/*
* Copyright 2001-2004 Unicode, Inc.
*
* Disclaimer
*
* This source code is provided as is by Unicode, Inc. No claims are
* made as to fitness for any particular purpose. No warranties of any
* kind are expressed or implied. The recipient agrees to determine
* applicability of information provided. If this file has been
* purchased on magnetic or optical media from Unicode, Inc., the
* sole remedy for any claim will be exchange of defective media
* within 90 days of receipt.
*
* Limitations on Rights to Redistribute This Code
*
* Unicode, Inc. hereby grants the right to freely use the information
* supplied in this file in the creation of products supporting the
* Unicode Standard, and to make copies of this file in any form
* for internal or external distribution as long as this notice
* remains attached.
*/
/* ---------------------------------------------------------------------
Conversions between UTF32, UTF-16, and UTF-8. Source code file.
Author: Mark E. Davis, 1994.
Rev History: Rick McGowan, fixes & updates May 2001.
Sept 2001: fixed const & error conditions per
mods suggested by S. Parent & A. Lillich.
June 2002: Tim Dodd added detection and handling of incomplete
source sequences, enhanced error detection, added casts
to eliminate compiler warnings.
July 2003: slight mods to back out aggressive FFFE detection.
Jan 2004: updated switches in from-UTF8 conversions.
Oct 2004: updated to use UNI_MAX_LEGAL_UTF32 in UTF-32 conversions.
See the header file "ConvertUTF.h" for complete documentation.
------------------------------------------------------------------------ */
#include "ConvertUTF.h"
static const int halfShift = 10; /* used for shifting by 10 bits */
static const UTF32 halfBase = 0x0010000UL;
static const UTF32 halfMask = 0x3FFUL;
static const UTF32 UNI_SUR_HIGH_START = 0xD800;
static const UTF32 UNI_SUR_HIGH_END = 0xDBFF;
static const UTF32 UNI_SUR_LOW_START = 0xDC00;
static const UTF32 UNI_SUR_LOW_END = 0xDFFF;
/* --------------------------------------------------------------------- */
ConversionResult ConvertUTF32toUTF16(const UTF32 **sourceStart, const UTF32 *sourceEnd, UTF16 **targetStart, UTF16 *targetEnd, ConversionFlags flags)
{
ConversionResult result = conversionOK;
const UTF32 *source = *sourceStart;
UTF16 *target = *targetStart;
while (source < sourceEnd)
{
if (target >= targetEnd)
{
result = targetExhausted;
break;
}
UTF32 ch = *source++;
if (ch <= UNI_MAX_BMP) /* Target is a character <= 0xFFFF */
{
/* UTF-16 surrogate values are illegal in UTF-32; 0xffff or 0xfffe are both reserved values */
if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_LOW_END)
{
if (flags == strictConversion)
{
--source; /* return to the illegal value itself */
result = sourceIllegal;
break;
}
else
*target++ = UNI_REPLACEMENT_CHAR;
}
else
*target++ = static_cast<UTF16>(ch); /* normal case */
}
else if (ch > UNI_MAX_LEGAL_UTF32)
{
if (flags == strictConversion)
result = sourceIllegal;
else
*target++ = UNI_REPLACEMENT_CHAR;
}
else
{
/* target is a character in range 0xFFFF - 0x10FFFF. */
if (target + 1 >= targetEnd)
{
--source; /* Back up source pointer! */
result = targetExhausted;
break;
}
ch -= halfBase;
*target++ = static_cast<UTF16>((ch >> halfShift) + UNI_SUR_HIGH_START);
*target++ = static_cast<UTF16>((ch & halfMask) + UNI_SUR_LOW_START);
}
}
*sourceStart = source;
*targetStart = target;
return result;
}
/* --------------------------------------------------------------------- */
ConversionResult ConvertUTF16toUTF32(const UTF16 **sourceStart, const UTF16 *sourceEnd, UTF32 **targetStart, UTF32 *targetEnd, ConversionFlags flags)
{
ConversionResult result = conversionOK;
const UTF16 *source = *sourceStart;
UTF32 *target = *targetStart;
while (source < sourceEnd)
{
const UTF16 *oldSource = source; /* In case we have to back up because of target overflow. */
UTF32 ch = *source++;
/* If we have a surrogate pair, convert to UTF32 first. */
if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_HIGH_END)
{
/* If the 16 bits following the high surrogate are in the source buffer... */
if (source < sourceEnd)
{
UTF32 ch2 = *source;
/* If it's a low surrogate, convert to UTF32. */
if (ch2 >= UNI_SUR_LOW_START && ch2 <= UNI_SUR_LOW_END)
{
ch = ((ch - UNI_SUR_HIGH_START) << halfShift) + (ch2 - UNI_SUR_LOW_START) + halfBase;
++source;
}
else if (flags == strictConversion) /* it's an unpaired high surrogate */
{
--source; /* return to the illegal value itself */
result = sourceIllegal;
break;
}
}
else /* We don't have the 16 bits following the high surrogate. */
{
--source; /* return to the high surrogate */
result = sourceExhausted;
break;
}
}
else if (flags == strictConversion)
{
/* UTF-16 surrogate values are illegal in UTF-32 */
if (ch >= UNI_SUR_LOW_START && ch <= UNI_SUR_LOW_END)
{
--source; /* return to the illegal value itself */
result = sourceIllegal;
break;
}
}
if (target >= targetEnd)
{
source = oldSource; /* Back up source pointer! */
result = targetExhausted;
break;
}
*target++ = ch;
}
*sourceStart = source;
*targetStart = target;
return result;
}
/* --------------------------------------------------------------------- */
/*
* Index into the table below with the first byte of a UTF-8 sequence to
* get the number of trailing bytes that are supposed to follow it.
* Note that *legal* UTF-8 values can't have 4 or 5-bytes. The table is
* left as-is for anyone who may want to do such conversion, which was
* allowed in earlier algorithms.
*/
static const char trailingBytesForUTF8[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, 3,3,3,3,3,3,3,3,4,4,4,4,5,5,5,5
};
/*
* Magic values subtracted from a buffer value during UTF8 conversion.
* This table contains as many values as there might be trailing bytes
* in a UTF-8 sequence.
*/
static const UTF32 offsetsFromUTF8[6] = { 0x00000000UL, 0x00003080UL, 0x000E2080UL, 0x03C82080UL, 0xFA082080UL, 0x82082080UL };
/*
* Once the bits are split out into bytes of UTF-8, this is a mask OR-ed
* into the first byte, depending on how many bytes follow. There are
* as many entries in this table as there are UTF-8 sequence types.
* (I.e., one byte sequence, two byte... etc.). Remember that sequencs
* for *legal* UTF-8 will be 4 or fewer bytes total.
*/
static const UTF8 firstByteMark[7] = { 0x00, 0x00, 0xC0, 0xE0, 0xF0, 0xF8, 0xFC };
/* --------------------------------------------------------------------- */
/* The interface converts a whole buffer to avoid function-call overhead.
* Constants have been gathered. Loops & conditionals have been removed as
* much as possible for efficiency, in favor of drop-through switches.
* (See "Note A" at the bottom of the file for equivalent code.)
* If your compiler supports it, the "isLegalUTF8" call can be turned
* into an inline function.
*/
/* --------------------------------------------------------------------- */
ConversionResult ConvertUTF16toUTF8(const UTF16 **sourceStart, const UTF16 *sourceEnd, UTF8 **targetStart, UTF8 *targetEnd, ConversionFlags flags)
{
ConversionResult result = conversionOK;
const UTF16 *source = *sourceStart;
UTF8 *target = *targetStart;
while (source < sourceEnd)
{
const UTF32 byteMask = 0xBF, byteMark = 0x80;
const UTF16 *oldSource = source; /* In case we have to back up because of target overflow. */
UTF32 ch = *source++;
/* If we have a surrogate pair, convert to UTF32 first. */
if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_HIGH_END)
{
/* If the 16 bits following the high surrogate are in the source buffer... */
if (source < sourceEnd)
{
UTF32 ch2 = *source;
/* If it's a low surrogate, convert to UTF32. */
if (ch2 >= UNI_SUR_LOW_START && ch2 <= UNI_SUR_LOW_END)
{
ch = ((ch - UNI_SUR_HIGH_START) << halfShift) + (ch2 - UNI_SUR_LOW_START) + halfBase;
++source;
}
else if (flags == strictConversion) /* it's an unpaired high surrogate */
{
--source; /* return to the illegal value itself */
result = sourceIllegal;
break;
}
}
else /* We don't have the 16 bits following the high surrogate. */
{
--source; /* return to the high surrogate */
result = sourceExhausted;
break;
}
}
else if (flags == strictConversion)
{
/* UTF-16 surrogate values are illegal in UTF-32 */
if (ch >= UNI_SUR_LOW_START && ch <= UNI_SUR_LOW_END)
{
--source; /* return to the illegal value itself */
result = sourceIllegal;
break;
}
}
/* Figure out how many bytes the result will require */
unsigned short bytesToWrite = 0;
if (ch < 0x80)
bytesToWrite = 1;
else if (ch < 0x800)
bytesToWrite = 2;
else if (ch < 0x10000)
bytesToWrite = 3;
else if (ch < 0x110000)
bytesToWrite = 4;
else
{
bytesToWrite = 3;
ch = UNI_REPLACEMENT_CHAR;
}
target += bytesToWrite;
if (target > targetEnd)
{
source = oldSource; /* Back up source pointer! */
target -= bytesToWrite;
result = targetExhausted;
break;
}
switch (bytesToWrite) /* note: everything falls through. */
{
case 4: *--target = static_cast<UTF8>((ch | byteMark) & byteMask); ch >>= 6;
case 3: *--target = static_cast<UTF8>((ch | byteMark) & byteMask); ch >>= 6;
case 2: *--target = static_cast<UTF8>((ch | byteMark) & byteMask); ch >>= 6;
case 1: *--target = static_cast<UTF8>(ch | firstByteMark[bytesToWrite]);
}
target += bytesToWrite;
}
*sourceStart = source;
*targetStart = target;
return result;
}
/* --------------------------------------------------------------------- */
/*
* Utility routine to tell whether a sequence of bytes is legal UTF-8.
* This must be called with the length pre-determined by the first byte.
* If not calling this from ConvertUTF8to*, then the length can be set by:
* length = trailingBytesForUTF8[*source]+1;
* and the sequence is illegal right away if there aren't that many bytes
* available.
* If presented with a length > 4, this returns false. The Unicode
* definition of UTF-8 goes up to 4-byte sequences.
*/
static bool isLegalUTF8(const UTF8 *source, int length)
{
const UTF8 *srcptr = source + length;
UTF8 a;
switch (length)
{
default: return false;
/* Everything else falls through when "true"... */
case 4: if ((a = (*--srcptr)) < 0x80 || a > 0xBF) return false;
case 3: if ((a = (*--srcptr)) < 0x80 || a > 0xBF) return false;
case 2: if ((a = (*--srcptr)) > 0xBF) return false;
switch (*source)
{
/* no fall-through in this inner switch */
case 0xE0: if (a < 0xA0) return false; break;
case 0xED: if (a > 0x9F) return false; break;
case 0xF0: if (a < 0x90) return false; break;
case 0xF4: if (a > 0x8F) return false; break;
default: if (a < 0x80) return false;
}
case 1: if (*source >= 0x80 && *source < 0xC2) return false;
}
if (*source > 0xF4)
return false;
return true;
}
/* --------------------------------------------------------------------- */
/*
* Exported function to return whether a UTF-8 sequence is legal or not.
* This is not used here; it's just exported.
*/
bool isLegalUTF8Sequence(const UTF8 *source, const UTF8 *sourceEnd)
{
int length = trailingBytesForUTF8[*source] + 1;
if (source + length > sourceEnd)
return false;
return isLegalUTF8(source, length);
}
/* --------------------------------------------------------------------- */
ConversionResult ConvertUTF8toUTF16(const UTF8 **sourceStart, const UTF8 *sourceEnd, UTF16 **targetStart, UTF16 *targetEnd, ConversionFlags flags)
{
ConversionResult result = conversionOK;
const UTF8 *source = *sourceStart;
UTF16 *target = *targetStart;
while (source < sourceEnd)
{
UTF32 ch = 0;
unsigned short extraBytesToRead = trailingBytesForUTF8[*source];
if (source + extraBytesToRead >= sourceEnd)
{
result = sourceExhausted;
break;
}
/* Do this check whether lenient or strict */
if (!isLegalUTF8(source, extraBytesToRead + 1))
{
result = sourceIllegal;
break;
}
/*
* The cases all fall through. See "Note A" below.
*/
switch (extraBytesToRead)
{
case 5: ch += *source++; ch <<= 6; /* remember, illegal UTF-8 */
case 4: ch += *source++; ch <<= 6; /* remember, illegal UTF-8 */
case 3: ch += *source++; ch <<= 6;
case 2: ch += *source++; ch <<= 6;
case 1: ch += *source++; ch <<= 6;
case 0: ch += *source++;
}
ch -= offsetsFromUTF8[extraBytesToRead];
if (target >= targetEnd)
{
source -= extraBytesToRead + 1; /* Back up source pointer! */
result = targetExhausted;
break;
}
if (ch <= UNI_MAX_BMP) /* Target is a character <= 0xFFFF */
{
/* UTF-16 surrogate values are illegal in UTF-32 */
if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_LOW_END)
{
if (flags == strictConversion)
{
source -= extraBytesToRead + 1; /* return to the illegal value itself */
result = sourceIllegal;
break;
}
else
*target++ = UNI_REPLACEMENT_CHAR;
}
else
*target++ = static_cast<UTF16>(ch); /* normal case */
}
else if (ch > UNI_MAX_UTF16)
{
if (flags == strictConversion)
{
result = sourceIllegal;
source -= extraBytesToRead + 1; /* return to the start */
break; /* Bail out; shouldn't continue */
}
else
*target++ = UNI_REPLACEMENT_CHAR;
}
else
{
/* target is a character in range 0xFFFF - 0x10FFFF. */
if (target + 1 >= targetEnd)
{
source -= extraBytesToRead + 1; /* Back up source pointer! */
result = targetExhausted;
break;
}
ch -= halfBase;
*target++ = static_cast<UTF16>((ch >> halfShift) + UNI_SUR_HIGH_START);
*target++ = static_cast<UTF16>((ch & halfMask) + UNI_SUR_LOW_START);
}
}
*sourceStart = source;
*targetStart = target;
return result;
}
/* --------------------------------------------------------------------- */
ConversionResult ConvertUTF32toUTF8(const UTF32 **sourceStart, const UTF32 *sourceEnd, UTF8 **targetStart, UTF8 *targetEnd, ConversionFlags flags)
{
ConversionResult result = conversionOK;
const UTF32 *source = *sourceStart;
UTF8 *target = *targetStart;
while (source < sourceEnd)
{
const UTF32 byteMask = 0xBF, byteMark = 0x80;
UTF32 ch = *source++;
if (flags == strictConversion)
{
/* UTF-16 surrogate values are illegal in UTF-32 */
if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_LOW_END)
{
--source; /* return to the illegal value itself */
result = sourceIllegal;
break;
}
}
/*
* Figure out how many bytes the result will require. Turn any
* illegally large UTF32 things (> Plane 17) into replacement chars.
*/
unsigned short bytesToWrite = 0;
if (ch < 0x80)
bytesToWrite = 1;
else if (ch < 0x800)
bytesToWrite = 2;
else if (ch < 0x10000)
bytesToWrite = 3;
else if (ch <= UNI_MAX_LEGAL_UTF32)
bytesToWrite = 4;
else
{
bytesToWrite = 3;
ch = UNI_REPLACEMENT_CHAR;
result = sourceIllegal;
}
target += bytesToWrite;
if (target > targetEnd)
{
--source; /* Back up source pointer! */
target -= bytesToWrite;
result = targetExhausted;
break;
}
switch (bytesToWrite) /* note: everything falls through. */
{
case 4: *--target = static_cast<UTF8>((ch | byteMark) & byteMask); ch >>= 6;
case 3: *--target = static_cast<UTF8>((ch | byteMark) & byteMask); ch >>= 6;
case 2: *--target = static_cast<UTF8>((ch | byteMark) & byteMask); ch >>= 6;
case 1: *--target = static_cast<UTF8>(ch | firstByteMark[bytesToWrite]);
}
target += bytesToWrite;
}
*sourceStart = source;
*targetStart = target;
return result;
}
/* --------------------------------------------------------------------- */
ConversionResult ConvertUTF8toUTF32(const UTF8 **sourceStart, const UTF8 *sourceEnd, UTF32 **targetStart, UTF32 *targetEnd, ConversionFlags flags)
{
ConversionResult result = conversionOK;
const UTF8 *source = *sourceStart;
UTF32 *target = *targetStart;
while (source < sourceEnd)
{
UTF32 ch = 0;
unsigned short extraBytesToRead = trailingBytesForUTF8[*source];
if (source + extraBytesToRead >= sourceEnd)
{
result = sourceExhausted;
break;
}
/* Do this check whether lenient or strict */
if (!isLegalUTF8(source, extraBytesToRead + 1))
{
result = sourceIllegal;
break;
}
/*
* The cases all fall through. See "Note A" below.
*/
switch (extraBytesToRead)
{
case 5: ch += *source++; ch <<= 6;
case 4: ch += *source++; ch <<= 6;
case 3: ch += *source++; ch <<= 6;
case 2: ch += *source++; ch <<= 6;
case 1: ch += *source++; ch <<= 6;
case 0: ch += *source++;
}
ch -= offsetsFromUTF8[extraBytesToRead];
if (target >= targetEnd)
{
source -= extraBytesToRead + 1; /* Back up the source pointer! */
result = targetExhausted;
break;
}
if (ch <= UNI_MAX_LEGAL_UTF32)
{
/*
* UTF-16 surrogate values are illegal in UTF-32, and anything
* over Plane 17 (> 0x10FFFF) is illegal.
*/
if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_LOW_END)
{
if (flags == strictConversion)
{
source -= extraBytesToRead + 1; /* return to the illegal value itself */
result = sourceIllegal;
break;
}
else
*target++ = UNI_REPLACEMENT_CHAR;
}
else
*target++ = ch;
}
else /* i.e., ch > UNI_MAX_LEGAL_UTF32 */
{
result = sourceIllegal;
*target++ = UNI_REPLACEMENT_CHAR;
}
}
*sourceStart = source;
*targetStart = target;
return result;
}
/* ---------------------------------------------------------------------
Note A.
The fall-through switches in UTF-8 reading code save a
temp variable, some decrements & conditionals. The switches
are equivalent to the following loop:
{
int tmpBytesToRead = extraBytesToRead+1;
do {
ch += *source++;
--tmpBytesToRead;
if (tmpBytesToRead) ch <<= 6;
} while (tmpBytesToRead > 0);
}
In UTF-8 writing code, the switches on "bytesToWrite" are
similarly unrolled loops.
--------------------------------------------------------------------- */