1/*
2******************************************************************************
3*
4*   Copyright (C) 1999-2006, 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
27/*
28 * This table could be replaced on many machines by
29 * a few lines of assembler code using an
30 * "index of first 0-bit from msb" instruction and
31 * one or two more integer instructions.
32 *
33 * For example, on an i386, do something like
34 * - MOV AL, leadByte
35 * - NOT AL         (8-bit, leave b15..b8==0..0, reverse only b7..b0)
36 * - MOV AH, 0
37 * - BSR BX, AX     (16-bit)
38 * - MOV AX, 6      (result)
39 * - JZ finish      (ZF==1 if leadByte==0xff)
40 * - SUB AX, BX (result)
41 * -finish:
42 * (BSR: Bit Scan Reverse, scans for a 1-bit, starting from the MSB)
43 *
44 * In Unicode, all UTF-8 byte sequences with more than 4 bytes are illegal;
45 * lead bytes above 0xf4 are illegal.
46 * We keep them in this table for skipping long ISO 10646-UTF-8 sequences.
47 */
48U_EXPORT const uint8_t
49utf8_countTrailBytes[256]={
50    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
51    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
52    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
53    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
54
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    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
59
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    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
64
65    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
66    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
67
68    2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
69    3, 3, 3, 3, 3,
70    3, 3, 3,    /* illegal in Unicode */
71    4, 4, 4, 4, /* illegal in Unicode */
72    5, 5,       /* illegal in Unicode */
73    0, 0        /* illegal bytes 0xfe and 0xff */
74};
75
76static const UChar32
77utf8_minLegal[4]={ 0, 0x80, 0x800, 0x10000 };
78
79static const UChar32
80utf8_errorValue[6]={
81    UTF8_ERROR_VALUE_1, UTF8_ERROR_VALUE_2, UTF_ERROR_VALUE, 0x10ffff,
82    0x3ffffff, 0x7fffffff
83};
84
85/*
86 * Handle the non-inline part of the U8_NEXT() macro and its obsolete sibling
87 * UTF8_NEXT_CHAR_SAFE().
88 *
89 * The "strict" parameter controls the error behavior:
90 * <0  "Safe" behavior of U8_NEXT(): All illegal byte sequences yield a negative
91 *     code point result.
92 *  0  Obsolete "safe" behavior of UTF8_NEXT_CHAR_SAFE(..., FALSE):
93 *     All illegal byte sequences yield a positive code point such that this
94 *     result code point would be encoded with the same number of bytes as
95 *     the illegal sequence.
96 * >0  Obsolete "strict" behavior of UTF8_NEXT_CHAR_SAFE(..., TRUE):
97 *     Same as the obsolete "safe" behavior, but non-characters are also treated
98 *     like illegal sequences.
99 *
100 * The special negative (<0) value -2 is used for lenient treatment of surrogate
101 * code points as legal. Some implementations use this for roundtripping of
102 * Unicode 16-bit strings that are not well-formed UTF-16, that is, they
103 * contain unpaired surrogates.
104 *
105 * Note that a UBool is the same as an int8_t.
106 */
107U_CAPI UChar32 U_EXPORT2
108utf8_nextCharSafeBody(const uint8_t *s, int32_t *pi, int32_t length, UChar32 c, UBool strict) {
109    int32_t i=*pi;
110    uint8_t count=UTF8_COUNT_TRAIL_BYTES(c);
111    if((i)+count<=(length)) {
112        uint8_t trail, illegal=0;
113
114        UTF8_MASK_LEAD_BYTE((c), count);
115        /* count==0 for illegally leading trail bytes and the illegal bytes 0xfe and 0xff */
116        switch(count) {
117        /* each branch falls through to the next one */
118        case 5:
119        case 4:
120            /* count>=4 is always illegal: no more than 3 trail bytes in Unicode's UTF-8 */
121            illegal=1;
122            break;
123        case 3:
124            trail=s[(i)++];
125            (c)=((c)<<6)|(trail&0x3f);
126            if(c<0x110) {
127                illegal|=(trail&0xc0)^0x80;
128            } else {
129                /* code point>0x10ffff, outside Unicode */
130                illegal=1;
131                break;
132            }
133        case 2:
134            trail=s[(i)++];
135            (c)=((c)<<6)|(trail&0x3f);
136            illegal|=(trail&0xc0)^0x80;
137        case 1:
138            trail=s[(i)++];
139            (c)=((c)<<6)|(trail&0x3f);
140            illegal|=(trail&0xc0)^0x80;
141            break;
142        case 0:
143            if(strict>=0) {
144                return UTF8_ERROR_VALUE_1;
145            } else {
146                return U_SENTINEL;
147            }
148        /* no default branch to optimize switch()  - all values are covered */
149        }
150
151        /*
152         * All the error handling should return a value
153         * that needs count bytes so that UTF8_GET_CHAR_SAFE() works right.
154         *
155         * Starting with Unicode 3.0.1, non-shortest forms are illegal.
156         * Starting with Unicode 3.2, surrogate code points must not be
157         * encoded in UTF-8, and there are no irregular sequences any more.
158         *
159         * U8_ macros (new in ICU 2.4) return negative values for error conditions.
160         */
161
162        /* correct sequence - all trail bytes have (b7..b6)==(10)? */
163        /* illegal is also set if count>=4 */
164        if(illegal || (c)<utf8_minLegal[count] || (UTF_IS_SURROGATE(c) && strict!=-2)) {
165            /* error handling */
166            uint8_t errorCount=count;
167            /* don't go beyond this sequence */
168            i=*pi;
169            while(count>0 && UTF8_IS_TRAIL(s[i])) {
170                ++(i);
171                --count;
172            }
173            if(strict>=0) {
174                c=utf8_errorValue[errorCount-count];
175            } else {
176                c=U_SENTINEL;
177            }
178        } else if((strict)>0 && UTF_IS_UNICODE_NONCHAR(c)) {
179            /* strict: forbid non-characters like U+fffe */
180            c=utf8_errorValue[count];
181        }
182    } else /* too few bytes left */ {
183        /* error handling */
184        int32_t i0=i;
185        /* don't just set (i)=(length) in case there is an illegal sequence */
186        while((i)<(length) && UTF8_IS_TRAIL(s[i])) {
187            ++(i);
188        }
189        if(strict>=0) {
190            c=utf8_errorValue[i-i0];
191        } else {
192            c=U_SENTINEL;
193        }
194    }
195    *pi=i;
196    return c;
197}
198
199U_CAPI int32_t U_EXPORT2
200utf8_appendCharSafeBody(uint8_t *s, int32_t i, int32_t length, UChar32 c, UBool *pIsError) {
201    if((uint32_t)(c)<=0x7ff) {
202        if((i)+1<(length)) {
203            (s)[(i)++]=(uint8_t)(((c)>>6)|0xc0);
204            (s)[(i)++]=(uint8_t)(((c)&0x3f)|0x80);
205            return i;
206        }
207    } else if((uint32_t)(c)<=0xffff) {
208        /* Starting with Unicode 3.2, surrogate code points must not be encoded in UTF-8. */
209        if((i)+2<(length) && !U_IS_SURROGATE(c)) {
210            (s)[(i)++]=(uint8_t)(((c)>>12)|0xe0);
211            (s)[(i)++]=(uint8_t)((((c)>>6)&0x3f)|0x80);
212            (s)[(i)++]=(uint8_t)(((c)&0x3f)|0x80);
213            return i;
214        }
215    } else if((uint32_t)(c)<=0x10ffff) {
216        if((i)+3<(length)) {
217            (s)[(i)++]=(uint8_t)(((c)>>18)|0xf0);
218            (s)[(i)++]=(uint8_t)((((c)>>12)&0x3f)|0x80);
219            (s)[(i)++]=(uint8_t)((((c)>>6)&0x3f)|0x80);
220            (s)[(i)++]=(uint8_t)(((c)&0x3f)|0x80);
221            return i;
222        }
223    }
224    /* c>0x10ffff or not enough space, write an error value */
225    if(pIsError!=NULL) {
226        *pIsError=TRUE;
227    } else {
228        length-=i;
229        if(length>0) {
230            int32_t offset;
231            if(length>3) {
232                length=3;
233            }
234            s+=i;
235            offset=0;
236            c=utf8_errorValue[length-1];
237            UTF8_APPEND_CHAR_UNSAFE(s, offset, c);
238            i=i+offset;
239        }
240    }
241    return i;
242}
243
244U_CAPI UChar32 U_EXPORT2
245utf8_prevCharSafeBody(const uint8_t *s, int32_t start, int32_t *pi, UChar32 c, UBool strict) {
246    int32_t i=*pi;
247    uint8_t b, count=1, shift=6;
248
249    /* extract value bits from the last trail byte */
250    c&=0x3f;
251
252    for(;;) {
253        if(i<=start) {
254            /* no lead byte at all */
255            if(strict>=0) {
256                return UTF8_ERROR_VALUE_1;
257            } else {
258                return U_SENTINEL;
259            }
260            /*break;*/
261        }
262
263        /* read another previous byte */
264        b=s[--i];
265        if((uint8_t)(b-0x80)<0x7e) { /* 0x80<=b<0xfe */
266            if(b&0x40) {
267                /* lead byte, this will always end the loop */
268                uint8_t shouldCount=UTF8_COUNT_TRAIL_BYTES(b);
269
270                if(count==shouldCount) {
271                    /* set the new position */
272                    *pi=i;
273                    UTF8_MASK_LEAD_BYTE(b, count);
274                    c|=(UChar32)b<<shift;
275                    if(count>=4 || c>0x10ffff || c<utf8_minLegal[count] || (UTF_IS_SURROGATE(c) && strict!=-2) || (strict>0 && UTF_IS_UNICODE_NONCHAR(c))) {
276                        /* illegal sequence or (strict and non-character) */
277                        if(count>=4) {
278                            count=3;
279                        }
280                        if(strict>=0) {
281                            c=utf8_errorValue[count];
282                        } else {
283                            c=U_SENTINEL;
284                        }
285                    } else {
286                        /* exit with correct c */
287                    }
288                } else {
289                    /* the lead byte does not match the number of trail bytes */
290                    /* only set the position to the lead byte if it would
291                       include the trail byte that we started with */
292                    if(count<shouldCount) {
293                        *pi=i;
294                        if(strict>=0) {
295                            c=utf8_errorValue[count];
296                        } else {
297                            c=U_SENTINEL;
298                        }
299                    } else {
300                        if(strict>=0) {
301                            c=UTF8_ERROR_VALUE_1;
302                        } else {
303                            c=U_SENTINEL;
304                        }
305                    }
306                }
307                break;
308            } else if(count<5) {
309                /* trail byte */
310                c|=(UChar32)(b&0x3f)<<shift;
311                ++count;
312                shift+=6;
313            } else {
314                /* more than 5 trail bytes is illegal */
315                if(strict>=0) {
316                    c=UTF8_ERROR_VALUE_1;
317                } else {
318                    c=U_SENTINEL;
319                }
320                break;
321            }
322        } else {
323            /* single-byte character precedes trailing bytes */
324            if(strict>=0) {
325                c=UTF8_ERROR_VALUE_1;
326            } else {
327                c=U_SENTINEL;
328            }
329            break;
330        }
331    }
332    return c;
333}
334
335U_CAPI int32_t U_EXPORT2
336utf8_back1SafeBody(const uint8_t *s, int32_t start, int32_t i) {
337    /* i had been decremented once before the function call */
338    int32_t I=i, Z;
339    uint8_t b;
340
341    /* read at most the 6 bytes s[Z] to s[i], inclusively */
342    if(I-5>start) {
343        Z=I-5;
344    } else {
345        Z=start;
346    }
347
348    /* return I if the sequence starting there is long enough to include i */
349    do {
350        b=s[I];
351        if((uint8_t)(b-0x80)>=0x7e) { /* not 0x80<=b<0xfe */
352            break;
353        } else if(b>=0xc0) {
354            if(UTF8_COUNT_TRAIL_BYTES(b)>=(i-I)) {
355                return I;
356            } else {
357                break;
358            }
359        }
360    } while(Z<=--I);
361
362    /* return i itself to be consistent with the FWD_1 macro */
363    return i;
364}
365