1 /*
2 ******************************************************************************
3 *
4 * Copyright (C) 1999-2012, International Business Machines
5 * Corporation and others. All Rights Reserved.
6 *
7 ******************************************************************************
8 * file name: utf_impl.c
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 * This file provides implementation functions for macros in the utfXX.h
17 * that would otherwise be too long as macros.
18 */
19
20 /* set import/export definitions */
21 #ifndef U_UTF8_IMPL
22 # define U_UTF8_IMPL
23 #endif
24
25 #include "unicode/utypes.h"
26 #include "unicode/utf.h"
27 #include "unicode/utf8.h"
28 #include "unicode/utf_old.h"
29 #include "uassert.h"
30
31 /*
32 * This table could be replaced on many machines by
33 * a few lines of assembler code using an
34 * "index of first 0-bit from msb" instruction and
35 * one or two more integer instructions.
36 *
37 * For example, on an i386, do something like
38 * - MOV AL, leadByte
39 * - NOT AL (8-bit, leave b15..b8==0..0, reverse only b7..b0)
40 * - MOV AH, 0
41 * - BSR BX, AX (16-bit)
42 * - MOV AX, 6 (result)
43 * - JZ finish (ZF==1 if leadByte==0xff)
44 * - SUB AX, BX (result)
45 * -finish:
46 * (BSR: Bit Scan Reverse, scans for a 1-bit, starting from the MSB)
47 *
48 * In Unicode, all UTF-8 byte sequences with more than 4 bytes are illegal;
49 * lead bytes above 0xf4 are illegal.
50 * We keep them in this table for skipping long ISO 10646-UTF-8 sequences.
51 */
52 U_EXPORT const uint8_t
53 utf8_countTrailBytes[256]={
54 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
55 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
56 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
57 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
58
59 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
60 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
61 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
62 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
63
64 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
65 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
66 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
67 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
68
69 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
70 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
71
72 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
73 3, 3, 3, 3, 3,
74 3, 3, 3, /* illegal in Unicode */
75 4, 4, 4, 4, /* illegal in Unicode */
76 5, 5, /* illegal in Unicode */
77 0, 0 /* illegal bytes 0xfe and 0xff */
78 };
79
80 static const UChar32
81 utf8_minLegal[4]={ 0, 0x80, 0x800, 0x10000 };
82
83 static const UChar32
84 utf8_errorValue[6]={
85 UTF8_ERROR_VALUE_1, UTF8_ERROR_VALUE_2, UTF_ERROR_VALUE, 0x10ffff,
86 0x3ffffff, 0x7fffffff
87 };
88
89 /*
90 * Handle the non-inline part of the U8_NEXT() macro and its obsolete sibling
91 * UTF8_NEXT_CHAR_SAFE().
92 *
93 * The "strict" parameter controls the error behavior:
94 * <0 "Safe" behavior of U8_NEXT(): All illegal byte sequences yield a negative
95 * code point result.
96 * 0 Obsolete "safe" behavior of UTF8_NEXT_CHAR_SAFE(..., FALSE):
97 * All illegal byte sequences yield a positive code point such that this
98 * result code point would be encoded with the same number of bytes as
99 * the illegal sequence.
100 * >0 Obsolete "strict" behavior of UTF8_NEXT_CHAR_SAFE(..., TRUE):
101 * Same as the obsolete "safe" behavior, but non-characters are also treated
102 * like illegal sequences.
103 *
104 * The special negative (<0) value -2 is used for lenient treatment of surrogate
105 * code points as legal. Some implementations use this for roundtripping of
106 * Unicode 16-bit strings that are not well-formed UTF-16, that is, they
107 * contain unpaired surrogates.
108 *
109 * Note that a UBool is the same as an int8_t.
110 */
111 U_CAPI UChar32 U_EXPORT2
utf8_nextCharSafeBody(const uint8_t * s,int32_t * pi,int32_t length,UChar32 c,UBool strict)112 utf8_nextCharSafeBody(const uint8_t *s, int32_t *pi, int32_t length, UChar32 c, UBool strict) {
113 int32_t i=*pi;
114 uint8_t count=U8_COUNT_TRAIL_BYTES(c);
115 U_ASSERT(count <= 5); /* U8_COUNT_TRAIL_BYTES returns value 0...5 */
116 if((i)+count<=(length)) {
117 uint8_t trail, illegal=0;
118
119 U8_MASK_LEAD_BYTE((c), count);
120 /* count==0 for illegally leading trail bytes and the illegal bytes 0xfe and 0xff */
121 switch(count) {
122 /* each branch falls through to the next one */
123 case 5:
124 case 4:
125 /* count>=4 is always illegal: no more than 3 trail bytes in Unicode's UTF-8 */
126 illegal=1;
127 break;
128 case 3:
129 trail=s[(i)++];
130 (c)=((c)<<6)|(trail&0x3f);
131 if(c<0x110) {
132 illegal|=(trail&0xc0)^0x80;
133 } else {
134 /* code point>0x10ffff, outside Unicode */
135 illegal=1;
136 break;
137 }
138 case 2:
139 trail=s[(i)++];
140 (c)=((c)<<6)|(trail&0x3f);
141 illegal|=(trail&0xc0)^0x80;
142 case 1:
143 trail=s[(i)++];
144 (c)=((c)<<6)|(trail&0x3f);
145 illegal|=(trail&0xc0)^0x80;
146 break;
147 case 0:
148 if(strict>=0) {
149 return UTF8_ERROR_VALUE_1;
150 } else {
151 return U_SENTINEL;
152 }
153 /* no default branch to optimize switch() - all values are covered */
154 }
155
156 /*
157 * All the error handling should return a value
158 * that needs count bytes so that UTF8_GET_CHAR_SAFE() works right.
159 *
160 * Starting with Unicode 3.0.1, non-shortest forms are illegal.
161 * Starting with Unicode 3.2, surrogate code points must not be
162 * encoded in UTF-8, and there are no irregular sequences any more.
163 *
164 * U8_ macros (new in ICU 2.4) return negative values for error conditions.
165 */
166
167 /* correct sequence - all trail bytes have (b7..b6)==(10)? */
168 /* illegal is also set if count>=4 */
169 if(illegal || (c)<utf8_minLegal[count] || (U_IS_SURROGATE(c) && strict!=-2)) {
170 /* error handling */
171 uint8_t errorCount=count;
172 /* don't go beyond this sequence */
173 i=*pi;
174 while(count>0 && U8_IS_TRAIL(s[i])) {
175 ++(i);
176 --count;
177 }
178 if(strict>=0) {
179 c=utf8_errorValue[errorCount-count];
180 } else {
181 c=U_SENTINEL;
182 }
183 } else if((strict)>0 && U_IS_UNICODE_NONCHAR(c)) {
184 /* strict: forbid non-characters like U+fffe */
185 c=utf8_errorValue[count];
186 }
187 } else /* too few bytes left */ {
188 /* error handling */
189 int32_t i0=i;
190 /* don't just set (i)=(length) in case there is an illegal sequence */
191 while((i)<(length) && U8_IS_TRAIL(s[i])) {
192 ++(i);
193 }
194 if(strict>=0) {
195 c=utf8_errorValue[i-i0];
196 } else {
197 c=U_SENTINEL;
198 }
199 }
200 *pi=i;
201 return c;
202 }
203
204 U_CAPI int32_t U_EXPORT2
utf8_appendCharSafeBody(uint8_t * s,int32_t i,int32_t length,UChar32 c,UBool * pIsError)205 utf8_appendCharSafeBody(uint8_t *s, int32_t i, int32_t length, UChar32 c, UBool *pIsError) {
206 if((uint32_t)(c)<=0x7ff) {
207 if((i)+1<(length)) {
208 (s)[(i)++]=(uint8_t)(((c)>>6)|0xc0);
209 (s)[(i)++]=(uint8_t)(((c)&0x3f)|0x80);
210 return i;
211 }
212 } else if((uint32_t)(c)<=0xffff) {
213 /* Starting with Unicode 3.2, surrogate code points must not be encoded in UTF-8. */
214 if((i)+2<(length) && !U_IS_SURROGATE(c)) {
215 (s)[(i)++]=(uint8_t)(((c)>>12)|0xe0);
216 (s)[(i)++]=(uint8_t)((((c)>>6)&0x3f)|0x80);
217 (s)[(i)++]=(uint8_t)(((c)&0x3f)|0x80);
218 return i;
219 }
220 } else if((uint32_t)(c)<=0x10ffff) {
221 if((i)+3<(length)) {
222 (s)[(i)++]=(uint8_t)(((c)>>18)|0xf0);
223 (s)[(i)++]=(uint8_t)((((c)>>12)&0x3f)|0x80);
224 (s)[(i)++]=(uint8_t)((((c)>>6)&0x3f)|0x80);
225 (s)[(i)++]=(uint8_t)(((c)&0x3f)|0x80);
226 return i;
227 }
228 }
229 /* c>0x10ffff or not enough space, write an error value */
230 if(pIsError!=NULL) {
231 *pIsError=TRUE;
232 } else {
233 length-=i;
234 if(length>0) {
235 int32_t offset;
236 if(length>3) {
237 length=3;
238 }
239 s+=i;
240 offset=0;
241 c=utf8_errorValue[length-1];
242 UTF8_APPEND_CHAR_UNSAFE(s, offset, c);
243 i=i+offset;
244 }
245 }
246 return i;
247 }
248
249 U_CAPI UChar32 U_EXPORT2
utf8_prevCharSafeBody(const uint8_t * s,int32_t start,int32_t * pi,UChar32 c,UBool strict)250 utf8_prevCharSafeBody(const uint8_t *s, int32_t start, int32_t *pi, UChar32 c, UBool strict) {
251 int32_t i=*pi;
252 uint8_t b, count=1, shift=6;
253
254 /* extract value bits from the last trail byte */
255 c&=0x3f;
256
257 for(;;) {
258 if(i<=start) {
259 /* no lead byte at all */
260 if(strict>=0) {
261 return UTF8_ERROR_VALUE_1;
262 } else {
263 return U_SENTINEL;
264 }
265 /*break;*/
266 }
267
268 /* read another previous byte */
269 b=s[--i];
270 if((uint8_t)(b-0x80)<0x7e) { /* 0x80<=b<0xfe */
271 if(b&0x40) {
272 /* lead byte, this will always end the loop */
273 uint8_t shouldCount=U8_COUNT_TRAIL_BYTES(b);
274
275 if(count==shouldCount) {
276 /* set the new position */
277 *pi=i;
278 U8_MASK_LEAD_BYTE(b, count);
279 c|=(UChar32)b<<shift;
280 if(count>=4 || c>0x10ffff || c<utf8_minLegal[count] || (U_IS_SURROGATE(c) && strict!=-2) || (strict>0 && U_IS_UNICODE_NONCHAR(c))) {
281 /* illegal sequence or (strict and non-character) */
282 if(count>=4) {
283 count=3;
284 }
285 if(strict>=0) {
286 c=utf8_errorValue[count];
287 } else {
288 c=U_SENTINEL;
289 }
290 } else {
291 /* exit with correct c */
292 }
293 } else {
294 /* the lead byte does not match the number of trail bytes */
295 /* only set the position to the lead byte if it would
296 include the trail byte that we started with */
297 if(count<shouldCount) {
298 *pi=i;
299 if(strict>=0) {
300 c=utf8_errorValue[count];
301 } else {
302 c=U_SENTINEL;
303 }
304 } else {
305 if(strict>=0) {
306 c=UTF8_ERROR_VALUE_1;
307 } else {
308 c=U_SENTINEL;
309 }
310 }
311 }
312 break;
313 } else if(count<5) {
314 /* trail byte */
315 c|=(UChar32)(b&0x3f)<<shift;
316 ++count;
317 shift+=6;
318 } else {
319 /* more than 5 trail bytes is illegal */
320 if(strict>=0) {
321 c=UTF8_ERROR_VALUE_1;
322 } else {
323 c=U_SENTINEL;
324 }
325 break;
326 }
327 } else {
328 /* single-byte character precedes trailing bytes */
329 if(strict>=0) {
330 c=UTF8_ERROR_VALUE_1;
331 } else {
332 c=U_SENTINEL;
333 }
334 break;
335 }
336 }
337 return c;
338 }
339
340 U_CAPI int32_t U_EXPORT2
utf8_back1SafeBody(const uint8_t * s,int32_t start,int32_t i)341 utf8_back1SafeBody(const uint8_t *s, int32_t start, int32_t i) {
342 /* i had been decremented once before the function call */
343 int32_t I=i, Z;
344 uint8_t b;
345
346 /* read at most the 6 bytes s[Z] to s[i], inclusively */
347 if(I-5>start) {
348 Z=I-5;
349 } else {
350 Z=start;
351 }
352
353 /* return I if the sequence starting there is long enough to include i */
354 do {
355 b=s[I];
356 if((uint8_t)(b-0x80)>=0x7e) { /* not 0x80<=b<0xfe */
357 break;
358 } else if(b>=0xc0) {
359 if(U8_COUNT_TRAIL_BYTES(b)>=(i-I)) {
360 return I;
361 } else {
362 break;
363 }
364 }
365 } while(Z<=--I);
366
367 /* return i itself to be consistent with the FWD_1 macro */
368 return i;
369 }
370