[apple/icu.git] / icuSources / common / utf_impl.c

/*
******************************************************************************
*
*   Copyright (C) 1999-2006, International Business Machines
*   Corporation and others.  All Rights Reserved.
*
******************************************************************************
*   file name:  utf_impl.c
*   encoding:   US-ASCII
*   tab size:   8 (not used)
*   indentation:4
*
*   created on: 1999sep13
*   created by: Markus W. Scherer
*
*   This file provides implementation functions for macros in the utfXX.h
*   that would otherwise be too long as macros.
*/

/* set import/export definitions */
#ifndef U_UTF8_IMPL
#   define U_UTF8_IMPL
#endif

#include "unicode/utypes.h"

/*
 * This table could be replaced on many machines by
 * a few lines of assembler code using an
 * "index of first 0-bit from msb" instruction and
 * one or two more integer instructions.
 *
 * For example, on an i386, do something like
 * - MOV AL, leadByte
 * - NOT AL         (8-bit, leave b15..b8==0..0, reverse only b7..b0)
 * - MOV AH, 0
 * - BSR BX, AX     (16-bit)
 * - MOV AX, 6      (result)
 * - JZ finish      (ZF==1 if leadByte==0xff)
 * - SUB AX, BX (result)
 * -finish:
 * (BSR: Bit Scan Reverse, scans for a 1-bit, starting from the MSB)
 *
 * In Unicode, all UTF-8 byte sequences with more than 4 bytes are illegal;
 * lead bytes above 0xf4 are illegal.
 * We keep them in this table for skipping long ISO 10646-UTF-8 sequences.
 */
U_EXPORT const uint8_t 
utf8_countTrailBytes[256]={
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,

    2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
    3, 3, 3, 3, 3,
    3, 3, 3,    /* illegal in Unicode */
    4, 4, 4, 4, /* illegal in Unicode */
    5, 5,       /* illegal in Unicode */
    0, 0        /* illegal bytes 0xfe and 0xff */
};

static const UChar32
utf8_minLegal[4]={ 0, 0x80, 0x800, 0x10000 };

static const UChar32
utf8_errorValue[6]={
    UTF8_ERROR_VALUE_1, UTF8_ERROR_VALUE_2, UTF_ERROR_VALUE, 0x10ffff,
    0x3ffffff, 0x7fffffff
};

/*
 * Handle the non-inline part of the U8_NEXT() macro and its obsolete sibling
 * UTF8_NEXT_CHAR_SAFE().
 *
 * The "strict" parameter controls the error behavior:
 * <0  "Safe" behavior of U8_NEXT(): All illegal byte sequences yield a negative
 *     code point result.
 *  0  Obsolete "safe" behavior of UTF8_NEXT_CHAR_SAFE(..., FALSE):
 *     All illegal byte sequences yield a positive code point such that this
 *     result code point would be encoded with the same number of bytes as
 *     the illegal sequence.
 * >0  Obsolete "strict" behavior of UTF8_NEXT_CHAR_SAFE(..., TRUE):
 *     Same as the obsolete "safe" behavior, but non-characters are also treated
 *     like illegal sequences.
 *
 * The special negative (<0) value -2 is used for lenient treatment of surrogate
 * code points as legal. Some implementations use this for roundtripping of
 * Unicode 16-bit strings that are not well-formed UTF-16, that is, they
 * contain unpaired surrogates.
 *
 * Note that a UBool is the same as an int8_t.
 */
U_CAPI UChar32 U_EXPORT2
utf8_nextCharSafeBody(const uint8_t *s, int32_t *pi, int32_t length, UChar32 c, UBool strict) {
    int32_t i=*pi;
    uint8_t count=UTF8_COUNT_TRAIL_BYTES(c);
    if((i)+count<=(length)) {
        uint8_t trail, illegal=0;

        UTF8_MASK_LEAD_BYTE((c), count);
        /* count==0 for illegally leading trail bytes and the illegal bytes 0xfe and 0xff */
        switch(count) {
        /* each branch falls through to the next one */
        case 5:
        case 4:
            /* count>=4 is always illegal: no more than 3 trail bytes in Unicode's UTF-8 */
            illegal=1;
            break;
        case 3:
            trail=s[(i)++];
            (c)=((c)<<6)|(trail&0x3f);
            if(c<0x110) {
                illegal|=(trail&0xc0)^0x80;
            } else {
                /* code point>0x10ffff, outside Unicode */
                illegal=1;
                break;
            }
        case 2:
            trail=s[(i)++];
            (c)=((c)<<6)|(trail&0x3f);
            illegal|=(trail&0xc0)^0x80;
        case 1:
            trail=s[(i)++];
            (c)=((c)<<6)|(trail&0x3f);
            illegal|=(trail&0xc0)^0x80;
            break;
        case 0:
            if(strict>=0) {
                return UTF8_ERROR_VALUE_1;
            } else {
                return U_SENTINEL;
            }
        /* no default branch to optimize switch()  - all values are covered */
        }

        /*
         * All the error handling should return a value
         * that needs count bytes so that UTF8_GET_CHAR_SAFE() works right.
         *
         * Starting with Unicode 3.0.1, non-shortest forms are illegal.
         * Starting with Unicode 3.2, surrogate code points must not be
         * encoded in UTF-8, and there are no irregular sequences any more.
         *
         * U8_ macros (new in ICU 2.4) return negative values for error conditions.
         */

        /* correct sequence - all trail bytes have (b7..b6)==(10)? */
        /* illegal is also set if count>=4 */
        if(illegal || (c)<utf8_minLegal[count] || (UTF_IS_SURROGATE(c) && strict!=-2)) {
            /* error handling */
            uint8_t errorCount=count;
            /* don't go beyond this sequence */
            i=*pi;
            while(count>0 && UTF8_IS_TRAIL(s[i])) {
                ++(i);
                --count;
            }
            if(strict>=0) {
                c=utf8_errorValue[errorCount-count];
            } else {
                c=U_SENTINEL;
            }
        } else if((strict)>0 && UTF_IS_UNICODE_NONCHAR(c)) {
            /* strict: forbid non-characters like U+fffe */
            c=utf8_errorValue[count];
        }
    } else /* too few bytes left */ {
        /* error handling */
        int32_t i0=i;
        /* don't just set (i)=(length) in case there is an illegal sequence */
        while((i)<(length) && UTF8_IS_TRAIL(s[i])) {
            ++(i);
        }
        if(strict>=0) {
            c=utf8_errorValue[i-i0];
        } else {
            c=U_SENTINEL;
        }
    }
    *pi=i;
    return c;
}

U_CAPI int32_t U_EXPORT2
utf8_appendCharSafeBody(uint8_t *s, int32_t i, int32_t length, UChar32 c, UBool *pIsError) {
    if((uint32_t)(c)<=0x7ff) {
        if((i)+1<(length)) {
            (s)[(i)++]=(uint8_t)(((c)>>6)|0xc0);
            (s)[(i)++]=(uint8_t)(((c)&0x3f)|0x80);
            return i;
        }
    } else if((uint32_t)(c)<=0xffff) {
        /* Starting with Unicode 3.2, surrogate code points must not be encoded in UTF-8. */
        if((i)+2<(length) && !U_IS_SURROGATE(c)) {
            (s)[(i)++]=(uint8_t)(((c)>>12)|0xe0);
            (s)[(i)++]=(uint8_t)((((c)>>6)&0x3f)|0x80);
            (s)[(i)++]=(uint8_t)(((c)&0x3f)|0x80);
            return i;
        }
    } else if((uint32_t)(c)<=0x10ffff) {
        if((i)+3<(length)) {
            (s)[(i)++]=(uint8_t)(((c)>>18)|0xf0);
            (s)[(i)++]=(uint8_t)((((c)>>12)&0x3f)|0x80);
            (s)[(i)++]=(uint8_t)((((c)>>6)&0x3f)|0x80);
            (s)[(i)++]=(uint8_t)(((c)&0x3f)|0x80);
            return i;
        }
    }
    /* c>0x10ffff or not enough space, write an error value */
    if(pIsError!=NULL) {
        *pIsError=TRUE;
    } else {
        length-=i;
        if(length>0) {
            int32_t offset;
            if(length>3) {
                length=3;
            }
            s+=i;
            offset=0;
            c=utf8_errorValue[length-1];
            UTF8_APPEND_CHAR_UNSAFE(s, offset, c);
            i=i+offset;
        }
    }
    return i;
}

U_CAPI UChar32 U_EXPORT2
utf8_prevCharSafeBody(const uint8_t *s, int32_t start, int32_t *pi, UChar32 c, UBool strict) {
    int32_t i=*pi;
    uint8_t b, count=1, shift=6;

    /* extract value bits from the last trail byte */
    c&=0x3f;

    for(;;) {
        if(i<=start) {
            /* no lead byte at all */
            if(strict>=0) {
                return UTF8_ERROR_VALUE_1;
            } else {
                return U_SENTINEL;
            }
            /*break;*/
        }

        /* read another previous byte */
        b=s[--i];
        if((uint8_t)(b-0x80)<0x7e) { /* 0x80<=b<0xfe */
            if(b&0x40) {
                /* lead byte, this will always end the loop */
                uint8_t shouldCount=UTF8_COUNT_TRAIL_BYTES(b);

                if(count==shouldCount) {
                    /* set the new position */
                    *pi=i;
                    UTF8_MASK_LEAD_BYTE(b, count);
                    c|=(UChar32)b<<shift;
                    if(count>=4 || c>0x10ffff || c<utf8_minLegal[count] || (UTF_IS_SURROGATE(c) && strict!=-2) || (strict>0 && UTF_IS_UNICODE_NONCHAR(c))) {
                        /* illegal sequence or (strict and non-character) */
                        if(count>=4) {
                            count=3;
                        }
                        if(strict>=0) {
                            c=utf8_errorValue[count];
                        } else {
                            c=U_SENTINEL;
                        }
                    } else {
                        /* exit with correct c */
                    }
                } else {
                    /* the lead byte does not match the number of trail bytes */
                    /* only set the position to the lead byte if it would
                       include the trail byte that we started with */
                    if(count<shouldCount) {
                        *pi=i;
                        if(strict>=0) {
                            c=utf8_errorValue[count];
                        } else {
                            c=U_SENTINEL;
                        }
                    } else {
                        if(strict>=0) {
                            c=UTF8_ERROR_VALUE_1;
                        } else {
                            c=U_SENTINEL;
                        }
                    }
                }
                break;
            } else if(count<5) {
                /* trail byte */
                c|=(UChar32)(b&0x3f)<<shift;
                ++count;
                shift+=6;
            } else {
                /* more than 5 trail bytes is illegal */
                if(strict>=0) {
                    c=UTF8_ERROR_VALUE_1;
                } else {
                    c=U_SENTINEL;
                }
                break;
            }
        } else {
            /* single-byte character precedes trailing bytes */
            if(strict>=0) {
                c=UTF8_ERROR_VALUE_1;
            } else {
                c=U_SENTINEL;
            }
            break;
        }
    }
    return c;
}

U_CAPI int32_t U_EXPORT2
utf8_back1SafeBody(const uint8_t *s, int32_t start, int32_t i) {
    /* i had been decremented once before the function call */
    int32_t I=i, Z;
    uint8_t b;

    /* read at most the 6 bytes s[Z] to s[i], inclusively */
    if(I-5>start) {
        Z=I-5;
    } else {
        Z=start;
    }

    /* return I if the sequence starting there is long enough to include i */
    do {
        b=s[I];
        if((uint8_t)(b-0x80)>=0x7e) { /* not 0x80<=b<0xfe */
            break;
        } else if(b>=0xc0) {
            if(UTF8_COUNT_TRAIL_BYTES(b)>=(i-I)) {
                return I;
            } else {
                break;
            }
        }
    } while(Z<=--I);

    /* return i itself to be consistent with the FWD_1 macro */
    return i;
}
Commit	Line	Data
b75a7d8f A	1	/*
	2	******************************************************************************
	3	*
73c04bcf	4	* Copyright (C) 1999-2006, International Business Machines
b75a7d8f A	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	*/
	48	U_EXPORT const uint8_t
	49	utf8_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
76	static const UChar32
77	utf8_minLegal[4]={ 0, 0x80, 0x800, 0x10000 };
78
79	static const UChar32
80	utf8_errorValue[6]={
81	UTF8_ERROR_VALUE_1, UTF8_ERROR_VALUE_2, UTF_ERROR_VALUE, 0x10ffff,
82	0x3ffffff, 0x7fffffff
83	};
84
73c04bcf A	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	*/
b75a7d8f A	107	U_CAPI UChar32 U_EXPORT2
	108	utf8_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 */
73c04bcf	164	if(illegal \|\| (c)<utf8_minLegal[count] \|\| (UTF_IS_SURROGATE(c) && strict!=-2)) {
b75a7d8f A	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
	199	U_CAPI int32_t U_EXPORT2
	200	utf8_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
244	U_CAPI UChar32 U_EXPORT2
245	utf8_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	}
73c04bcf	260	/break;/
b75a7d8f A	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;
73c04bcf	275	if(count>=4 \|\| c>0x10ffff \|\| c<utf8_minLegal[count] \|\| (UTF_IS_SURROGATE(c) && strict!=-2) \|\| (strict>0 && UTF_IS_UNICODE_NONCHAR(c))) {
b75a7d8f A	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
	335	U_CAPI int32_t U_EXPORT2
	336	utf8_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	}