/*
******************************************************************************
*
* 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;
}