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.
   */
  
  /* $Id: ConvertUTF.c 8178 2007-08-05 13:55:26Z leonardo $ */
  
  /* ---------------------------------------------------------------------
  
      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 "nim_wrapper_util/convert_utf.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 = 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.
  
     --------------------------------------------------------------------- */
  