 * Function for handling "next code point" with error-checking.
112 *
113 * This is internal since it is not meant to be called directly by external clients;
114 * however it is U_STABLE (not U_INTERNAL) since it is called by public macros in this
115 * file and thus must remain stable, and should not be hidden when other internal
116 * functions are hidden (otherwise public macros would fail to compile).
117 * @internal
118 */
119U_STABLE UChar32 U_EXPORT2
120utf8_nextCharSafeBody(const uint8_t *s, int32_t *pi, int32_t length, UChar32 c, UBool strict);
121
122/**
123 * Function for handling "append code point" with error-checking.
124 *
125 * This is internal since it is not meant to be called directly by external clients;
126 * however it is U_STABLE (not U_INTERNAL) since it is called by public macros in this
127 * file and thus must remain stable, and should not be hidden when other internal
128 * functions are hidden (otherwise public macros would fail to compile).
129 * @internal
130 */
131U_STABLE int32_t U_EXPORT2
132utf8_appendCharSafeBody(uint8_t *s, int32_t i, int32_t length, UChar32 c, UBool *pIsError);
133
134/**
135 * Function for handling "previous code point" with error-checking.
136 *
137 * This is internal since it is not meant to be called directly by external clients;
138 * however it is U_STABLE (not U_INTERNAL) since it is called by public macros in this
139 * file and thus must remain stable, and should not be hidden when other internal
140 * functions are hidden (otherwise public macros would fail to compile).
141 * @internal
142 */
143U_STABLE UChar32 U_EXPORT2
144utf8_prevCharSafeBody(const uint8_t *s, int32_t start, int32_t *pi, UChar32 c, UBool strict);
145
146/**
147 * Function for handling "skip backward one code point" with error-checking.
148 *
149 * This is internal since it is not meant to be called directly by external clients;
150 * however it is U_STABLE (not U_INTERNAL) since it is called by public macros in this
151 * file and thus must remain stable, and should not be hidden when other internal
152 * functions are hidden (otherwise public macros would fail to compile).
153 * @internal
154 */
155U_STABLE int32_t U_EXPORT2
156utf8_back1SafeBody(const uint8_t *s, int32_t start, int32_t i);
157
158/* single-code point definitions -------------------------------------------- */
159
160/**
161 * Does this code unit (byte) encode a code point by itself (US-ASCII 0..0x7f)?
162 * @param c 8-bit code unit (byte)
163 * @return TRUE or FALSE
164 * @stable ICU 2.4
165 */
166#define U8_IS_SINGLE(c) (((c)&0x80)==0)
167
168/**
169 * Is this code unit (byte) a UTF-8 lead byte?
170 * @param c 8-bit code unit (byte)
171 * @return TRUE or FALSE
172 * @stable ICU 2.4
173 */
174#define U8_IS_LEAD(c) ((uint8_t)((c)-0xc0)<0x3e)
175
176/**
177 * Is this code unit (byte) a UTF-8 trail byte?
178 * @param c 8-bit code unit (byte)
179 * @return TRUE or FALSE
180 * @stable ICU 2.4
181 */
182#define U8_IS_TRAIL(c) (((c)&0xc0)==0x80)
183
184/**
185 * How many code units (bytes) are used for the UTF-8 encoding
186 * of this Unicode code point?
187 * @param c 32-bit code point
188 * @return 1..4, or 0 if c is a surrogate or not a Unicode code point
189 * @stable ICU 2.4
190 */
191#define U8_LENGTH(c) \
192    ((uint32_t)(c)<=0x7f ? 1 : \
193        ((uint32_t)(c)<=0x7ff ? 2 : \
194            ((uint32_t)(c)<=0xd7ff ? 3 : \
195                ((uint32_t)(c)<=0xdfff || (uint32_t)(c)>0x10ffff ? 0 : \
196                    ((uint32_t)(c)<=0xffff ? 3 : 4)\
197                ) \
198            ) \
199        ) \
200    )
201
202/**
203 * The maximum number of UTF-8 code units (bytes) per Unicode code point (U+0000..U+10ffff).
204 * @return 4
205 * @stable ICU 2.4
206 */
207#define U8_MAX_LENGTH 4
208
209/**
210 * Get a code point from a string at a random-access offset,
211 * without changing the offset.
212 * The offset may point to either the lead byte or one of the trail bytes
213 * for a code point, in which case the macro will read all of the bytes
214 * for the code point.
215 * The result is undefined if the offset points to an illegal UTF-8
216 * byte sequence.
217 * Iteration through a string is more efficient with U8_NEXT_UNSAFE or U8_NEXT.
218 *
219 * @param s const uint8_t * string
220 * @param i string offset
221 * @param c output UChar32 variable
222 * @see U8_GET
223 * @stable ICU 2.4
224 */
225#define U8_GET_UNSAFE(s, i, c) { \
226    int32_t _u8_get_unsafe_index=(int32_t)(i); \
227    U8_SET_CP_START_UNSAFE(s, _u8_get_unsafe_index); \
228    U8_NEXT_UNSAFE(s, _u8_get_unsafe_index, c); \
229}
230
231/**
232 * Get a code point from a string at a random-access offset,
233 * without changing the offset.
234 * The offset may point to either the lead byte or one of the trail bytes
235 * for a code point, in which case the macro will read all of the bytes
236 * for the code point.
237 *
238 * The length can be negative for a NUL-terminated string.
239 *
240 * If the offset points to an illegal UTF-8 byte sequence, then
241 * c is set to a negative value.
242 * Iteration through a string is more efficient with U8_NEXT_UNSAFE or U8_NEXT.
243 *
244 * @param s const uint8_t * string
245 * @param start int32_t starting string offset
246 * @param i int32_t string offset, must be start<=i<length
247 * @param length int32_t string length
248 * @param c output UChar32 variable, set to <0 in case of an error
249 * @see U8_GET_UNSAFE
250 * @stable ICU 2.4
251 */
252#define U8_GET(s, start, i, length, c) { \
253    int32_t _u8_get_index=(i); \
254    U8_SET_CP_START(s, start, _u8_get_index); \
255    U8_NEXT(s, _u8_get_index, length, c); \
256}
257
258/**
259 * Get a code point from a string at a random-access offset,
260 * without changing the offset.
261 * The offset may point to either the lead byte or one of the trail bytes
262 * for a code point, in which case the macro will read all of the bytes
263 * for the code point.
264 *
265 * The length can be negative for a NUL-terminated string.
266 *
267 * If the offset points to an illegal UTF-8 byte sequence, then
268 * c is set to U+FFFD.
269 * Iteration through a string is more efficient with U8_NEXT_UNSAFE or U8_NEXT_OR_FFFD.
270 *
271 * This macro does not distinguish between a real U+FFFD in the text
272 * and U+FFFD returned for an ill-formed sequence.
273 * Use U8_GET() if that distinction is important.
274 *
275 * @param s const uint8_t * string
276 * @param start int32_t starting string offset
277 * @param i int32_t string offset, must be start<=i<length
278 * @param length int32_t string length
279 * @param c output UChar32 variable, set to U+FFFD in case of an error
280 * @see U8_GET
281 * @stable ICU 51
282 */
283#define U8_GET_OR_FFFD(s, start, i, length, c) { \
284    int32_t _u8_get_index=(i); \
285    U8_SET_CP_START(s, start, _u8_get_index); \
286    U8_NEXT_OR_FFFD(s, _u8_get_index, length, c); \
287}
288
289/* definitions with forward iteration --------------------------------------- */
290
291/**
292 * Get a code point from a string at a code point boundary offset,
293 * and advance the offset to the next code point boundary.
294 * (Post-incrementing forward iteration.)
295 * "Unsafe" macro, assumes well-formed UTF-8.
296 *
297 * The offset may point to the lead byte of a multi-byte sequence,
298 * in which case the macro will read the whole sequence.
299 * The result is undefined if the offset points to a trail byte
300 * or an illegal UTF-8 sequence.
301 *
302 * @param s const uint8_t * string
303 * @param i string offset
304 * @param c output UChar32 variable
305 * @see U8_NEXT
306 * @stable ICU 2.4
307 */
308#define U8_NEXT_UNSAFE(s, i, c) { \
309    (c)=(uint8_t)(s)[(i)++]; \
310    if((c)>=0x80) { \
311        if((c)<0xe0) { \
312            (c)=(((c)&0x1f)<<6)|((s)[(i)++]&0x3f); \
313        } else if((c)<0xf0) { \
314            /* no need for (c&0xf) because the upper bits are truncated after <<12 in the cast to (UChar) */ \
315            (c)=(UChar)(((c)<<12)|(((s)[i]&0x3f)<<6)|((s)[(i)+1]&0x3f)); \
316            (i)+=2; \
317        } else { \
318            (c)=(((c)&7)<<18)|(((s)[i]&0x3f)<<12)|(((s)[(i)+1]&0x3f)<<6)|((s)[(i)+2]&0x3f); \
319            (i)+=3; \
320        } \
321    } \
322}
323
324/**
325 * Get a code point from a string at a code point boundary offset,
326 * and advance the offset to the next code point boundary.
327 * (Post-incrementing forward iteration.)
328 * "Safe" macro, checks for illegal sequences and for string boundaries.
329 *
330 * The length can be negative for a NUL-terminated string.
331 *
332 * The offset may point to the lead byte of a multi-byte sequence,
333 * in which case the macro will read the whole sequence.
334 * If the offset points to a trail byte or an illegal UTF-8 sequence, then
335 * c is set to a negative value.
336 *
337 * @param s const uint8_t * string
338 * @param i int32_t string offset, must be i<length
339 * @param length int32_t string length
340 * @param c output UChar32 variable, set to <0 in case of an error
341 * @see U8_NEXT_UNSAFE
342 * @stable ICU 2.4
343 */
344#define U8_NEXT(s, i, length, c) { \
345    (c)=(uint8_t)(s)[(i)++]; \
346    if((c)>=0x80) { \
347        uint8_t __t1, __t2; \
348        if( /* handle U+1000..U+CFFF inline */ \
349            (0xe0<(c) && (c)<=0xec) && \
350            (((i)+1)<(length) || (length)<0) && \
351            (__t1=(uint8_t)((s)[i]-0x80))<=0x3f && \
352            (__t2=(uint8_t)((s)[(i)+1]-0x80))<= 0x3f \
353        ) { \
354            /* no need for (c&0xf) because the upper bits are truncated after <<12 in the cast to (UChar) */ \
355            (c)=(UChar)(((c)<<12)|(__t1<<6)|__t2); \
356            (i)+=2; \
357        } else if( /* handle U+0080..U+07FF inline */ \
358            ((c)<0xe0 && (c)>=0xc2) && \
359            ((i)!=(length)) && \
360            (__t1=(uint8_t)((s)[i]-0x80))<=0x3f \
361        ) { \
362            (c)=(((c)&0x1f)<<6)|__t1; \
363            ++(i); \
364        } else { \
365            /* function call for "complicated" and error cases */ \
366            (c)=utf8_nextCharSafeBody((const uint8_t *)s, &(i), (length), c, -1); \
367        } \
368    } \
369}
370
371/**
372 * Get a code point from a string at a code point boundary offset,
373 * and advance the offset to the next code point boundary.
374 * (Post-incrementing forward iteration.)
375 * "Safe" macro, checks for illegal sequences and for string boundaries.
376 *
377 * The length can be negative for a NUL-terminated string.
378 *
379 * The offset may point to the lead byte of a multi-byte sequence,
380 * in which case the macro will read the whole sequence.
381 * If the offset points to a trail byte or an illegal UTF-8 sequence, then
382 * c is set to U+FFFD.
383 *
384 * This macro does not distinguish between a real U+FFFD in the text
385 * and U+FFFD returned for an ill-formed sequence.
386 * Use U8_NEXT() if that distinction is important.
387 *
388 * @param s const uint8_t * string
389 * @param i int32_t string offset, must be i<length
390 * @param length int32_t string length
391 * @param c output UChar32 variable, set to U+FFFD in case of an error
392 * @see U8_NEXT
393 * @stable ICU 51
394 */
395#define U8_NEXT_OR_FFFD(s, i, length, c) { \
396    (c)=(uint8_t)(s)[(i)++]; \
397    if((c)>=0x80) { \
398        uint8_t __t1, __t2; \
399        if( /* handle U+1000..U+CFFF inline */ \
400            (0xe0<(c) && (c)<=0xec) && \
401            (((i)+1)<(length) || (length)<0) && \
402            (__t1=(uint8_t)((s)[i]-0x80))<=0x3f && \
403            (__t2=(uint8_t)((s)[(i)+1]-0x80))<= 0x3f \
404        ) { \
405            /* no need for (c&0xf) because the upper bits are truncated after <<12 in the cast to (UChar) */ \
406            (c)=(UChar)(((c)<<12)|(__t1<<6)|__t2); \
407            (i)+=2; \
408        } else if( /* handle U+0080..U+07FF inline */ \
409            ((c)<0xe0 && (c)>=0xc2) && \
410            ((i)!=(length)) && \
411            (__t1=(uint8_t)((s)[i]-0x80))<=0x3f \
412        ) { \
413            (c)=(((c)&0x1f)<<6)|__t1; \
414            ++(i); \
415        } else { \
416            /* function call for "complicated" and error cases */ \
417            (c)=utf8_nextCharSafeBody((const uint8_t *)s, &(i), (length), c, -3); \
418        } \
419    } \
420}
421
422/**
423 * Append a code point to a string, overwriting 1 to 4 bytes.
424 * The offset points to the current end of the string contents
425 * and is advanced (post-increment).
426 * "Unsafe" macro, assumes a valid code point and sufficient space in the string.
427 * Otherwise, the result is undefined.
428 *
429 * @param s const uint8_t * string buffer
430 * @param i string offset
431 * @param c code point to append
432 * @see U8_APPEND
433 * @stable ICU 2.4
434 */
435#define U8_APPEND_UNSAFE(s, i, c) { \
436    if((uint32_t)(c)<=0x7f) { \
437        (s)[(i)++]=(uint8_t)(c); \
438    } else { \
439        if((uint32_t)(c)<=0x7ff) { \
440            (s)[(i)++]=(uint8_t)(((c)>>6)|0xc0); \
441        } else { \
442            if((uint32_t)(c)<=0xffff) { \
443                (s)[(i)++]=(uint8_t)(((c)>>12)|0xe0); \
444            } else { \
445                (s)[(i)++]=(uint8_t)(((c)>>18)|0xf0); \
446                (s)[(i)++]=(uint8_t)((((c)>>12)&0x3f)|0x80); \
447            } \
448            (s)[(i)++]=(uint8_t)((((c)>>6)&0x3f)|0x80); \
449        } \
450        (s)[(i)++]=(uint8_t)(((c)&0x3f)|0x80); \
451    } \
452}
453
454/**
455 * Append a code point to a string, overwriting 1 to 4 bytes.
456 * The offset points to the current end of the string contents
457 * and is advanced (post-increment).
458 * "Safe" macro, checks for a valid code point.
459 * If a non-ASCII code point is written, checks for sufficient space in the string.
460 * If the code point is not valid or trail bytes do not fit,
461 * then isError is set to TRUE.
462 *
463 * @param s const uint8_t * string buffer
464 * @param i int32_t string offset, must be i<capacity
465 * @param capacity int32_t size of the string buffer
466 * @param c UChar32 code point to append
467 * @param isError output UBool set to TRUE if an error occurs, otherwise not modified
468 * @see U8_APPEND_UNSAFE
469 * @stable ICU 2.4
470 */
471#define U8_APPEND(s, i, capacity, c, isError) { \
472    if((uint32_t)(c)<=0x7f) { \
473        (s)[(i)++]=(uint8_t)(c); \
474    } else if((uint32_t)(c)<=0x7ff && (i)+1<(capacity)) { \
475        (s)[(i)++]=(uint8_t)(((c)>>6)|0xc0); \
476        (s)[(i)++]=(uint8_t)(((c)&0x3f)|0x80); \
477    } else if((uint32_t)(c)<=0xd7ff && (i)+2<(capacity)) { \
478        (s)[(i)++]=(uint8_t)(((c)>>12)|0xe0); \
479        (s)[(i)++]=(uint8_t)((((c)>>6)&0x3f)|0x80); \
480        (s)[(i)++]=(uint8_t)(((c)&0x3f)|0x80); \
481    } else { \
482        (i)=utf8_appendCharSafeBody(s, (i), (capacity), c, &(isError)); \
483    } \
484}
485
486/**
487 * Advance the string offset from one code point boundary to the next.
488 * (Post-incrementing iteration.)
489 * "Unsafe" macro, assumes well-formed UTF-8.
490 *
491 * @param s const uint8_t * string
492 * @param i string offset
493 * @see U8_FWD_1
494 * @stable ICU 2.4
495 */
496#define U8_FWD_1_UNSAFE(s, i) { \
497    (i)+=1+U8_COUNT_TRAIL_BYTES_UNSAFE((uint8_t)(s)[i]); \
498}
499
500/**
501 * Advance the string offset from one code point boundary to the next.
502 * (Post-incrementing iteration.)
503 * "Safe" macro, checks for illegal sequences and for string boundaries.
504 *
505 * The length can be negative for a NUL-terminated string.
506 *
507 * @param s const uint8_t * string
508 * @param i int32_t string offset, must be i<length
509 * @param length int32_t string length
510 * @see U8_FWD_1_UNSAFE
511 * @stable ICU 2.4
512 */
513#define U8_FWD_1(s, i, length) { \
514    uint8_t __b=(uint8_t)(s)[(i)++]; \
515    if(U8_IS_LEAD(__b)) { \
516        uint8_t __count=U8_COUNT_TRAIL_BYTES(__b); \
517        if((i)+__count>(length) && (length)>=0) { \
518            __count=(uint8_t)((length)-(i)); \
519        } \
520        while(__count>0 && U8_IS_TRAIL((s)[i])) { \
521            ++(i); \
522            --__count; \
523        } \
524    } \
525}
526
527/**
528 * Advance the string offset from one code point boundary to the n-th next one,
529 * i.e., move forward by n code points.
530 * (Post-incrementing iteration.)
531 * "Unsafe" macro, assumes well-formed UTF-8.
532 *
533 * @param s const uint8_t * string
534 * @param i string offset
535 * @param n number of code points to skip
536 * @see U8_FWD_N
537 * @stable ICU 2.4
538 */
539#define U8_FWD_N_UNSAFE(s, i, n) { \
540    int32_t __N=(n); \
541    while(__N>0) { \
542        U8_FWD_1_UNSAFE(s, i); \
543        --__N; \
544    } \
545}
546
547/**
548 * Advance the string offset from one code point boundary to the n-th next one,
549 * i.e., move forward by n code points.
550 * (Post-incrementing iteration.)
551 * "Safe" macro, checks for illegal sequences and for string boundaries.
552 *
553 * The length can be negative for a NUL-terminated string.
554 *
555 * @param s const uint8_t * string
556 * @param i int32_t string offset, must be i<length
557 * @param length int32_t string length
558 * @param n number of code points to skip
559 * @see U8_FWD_N_UNSAFE
560 * @stable ICU 2.4
561 */
562#define U8_FWD_N(s, i, length, n) { \
563    int32_t __N=(n); \
564    while(__N>0 && ((i)<(length) || ((length)<0 && (s)[i]!=0))) { \
565        U8_FWD_1(s, i, length); \
566        --__N; \
567    } \
568}
569
570/**
571 * Adjust a random-access offset to a code point boundary
572 * at the start of a code point.
573 * If the offset points to a UTF-8 trail byte,
574 * then the offset is moved backward to the corresponding lead byte.
575 * Otherwise, it is not modified.
576 * "Unsafe" macro, assumes well-formed UTF-8.
577 *
578 * @param s const uint8_t * string
579 * @param i string offset
580 * @see U8_SET_CP_START
581 * @stable ICU 2.4
582 */
583#define U8_SET_CP_START_UNSAFE(s, i) { \
584    while(U8_IS_TRAIL((s)[i])) { --(i); } \
585}
586
587/**
588 * Adjust a random-access offset to a code point boundary
589 * at the start of a code point.
590 * If the offset points to a UTF-8 trail byte,
591 * then the offset is moved backward to the corresponding lead byte.
592 * Otherwise, it is not modified.
593 * "Safe" macro, checks for illegal sequences and for string boundaries.
594 *
595 * @param s const uint8_t * string
596 * @param start int32_t starting string offset (usually 0)
597 * @param i int32_t string offset, must be start<=i
598 * @see U8_SET_CP_START_UNSAFE
599 * @stable ICU 2.4
600 */
601#define U8_SET_CP_START(s, start, i) { \
602    if(U8_IS_TRAIL((s)[(i)])) { \
603        (i)=utf8_back1SafeBody(s, start, (i)); \
604    } \
605}
606
607/* definitions with backward iteration -------------------------------------- */
608
609/**
610 * Move the string offset from one code point boundary to the previous one
611 * and get the code point between them.
612 * (Pre-decrementing backward iteration.)
613 * "Unsafe" macro, assumes well-formed UTF-8.
614 *
615 * The input offset may be the same as the string length.
616 * If the offset is behind a multi-byte sequence, then the macro will read
617 * the whole sequence.
618 * If the offset is behind a lead byte, then that itself
619 * will be returned as the code point.
620 * The result is undefined if the offset is behind an illegal UTF-8 sequence.
621 *
622 * @param s const uint8_t * string
623 * @param i string offset
624 * @param c output UChar32 variable
625 * @see U8_PREV
626 * @stable ICU 2.4
627 */
628#define U8_PREV_UNSAFE(s, i, c) { \
629    (c)=(uint8_t)(s)[--(i)]; \
630    if(U8_IS_TRAIL(c)) { \
631        uint8_t __b, __count=1, __shift=6; \
632\
633        /* c is a trail byte */ \
634        (c)&=0x3f; \
635        for(;;) { \
636            __b=(uint8_t)(s)[--(i)]; \
637            if(__b>=0xc0) { \
638                U8_MASK_LEAD_BYTE(__b, __count); \
639                (c)|=(UChar32)__b<<__shift; \
640                break; \
641            } else { \
642                (c)|=(UChar32)(__b&0x3f)<<__shift; \
643                ++__count; \
644                __shift+=6; \
645            } \
646        } \
647    } \
648}
649
650/**
651 * Move the string offset from one code point boundary to the previous one
652 * and get the code point between them.
653 * (Pre-decrementing backward iteration.)
654 * "Safe" macro, checks for illegal sequences and for string boundaries.
655 *
656 * The input offset may be the same as the string length.
657 * If the offset is behind a multi-byte sequence, then the macro will read
658 * the whole sequence.
659 * If the offset is behind a lead byte, then that itself
660 * will be returned as the code point.
661 * If the offset is behind an illegal UTF-8 sequence, then c is set to a negative value.
662 *
663 * @param s const uint8_t * string
664 * @param start int32_t starting string offset (usually 0)
665 * @param i int32_t string offset, must be start<i
666 * @param c output UChar32 variable, set to <0 in case of an error
667 * @see U8_PREV_UNSAFE
668 * @stable ICU 2.4
669 */
670#define U8_PREV(s, start, i, c) { \
671    (c)=(uint8_t)(s)[--(i)]; \
672    if((c)>=0x80) { \
673        (c)=utf8_prevCharSafeBody((const uint8_t *)s, start, &(i), c, -1); \
674    } \
675}
676
677/**
678 * Move the string offset from one code point boundary to the previous one
679 * and get the code point between them.
680 * (Pre-decrementing backward iteration.)
681 * "Safe" macro, checks for illegal sequences and for string boundaries.
682 *
683 * The input offset may be the same as the string length.
684 * If the offset is behind a multi-byte sequence, then the macro will read
685 * the whole sequence.
686 * If the offset is behind a lead byte, then that itself
687 * will be returned as the code point.
688 * If the offset is behind an illegal UTF-8 sequence, then c is set to U+FFFD.
689 *
690 * This macro does not distinguish between a real U+FFFD in the text
691 * and U+FFFD returned for an ill-formed sequence.
692 * Use U8_PREV() if that distinction is important.
693 *
694 * @param s const uint8_t * string
695 * @param start int32_t starting string offset (usually 0)
696 * @param i int32_t string offset, must be start<i
697 * @param c output UChar32 variable, set to U+FFFD in case of an error
698 * @see U8_PREV
699 * @stable ICU 51
700 */
701#define U8_PREV_OR_FFFD(s, start, i, c) { \
702    (c)=(uint8_t)(s)[--(i)]; \
703    if((c)>=0x80) { \
704        (c)=utf8_prevCharSafeBody((const uint8_t *)s, start, &(i), c, -3); \
705    } \
706}
707
708/**
709 * Move the string offset from one code point boundary to the previous one.
710 * (Pre-decrementing backward iteration.)
711 * The input offset may be the same as the string length.
712 * "Unsafe" macro, assumes well-formed UTF-8.
713 *
714 * @param s const uint8_t * string
715 * @param i string offset
716 * @see U8_BACK_1
717 * @stable ICU 2.4
718 */
719#define U8_BACK_1_UNSAFE(s, i) { \
720    while(U8_IS_TRAIL((s)[--(i)])) {} \
721}
722
723/**
724 * Move the string offset from one code point boundary to the previous one.
725 * (Pre-decrementing backward iteration.)
726 * The input offset may be the same as the string length.
727 * "Safe" macro, checks for illegal sequences and for string boundaries.
728 *
729 * @param s const uint8_t * string
730 * @param start int32_t starting string offset (usually 0)
731 * @param i int32_t string offset, must be start<i
732 * @see U8_BACK_1_UNSAFE
733 * @stable ICU 2.4
734 */
735#define U8_BACK_1(s, start, i) { \
736    if(U8_IS_TRAIL((s)[--(i)])) { \
737        (i)=utf8_back1SafeBody(s, start, (i)); \
738    } \
739}
740
741/**
742 * Move the string offset from one code point boundary to the n-th one before it,
743 * i.e., move backward by n code points.
744 * (Pre-decrementing backward iteration.)
745 * The input offset may be the same as the string length.
746 * "Unsafe" macro, assumes well-formed UTF-8.
747 *
748 * @param s const uint8_t * string
749 * @param i string offset
750 * @param n number of code points to skip
751 * @see U8_BACK_N
752 * @stable ICU 2.4
753 */
754#define U8_BACK_N_UNSAFE(s, i, n) { \
755    int32_t __N=(n); \
756    while(__N>0) { \
757        U8_BACK_1_UNSAFE(s, i); \
758        --__N; \
759    } \
760}
761
762/**
763 * Move the string offset from one code point boundary to the n-th one before it,
764 * i.e., move backward by n code points.
765 * (Pre-decrementing backward iteration.)
766 * The input offset may be the same as the string length.
767 * "Safe" macro, checks for illegal sequences and for string boundaries.
768 *
769 * @param s const uint8_t * string
770 * @param start int32_t index of the start of the string
771 * @param i int32_t string offset, must be start<i
772 * @param n number of code points to skip
773 * @see U8_BACK_N_UNSAFE
774 * @stable ICU 2.4
775 */
776#define U8_BACK_N(s, start, i, n) { \
777    int32_t __N=(n); \
778    while(__N>0 && (i)>(start)) { \
779        U8_BACK_1(s, start, i); \
780        --__N; \
781    } \
782}
783
784/**
785 * Adjust a random-access offset to a code point boundary after a code point.
786 * If the offset is behind a partial multi-byte sequence,
787 * then the offset is incremented to behind the whole sequence.
788 * Otherwise, it is not modified.
789 * The input offset may be the same as the string length.
790 * "Unsafe" macro, assumes well-formed UTF-8.
791 *
792 * @param s const uint8_t * string
793 * @param i string offset
794 * @see U8_SET_CP_LIMIT
795 * @stable ICU 2.4
796 */
797#define U8_SET_CP_LIMIT_UNSAFE(s, i) { \
798    U8_BACK_1_UNSAFE(s, i); \
799    U8_FWD_1_UNSAFE(s, i); \
800}
801
802/**
803 * Adjust a random-access offset to a code point boundary after a code point.
804 * If the offset is behind a partial multi-byte sequence,
805 * then the offset is incremented to behind the whole sequence.
806 * Otherwise, it is not modified.
807 * The input offset may be the same as the string length.
808 * "Safe" macro, checks for illegal sequences and for string boundaries.
809 *
810 * The length can be negative for a NUL-terminated string.
811 *
812 * @param s const uint8_t * string
813 * @param start int32_t starting string offset (usually 0)
814 * @param i int32_t string offset, must be start<=i<=length
815 * @param length int32_t string length
816 * @see U8_SET_CP_LIMIT_UNSAFE
817 * @stable ICU 2.4
818 */
819#define U8_SET_CP_LIMIT(s, start, i, length) { \
820    if((start)<(i) && ((i)<(length) || (length)<0)) { \
821        U8_BACK_1(s, start, i); \
822        U8_FWD_1(s, i, length); \
823    } \
824}
825
826#endif
827