forked from minhngoc25a/freetype2
307 lines
7.7 KiB
C
307 lines
7.7 KiB
C
/***************************************************************************/
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/* */
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/* ttkern.c */
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/* */
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/* Load the basic TrueType kerning table. This doesn't handle */
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/* kerning data within the GPOS table at the moment. */
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/* */
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/* Copyright 1996-2001, 2002, 2003, 2004, 2005, 2006, 2007, 2009, 2010 by */
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/* David Turner, Robert Wilhelm, and Werner Lemberg. */
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/* */
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/* This file is part of the FreeType project, and may only be used, */
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/* modified, and distributed under the terms of the FreeType project */
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/* license, LICENSE.TXT. By continuing to use, modify, or distribute */
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/* this file you indicate that you have read the license and */
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/* understand and accept it fully. */
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/* */
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/***************************************************************************/
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#include <ft2build.h>
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#include FT_INTERNAL_DEBUG_H
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#include FT_INTERNAL_STREAM_H
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#include FT_TRUETYPE_TAGS_H
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#include "ttkern.h"
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#include "sferrors.h"
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/*************************************************************************/
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/* */
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/* The macro FT_COMPONENT is used in trace mode. It is an implicit */
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/* parameter of the FT_TRACE() and FT_ERROR() macros, used to print/log */
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/* messages during execution. */
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/* */
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#undef FT_COMPONENT
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#define FT_COMPONENT trace_ttkern
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#undef TT_KERN_INDEX
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#define TT_KERN_INDEX( g1, g2 ) ( ( (FT_ULong)(g1) << 16 ) | (g2) )
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FT_LOCAL_DEF( FT_Error )
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tt_face_load_kern( TT_Face face,
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FT_Stream stream )
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{
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FT_Error error;
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FT_ULong table_size;
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FT_Byte* p;
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FT_Byte* p_limit;
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FT_UInt nn, num_tables;
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FT_UInt32 avail = 0, ordered = 0;
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/* the kern table is optional; exit silently if it is missing */
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error = face->goto_table( face, TTAG_kern, stream, &table_size );
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if ( error )
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goto Exit;
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if ( table_size < 4 ) /* the case of a malformed table */
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{
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FT_ERROR(( "tt_face_load_kern:"
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" kerning table is too small - ignored\n" ));
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error = FT_THROW( Table_Missing );
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goto Exit;
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}
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if ( FT_FRAME_EXTRACT( table_size, face->kern_table ) )
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{
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FT_ERROR(( "tt_face_load_kern:"
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" could not extract kerning table\n" ));
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goto Exit;
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}
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face->kern_table_size = table_size;
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p = face->kern_table;
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p_limit = p + table_size;
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p += 2; /* skip version */
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num_tables = FT_NEXT_USHORT( p );
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if ( num_tables > 32 ) /* we only support up to 32 sub-tables */
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num_tables = 32;
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for ( nn = 0; nn < num_tables; nn++ )
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{
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FT_UInt num_pairs, length, coverage;
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FT_Byte* p_next;
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FT_UInt32 mask = (FT_UInt32)1UL << nn;
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if ( p + 6 > p_limit )
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break;
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p_next = p;
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p += 2; /* skip version */
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length = FT_NEXT_USHORT( p );
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coverage = FT_NEXT_USHORT( p );
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if ( length <= 6 )
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break;
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p_next += length;
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if ( p_next > p_limit ) /* handle broken table */
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p_next = p_limit;
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/* only use horizontal kerning tables */
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if ( ( coverage & ~8 ) != 0x0001 ||
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p + 8 > p_limit )
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goto NextTable;
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num_pairs = FT_NEXT_USHORT( p );
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p += 6;
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if ( ( p_next - p ) < 6 * (int)num_pairs ) /* handle broken count */
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num_pairs = (FT_UInt)( ( p_next - p ) / 6 );
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avail |= mask;
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/*
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* Now check whether the pairs in this table are ordered.
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* We then can use binary search.
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*/
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if ( num_pairs > 0 )
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{
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FT_ULong count;
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FT_ULong old_pair;
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old_pair = FT_NEXT_ULONG( p );
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p += 2;
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for ( count = num_pairs - 1; count > 0; count-- )
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{
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FT_UInt32 cur_pair;
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cur_pair = FT_NEXT_ULONG( p );
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if ( cur_pair <= old_pair )
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break;
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p += 2;
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old_pair = cur_pair;
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}
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if ( count == 0 )
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ordered |= mask;
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}
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NextTable:
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p = p_next;
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}
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face->num_kern_tables = nn;
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face->kern_avail_bits = avail;
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face->kern_order_bits = ordered;
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Exit:
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return error;
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}
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FT_LOCAL_DEF( void )
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tt_face_done_kern( TT_Face face )
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{
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FT_Stream stream = face->root.stream;
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FT_FRAME_RELEASE( face->kern_table );
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face->kern_table_size = 0;
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face->num_kern_tables = 0;
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face->kern_avail_bits = 0;
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face->kern_order_bits = 0;
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}
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FT_LOCAL_DEF( FT_Int )
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tt_face_get_kerning( TT_Face face,
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FT_UInt left_glyph,
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FT_UInt right_glyph )
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{
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FT_Int result = 0;
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FT_UInt count, mask = 1;
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FT_Byte* p = face->kern_table;
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FT_Byte* p_limit = p + face->kern_table_size;
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p += 4;
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mask = 0x0001;
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for ( count = face->num_kern_tables;
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count > 0 && p + 6 <= p_limit;
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count--, mask <<= 1 )
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{
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FT_Byte* base = p;
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FT_Byte* next = base;
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FT_UInt version = FT_NEXT_USHORT( p );
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FT_UInt length = FT_NEXT_USHORT( p );
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FT_UInt coverage = FT_NEXT_USHORT( p );
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FT_UInt num_pairs;
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FT_Int value = 0;
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FT_UNUSED( version );
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next = base + length;
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if ( next > p_limit ) /* handle broken table */
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next = p_limit;
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if ( ( face->kern_avail_bits & mask ) == 0 )
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goto NextTable;
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if ( p + 8 > next )
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goto NextTable;
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num_pairs = FT_NEXT_USHORT( p );
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p += 6;
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if ( ( next - p ) < 6 * (int)num_pairs ) /* handle broken count */
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num_pairs = (FT_UInt)( ( next - p ) / 6 );
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switch ( coverage >> 8 )
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{
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case 0:
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{
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FT_ULong key0 = TT_KERN_INDEX( left_glyph, right_glyph );
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if ( face->kern_order_bits & mask ) /* binary search */
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{
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FT_UInt min = 0;
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FT_UInt max = num_pairs;
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while ( min < max )
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{
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FT_UInt mid = ( min + max ) >> 1;
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FT_Byte* q = p + 6 * mid;
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FT_ULong key;
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key = FT_NEXT_ULONG( q );
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if ( key == key0 )
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{
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value = FT_PEEK_SHORT( q );
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goto Found;
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}
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if ( key < key0 )
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min = mid + 1;
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else
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max = mid;
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}
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}
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else /* linear search */
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{
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FT_UInt count2;
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for ( count2 = num_pairs; count2 > 0; count2-- )
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{
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FT_ULong key = FT_NEXT_ULONG( p );
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if ( key == key0 )
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{
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value = FT_PEEK_SHORT( p );
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goto Found;
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}
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p += 2;
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}
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}
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}
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break;
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/*
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* We don't support format 2 because we haven't seen a single font
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* using it in real life...
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*/
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default:
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;
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}
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goto NextTable;
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Found:
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if ( coverage & 8 ) /* override or add */
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result = value;
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else
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result += value;
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NextTable:
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p = next;
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}
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return result;
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}
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#undef TT_KERN_INDEX
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/* END */
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