Add GPOS table support.
- Added src/gpos.{cc,h} for supporting GPOS table.
- Some lookup type subtables (e.g. context positioning subtable and chaining
contexual positioning subtable) have the same structure as those in GSUB
table. So I implemented such lookup type subtable parsers in lookup.cc.
These will also be used for parsing GSUB table when I add GSUB support.
- In parsing ClassDefFormat, we now allow class value is 0 because there is no
reason to reject such value.
- Changed some interface/implementation of parsing lookup list table to make
them more clear.
As far as I checked, some fonts contain invalid GPOS table and OTS will drop
GPOS table of them. See comments in gpos.cc for more detail.
BUG=27131
TEST=http://code.google.com/p/ots/wiki/HowToTestOts (Verified with ~4000 TrueType/OpenType fonts)
git-svn-id: http://ots.googlecode.com/svn/trunk@52 a4e77c2c-9104-11de-800e-5b313e0d2bf3
diff --git a/src/gpos.cc b/src/gpos.cc
new file mode 100644
index 0000000..fba1456
--- /dev/null
+++ b/src/gpos.cc
@@ -0,0 +1,803 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "gpos.h"
+
+#include <limits>
+#include <vector>
+
+#include "layout.h"
+#include "maxp.h"
+
+// GPOS - The Glyph Positioning Table
+// http://www.microsoft.com/typography/otspec/gpos.htm
+
+namespace {
+
+enum GPOS_TYPE {
+ SINGLE_ADJUSTMENT = 1,
+ PAIR_ADJUSTMENT = 2,
+ CURSIVE_ATTACHMENT = 3,
+ MARK_TO_BASE_ATTACHMENT = 4,
+ MARK_TO_LIGATURE_ATTACHMENT = 5,
+ MARK_TO_MARK_ATTACHMENT = 6,
+ CONTEXT_POSITIONING = 7,
+ CHAINED_CONTEXT_POSITIONING = 8,
+ EXTENSION_POSITIONING = 9,
+ GPOS_TYPE_RESERVED = 10
+};
+
+// The size of gpos header.
+const unsigned kGposHeaderSize = 10;
+// The maximum format number for anchor tables.
+const uint16_t kMaxAnchorFormat = 3;
+// The maximum number of class value.
+const uint16_t kMaxClassDefValue = 0xFFFF;
+
+// Lookup type parsers.
+bool ParseSingleAdjustment(const ots::OpenTypeFile *file,
+ const uint8_t *data, const size_t length);
+bool ParsePairAdjustment(const ots::OpenTypeFile *file,
+ const uint8_t *data, const size_t length);
+bool ParseCursiveAttachment(const ots::OpenTypeFile *file,
+ const uint8_t *data, const size_t length);
+bool ParseMarkToBaseAttachment(const ots::OpenTypeFile *file,
+ const uint8_t *data, const size_t length);
+bool ParseMarkToLigatureAttachment(const ots::OpenTypeFile *file,
+ const uint8_t *data, const size_t length);
+bool ParseMarkToMarkAttachment(const ots::OpenTypeFile *file,
+ const uint8_t *data, const size_t length);
+bool ParseContextPositioning(const ots::OpenTypeFile *file,
+ const uint8_t *data, const size_t length);
+bool ParseChainedContextPositioning(const ots::OpenTypeFile *file,
+ const uint8_t *data, const size_t length);
+bool ParseExtensionPositioning(const ots::OpenTypeFile *file,
+ const uint8_t *data, const size_t length);
+
+const ots::LookupSubtableParser::TypeParser kGposTypeParsers[] = {
+ {SINGLE_ADJUSTMENT, ParseSingleAdjustment},
+ {PAIR_ADJUSTMENT, ParsePairAdjustment},
+ {CURSIVE_ATTACHMENT, ParseCursiveAttachment},
+ {MARK_TO_BASE_ATTACHMENT, ParseMarkToBaseAttachment},
+ {MARK_TO_LIGATURE_ATTACHMENT, ParseMarkToLigatureAttachment},
+ {MARK_TO_MARK_ATTACHMENT, ParseMarkToMarkAttachment},
+ {CONTEXT_POSITIONING, ParseContextPositioning},
+ {CHAINED_CONTEXT_POSITIONING, ParseChainedContextPositioning},
+ {EXTENSION_POSITIONING, ParseExtensionPositioning}
+};
+
+const ots::LookupSubtableParser kGposLookupSubtableParser = {
+ GPOS_TYPE_RESERVED, EXTENSION_POSITIONING, kGposTypeParsers
+};
+
+// Shared Tables: ValueRecord, Anchor Table, and MarkArray
+
+bool ParseValueRecord(ots::Buffer* subtable, const uint8_t *data,
+ const size_t length, const uint16_t value_format) {
+ // Check existence of adjustment fields.
+ for (unsigned i = 0; i < 4; ++i) {
+ if ((value_format >> i) & 0x1) {
+ // Just read the field since these fileds could take an arbitrary values.
+ if (!subtable->Skip(2)) {
+ return OTS_FAILURE();
+ }
+ }
+ }
+
+ // Check existence of offsets to device table.
+ for (unsigned i = 0; i < 4; ++i) {
+ if ((value_format >> (i + 4)) & 0x1) {
+ uint16_t offset = 0;
+ if (!subtable->ReadU16(&offset)) {
+ return OTS_FAILURE();
+ }
+ if (offset) {
+ // TODO(bashi): Is it possible that device tables locate before
+ // this record? No fonts contain such offset AKAIF.
+ if (offset >= length) {
+ return OTS_FAILURE();
+ }
+ if (!ots::ParseDeviceTable(data + offset, length - offset)) {
+ return OTS_FAILURE();
+ }
+ }
+ }
+ }
+ return true;
+}
+
+bool ParseAnchorTable(const uint8_t *data, const size_t length) {
+ ots::Buffer subtable(data, length);
+
+ uint16_t format = 0;
+ // Read format and skip 2 2-byte fields that could be arbitrary values.
+ if (!subtable.ReadU16(&format) ||
+ !subtable.Skip(4)) {
+ return OTS_FAILURE();
+ }
+
+ if (format == 0 || format > kMaxAnchorFormat) {
+ return OTS_FAILURE();
+ }
+
+ // Format 2 and 3 has additional fields.
+ if (format == 2) {
+ // Format 2 provides an index to a glyph contour point, which will take
+ // arbitrary value.
+ uint16_t anchor_point = 0;
+ if (!subtable.ReadU16(&anchor_point)) {
+ return OTS_FAILURE();
+ }
+ } else if (format == 3) {
+ uint16_t offset_x_device = 0;
+ uint16_t offset_y_device = 0;
+ if (!subtable.ReadU16(&offset_x_device) ||
+ !subtable.ReadU16(&offset_y_device)) {
+ return OTS_FAILURE();
+ }
+ const unsigned format_end = static_cast<unsigned>(10);
+ if (offset_x_device) {
+ if (offset_x_device < format_end || offset_x_device >= length) {
+ return OTS_FAILURE();
+ }
+ if (!ots::ParseDeviceTable(data + offset_x_device,
+ length - offset_x_device)) {
+ return OTS_FAILURE();
+ }
+ }
+ if (offset_y_device) {
+ if (offset_y_device < format_end || offset_y_device >= length) {
+ return OTS_FAILURE();
+ }
+ if (!ots::ParseDeviceTable(data + offset_y_device,
+ length - offset_y_device)) {
+ return OTS_FAILURE();
+ }
+ }
+ }
+ return true;
+}
+
+bool ParseMarkArrayTable(const uint8_t *data, const size_t length,
+ const uint16_t class_count) {
+ ots::Buffer subtable(data, length);
+
+ uint16_t mark_count = 0;
+ if (!subtable.ReadU16(&mark_count)) {
+ return OTS_FAILURE();
+ }
+
+ // MarkRecord consists of 4-bytes.
+ const unsigned mark_records_end = static_cast<unsigned>(2) + mark_count * 4;
+ if (mark_records_end > std::numeric_limits<uint16_t>::max()) {
+ return OTS_FAILURE();
+ }
+ for (unsigned i = 0; i < mark_count; ++i) {
+ uint16_t class_value = 0;
+ uint16_t offset_mark_anchor = 0;
+ if (!subtable.ReadU16(&class_value) ||
+ !subtable.ReadU16(&offset_mark_anchor)) {
+ return OTS_FAILURE();
+ }
+ // |class_value| may take arbitrary values including 0 here so we don't
+ // check the value.
+ if (offset_mark_anchor < mark_records_end ||
+ offset_mark_anchor >= length) {
+ return OTS_FAILURE();
+ }
+ if (!ParseAnchorTable(data + offset_mark_anchor,
+ length - offset_mark_anchor)) {
+ return OTS_FAILURE();
+ }
+ }
+
+ return true;
+}
+
+// Lookup Type 1:
+// Single Adjustment Positioning Subtable
+bool ParseSingleAdjustment(const ots::OpenTypeFile *file, const uint8_t *data,
+ const size_t length) {
+ ots::Buffer subtable(data, length);
+
+ uint16_t format = 0;
+ uint16_t offset_coverage = 0;
+ uint16_t value_format = 0;
+ if (!subtable.ReadU16(&format) ||
+ !subtable.ReadU16(&offset_coverage) ||
+ !subtable.ReadU16(&value_format)) {
+ return OTS_FAILURE();
+ }
+
+ if (format == 1) {
+ // Format 1 exactly one value record.
+ if (!ParseValueRecord(&subtable, data, length, value_format)) {
+ return OTS_FAILURE();
+ }
+ } else if (format == 2) {
+ uint16_t value_count = 0;
+ if (!subtable.ReadU16(&value_count)) {
+ return OTS_FAILURE();
+ }
+ for (unsigned i = 0; i < value_count; ++i) {
+ if (!ParseValueRecord(&subtable, data, length, value_format)) {
+ return OTS_FAILURE();
+ }
+ }
+ } else {
+ return OTS_FAILURE();
+ }
+
+ if (offset_coverage < subtable.offset() || offset_coverage >= length) {
+ return OTS_FAILURE();
+ }
+
+ if (!ots::ParseCoverageTable(data + offset_coverage,
+ length - offset_coverage,
+ file->maxp->num_glyphs)) {
+ return OTS_FAILURE();
+ }
+
+ return true;
+}
+
+bool ParsePairSetTable(const uint8_t *data, const size_t length,
+ const uint16_t value_format1,
+ const uint16_t value_format2,
+ const uint16_t num_glyphs) {
+ ots::Buffer subtable(data, length);
+
+ uint16_t value_count = 0;
+ if (!subtable.ReadU16(&value_count)) {
+ return OTS_FAILURE();
+ }
+ for (unsigned i = 0; i < value_count; ++i) {
+ // Check pair value record.
+ uint16_t glyph_id = 0;
+ if (!subtable.ReadU16(&glyph_id)) {
+ return OTS_FAILURE();
+ }
+ if (glyph_id >= num_glyphs) {
+ return OTS_FAILURE();
+ }
+ if (!ParseValueRecord(&subtable, data, length, value_format1)) {
+ return OTS_FAILURE();
+ }
+ if (!ParseValueRecord(&subtable, data, length, value_format2)) {
+ return OTS_FAILURE();
+ }
+ }
+ return true;
+}
+
+bool ParsePairPosFormat1(const uint8_t *data, const size_t length,
+ const uint16_t value_format1,
+ const uint16_t value_format2,
+ const uint16_t num_glyphs) {
+ ots::Buffer subtable(data, length);
+
+ // Skip 8 bytes that are already read before.
+ if (!subtable.Skip(8)) {
+ return OTS_FAILURE();
+ }
+
+ uint16_t pair_set_count = 0;
+ if (!subtable.ReadU16(&pair_set_count)) {
+ return OTS_FAILURE();
+ }
+
+ const unsigned pair_pos_end = static_cast<unsigned>(10) +
+ pair_set_count * 2;
+ if (pair_pos_end > std::numeric_limits<uint16_t>::max()) {
+ return OTS_FAILURE();
+ }
+ for (unsigned i = 0; i < pair_set_count; ++i) {
+ uint16_t pair_set_offset = 0;
+ if (!subtable.ReadU16(&pair_set_offset)) {
+ return OTS_FAILURE();
+ }
+ if (pair_set_offset < pair_pos_end || pair_set_offset >= length) {
+ return OTS_FAILURE();
+ }
+ // Check pair set tables
+ if (!ParsePairSetTable(data + pair_set_offset, length - pair_set_offset,
+ value_format1, value_format2,
+ num_glyphs)) {
+ return OTS_FAILURE();
+ }
+ }
+
+ return true;
+}
+
+bool ParsePairPosFormat2(const uint8_t *data, const size_t length,
+ const uint16_t value_format1,
+ const uint16_t value_format2,
+ const uint16_t num_glyphs) {
+ ots::Buffer subtable(data, length);
+
+ // Skip 8 bytes that are already read before.
+ if (!subtable.Skip(8)) {
+ return OTS_FAILURE();
+ }
+
+ uint16_t offset_class_def1 = 0;
+ uint16_t offset_class_def2 = 0;
+ uint16_t class1_count = 0;
+ uint16_t class2_count = 0;
+ if (!subtable.ReadU16(&offset_class_def1) ||
+ !subtable.ReadU16(&offset_class_def2) ||
+ !subtable.ReadU16(&class1_count) ||
+ !subtable.ReadU16(&class2_count)) {
+ return OTS_FAILURE();
+ }
+
+ // Check class 1 records.
+ for (unsigned i = 0; i < class1_count; ++i) {
+ // Check class 2 records.
+ for (unsigned j = 0; j < class2_count; ++j) {
+ if (value_format1 && !ParseValueRecord(&subtable, data, length,
+ value_format1)) {
+ return OTS_FAILURE();
+ }
+ if (value_format2 && !ParseValueRecord(&subtable, data, length,
+ value_format2)) {
+ return OTS_FAILURE();
+ }
+ }
+ }
+
+ // Check class definition tables.
+ if (offset_class_def1 < subtable.offset() || offset_class_def1 >= length ||
+ offset_class_def2 < subtable.offset() || offset_class_def2 >= length) {
+ return OTS_FAILURE();
+ }
+ if (!ots::ParseClassDefTable(data + offset_class_def1,
+ length - offset_class_def1,
+ num_glyphs, kMaxClassDefValue)) {
+ return OTS_FAILURE();
+ }
+ if (!ots::ParseClassDefTable(data + offset_class_def2,
+ length - offset_class_def2,
+ num_glyphs, kMaxClassDefValue)) {
+ return OTS_FAILURE();
+ }
+
+ return true;
+}
+
+// Lookup Type 2:
+// Pair Adjustment Positioning Subtable
+bool ParsePairAdjustment(const ots::OpenTypeFile *file, const uint8_t *data,
+ const size_t length) {
+ ots::Buffer subtable(data, length);
+
+ uint16_t format = 0;
+ uint16_t offset_coverage = 0;
+ uint16_t value_format1 = 0;
+ uint16_t value_format2 = 0;
+ if (!subtable.ReadU16(&format) ||
+ !subtable.ReadU16(&offset_coverage) ||
+ !subtable.ReadU16(&value_format1) ||
+ !subtable.ReadU16(&value_format2)) {
+ return OTS_FAILURE();
+ }
+
+ if (format == 1) {
+ if (!ParsePairPosFormat1(data, length, value_format1, value_format2,
+ file->maxp->num_glyphs)) {
+ return OTS_FAILURE();
+ }
+ } else if (format == 2) {
+ if (!ParsePairPosFormat2(data, length, value_format1, value_format2,
+ file->maxp->num_glyphs)) {
+ return OTS_FAILURE();
+ }
+ } else {
+ return OTS_FAILURE();
+ }
+
+ if (offset_coverage < subtable.offset() || offset_coverage >= length) {
+ return OTS_FAILURE();
+ }
+ if (!ots::ParseCoverageTable(data + offset_coverage,
+ length - offset_coverage,
+ file->maxp->num_glyphs)) {
+ return OTS_FAILURE();
+ }
+
+ return true;
+}
+
+// Lookup Type 3
+// Cursive Attachment Positioning Subtable
+bool ParseCursiveAttachment(const ots::OpenTypeFile *file, const uint8_t *data,
+ const size_t length) {
+ ots::Buffer subtable(data, length);
+
+ uint16_t format = 0;
+ uint16_t offset_coverage = 0;
+ uint16_t entry_exit_count = 0;
+ if (!subtable.ReadU16(&format) ||
+ !subtable.ReadU16(&offset_coverage) ||
+ !subtable.ReadU16(&entry_exit_count)) {
+ return OTS_FAILURE();
+ }
+
+ if (format != 1) {
+ return OTS_FAILURE();
+ }
+
+ // Check entry exit records.
+ const unsigned entry_exit_records_end = static_cast<unsigned>(6) +
+ entry_exit_count * 2;
+ if (entry_exit_records_end > std::numeric_limits<uint16_t>::max()) {
+ return OTS_FAILURE();
+ }
+ for (unsigned i = 0; i < entry_exit_count; ++i) {
+ uint16_t offset_entry_anchor = 0;
+ uint16_t offset_exit_anchor = 0;
+ if (!subtable.ReadU16(&offset_entry_anchor) ||
+ !subtable.ReadU16(&offset_exit_anchor)) {
+ return OTS_FAILURE();
+ }
+ // These offsets could be NULL.
+ if (offset_entry_anchor) {
+ if (offset_entry_anchor < entry_exit_records_end ||
+ offset_entry_anchor >= length) {
+ return OTS_FAILURE();
+ }
+ if (!ParseAnchorTable(data + offset_entry_anchor,
+ length - offset_entry_anchor)) {
+ return OTS_FAILURE();
+ }
+ }
+ if (offset_exit_anchor) {
+ if (offset_exit_anchor < entry_exit_records_end ||
+ offset_exit_anchor >= length) {
+ return OTS_FAILURE();
+ }
+ if (!ParseAnchorTable(data + offset_exit_anchor,
+ length - offset_exit_anchor)) {
+ return OTS_FAILURE();
+ }
+ }
+ }
+
+ if (offset_coverage < subtable.offset() || offset_coverage >= length) {
+ return OTS_FAILURE();
+ }
+ if (!ots::ParseCoverageTable(data + offset_coverage,
+ length - offset_coverage,
+ file->maxp->num_glyphs)) {
+ return OTS_FAILURE();
+ }
+
+ return true;
+}
+
+bool ParseAnchorArrayTable(const uint8_t *data, const size_t length,
+ const uint16_t class_count) {
+ ots::Buffer subtable(data, length);
+
+ uint16_t record_count = 0;
+ if (!subtable.ReadU16(&record_count)) {
+ return OTS_FAILURE();
+ }
+
+ const unsigned anchor_array_end = static_cast<unsigned>(2) +
+ record_count * class_count * 2;
+ if (anchor_array_end > std::numeric_limits<uint16_t>::max()) {
+ return OTS_FAILURE();
+ }
+ for (unsigned i = 0; i < record_count; ++i) {
+ for (unsigned j = 0; j < class_count; ++j) {
+ uint16_t offset_record = 0;
+ if (!subtable.ReadU16(&offset_record)) {
+ return OTS_FAILURE();
+ }
+ // |offset_record| could be NULL.
+ if (offset_record) {
+ if (offset_record < anchor_array_end || offset_record >= length) {
+ return OTS_FAILURE();
+ }
+ if (!ParseAnchorTable(data + offset_record,
+ length - offset_record)) {
+ return OTS_FAILURE();
+ }
+ }
+ }
+ }
+ return true;
+}
+
+bool ParseLigatureArrayTable(const uint8_t *data, const size_t length,
+ const uint16_t class_count) {
+ ots::Buffer subtable(data, length);
+
+ uint16_t ligature_count = 0;
+ if (!subtable.ReadU16(&ligature_count)) {
+ return OTS_FAILURE();
+ }
+ for (unsigned i = 0; i < ligature_count; ++i) {
+ uint16_t offset_ligature_attach = 0;
+ if (!subtable.ReadU16(&offset_ligature_attach)) {
+ return OTS_FAILURE();
+ }
+ if (offset_ligature_attach < 2 || offset_ligature_attach >= length) {
+ return OTS_FAILURE();
+ }
+ if (!ParseAnchorArrayTable(data + offset_ligature_attach,
+ length - offset_ligature_attach, class_count)) {
+ return OTS_FAILURE();
+ }
+ }
+ return true;
+}
+
+// Common parser for Lookup Type 4, 5 and 6.
+bool ParseMarkToAttachmentSubtables(const ots::OpenTypeFile *file,
+ const uint8_t *data, const size_t length,
+ const GPOS_TYPE type) {
+ ots::Buffer subtable(data, length);
+
+ uint16_t format = 0;
+ uint16_t offset_coverage1 = 0;
+ uint16_t offset_coverage2 = 0;
+ uint16_t class_count = 0;
+ uint16_t offset_mark_array = 0;
+ uint16_t offset_type_specific_array = 0;
+ if (!subtable.ReadU16(&format) ||
+ !subtable.ReadU16(&offset_coverage1) ||
+ !subtable.ReadU16(&offset_coverage2) ||
+ !subtable.ReadU16(&class_count) ||
+ !subtable.ReadU16(&offset_mark_array) ||
+ !subtable.ReadU16(&offset_type_specific_array)) {
+ return OTS_FAILURE();
+ }
+
+ if (format != 1) {
+ return OTS_FAILURE();
+ }
+
+ const unsigned header_end = static_cast<unsigned>(subtable.offset());
+ if (header_end > std::numeric_limits<uint16_t>::max()) {
+ return OTS_FAILURE();
+ }
+ if (offset_coverage1 < header_end || offset_coverage1 >= length) {
+ return OTS_FAILURE();
+ }
+ if (!ots::ParseCoverageTable(data + offset_coverage1,
+ length - offset_coverage1,
+ file->maxp->num_glyphs)) {
+ return OTS_FAILURE();
+ }
+ if (offset_coverage2 < header_end || offset_coverage2 >= length) {
+ return OTS_FAILURE();
+ }
+ if (!ots::ParseCoverageTable(data + offset_coverage2,
+ length - offset_coverage2,
+ file->maxp->num_glyphs)) {
+ return OTS_FAILURE();
+ }
+
+ if (offset_mark_array < header_end || offset_mark_array >= length) {
+ return OTS_FAILURE();
+ }
+ if (!ParseMarkArrayTable(data + offset_mark_array,
+ length - offset_mark_array, class_count)) {
+ return OTS_FAILURE();
+ }
+
+ if (offset_type_specific_array < header_end ||
+ offset_type_specific_array >= length) {
+ return OTS_FAILURE();
+ }
+ if (type == MARK_TO_BASE_ATTACHMENT || type == MARK_TO_MARK_ATTACHMENT) {
+ if (!ParseAnchorArrayTable(data + offset_type_specific_array,
+ length - offset_type_specific_array,
+ class_count)) {
+ return OTS_FAILURE();
+ }
+ } else if (type == MARK_TO_LIGATURE_ATTACHMENT) {
+ if (!ParseLigatureArrayTable(data + offset_type_specific_array,
+ length - offset_type_specific_array,
+ class_count)) {
+ return OTS_FAILURE();
+ }
+ } else {
+ return OTS_FAILURE();
+ }
+
+ return true;
+}
+
+// Lookup Type 4:
+// MarkToBase Attachment Positioning Subtable
+bool ParseMarkToBaseAttachment(const ots::OpenTypeFile *file,
+ const uint8_t *data, const size_t length) {
+ return ParseMarkToAttachmentSubtables(file, data, length,
+ MARK_TO_BASE_ATTACHMENT);
+}
+
+// Lookup Type 5:
+// MarkToLigature Attachment Positioning Subtable
+bool ParseMarkToLigatureAttachment(const ots::OpenTypeFile *file,
+ const uint8_t *data, const size_t length) {
+ return ParseMarkToAttachmentSubtables(file, data, length,
+ MARK_TO_LIGATURE_ATTACHMENT);
+}
+
+// Lookup Type 6:
+// MarkToMark Attachment Positioning Subtable
+bool ParseMarkToMarkAttachment(const ots::OpenTypeFile *file,
+ const uint8_t *data, const size_t length) {
+ return ParseMarkToAttachmentSubtables(file, data, length,
+ MARK_TO_MARK_ATTACHMENT);
+}
+
+// Lookup Type 7:
+// Contextual Positioning Subtables
+bool ParseContextPositioning(const ots::OpenTypeFile *file,
+ const uint8_t *data, const size_t length) {
+ return ots::ParseContextSubtable(data, length, file->maxp->num_glyphs,
+ file->gpos->num_lookups);
+}
+
+// Lookup Type 8:
+// Chaining Contexual Positioning Subtable
+bool ParseChainedContextPositioning(const ots::OpenTypeFile *file,
+ const uint8_t *data, const size_t length) {
+ return ots::ParseChainingContextSubtable(data, length,
+ file->maxp->num_glyphs,
+ file->gpos->num_lookups);
+}
+
+// Lookup Type 9:
+// Extension Positioning
+bool ParseExtensionPositioning(const ots::OpenTypeFile *file,
+ const uint8_t *data, const size_t length) {
+ return ots::ParseExtensionSubtable(file, data, length,
+ &kGposLookupSubtableParser);
+}
+
+} // namespace
+
+#define DROP_THIS_TABLE \
+ do { delete file->gpos; file->gpos = 0; } while (0)
+
+namespace ots {
+
+// As far as I checked, following fonts contain invalid GPOS table and
+// OTS will drop their GPOS table.
+//
+// # invalid delta format in device table
+// samanata.ttf
+//
+// # bad size range in device table
+// Sarai_07.ttf
+//
+// # bad offset to PairSetTable
+// chandas1-2.ttf
+//
+// # bad offset to FeatureTable
+// glrso12.ttf
+// gllr12.ttf
+// glbo12.ttf
+// glb12.ttf
+// glro12.ttf
+// glbso12.ttf
+// glrc12.ttf
+// glrsc12.ttf
+// glbs12.ttf
+// glrs12.ttf
+// glr12.ttf
+//
+// # ScriptRecords aren't sorted by tag
+// Garogier_unhinted.otf
+//
+// # bad start coverage index in CoverageFormat2
+// AndBasR.ttf
+// CharisSILB.ttf
+// CharisSILBI.ttf
+// CharisSILI.ttf
+// CharisSILR.ttf
+// DoulosSILR.ttf
+// GenBasBI.ttf
+// GenBasI.ttf
+// GenBkBasI.ttf
+// GenBkBasB.ttf
+// GenBkBasR.ttf
+// Padauk-Bold.ttf
+// Padauk.ttf
+//
+// # Contour point indexes aren't sorted
+// Arial Unicode.ttf
+
+bool ots_gpos_parse(OpenTypeFile *file, const uint8_t *data, size_t length) {
+ // Parsing GPOS table requires num_glyphs which is contained in maxp table.
+ if (!file->maxp) {
+ return OTS_FAILURE();
+ }
+
+ Buffer table(data, length);
+
+ OpenTypeGPOS *gpos = new OpenTypeGPOS;
+ file->gpos = gpos;
+
+ uint32_t version = 0;
+ uint16_t offset_script_list = 0;
+ uint16_t offset_feature_list = 0;
+ uint16_t offset_lookup_list = 0;
+ if (!table.ReadU32(&version) ||
+ !table.ReadU16(&offset_script_list) ||
+ !table.ReadU16(&offset_feature_list) ||
+ !table.ReadU16(&offset_lookup_list)) {
+ return OTS_FAILURE();
+ }
+
+ if (version != 0x00010000) {
+ OTS_WARNING("bad GPOS version");
+ DROP_THIS_TABLE;
+ return true;
+ }
+ if ((offset_script_list < kGposHeaderSize ||
+ offset_script_list >= length) ||
+ (offset_feature_list < kGposHeaderSize ||
+ offset_feature_list >= length) ||
+ (offset_lookup_list < kGposHeaderSize ||
+ offset_lookup_list >= length)) {
+ OTS_WARNING("bad offset in GPOS header");
+ DROP_THIS_TABLE;
+ return true;
+ }
+
+ if (!ParseLookupListTable(file, data + offset_lookup_list,
+ length - offset_lookup_list,
+ &kGposLookupSubtableParser,
+ &gpos->num_lookups)) {
+ OTS_WARNING("faild to parse lookup list table");
+ DROP_THIS_TABLE;
+ return true;
+ }
+
+ uint16_t num_features = 0;
+ if (!ParseFeatureListTable(data + offset_feature_list,
+ length - offset_feature_list, gpos->num_lookups,
+ &num_features)) {
+ OTS_WARNING("faild to parse feature list table");
+ DROP_THIS_TABLE;
+ return true;
+ }
+
+ if (!ParseScriptListTable(data + offset_script_list,
+ length - offset_script_list, num_features)) {
+ OTS_WARNING("faild to parse script list table");
+ DROP_THIS_TABLE;
+ return true;
+ }
+
+ gpos->data = data;
+ gpos->length = length;
+ return true;
+}
+
+bool ots_gpos_should_serialise(OpenTypeFile *file) {
+ return file->gpos != NULL;
+}
+
+bool ots_gpos_serialise(OTSStream *out, OpenTypeFile *file) {
+ if (!out->Write(file->gpos->data, file->gpos->length)) {
+ return OTS_FAILURE();
+ }
+
+ return true;
+}
+
+void ots_gpos_free(OpenTypeFile *file) {
+ delete file->gpos;
+}
+
+} // namespace ots
+