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 static UChar32
errorValue(int32_t count,int8_t strict)90 errorValue(int32_t count, int8_t strict) {
91 if(strict>=0) {
92 return utf8_errorValue[count];
93 } else if(strict==-3) {
94 return 0xfffd;
95 } else {
96 return U_SENTINEL;
97 }
98 }
99
100 /*
101 * Handle the non-inline part of the U8_NEXT() and U8_NEXT_FFFD() macros
102 * and their obsolete sibling UTF8_NEXT_CHAR_SAFE().
103 *
104 * U8_NEXT() supports NUL-terminated strings indicated via length<0.
105 *
106 * The "strict" parameter controls the error behavior:
107 * <0 "Safe" behavior of U8_NEXT():
108 * -1: All illegal byte sequences yield U_SENTINEL=-1.
109 * -2: Same as -1, except for lenient treatment of surrogate code points as legal.
110 * Some implementations use this for roundtripping of
111 * Unicode 16-bit strings that are not well-formed UTF-16, that is, they
112 * contain unpaired surrogates.
113 * -3: All illegal byte sequences yield U+FFFD.
114 * 0 Obsolete "safe" behavior of UTF8_NEXT_CHAR_SAFE(..., FALSE):
115 * All illegal byte sequences yield a positive code point such that this
116 * result code point would be encoded with the same number of bytes as
117 * the illegal sequence.
118 * >0 Obsolete "strict" behavior of UTF8_NEXT_CHAR_SAFE(..., TRUE):
119 * Same as the obsolete "safe" behavior, but non-characters are also treated
120 * like illegal sequences.
121 *
122 * Note that a UBool is the same as an int8_t.
123 */
124 U_CAPI UChar32 U_EXPORT2
utf8_nextCharSafeBody(const uint8_t * s,int32_t * pi,int32_t length,UChar32 c,UBool strict)125 utf8_nextCharSafeBody(const uint8_t *s, int32_t *pi, int32_t length, UChar32 c, UBool strict) {
126 int32_t i=*pi;
127 uint8_t count=U8_COUNT_TRAIL_BYTES(c);
128 U_ASSERT(count <= 5); /* U8_COUNT_TRAIL_BYTES returns value 0...5 */
129 if(i+count<=length || length<0) {
130 uint8_t trail;
131
132 U8_MASK_LEAD_BYTE(c, count);
133 /* support NUL-terminated strings: do not read beyond the first non-trail byte */
134 switch(count) {
135 /* each branch falls through to the next one */
136 case 0:
137 /* count==0 for illegally leading trail bytes and the illegal bytes 0xfe and 0xff */
138 case 5:
139 case 4:
140 /* count>=4 is always illegal: no more than 3 trail bytes in Unicode's UTF-8 */
141 break;
142 case 3:
143 trail=s[i++]-0x80;
144 c=(c<<6)|trail;
145 /* c>=0x110 would result in code point>0x10ffff, outside Unicode */
146 if(c>=0x110 || trail>0x3f) { break; }
147 case 2:
148 trail=s[i++]-0x80;
149 c=(c<<6)|trail;
150 /*
151 * test for a surrogate d800..dfff unless we are lenient:
152 * before the last (c<<6), a surrogate is c=360..37f
153 */
154 if(((c&0xffe0)==0x360 && strict!=-2) || trail>0x3f) { break; }
155 case 1:
156 trail=s[i++]-0x80;
157 c=(c<<6)|trail;
158 if(trail>0x3f) { break; }
159 /* correct sequence - all trail bytes have (b7..b6)==(10) */
160 if(c>=utf8_minLegal[count] &&
161 /* strict: forbid non-characters like U+fffe */
162 (strict<=0 || !U_IS_UNICODE_NONCHAR(c))) {
163 *pi=i;
164 return c;
165 }
166 /* no default branch to optimize switch() - all values are covered */
167 }
168 } else {
169 /* too few bytes left */
170 count=length-i;
171 }
172
173 /* error handling */
174 i=*pi;
175 while(count>0 && U8_IS_TRAIL(s[i])) {
176 ++i;
177 --count;
178 }
179 c=errorValue(i-*pi, strict);
180 *pi=i;
181 return c;
182 }
183
184 U_CAPI int32_t U_EXPORT2
utf8_appendCharSafeBody(uint8_t * s,int32_t i,int32_t length,UChar32 c,UBool * pIsError)185 utf8_appendCharSafeBody(uint8_t *s, int32_t i, int32_t length, UChar32 c, UBool *pIsError) {
186 if((uint32_t)(c)<=0x7ff) {
187 if((i)+1<(length)) {
188 (s)[(i)++]=(uint8_t)(((c)>>6)|0xc0);
189 (s)[(i)++]=(uint8_t)(((c)&0x3f)|0x80);
190 return i;
191 }
192 } else if((uint32_t)(c)<=0xffff) {
193 /* Starting with Unicode 3.2, surrogate code points must not be encoded in UTF-8. */
194 if((i)+2<(length) && !U_IS_SURROGATE(c)) {
195 (s)[(i)++]=(uint8_t)(((c)>>12)|0xe0);
196 (s)[(i)++]=(uint8_t)((((c)>>6)&0x3f)|0x80);
197 (s)[(i)++]=(uint8_t)(((c)&0x3f)|0x80);
198 return i;
199 }
200 } else if((uint32_t)(c)<=0x10ffff) {
201 if((i)+3<(length)) {
202 (s)[(i)++]=(uint8_t)(((c)>>18)|0xf0);
203 (s)[(i)++]=(uint8_t)((((c)>>12)&0x3f)|0x80);
204 (s)[(i)++]=(uint8_t)((((c)>>6)&0x3f)|0x80);
205 (s)[(i)++]=(uint8_t)(((c)&0x3f)|0x80);
206 return i;
207 }
208 }
209 /* c>0x10ffff or not enough space, write an error value */
210 if(pIsError!=NULL) {
211 *pIsError=TRUE;
212 } else {
213 length-=i;
214 if(length>0) {
215 int32_t offset;
216 if(length>3) {
217 length=3;
218 }
219 s+=i;
220 offset=0;
221 c=utf8_errorValue[length-1];
222 UTF8_APPEND_CHAR_UNSAFE(s, offset, c);
223 i=i+offset;
224 }
225 }
226 return i;
227 }
228
229 U_CAPI UChar32 U_EXPORT2
utf8_prevCharSafeBody(const uint8_t * s,int32_t start,int32_t * pi,UChar32 c,UBool strict)230 utf8_prevCharSafeBody(const uint8_t *s, int32_t start, int32_t *pi, UChar32 c, UBool strict) {
231 int32_t i=*pi;
232 uint8_t b, count=1, shift=6;
233
234 if(!U8_IS_TRAIL(c)) { return errorValue(0, strict); }
235
236 /* extract value bits from the last trail byte */
237 c&=0x3f;
238
239 for(;;) {
240 if(i<=start) {
241 /* no lead byte at all */
242 return errorValue(0, strict);
243 }
244
245 /* read another previous byte */
246 b=s[--i];
247 if((uint8_t)(b-0x80)<0x7e) { /* 0x80<=b<0xfe */
248 if(b&0x40) {
249 /* lead byte, this will always end the loop */
250 uint8_t shouldCount=U8_COUNT_TRAIL_BYTES(b);
251
252 if(count==shouldCount) {
253 /* set the new position */
254 *pi=i;
255 U8_MASK_LEAD_BYTE(b, count);
256 c|=(UChar32)b<<shift;
257 if(count>=4 || c>0x10ffff || c<utf8_minLegal[count] || (U_IS_SURROGATE(c) && strict!=-2) || (strict>0 && U_IS_UNICODE_NONCHAR(c))) {
258 /* illegal sequence or (strict and non-character) */
259 if(count>=4) {
260 count=3;
261 }
262 c=errorValue(count, strict);
263 } else {
264 /* exit with correct c */
265 }
266 } else {
267 /* the lead byte does not match the number of trail bytes */
268 /* only set the position to the lead byte if it would
269 include the trail byte that we started with */
270 if(count<shouldCount) {
271 *pi=i;
272 c=errorValue(count, strict);
273 } else {
274 c=errorValue(0, strict);
275 }
276 }
277 break;
278 } else if(count<5) {
279 /* trail byte */
280 c|=(UChar32)(b&0x3f)<<shift;
281 ++count;
282 shift+=6;
283 } else {
284 /* more than 5 trail bytes is illegal */
285 c=errorValue(0, strict);
286 break;
287 }
288 } else {
289 /* single-byte character precedes trailing bytes */
290 c=errorValue(0, strict);
291 break;
292 }
293 }
294 return c;
295 }
296
297 U_CAPI int32_t U_EXPORT2
utf8_back1SafeBody(const uint8_t * s,int32_t start,int32_t i)298 utf8_back1SafeBody(const uint8_t *s, int32_t start, int32_t i) {
299 /* i had been decremented once before the function call */
300 int32_t I=i, Z;
301 uint8_t b;
302
303 /* read at most the 6 bytes s[Z] to s[i], inclusively */
304 if(I-5>start) {
305 Z=I-5;
306 } else {
307 Z=start;
308 }
309
310 /* return I if the sequence starting there is long enough to include i */
311 do {
312 b=s[I];
313 if((uint8_t)(b-0x80)>=0x7e) { /* not 0x80<=b<0xfe */
314 break;
315 } else if(b>=0xc0) {
316 if(U8_COUNT_TRAIL_BYTES(b)>=(i-I)) {
317 return I;
318 } else {
319 break;
320 }
321 }
322 } while(Z<=--I);
323
324 /* return i itself to be consistent with the FWD_1 macro */
325 return i;
326 }
327