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) 1999-2012, International Business Machines
7 * Corporation and others. All Rights Reserved.
8 *
9 ******************************************************************************
10 * file name: utf_impl.c
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 * This file provides implementation functions for macros in the utfXX.h
19 * that would otherwise be too long as macros.
20 */
21
22 /* set import/export definitions */
23 #ifndef U_UTF8_IMPL
24 # define U_UTF8_IMPL
25 #endif
26
27 #include "unicode/utypes.h"
28 #include "unicode/utf.h"
29 #include "unicode/utf8.h"
30 #include "unicode/utf_old.h"
31 #include "uassert.h"
32
33 /*
34 * This table could be replaced on many machines by
35 * a few lines of assembler code using an
36 * "index of first 0-bit from msb" instruction and
37 * one or two more integer instructions.
38 *
39 * For example, on an i386, do something like
40 * - MOV AL, leadByte
41 * - NOT AL (8-bit, leave b15..b8==0..0, reverse only b7..b0)
42 * - MOV AH, 0
43 * - BSR BX, AX (16-bit)
44 * - MOV AX, 6 (result)
45 * - JZ finish (ZF==1 if leadByte==0xff)
46 * - SUB AX, BX (result)
47 * -finish:
48 * (BSR: Bit Scan Reverse, scans for a 1-bit, starting from the MSB)
49 *
50 * In Unicode, all UTF-8 byte sequences with more than 4 bytes are illegal;
51 * lead bytes above 0xf4 are illegal.
52 * We keep them in this table for skipping long ISO 10646-UTF-8 sequences.
53 */
54 U_EXPORT const uint8_t
55 utf8_countTrailBytes[256]={
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 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
59 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
60
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 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
64 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
65
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 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
69 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
70
71 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
72 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
73
74 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
75 3, 3, 3, 3, 3,
76 3, 3, 3, /* illegal in Unicode */
77 4, 4, 4, 4, /* illegal in Unicode */
78 5, 5, /* illegal in Unicode */
79 0, 0 /* illegal bytes 0xfe and 0xff */
80 };
81
82 static const UChar32
83 utf8_minLegal[4]={ 0, 0x80, 0x800, 0x10000 };
84
85 static const UChar32
86 utf8_errorValue[6]={
87 UTF8_ERROR_VALUE_1, UTF8_ERROR_VALUE_2, UTF_ERROR_VALUE, 0x10ffff,
88 0x3ffffff, 0x7fffffff
89 };
90
91 static UChar32
errorValue(int32_t count,int8_t strict)92 errorValue(int32_t count, int8_t strict) {
93 if(strict>=0) {
94 return utf8_errorValue[count];
95 } else if(strict==-3) {
96 return 0xfffd;
97 } else {
98 return U_SENTINEL;
99 }
100 }
101
102 /*
103 * Handle the non-inline part of the U8_NEXT() and U8_NEXT_FFFD() macros
104 * and their obsolete sibling UTF8_NEXT_CHAR_SAFE().
105 *
106 * U8_NEXT() supports NUL-terminated strings indicated via length<0.
107 *
108 * The "strict" parameter controls the error behavior:
109 * <0 "Safe" behavior of U8_NEXT():
110 * -1: All illegal byte sequences yield U_SENTINEL=-1.
111 * -2: Same as -1, except for lenient treatment of surrogate code points as legal.
112 * Some implementations use this for roundtripping of
113 * Unicode 16-bit strings that are not well-formed UTF-16, that is, they
114 * contain unpaired surrogates.
115 * -3: All illegal byte sequences yield U+FFFD.
116 * 0 Obsolete "safe" behavior of UTF8_NEXT_CHAR_SAFE(..., FALSE):
117 * All illegal byte sequences yield a positive code point such that this
118 * result code point would be encoded with the same number of bytes as
119 * the illegal sequence.
120 * >0 Obsolete "strict" behavior of UTF8_NEXT_CHAR_SAFE(..., TRUE):
121 * Same as the obsolete "safe" behavior, but non-characters are also treated
122 * like illegal sequences.
123 *
124 * Note that a UBool is the same as an int8_t.
125 */
126 U_CAPI UChar32 U_EXPORT2
utf8_nextCharSafeBody(const uint8_t * s,int32_t * pi,int32_t length,UChar32 c,UBool strict)127 utf8_nextCharSafeBody(const uint8_t *s, int32_t *pi, int32_t length, UChar32 c, UBool strict) {
128 int32_t i=*pi;
129 uint8_t count=U8_COUNT_TRAIL_BYTES(c);
130 U_ASSERT(count <= 5); /* U8_COUNT_TRAIL_BYTES returns value 0...5 */
131 if(i+count<=length || length<0) {
132 uint8_t trail;
133
134 U8_MASK_LEAD_BYTE(c, count);
135 /* support NUL-terminated strings: do not read beyond the first non-trail byte */
136 switch(count) {
137 /* each branch falls through to the next one */
138 case 0:
139 /* count==0 for illegally leading trail bytes and the illegal bytes 0xfe and 0xff */
140 case 5:
141 case 4:
142 /* count>=4 is always illegal: no more than 3 trail bytes in Unicode's UTF-8 */
143 break;
144 case 3:
145 trail=s[i++]-0x80;
146 c=(c<<6)|trail;
147 /* c>=0x110 would result in code point>0x10ffff, outside Unicode */
148 if(c>=0x110 || trail>0x3f) { break; }
149 case 2:
150 trail=s[i++]-0x80;
151 c=(c<<6)|trail;
152 /*
153 * test for a surrogate d800..dfff unless we are lenient:
154 * before the last (c<<6), a surrogate is c=360..37f
155 */
156 if(((c&0xffe0)==0x360 && strict!=-2) || trail>0x3f) { break; }
157 case 1:
158 trail=s[i++]-0x80;
159 c=(c<<6)|trail;
160 if(trail>0x3f) { break; }
161 /* correct sequence - all trail bytes have (b7..b6)==(10) */
162 if(c>=utf8_minLegal[count] &&
163 /* strict: forbid non-characters like U+fffe */
164 (strict<=0 || !U_IS_UNICODE_NONCHAR(c))) {
165 *pi=i;
166 return c;
167 }
168 /* no default branch to optimize switch() - all values are covered */
169 }
170 } else {
171 /* too few bytes left */
172 count=length-i;
173 }
174
175 /* error handling */
176 i=*pi;
177 while(count>0 && U8_IS_TRAIL(s[i])) {
178 ++i;
179 --count;
180 }
181 c=errorValue(i-*pi, strict);
182 *pi=i;
183 return c;
184 }
185
186 U_CAPI int32_t U_EXPORT2
utf8_appendCharSafeBody(uint8_t * s,int32_t i,int32_t length,UChar32 c,UBool * pIsError)187 utf8_appendCharSafeBody(uint8_t *s, int32_t i, int32_t length, UChar32 c, UBool *pIsError) {
188 if((uint32_t)(c)<=0x7ff) {
189 if((i)+1<(length)) {
190 (s)[(i)++]=(uint8_t)(((c)>>6)|0xc0);
191 (s)[(i)++]=(uint8_t)(((c)&0x3f)|0x80);
192 return i;
193 }
194 } else if((uint32_t)(c)<=0xffff) {
195 /* Starting with Unicode 3.2, surrogate code points must not be encoded in UTF-8. */
196 if((i)+2<(length) && !U_IS_SURROGATE(c)) {
197 (s)[(i)++]=(uint8_t)(((c)>>12)|0xe0);
198 (s)[(i)++]=(uint8_t)((((c)>>6)&0x3f)|0x80);
199 (s)[(i)++]=(uint8_t)(((c)&0x3f)|0x80);
200 return i;
201 }
202 } else if((uint32_t)(c)<=0x10ffff) {
203 if((i)+3<(length)) {
204 (s)[(i)++]=(uint8_t)(((c)>>18)|0xf0);
205 (s)[(i)++]=(uint8_t)((((c)>>12)&0x3f)|0x80);
206 (s)[(i)++]=(uint8_t)((((c)>>6)&0x3f)|0x80);
207 (s)[(i)++]=(uint8_t)(((c)&0x3f)|0x80);
208 return i;
209 }
210 }
211 /* c>0x10ffff or not enough space, write an error value */
212 if(pIsError!=NULL) {
213 *pIsError=TRUE;
214 } else {
215 length-=i;
216 if(length>0) {
217 int32_t offset;
218 if(length>3) {
219 length=3;
220 }
221 s+=i;
222 offset=0;
223 c=utf8_errorValue[length-1];
224 UTF8_APPEND_CHAR_UNSAFE(s, offset, c);
225 i=i+offset;
226 }
227 }
228 return i;
229 }
230
231 U_CAPI UChar32 U_EXPORT2
utf8_prevCharSafeBody(const uint8_t * s,int32_t start,int32_t * pi,UChar32 c,UBool strict)232 utf8_prevCharSafeBody(const uint8_t *s, int32_t start, int32_t *pi, UChar32 c, UBool strict) {
233 int32_t i=*pi;
234 uint8_t b, count=1, shift=6;
235
236 if(!U8_IS_TRAIL(c)) { return errorValue(0, strict); }
237
238 /* extract value bits from the last trail byte */
239 c&=0x3f;
240
241 for(;;) {
242 if(i<=start) {
243 /* no lead byte at all */
244 return errorValue(0, strict);
245 }
246
247 /* read another previous byte */
248 b=s[--i];
249 if((uint8_t)(b-0x80)<0x7e) { /* 0x80<=b<0xfe */
250 if(b&0x40) {
251 /* lead byte, this will always end the loop */
252 uint8_t shouldCount=U8_COUNT_TRAIL_BYTES(b);
253
254 if(count==shouldCount) {
255 /* set the new position */
256 *pi=i;
257 U8_MASK_LEAD_BYTE(b, count);
258 c|=(UChar32)b<<shift;
259 if(count>=4 || c>0x10ffff || c<utf8_minLegal[count] || (U_IS_SURROGATE(c) && strict!=-2) || (strict>0 && U_IS_UNICODE_NONCHAR(c))) {
260 /* illegal sequence or (strict and non-character) */
261 if(count>=4) {
262 count=3;
263 }
264 c=errorValue(count, strict);
265 } else {
266 /* exit with correct c */
267 }
268 } else {
269 /* the lead byte does not match the number of trail bytes */
270 /* only set the position to the lead byte if it would
271 include the trail byte that we started with */
272 if(count<shouldCount) {
273 *pi=i;
274 c=errorValue(count, strict);
275 } else {
276 c=errorValue(0, strict);
277 }
278 }
279 break;
280 } else if(count<5) {
281 /* trail byte */
282 c|=(UChar32)(b&0x3f)<<shift;
283 ++count;
284 shift+=6;
285 } else {
286 /* more than 5 trail bytes is illegal */
287 c=errorValue(0, strict);
288 break;
289 }
290 } else {
291 /* single-byte character precedes trailing bytes */
292 c=errorValue(0, strict);
293 break;
294 }
295 }
296 return c;
297 }
298
299 U_CAPI int32_t U_EXPORT2
utf8_back1SafeBody(const uint8_t * s,int32_t start,int32_t i)300 utf8_back1SafeBody(const uint8_t *s, int32_t start, int32_t i) {
301 /* i had been decremented once before the function call */
302 int32_t I=i, Z;
303 uint8_t b;
304
305 /* read at most the 6 bytes s[Z] to s[i], inclusively */
306 if(I-5>start) {
307 Z=I-5;
308 } else {
309 Z=start;
310 }
311
312 /* return I if the sequence starting there is long enough to include i */
313 do {
314 b=s[I];
315 if((uint8_t)(b-0x80)>=0x7e) { /* not 0x80<=b<0xfe */
316 break;
317 } else if(b>=0xc0) {
318 if(U8_COUNT_TRAIL_BYTES(b)>=(i-I)) {
319 return I;
320 } else {
321 break;
322 }
323 }
324 } while(Z<=--I);
325
326 /* return i itself to be consistent with the FWD_1 macro */
327 return i;
328 }
329