Edit
kc3-lang/freetype/src/sfnt/ttkern.c
Werner Lemberg
- src/sfnt/ttkern.c
-
/***************************************************************************/ /* */ /* ttkern.c */ /* */ /* Load the basic TrueType kerning table. This doesn't handle */ /* kerning data within the GPOS table at the moment. */ /* */ /* Copyright 1996-2001, 2002, 2003, 2004, 2005, 2006, 2007, 2009, 2010 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 <ft2build.h> #include FT_INTERNAL_DEBUG_H #include FT_INTERNAL_STREAM_H #include FT_TRUETYPE_TAGS_H #include "ttkern.h" #include "sferrors.h" /*************************************************************************/ /* */ /* The macro FT_COMPONENT is used in trace mode. It is an implicit */ /* parameter of the FT_TRACE() and FT_ERROR() macros, used to print/log */ /* messages during execution. */ /* */ #undef FT_COMPONENT #define FT_COMPONENT trace_ttkern #undef TT_KERN_INDEX #define TT_KERN_INDEX( g1, g2 ) ( ( (FT_ULong)(g1) << 16 ) | (g2) ) FT_LOCAL_DEF( FT_Error ) tt_face_load_kern( TT_Face face, FT_Stream stream ) { FT_Error error; FT_ULong table_size; FT_Byte* p; FT_Byte* p_limit; FT_UInt nn, num_tables; FT_UInt32 avail = 0, ordered = 0; /* the kern table is optional; exit silently if it is missing */ error = face->goto_table( face, TTAG_kern, stream, &table_size ); if ( error ) goto Exit; if ( table_size < 4 ) /* the case of a malformed table */ { FT_ERROR(( "tt_face_load_kern:" " kerning table is too small - ignored\n" )); error = SFNT_Err_Table_Missing; goto Exit; } if ( FT_FRAME_EXTRACT( table_size, face->kern_table ) ) { FT_ERROR(( "tt_face_load_kern:" " could not extract kerning table\n" )); goto Exit; } face->kern_table_size = table_size; p = face->kern_table; p_limit = p + table_size; p += 2; /* skip version */ num_tables = FT_NEXT_USHORT( p ); if ( num_tables > 32 ) /* we only support up to 32 sub-tables */ num_tables = 32; for ( nn = 0; nn < num_tables; nn++ ) { FT_UInt num_pairs, length, coverage; FT_Byte* p_next; FT_UInt32 mask = (FT_UInt32)1UL << nn; if ( p + 6 > p_limit ) break; p_next = p; p += 2; /* skip version */ length = FT_NEXT_USHORT( p ); coverage = FT_NEXT_USHORT( p ); if ( length <= 6 ) break; p_next += length; if ( p_next > p_limit ) /* handle broken table */ p_next = p_limit; /* only use horizontal kerning tables */ if ( ( coverage & ~8 ) != 0x0001 || p + 8 > p_limit ) goto NextTable; num_pairs = FT_NEXT_USHORT( p ); p += 6; if ( ( p_next - p ) < 6 * (int)num_pairs ) /* handle broken count */ num_pairs = (FT_UInt)( ( p_next - p ) / 6 ); avail |= mask; /* * Now check whether the pairs in this table are ordered. * We then can use binary search. */ if ( num_pairs > 0 ) { FT_ULong count; FT_ULong old_pair; old_pair = FT_NEXT_ULONG( p ); p += 2; for ( count = num_pairs - 1; count > 0; count-- ) { FT_UInt32 cur_pair; cur_pair = FT_NEXT_ULONG( p ); if ( cur_pair <= old_pair ) break; p += 2; old_pair = cur_pair; } if ( count == 0 ) ordered |= mask; } NextTable: p = p_next; } face->num_kern_tables = nn; face->kern_avail_bits = avail; face->kern_order_bits = ordered; Exit: return error; } FT_LOCAL_DEF( void ) tt_face_done_kern( TT_Face face ) { FT_Stream stream = face->root.stream; FT_FRAME_RELEASE( face->kern_table ); face->kern_table_size = 0; face->num_kern_tables = 0; face->kern_avail_bits = 0; face->kern_order_bits = 0; } FT_LOCAL_DEF( FT_Int ) tt_face_get_kerning( TT_Face face, FT_UInt left_glyph, FT_UInt right_glyph ) { FT_Int result = 0; FT_UInt count, mask = 1; FT_Byte* p = face->kern_table; FT_Byte* p_limit = p + face->kern_table_size; p += 4; mask = 0x0001; for ( count = face->num_kern_tables; count > 0 && p + 6 <= p_limit; count--, mask <<= 1 ) { FT_Byte* base = p; FT_Byte* next = base; FT_UInt version = FT_NEXT_USHORT( p ); FT_UInt length = FT_NEXT_USHORT( p ); FT_UInt coverage = FT_NEXT_USHORT( p ); FT_UInt num_pairs; FT_Int value = 0; FT_UNUSED( version ); next = base + length; if ( next > p_limit ) /* handle broken table */ next = p_limit; if ( ( face->kern_avail_bits & mask ) == 0 ) goto NextTable; if ( p + 8 > next ) goto NextTable; num_pairs = FT_NEXT_USHORT( p ); p += 6; if ( ( next - p ) < 6 * (int)num_pairs ) /* handle broken count */ num_pairs = (FT_UInt)( ( next - p ) / 6 ); switch ( coverage >> 8 ) { case 0: { FT_ULong key0 = TT_KERN_INDEX( left_glyph, right_glyph ); if ( face->kern_order_bits & mask ) /* binary search */ { FT_UInt min = 0; FT_UInt max = num_pairs; while ( min < max ) { FT_UInt mid = ( min + max ) >> 1; FT_Byte* q = p + 6 * mid; FT_ULong key; key = FT_NEXT_ULONG( q ); if ( key == key0 ) { value = FT_PEEK_SHORT( q ); goto Found; } if ( key < key0 ) min = mid + 1; else max = mid; } } else /* linear search */ { FT_UInt count2; for ( count2 = num_pairs; count2 > 0; count2-- ) { FT_ULong key = FT_NEXT_ULONG( p ); if ( key == key0 ) { value = FT_PEEK_SHORT( p ); goto Found; } p += 2; } } } break; /* * We don't support format 2 because we haven't seen a single font * using it in real life... */ default: ; } goto NextTable; Found: if ( coverage & 8 ) /* override or add */ result = value; else result += value; NextTable: p = next; } return result; } #undef TT_KERN_INDEX /* END */