ttcmap0.c

a very goog book

    FT_UInt32  result   = 0;
    FT_UInt32  charcode = *pcharcode + 1;
    FT_Byte*   subheader;


    while ( charcode < 0x10000UL )
    {
      subheader = tt_cmap2_get_subheader( table, charcode );
      if ( subheader )
      {
        FT_Byte*  p       = subheader;
        FT_UInt   start   = TT_NEXT_USHORT( p );
        FT_UInt   count   = TT_NEXT_USHORT( p );
        FT_Int    delta   = TT_NEXT_SHORT ( p );
        FT_UInt   offset  = TT_PEEK_USHORT( p );
        FT_UInt   char_lo = (FT_UInt)( charcode & 0xFF );
        FT_UInt   pos, idx;


        if ( offset == 0 )
          goto Next_SubHeader;

        if ( char_lo < start )
        {
          char_lo = start;
          pos     = 0;
        }
        else
          pos = (FT_UInt)( char_lo - start );

        p       += offset + pos * 2;
        charcode = ( charcode & -256 ) + char_lo;

        for ( ; pos < count; pos++, charcode++ )
        {
          idx = TT_NEXT_USHORT( p );

          if ( idx != 0 )
          {
            gindex = ( idx + delta ) & 0xFFFFU;
            if ( gindex != 0 )
            {
              result = charcode;
              goto Exit;
            }
          }
        }
      }

      /* jump to next sub-header, i.e. higher byte value */
    Next_SubHeader:
      charcode = ( charcode & -256 ) + 256;
    }

  Exit:
    *pcharcode = result;

    return gindex;
  }


  FT_CALLBACK_TABLE_DEF
  const TT_CMap_ClassRec  tt_cmap2_class_rec =
  {
    {
      sizeof( TT_CMapRec ),

      (FT_CMap_InitFunc)     tt_cmap_init,
      (FT_CMap_DoneFunc)     NULL,
      (FT_CMap_CharIndexFunc)tt_cmap2_char_index,
      (FT_CMap_CharNextFunc) tt_cmap2_char_next
    },
    2,
    (TT_CMap_ValidateFunc)   tt_cmap2_validate
  };

#endif /* TT_CONFIG_CMAP_FORMAT_2 */


  /*************************************************************************/
  /*************************************************************************/
  /*****                                                               *****/
  /*****                           FORMAT 4                            *****/
  /*****                                                               *****/
  /*************************************************************************/
  /*************************************************************************/

  /*************************************************************************/
  /*                                                                       */
  /* TABLE OVERVIEW                                                        */
  /* --------------                                                        */
  /*                                                                       */
  /*   NAME          OFFSET         TYPE              DESCRIPTION          */
  /*                                                                       */
  /*   format        0              USHORT            must be 4            */
  /*   length        2              USHORT            table length         */
  /*                                                  in bytes             */
  /*   language      4              USHORT            Mac language code    */
  /*                                                                       */
  /*   segCountX2    6              USHORT            2*NUM_SEGS           */
  /*   searchRange   8              USHORT            2*(1 << LOG_SEGS)    */
  /*   entrySelector 10             USHORT            LOG_SEGS             */
  /*   rangeShift    12             USHORT            segCountX2 -         */
  /*                                                    searchRange        */
  /*                                                                       */
  /*   endCount      14             USHORT[NUM_SEGS]  end charcode for     */
  /*                                                  each segment; last   */
  /*                                                  is 0xFFFF            */
  /*                                                                       */
  /*   pad           14+NUM_SEGS*2  USHORT            padding              */
  /*                                                                       */
  /*   startCount    16+NUM_SEGS*2  USHORT[NUM_SEGS]  first charcode for   */
  /*                                                  each segment         */
  /*                                                                       */
  /*   idDelta       16+NUM_SEGS*4  SHORT[NUM_SEGS]   delta for each       */
  /*                                                  segment              */
  /*   idOffset      16+NUM_SEGS*6  SHORT[NUM_SEGS]   range offset for     */
  /*                                                  each segment; can be */
  /*                                                  zero                 */
  /*                                                                       */
  /*   glyphIds      16+NUM_SEGS*8  USHORT[]          array of glyph id    */
  /*                                                  ranges               */
  /*                                                                       */
  /* Character codes are modelled by a series of ordered (increasing)      */
  /* intervals called segments.  Each segment has start and end codes,     */
  /* provided by the `startCount' and `endCount' arrays.  Segments must    */
  /* not be overlapping and the last segment should always contain the     */
  /* `0xFFFF' endCount.                                                    */
  /*                                                                       */
  /* The fields `searchRange', `entrySelector' and `rangeShift' are better */
  /* ignored (they are traces of over-engineering in the TrueType          */
  /* specification).                                                       */
  /*                                                                       */
  /* Each segment also has a signed `delta', as well as an optional offset */
  /* within the `glyphIds' table.                                          */
  /*                                                                       */
  /* If a segment's idOffset is 0, the glyph index corresponding to any    */
  /* charcode within the segment is obtained by adding the value of        */
  /* `idDelta' directly to the charcode, modulo 65536.                     */
  /*                                                                       */
  /* Otherwise, a glyph index is taken from the glyph ids sub-array for    */
  /* the segment, and the value of `idDelta' is added to it.               */
  /*                                                                       */

#ifdef TT_CONFIG_CMAP_FORMAT_4

  FT_CALLBACK_DEF( void )
  tt_cmap4_validate( FT_Byte*      table,
                     FT_Validator  valid )
  {
    FT_Byte*  p      = table + 2;               /* skip format */
    FT_UInt   length = TT_NEXT_USHORT( p );
    FT_Byte   *ends, *starts, *offsets, *deltas, *glyph_ids;
    FT_UInt   num_segs;


    if ( table + length > valid->limit || length < 16 )
      FT_INVALID_TOO_SHORT;

    p        = table + 6;
    num_segs = TT_NEXT_USHORT( p );   /* read segCountX2 */

    if ( valid->level >= FT_VALIDATE_PARANOID )
    {
      /* check that we have an even value here */
      if ( num_segs & 1 )
        FT_INVALID_DATA;
    }

    num_segs /= 2;

    /* check the search parameters - even though we never use them */
    /*                                                             */
    if ( valid->level >= FT_VALIDATE_PARANOID )
    {
      /* check the values of 'searchRange', 'entrySelector', 'rangeShift' */
      FT_UInt  search_range   = TT_NEXT_USHORT( p );
      FT_UInt  entry_selector = TT_NEXT_USHORT( p );
      FT_UInt  range_shift    = TT_NEXT_USHORT( p );


      if ( ( search_range | range_shift ) & 1 )  /* must be even values */
        FT_INVALID_DATA;

      search_range /= 2;
      range_shift  /= 2;

      /* `search range' is the greatest power of 2 that is <= num_segs */

      if ( search_range                > num_segs                 ||
           search_range * 2            < num_segs                 ||
           search_range + range_shift != num_segs                 ||
           search_range               != ( 1U << entry_selector ) )
        FT_INVALID_DATA;
    }

    ends      = table   + 14;
    starts    = table   + 16 + num_segs * 2;
    deltas    = starts  + num_segs * 2;
    offsets   = deltas  + num_segs * 2;
    glyph_ids = offsets + num_segs * 2;

    if ( glyph_ids > table + length )
      FT_INVALID_TOO_SHORT;

    /* check last segment, its end count must be FFFF */
    if ( valid->level >= FT_VALIDATE_PARANOID )
    {
      p = ends + ( num_segs - 1 ) * 2;
      if ( TT_PEEK_USHORT( p ) != 0xFFFFU )
        FT_INVALID_DATA;
    }

    /* check that segments are sorted in increasing order and do not */
    /* overlap; check also the offsets                               */
    {
      FT_UInt  start, end, last = 0, offset, n;
      FT_Int   delta;


      for ( n = 0; n < num_segs; n++ )
      {
        p = starts + n * 2;
        start = TT_PEEK_USHORT( p );
        p = ends + n * 2;
        end = TT_PEEK_USHORT( p );
        p = deltas + n * 2;
        delta = TT_PEEK_SHORT( p );
        p = offsets + n * 2;
        offset = TT_PEEK_USHORT( p );

        if ( start > end )
          FT_INVALID_DATA;

        /* this test should be performed at default validation level;  */
        /* unfortunately, some popular Asian fonts present overlapping */
        /* ranges in their charmaps                                    */
        /*                                                             */
        if ( valid->level >= FT_VALIDATE_TIGHT )
        {
          if ( n > 0 && start <= last )
            FT_INVALID_DATA;
        }

        if ( offset )
        {
          p += offset;  /* start of glyph id array */

          /* check that we point within the glyph ids table only */
          if ( p < glyph_ids                                ||
               p + ( end - start + 1 ) * 2 > table + length )
            FT_INVALID_DATA;

          /* check glyph indices within the segment range */
          if ( valid->level >= FT_VALIDATE_TIGHT )
          {
            FT_UInt  idx;


            for ( ; start < end; )
            {
              idx = FT_NEXT_USHORT( p );
              if ( idx != 0 )
              {
                idx = (FT_UInt)( idx + delta ) & 0xFFFFU;

                if ( idx >= TT_VALID_GLYPH_COUNT( valid ) )
                  FT_INVALID_GLYPH_ID;
              }
            }
          }
        }

        last = end;
      }
    }
  }


  FT_CALLBACK_DEF( FT_UInt )
  tt_cmap4_char_index( TT_CMap    cmap,
                       FT_UInt32  char_code )
  {
    FT_Byte*  table  = cmap->data;
    FT_UInt   result = 0;


    if ( char_code < 0x10000UL )
    {
      FT_UInt   idx, num_segs2;
      FT_Int    delta;
      FT_UInt   code = (FT_UInt)char_code;
      FT_Byte*  p;


      p         = table + 6;
      num_segs2 = TT_PEEK_USHORT( p ) & -2;  /* be paranoid! */

#if 1
      /* Some fonts have more than 170 segments in their charmaps! */
      /* We changed this function to use a more efficient binary   */
      /* search for improving performance                          */
      {
        FT_UInt  min = 0;
        FT_UInt  max = num_segs2 >> 1;
        FT_UInt  mid, start, end, offset;


        while ( min < max )
        {
          mid   = ( min + max ) >> 1;
          p     = table + 14 + mid * 2;
          end   = TT_NEXT_USHORT( p );
          p    += num_segs2;
          start = TT_PEEK_USHORT( p);

          if ( code < start )
            max = mid;

          else if ( code > end )
            min = mid + 1;

          else
          {
            /* we found the segment */
            idx = code;

            p += num_segs2;
            delta = TT_PEEK_SHORT( p );

            p += num_segs2;
            offset = TT_PEEK_USHORT( p );

            if ( offset != 0 )
            {
              p  += offset + 2 * ( idx - start );
              idx = TT_PEEK_USHORT( p );
            }

            if ( idx != 0 )
              result = (FT_UInt)( idx + delta ) & 0xFFFFU;

            goto Exit;
          }
        }
      }

#else /* 0 - old code */

      {
        FT_UInt   n;
        FT_Byte*  q;


        p = table + 14;               /* ends table   */
        q = table + 16 + num_segs2;   /* starts table */


        for ( n = 0; n < num_segs2; n += 2 )
        {
          FT_UInt  end   = TT_NEXT_USHORT( p );
          FT_UInt  start = TT_NEXT_USHORT( q );
          FT_UInt  offset;


          if ( code < start )
            break;

          if ( code <= end )
          {
            idx = code;

            p = q + num_segs2 - 2;
            delta = TT_PEEK_SHORT( p );
            p += num_segs2;
            offset = TT_PEEK_USHORT( p );

            if ( offset != 0 )
            {
              p  += offset + 2 * ( idx - start );
              idx = TT_PEEK_USHORT( p );
            }

            if ( idx != 0 )
              result = (FT_UInt)( idx + delta ) & 0xFFFFU;
          }
        }
      }

#endif /* 0 */

    }

  Exit:
    return result;
  }


  FT_CALLBACK_DEF( FT_UInt )
  tt_cmap4_char_next( TT_CMap     cmap,
                      FT_UInt32  *pchar_code )
  {
    FT_Byte*   table     = cmap->data;
    FT_UInt32  result    = 0;
    FT_UInt32  char_code = *pchar_code + 1;
    FT_UInt    gindex    = 0;
    FT_Byte*   p;
    FT_Byte*   q;
    FT_UInt    code, num_segs2;


    if ( char_code >= 0x10000UL )
      goto Exit;

    code      = (FT_UInt)char_code;
    p         = table + 6;
    num_segs2 = TT_PEEK_USHORT(p) & -2;  /* ensure even-ness */

    for (;;)
    {
      FT_UInt  offset, n;
      FT_Int   delta;


      p = table + 14;              /* ends table  */
      q = table + 16 + num_segs2;  /* starts table */

      for ( n = 0; n < num_segs2; n += 2 )
      {
        FT_UInt  end   = TT_NEXT_USHORT( p );
        FT_UInt  start = TT_NEXT_USHORT( q );


        if ( code < start )
          code = start;

        if ( code <= end )
        {