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Implement binary search for SVG Document Lookup.

This commit is contained in:
Moazin Khatti 2019-07-25 16:24:33 +05:00
parent 6962986cf3
commit ba9e6f9d41
1 changed files with 52 additions and 14 deletions
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66
src/sfnt/ttsvg.c
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@ -127,8 +127,8 @@
{
FT_UShort start_glyph_id;
FT_UShort end_glyph_id;
FT_ULong cur_doc_offset;
FT_ULong cur_doc_length;
FT_ULong offset;
FT_ULong length;
} Svg_doc;
Svg_doc
@ -137,8 +137,8 @@
Svg_doc doc;
doc.start_glyph_id = FT_NEXT_USHORT( stream );
doc.end_glyph_id = FT_NEXT_USHORT( stream );
doc.cur_doc_offset = FT_NEXT_ULONG( stream );
doc.cur_doc_length = FT_NEXT_ULONG( stream );
doc.offset = FT_NEXT_ULONG( stream );
doc.length = FT_NEXT_ULONG( stream );
return doc;
}
@ -165,30 +165,68 @@
{
FT_Error error;
Svg_doc cur_doc;
Svg_doc start_doc;
Svg_doc mid_doc;
Svg_doc end_doc;
FT_Bool found = FALSE;
FT_UInt i = 0;
FT_UInt start_index = 0;
FT_UInt end_index = num_entries - 1;
FT_Int comp_res;
FT_Bool found = FALSE;
FT_UInt i = 0;
/* TODO: (OT-SVG) Convert to efficient search algorithm */
for ( i = 0; i < num_entries; i++)
/* search algo */
if ( num_entries == 0 )
{
cur_doc = extract_svg_doc( stream );
stream += 12;
if ( compare_svg_doc( cur_doc, glyph_index ) == 0 )
error = FT_THROW( Invalid_Table );
return error;
}
start_doc = extract_svg_doc( stream + start_index * 12 );
end_doc = extract_svg_doc( stream + end_index * 12 );
if ( ( compare_svg_doc( start_doc, glyph_index ) == -1 ) ||
( compare_svg_doc( end_doc, glyph_index ) == 1 ) )
{
error = FT_THROW( Invalid_Glyph_Index );
return error;
}
while ( start_index <= end_index )
{
i = ( start_index + end_index ) / 2;
mid_doc = extract_svg_doc( stream + i * 12 );
comp_res = compare_svg_doc( mid_doc, glyph_index );
if ( comp_res == 1 )
{
start_index = i + 1;
start_doc = extract_svg_doc( stream + start_index * 4 );
}
else if ( comp_res == -1 )
{
end_index = i - 1;
end_doc = extract_svg_doc( stream + end_index * 4 );
}
else
{
found = TRUE;
*doc_offset = cur_doc.cur_doc_offset;
*doc_length = cur_doc.cur_doc_length;
break;
}
}
/* search algo end */
/* must set `found', `doc_offset' and `doc_length'. */
/* also keep `cur_doc' alive */
if ( found != TRUE )
error = FT_THROW( Invalid_Glyph_Index );
else
{
*start_glyph = cur_doc.start_glyph_id;
*end_glyph = cur_doc.end_glyph_id;
*doc_offset = mid_doc.offset;
*doc_length = mid_doc.length;
*start_glyph = mid_doc.start_glyph_id;
*end_glyph = mid_doc.end_glyph_id;
error = FT_Err_Ok;
}
return error;