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cvtutf.c

/* tag: Tom Lord Tue Dec  4 14:41:20 2001 (cvtutf.c)
 */
/* ================================================================ */
/*
 * Copyright 2001 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.

    See the header file "ConvertUTF.h" for complete documentation.

------------------------------------------------------------------------ */

#include "hackerlab/tests/uni-tests/cvtutf.h"

#ifdef CVTUTF_DEBUG
#include <stdio.h>
#endif

static 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 */
                  if ((flags == strictConversion) && (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_LOW_END)) {
                        --source; /* return to the illegal value itself */
                        result = sourceIllegal;
                        break;
                  } else {
                      *target++ = ch;     /* normal case */
                  }
            } else if (ch > UNI_MAX_UTF16) {
                  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++ = (ch >> halfShift) + UNI_SUR_HIGH_START;
                  *target++ = (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 (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_HIGH_END && source < sourceEnd) {
                  ch2 = *source;
                  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 if ((flags == strictConversion) && (ch >= UNI_SUR_LOW_START && ch <= UNI_SUR_LOW_END)) {
                  /* an unpaired low surrogate */
                  --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_DEBUG
if (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.
 */
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... six byte sequence.)
 */
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 && source < sourceEnd) {
                  UTF32 ch2 = *source;
                  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 if ((flags == strictConversion) && (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)0x200000) {  bytesToWrite = 4;
            } else {                      bytesToWrite = 2;
                                          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 = (ch | byteMark) & byteMask; ch >>= 6;
                  case 3:     *--target = (ch | byteMark) & byteMask; ch >>= 6;
                  case 2:     *--target = (ch | byteMark) & byteMask; ch >>= 6;
                  case 1:     *--target =  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 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 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 */
                  if ((flags == strictConversion) && (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_LOW_END)) {
                        source -= (extraBytesToRead+1); /* return to the illegal value itself */
                        result = sourceIllegal;
                        break;
                  } else {
                      *target++ = 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++ = (ch >> halfShift) + UNI_SUR_HIGH_START;
                  *target++ = (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++;
            /* surrogates of any stripe are not legal UTF32 characters */
            if (flags == strictConversion ) {
                  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 */
            if (ch < (UTF32)0x80) {             bytesToWrite = 1;
            } else if (ch < (UTF32)0x800) {           bytesToWrite = 2;
            } else if (ch < (UTF32)0x10000) {   bytesToWrite = 3;
            } else if (ch < (UTF32)0x200000) {  bytesToWrite = 4;
            } else {                      bytesToWrite = 2;
                                          ch = UNI_REPLACEMENT_CHAR;
            }

            target += bytesToWrite;
            if (target > targetEnd) {
                  --source; /* Back up source pointer! */
                  target -= bytesToWrite; result = targetExhausted; break;
            }
            switch (bytesToWrite) { /* note: everything falls through. */
                  case 4:     *--target = (ch | byteMark) & byteMask; ch >>= 6;
                  case 3:     *--target = (ch | byteMark) & byteMask; ch >>= 6;
                  case 2:     *--target = (ch | byteMark) & byteMask; ch >>= 6;
                  case 1:     *--target =  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 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_UTF32) {
                  *target++ = ch;
            } else { /* i.e., ch > UNI_MAX_UTF32 */
                  *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.

   --------------------------------------------------------------------- */



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