一个在UTF32、UTF-16、UTF-8中相互转换的C++程序

首先是最重要的版权信息。

/*
 * 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.
 */

 

头文件：

 

typedef unsigned intUTF32;/* at least 32 bits */typedef unsigned shortUTF16;/* at least 16 bits */typedef unsigned charUTF8;/* typically 8 bits */typedef unsigned charBoolean; /* 0 or 1 *//* Some fundamental constants */#define UNI_REPLACEMENT_CHAR (UTF32)0x0000FFFD#define UNI_MAX_BMP (UTF32)0x0000FFFF#define UNI_MAX_UTF16 (UTF32)0x0010FFFF#define UNI_MAX_UTF32 (UTF32)0x7FFFFFFF#define UNI_MAX_LEGAL_UTF32 (UTF32)0x0010FFFFtypedef enum {conversionOK, /* conversion successful */sourceExhausted,/* partial character in source, but hit end */targetExhausted,/* insuff. room in target for conversion */sourceIllegal/* source sequence is illegal/malformed */} ConversionResult;typedef enum {strictConversion = 0,lenientConversion} ConversionFlags;/* This is for C++ and does no harm in C */#ifdef __cplusplusextern "C" {#endifConversionResult ConvertUTF8toUTF16 (const UTF8** sourceStart, const UTF8* sourceEnd, UTF16** targetStart, UTF16* targetEnd, ConversionFlags flags);ConversionResult ConvertUTF16toUTF8 (const UTF16** sourceStart, const UTF16* sourceEnd, UTF8** targetStart, UTF8* targetEnd, ConversionFlags flags);ConversionResult ConvertUTF8toUTF32 (const UTF8** sourceStart, const UTF8* sourceEnd, UTF32** targetStart, UTF32* targetEnd, ConversionFlags flags);ConversionResult ConvertUTF32toUTF8 (const UTF32** sourceStart, const UTF32* sourceEnd, UTF8** targetStart, UTF8* targetEnd, ConversionFlags flags);ConversionResult ConvertUTF16toUTF32 (const UTF16** sourceStart, const UTF16* sourceEnd, UTF32** targetStart, UTF32* targetEnd, ConversionFlags flags);ConversionResult ConvertUTF32toUTF16 (const UTF32** sourceStart, const UTF32* sourceEnd, UTF16** targetStart, UTF16* targetEnd, ConversionFlags flags);Boolean isLegalUTF8Sequence(const UTF8 *source, const UTF8 *sourceEnd);#ifdef __cplusplus}#endif

 

实现：

 

#include "ConvertUTF.h"#ifdef CVTUTF_DEBUG#include <stdio.h>#endifstatic const int halfShift = 10; /* used for shifting by 10 bits */static const UTF32 halfBase = 0x0010000UL;static const UTF32 halfMask = 0x3FFUL;#define UNI_SUR_HIGH_START (UTF32)0xD800#define UNI_SUR_HIGH_END (UTF32)0xDBFF#define UNI_SUR_LOW_START (UTF32)0xDC00#define UNI_SUR_LOW_END (UTF32)0xDFFF#define false 0#define true 1/* --------------------------------------------------------------------- */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) {UTF32 ch;if (target >= targetEnd) { result = targetExhausted; break;}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++ = (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++ = (UTF16)((ch >> halfShift) + UNI_SUR_HIGH_START); *target++ = (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; UTF32 ch, ch2; while (source < sourceEnd) {const UTF16* oldSource = source; /* In case we have to back up because of target overflow. */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) {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;#ifdef CVTUTF_DEBUGif (result == sourceIllegal) { fprintf(stderr, "ConvertUTF16toUTF32 illegal seq 0x%04x,%04x/n", ch, ch2); fflush(stderr);}#endif 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) {UTF32 ch;unsigned short bytesToWrite = 0;const UTF32 byteMask = 0xBF;const UTF32 byteMark = 0x80; const UTF16* oldSource = source; /* In case we have to back up because of target overflow. */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 */if (ch < (UTF32)0x80) { bytesToWrite = 1;} else if (ch < (UTF32)0x800) { bytesToWrite = 2;} else if (ch < (UTF32)0x10000) { bytesToWrite = 3;} else if (ch < (UTF32)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 = (UTF8)((ch | byteMark) & byteMask); ch >>= 6; case 3: *--target = (UTF8)((ch | byteMark) & byteMask); ch >>= 6; case 2: *--target = (UTF8)((ch | byteMark) & byteMask); ch >>= 6; case 1: *--target = (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 Boolean isLegalUTF8(const UTF8 *source, int length) { UTF8 a; const UTF8 *srcptr = source+length; 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. */Boolean 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++ = (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++ = (UTF16)((ch >> halfShift) + UNI_SUR_HIGH_START); *target++ = (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) {UTF32 ch;unsigned short bytesToWrite = 0;const UTF32 byteMask = 0xBF;const UTF32 byteMark = 0x80; 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. */if (ch < (UTF32)0x80) { bytesToWrite = 1;} else if (ch < (UTF32)0x800) { bytesToWrite = 2;} else if (ch < (UTF32)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 = (UTF8)((ch | byteMark) & byteMask); ch >>= 6; case 3: *--target = (UTF8)((ch | byteMark) & byteMask); ch >>= 6; case 2: *--target = (UTF8)((ch | byteMark) & byteMask); ch >>= 6; case 1: *--target = (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. --------------------------------------------------------------------- */