229 lines
7.5 KiB
C++
229 lines
7.5 KiB
C++
/*
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******************************************************************************
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*
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* Copyright (C) 1999-2006, 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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#include "base/third_party/icu/icu_utf.h"
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namespace base_icu {
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/**
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* UTF8_ERROR_VALUE_1 and UTF8_ERROR_VALUE_2 are special error values for UTF-8,
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* which need 1 or 2 bytes in UTF-8:
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* \code
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* U+0015 = NAK = Negative Acknowledge, C0 control character
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* U+009f = highest C1 control character
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* \endcode
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*
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* These are used by UTF8_..._SAFE macros so that they can return an error value
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* that needs the same number of code units (bytes) as were seen by
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* a macro. They should be tested with UTF_IS_ERROR() or UTF_IS_VALID().
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*
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* @deprecated ICU 2.4. Obsolete, see utf_old.h.
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*/
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#define CBUTF8_ERROR_VALUE_1 0x15
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/**
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* See documentation on UTF8_ERROR_VALUE_1 for details.
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*
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* @deprecated ICU 2.4. Obsolete, see utf_old.h.
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*/
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#define CBUTF8_ERROR_VALUE_2 0x9f
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/**
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* Error value for all UTFs. This code point value will be set by macros with e>
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* checking if an error is detected.
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*
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* @deprecated ICU 2.4. Obsolete, see utf_old.h.
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*/
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#define CBUTF_ERROR_VALUE 0xffff
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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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const uint8
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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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CBUTF8_ERROR_VALUE_1, CBUTF8_ERROR_VALUE_2, CBUTF_ERROR_VALUE, 0x10ffff,
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0x3ffffff, 0x7fffffff
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};
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/*
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* Handle the non-inline part of the U8_NEXT() macro and its obsolete sibling
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* UTF8_NEXT_CHAR_SAFE().
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*
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* The "strict" parameter controls the error behavior:
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* <0 "Safe" behavior of U8_NEXT(): All illegal byte sequences yield a negative
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* code point result.
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* 0 Obsolete "safe" behavior of UTF8_NEXT_CHAR_SAFE(..., FALSE):
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* All illegal byte sequences yield a positive code point such that this
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* result code point would be encoded with the same number of bytes as
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* the illegal sequence.
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* >0 Obsolete "strict" behavior of UTF8_NEXT_CHAR_SAFE(..., TRUE):
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* Same as the obsolete "safe" behavior, but non-characters are also treated
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* like illegal sequences.
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*
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* The special negative (<0) value -2 is used for lenient treatment of surrogate
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* code points as legal. Some implementations use this for roundtripping of
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* Unicode 16-bit strings that are not well-formed UTF-16, that is, they
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* contain unpaired surrogates.
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*
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* Note that a UBool is the same as an int8_t.
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*/
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UChar32
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utf8_nextCharSafeBody(const uint8 *s, int32 *pi, int32 length, UChar32 c, UBool strict) {
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int32 i=*pi;
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uint8 count=CBU8_COUNT_TRAIL_BYTES(c);
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if((i)+count<=(length)) {
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uint8 trail, illegal=0;
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CBU8_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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if(strict>=0) {
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return CBUTF8_ERROR_VALUE_1;
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} else {
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return CBU_SENTINEL;
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}
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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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* Starting with Unicode 3.2, surrogate code points must not be
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* encoded in UTF-8, and there are no irregular sequences any more.
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*
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* U8_ macros (new in ICU 2.4) return negative values for error conditions.
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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] || (CBU_IS_SURROGATE(c) && strict!=-2)) {
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/* error handling */
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uint8 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 && CBU8_IS_TRAIL(s[i])) {
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++(i);
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--count;
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}
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if(strict>=0) {
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c=utf8_errorValue[errorCount-count];
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} else {
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c=CBU_SENTINEL;
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}
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} else if((strict)>0 && CBU_IS_UNICODE_NONCHAR(c)) {
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/* strict: forbid non-characters like U+fffe */
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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 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) && CBU8_IS_TRAIL(s[i])) {
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++(i);
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}
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if(strict>=0) {
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c=utf8_errorValue[i-i0];
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} else {
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c=CBU_SENTINEL;
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}
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}
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*pi=i;
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return c;
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}
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} // namespace base_icu
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