otlcommn.c

下载来的一个看图软件的源代码

/***************************************************************************/
/*                                                                         */
/*  otlcommn.c                                                             */
/*                                                                         */
/*    OpenType layout support, common tables (body).                       */
/*                                                                         */
/*  Copyright 2002 by                                                      */
/*  David Turner, Robert Wilhelm, and Werner Lemberg.                      */
/*                                                                         */
/*  This file is part of the FreeType project, and may only be used,       */
/*  modified, and distributed under the terms of the FreeType project      */
/*  license, LICENSE.TXT.  By continuing to use, modify, or distribute     */
/*  this file you indicate that you have read the license and              */
/*  understand and accept it fully.                                        */
/*                                                                         */
/***************************************************************************/


#include "otlayout.h"


 /*************************************************************************/
 /*************************************************************************/
 /*****                                                               *****/
 /*****                       COVERAGE TABLE                          *****/
 /*****                                                               *****/
 /*************************************************************************/
 /*************************************************************************/

  OTL_LOCALDEF( void )
  otl_coverage_validate( OTL_Bytes      table,
                         OTL_Validator  valid )
  {
    OTL_Bytes  p;
    OTL_UInt   format;


    if ( table + 4 > valid->limit )
      OTL_INVALID_TOO_SHORT;

    format = OTL_NEXT_USHORT( p );
    switch ( format )
    {
    case 1:
      {
        OTL_UInt  count = OTL_NEXT_USHORT( p );


        if ( p + count * 2 >= valid->limit )
          OTL_INVALID_TOO_SHORT;

        /* XXX: check glyph indices */
      }
      break;

    case 2:
      {
        OTL_UInt  n, num_ranges = OTL_NEXT_USHORT( p );
        OTL_UInt  start, end, start_cover, total = 0, last = 0;


        if ( p + num_ranges * 6 >= valid->limit )
          OTL_INVALID_TOO_SHORT;

        for ( n = 0; n < num_ranges; n++ )
        {
          start       = OTL_NEXT_USHORT( p );
          end         = OTL_NEXT_USHORT( p );
          start_cover = OTL_NEXT_USHORT( p );

          if ( start > end || start_cover != total )
            OTL_INVALID_DATA;

          if ( n > 0 && start <= last )
            OTL_INVALID_DATA;

          total += end - start + 1;
          last   = end;
        }
      }
      break;

    default:
      OTL_INVALID_FORMAT;
    }
  }


  OTL_LOCALDEF( OTL_UInt )
  otl_coverage_get_count( OTL_Bytes  table )
  {
    OTL_Bytes  p      = table;
    OTL_UInt   format = OTL_NEXT_USHORT( p );
    OTL_UInt   count  = OTL_NEXT_USHORT( p );
    OTL_UInt   result = 0;


    switch ( format )
    {
    case 1:
      return count;

    case 2:
      {
        OTL_UInt  start, end;


        for ( ; count > 0; count-- )
        {
          start = OTL_NEXT_USHORT( p );
          end   = OTL_NEXT_USHORT( p );
          p    += 2;                    /* skip start_index */

          result += end - start + 1;
        }
      }
      break;

    default:
      ;
    }

    return result;
  }


  OTL_LOCALDEF( OTL_Int )
  otl_coverage_get_index( OTL_Bytes  table,
                          OTL_UInt   glyph_index )
  {
    OTL_Bytes  p      = table;
    OTL_UInt   format = OTL_NEXT_USHORT( p );
    OTL_UInt   count  = OTL_NEXT_USHORT( p );


    switch ( format )
    {
    case 1:
      {
        OTL_UInt  min = 0, max = count, mid, gindex;


        table += 4;
        while ( min < max )
        {
          mid    = ( min + max ) >> 1;
          p      = table + 2 * mid;
          gindex = OTL_PEEK_USHORT( p );

          if ( glyph_index == gindex )
            return (OTL_Int)mid;

          if ( glyph_index < gindex )
            max = mid;
          else
            min = mid + 1;
        }
      }
      break;

    case 2:
      {
        OTL_UInt  min = 0, max = count, mid;
        OTL_UInt  start, end, delta, start_cover;


        table += 4;
        while ( min < max )
        {
          mid    = ( min + max ) >> 1;
          p      = table + 6 * mid;
          start  = OTL_NEXT_USHORT( p );
          end    = OTL_NEXT_USHORT( p );

          if ( glyph_index < start )
            max = mid;
          else if ( glyph_index > end )
            min = mid + 1;
          else
            return (OTL_Int)( glyph_index + OTL_NEXT_USHORT( p ) - start );
        }
      }
      break;

    default:
      ;
    }

    return -1;
  }


  /*************************************************************************/
  /*************************************************************************/
  /*****                                                               *****/
  /*****                  CLASS DEFINITION TABLE                       *****/
  /*****                                                               *****/
  /*************************************************************************/
  /*************************************************************************/

  OTL_LOCALDEF( void )
  otl_class_definition_validate( OTL_Bytes      table,
                                 OTL_Validator  valid )
  {
    OTL_Bytes  p = table;
    OTL_UInt   format;


    if ( p + 4 > valid->limit )
      OTL_INVALID_TOO_SHORT;

    format = OTL_NEXT_USHORT( p );
    switch ( format )
    {
    case 1:
      {
        OTL_UInt  count, start = OTL_NEXT_USHORT( p );


        if ( p + 2 > valid->limit )
          OTL_INVALID_TOO_SHORT;

        count = OTL_NEXT_USHORT( p );

        if ( p + count * 2 > valid->limit )
          OTL_INVALID_TOO_SHORT;

        /* XXX: check glyph indices */
      }
      break;

    case 2:
      {
        OTL_UInt  n, num_ranges = OTL_NEXT_USHORT( p );
        OTL_UInt  start, end, value, last = 0;


        if ( p + num_ranges * 6 > valid->limit )
          OTL_INVALID_TOO_SHORT;

        for ( n = 0; n < num_ranges; n++ )
        {
          start = OTL_NEXT_USHORT( p );
          end   = OTL_NEXT_USHORT( p );
          value = OTL_NEXT_USHORT( p );  /* ignored */

          if ( start > end || ( n > 0 && start <= last ) )
            OTL_INVALID_DATA;

          last = end;
        }
      }
      break;

    default:
      OTL_INVALID_FORMAT;
    }
  }


  OTL_LOCALDEF( OTL_UInt )
  otl_class_definition_get_value( OTL_Bytes  table,
                                  OTL_UInt   glyph_index )
  {
    OTL_Bytes  p      = table;
    OTL_UInt   format = OTL_NEXT_USHORT( p );


    switch ( format )
    {
    case 1:
      {
        OTL_UInt  start = OTL_NEXT_USHORT( p );
        OTL_UInt  count = OTL_NEXT_USHORT( p );
        OTL_UInt  idx   = (OTL_UInt)( glyph_index - start );


        if ( idx < count )
        {
          p += 2 * idx;
          return OTL_PEEK_USHORT( p );
        }
      }
      break;

    case 2:
      {
        OTL_UInt  count = OTL_NEXT_USHORT( p );
        OTL_UInt  min = 0, max = count, mid, gindex;


        table += 4;
        while ( min < max )
        {
          mid   = ( min + max ) >> 1;
          p     = table + 6 * mid;
          start = OTL_NEXT_USHORT( p );
          end   = OTL_NEXT_USHORT( p );

          if ( glyph_index < start )
            max = mid;
          else if ( glyph_index > end )
            min = mid + 1;
          else
            return OTL_PEEK_USHORT( p );
        }
      }
      break;

    default:
      ;
    }

    return 0;
  }


  /*************************************************************************/
  /*************************************************************************/
  /*****                                                               *****/
  /*****                      DEVICE TABLE                             *****/
  /*****                                                               *****/
  /*************************************************************************/
  /*************************************************************************/

  OTL_LOCALDEF( void )
  otl_device_table_validate( OTL_Bytes      table,
                             OTL_Validator  valid )
  {
    OTL_Bytes  p = table;
    OTL_UInt   start, end, count, format, count;


    if ( p + 8 > valid->limit )
      OTL_INVALID_TOO_SHORT;

    start  = OTL_NEXT_USHORT( p );
    end    = OTL_NEXT_USHORT( p );
    format = OTL_NEXT_USHORT( p );

    if ( format < 1 || format > 3 || end < start )
      OTL_INVALID_DATA;

    count = (OTL_UInt)( end - start + 1 );

    if ( p + ( ( 1 << format ) * count ) / 8 > valid->limit )
      OTL_INVALID_TOO_SHORT;
  }


  OTL_LOCALDEF( OTL_UInt )
  otl_device_table_get_start( OTL_Bytes  table )
  {
    OTL_Bytes  p = table;


    return OTL_PEEK_USHORT( p );
  }


  OTL_LOCALDEF( OTL_UInt )
  otl_device_table_get_end( OTL_Bytes  table )
  {
    OTL_Bytes  p = table + 2;


    return OTL_PEEK_USHORT( p );
  }


  OTL_LOCALDEF( OTL_Int )
  otl_device_table_get_delta( OTL_Bytes  table,
                              OTL_UInt   size )
  {
    OTL_Bytes  p = table;
    OTL_Int    result = 0;
    OTL_UInt   start, end, format, idx, value;


    start  = OTL_NEXT_USHORT( p );
    end    = OTL_NEXT_USHORT( p );
    format = OTL_NEXT_USHORT( p );

    if ( size >= start && size <= end )
    {
      /* we could do that with clever bit operations, but a switch is */
      /* much simpler to understand and maintain                      */
      /*                                                              */
      switch ( format )
      {
      case 1:
        idx    = (OTL_UInt)( ( size - start ) * 2 );
        p     += idx / 16;
        value  = OTL_PEEK_USHORT( p );
        shift  = idx & 15;
        result = (OTL_Short)( value << shift ) >> ( 14 - shift );

        break;

      case 2:
        idx    = (OTL_UInt)( ( size - start ) * 4 );
        p     += idx / 16;
        value  = OTL_PEEK_USHORT( p );
        shift  = idx & 15;
        result = (OTL_Short)( value << shift ) >> ( 12 - shift );

        break;

      case 3:
        idx    = (OTL_UInt)( ( size - start ) * 8 );
        p     += idx / 16;
        value  = OTL_PEEK_USHORT( p );
        shift  = idx & 15;
        result = (OTL_Short)( value << shift ) >> ( 8 - shift );

        break;

      default:
        ;
      }
    }

    return result;
  }


  /*************************************************************************/
  /*************************************************************************/
  /*****                                                               *****/
  /*****                      LOOKUP LISTS                             *****/
  /*****                                                               *****/
  /*************************************************************************/
  /*************************************************************************/

  OTL_LOCALDEF( void )
  otl_lookup_validate( OTL_Bytes      table,
                       OTL_Validator  valid )
  {
    OTL_Bytes  p = table;
    OTL_UInt   num_tables;


    if ( table + 6 > valid->limit )
      OTL_INVALID_TOO_SHORT;

    p += 4;
    num_tables = OTL_NEXT_USHORT( p );

    if ( p + num_tables * 2 > valid->limit )
      OTL_INVALID_TOO_SHORT;

    for ( ; num_tables > 0; num_tables-- )
    {
      offset = OTL_NEXT_USHORT( p );

      if ( table + offset >= valid->limit )
        OTL_INVALID_OFFSET;
    }

    /* XXX: check sub-tables? */
  }


  OTL_LOCALDEF( OTL_UInt )
  otl_lookup_get_count( OTL_Bytes  table )
  {
    OTL_Bytes  p = table + 4;


    return OTL_PEEK_USHORT( p );
  }