298 lines
9.2 KiB
C
298 lines
9.2 KiB
C
/*
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******************************************************************************
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*
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* Copyright (C) 1999-2001, International Business Machines
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* Corporation and others. All Rights Reserved.
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*
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******************************************************************************
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* file name: utf_impl.c
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* encoding: US-ASCII
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* tab size: 8 (not used)
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* indentation:4
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*
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* created on: 1999sep13
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* created by: Markus W. Scherer
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*
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* This file provides implementation functions for macros in the utfXX.h
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* that would otherwise be too long as macros.
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*/
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/* set import/export definitions */
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#ifndef U_UTF8_IMPL
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# define U_UTF8_IMPL
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#endif
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#include "unicode/utypes.h"
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/*
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* This table could be replaced on many machines by
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* a few lines of assembler code using an
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* "index of first 0-bit from msb" instruction and
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* one or two more integer instructions.
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*
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* For example, on an i386, do something like
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* - MOV AL, leadByte
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* - NOT AL (8-bit, leave b15..b8==0..0, reverse only b7..b0)
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* - MOV AH, 0
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* - BSR BX, AX (16-bit)
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* - MOV AX, 6 (result)
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* - JZ finish (ZF==1 if leadByte==0xff)
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* - SUB AX, BX (result)
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* -finish:
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* (BSR: Bit Scan Reverse, scans for a 1-bit, starting from the MSB)
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*
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* In Unicode, all UTF-8 byte sequences with more than 4 bytes are illegal;
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* lead bytes above 0xf4 are illegal.
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* We keep them in this table for skipping long ISO 10646-UTF-8 sequences.
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*/
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U_EXPORT const uint8_t
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utf8_countTrailBytes[256]={
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
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2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
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3, 3, 3, 3, 3,
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3, 3, 3, /* illegal in Unicode */
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4, 4, 4, 4, /* illegal in Unicode */
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5, 5, /* illegal in Unicode */
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0, 0 /* illegal bytes 0xfe and 0xff */
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};
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static const UChar32
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utf8_minLegal[4]={ 0, 0x80, 0x800, 0x10000 };
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static const UChar32
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utf8_errorValue[6]={
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UTF8_ERROR_VALUE_1, UTF8_ERROR_VALUE_2, UTF_ERROR_VALUE, 0x10ffff,
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0x3ffffff, 0x7fffffff
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};
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U_CAPI UChar32 U_EXPORT2
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utf8_nextCharSafeBody(const uint8_t *s, int32_t *pi, int32_t length, UChar32 c, UBool strict) {
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int32_t i=*pi;
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uint8_t count=UTF8_COUNT_TRAIL_BYTES(c);
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if((i)+count<=(length)) {
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uint8_t trail, illegal=0;
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UTF8_MASK_LEAD_BYTE((c), count);
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/* count==0 for illegally leading trail bytes and the illegal bytes 0xfe and 0xff */
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switch(count) {
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/* each branch falls through to the next one */
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case 5:
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case 4:
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/* count>=4 is always illegal: no more than 3 trail bytes in Unicode's UTF-8 */
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illegal=1;
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break;
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case 3:
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trail=s[(i)++];
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(c)=((c)<<6)|(trail&0x3f);
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if(c<0x110) {
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illegal|=(trail&0xc0)^0x80;
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} else {
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/* code point>0x10ffff, outside Unicode */
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illegal=1;
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break;
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}
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case 2:
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trail=s[(i)++];
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(c)=((c)<<6)|(trail&0x3f);
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illegal|=(trail&0xc0)^0x80;
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case 1:
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trail=s[(i)++];
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(c)=((c)<<6)|(trail&0x3f);
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illegal|=(trail&0xc0)^0x80;
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break;
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case 0:
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return UTF8_ERROR_VALUE_1;
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/* no default branch to optimize switch() - all values are covered */
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}
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/*
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* All the error handling should return a value
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* that needs count bytes so that UTF8_GET_CHAR_SAFE() works right.
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*
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* Starting with Unicode 3.0.1, non-shortest forms are illegal.
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*/
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/* correct sequence - all trail bytes have (b7..b6)==(10)? */
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/* illegal is also set if count>=4 */
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if(illegal || (c)<utf8_minLegal[count]) {
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/* error handling */
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uint8_t errorCount=count;
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/* don't go beyond this sequence */
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i=*pi;
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while(count>0 && UTF8_IS_TRAIL(s[i])) {
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++(i);
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--count;
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}
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c=utf8_errorValue[errorCount-count];
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} else if((strict) && !UTF_IS_UNICODE_CHAR(c)) {
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/* irregular sequence */
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c=utf8_errorValue[count];
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}
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} else /* too few bytes left */ {
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/* error handling */
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int32_t i0=i;
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/* don't just set (i)=(length) in case there is an illegal sequence */
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while((i)<(length) && UTF8_IS_TRAIL(s[i])) {
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++(i);
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}
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c=utf8_errorValue[i-i0];
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}
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*pi=i;
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return c;
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}
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U_CAPI int32_t U_EXPORT2
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utf8_appendCharSafeBody(uint8_t *s, int32_t i, int32_t length, UChar32 c) {
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if((c)<=0x7ff) {
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if((i)+1<(length)) {
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(s)[(i)++]=(uint8_t)(((c)>>6)|0xc0);
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(s)[(i)++]=(uint8_t)(((c)&0x3f)|0x80);
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return i;
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}
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} else if((uint32_t)(c)<=0xffff) {
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if((i)+2<(length)) {
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(s)[(i)++]=(uint8_t)(((c)>>12)|0xe0);
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(s)[(i)++]=(uint8_t)((((c)>>6)&0x3f)|0x80);
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(s)[(i)++]=(uint8_t)(((c)&0x3f)|0x80);
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return i;
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}
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} else if((uint32_t)(c)<=0x10ffff) {
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if((i)+3<(length)) {
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(s)[(i)++]=(uint8_t)(((c)>>18)|0xf0);
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(s)[(i)++]=(uint8_t)((((c)>>12)&0x3f)|0x80);
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(s)[(i)++]=(uint8_t)((((c)>>6)&0x3f)|0x80);
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(s)[(i)++]=(uint8_t)(((c)&0x3f)|0x80);
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return i;
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}
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}
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/* c>0x10ffff or not enough space, write an error value */
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length-=i;
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if(length>0) {
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int32_t offset;
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if(length>3) {
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length=3;
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}
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s+=i;
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offset=0;
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c=utf8_errorValue[length-1];
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UTF8_APPEND_CHAR_UNSAFE(s, offset, c);
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i=i+offset;
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}
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return i;
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}
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U_CAPI UChar32 U_EXPORT2
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utf8_prevCharSafeBody(const uint8_t *s, int32_t start, int32_t *pi, UChar32 c, UBool strict) {
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int32_t i=*pi;
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uint8_t b, count=1, shift=6;
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/* extract value bits from the last trail byte */
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c&=0x3f;
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for(;;) {
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if(i<=start) {
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/* no lead byte at all */
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c=UTF8_ERROR_VALUE_1;
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break;
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}
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/* read another previous byte */
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b=s[--i];
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if((uint8_t)(b-0x80)<0x7e) { /* 0x80<=b<0xfe */
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if(b&0x40) {
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/* lead byte, this will always end the loop */
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uint8_t shouldCount=UTF8_COUNT_TRAIL_BYTES(b);
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if(count==shouldCount) {
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/* set the new position */
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*pi=i;
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UTF8_MASK_LEAD_BYTE(b, count);
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c|=(UChar32)b<<shift;
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if(count>=4 || c>0x10ffff || c<utf8_minLegal[count] || (strict && !UTF_IS_UNICODE_CHAR(c))) {
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/* illegal or irregular sequence */
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if(count>=4) {
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count=3;
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}
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c=utf8_errorValue[count];
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} else {
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/* exit with correct c */
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}
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} else {
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/* the lead byte does not match the number of trail bytes */
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/* only set the position to the lead byte if it would
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include the trail byte that we started with */
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if(count<shouldCount) {
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*pi=i;
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c=utf8_errorValue[count];
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} else {
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c=UTF8_ERROR_VALUE_1;
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}
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}
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break;
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} else if(count<5) {
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/* trail byte */
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c|=(UChar32)(b&0x3f)<<shift;
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++count;
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shift+=6;
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} else {
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/* more than 5 trail bytes is illegal */
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c=UTF8_ERROR_VALUE_1;
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break;
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}
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} else {
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/* single-byte character precedes trailing bytes */
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c=UTF8_ERROR_VALUE_1;
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break;
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}
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}
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return c;
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}
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U_CAPI int32_t U_EXPORT2
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utf8_back1SafeBody(const uint8_t *s, int32_t start, int32_t i) {
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/* i had been decremented once before the function call */
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int32_t I=i, Z;
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uint8_t b;
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/* read at most the 6 bytes s[Z] to s[i], inclusively */
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if(I-5>start) {
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Z=I-5;
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} else {
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Z=start;
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}
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/* return I if the sequence starting there is long enough to include i */
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do {
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b=s[I];
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if((uint8_t)(b-0x80)>=0x7e) { /* not 0x80<=b<0xfe */
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break;
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} else if(b>=0xc0) {
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if(UTF8_COUNT_TRAIL_BYTES(b)>=(i-I)) {
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return I;
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} else {
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break;
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}
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}
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} while(Z<=--I);
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/* return i itself to be consistent with the FWD_1 macro */
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return i;
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}
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