text: /*
   * 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 <stdio.h>
  #include "ConvertUTF.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 */
  	    /* 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_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.
   * 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 = (unsigned short)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.
  
     --------------------------------------------------------------------- */
  