tor-browser

gpos.cc (26036B)

---

// Copyright (c) 2011-2017 The OTS 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

#define TABLE_NAME "GPOS"

namespace {

enum GPOS_TYPE {
 GPOS_TYPE_SINGLE_ADJUSTMENT = 1,
 GPOS_TYPE_PAIR_ADJUSTMENT = 2,
 GPOS_TYPE_CURSIVE_ATTACHMENT = 3,
 GPOS_TYPE_MARK_TO_BASE_ATTACHMENT = 4,
 GPOS_TYPE_MARK_TO_LIGATURE_ATTACHMENT = 5,
 GPOS_TYPE_MARK_TO_MARK_ATTACHMENT = 6,
 GPOS_TYPE_CONTEXT_POSITIONING = 7,
 GPOS_TYPE_CHAINED_CONTEXT_POSITIONING = 8,
 GPOS_TYPE_EXTENSION_POSITIONING = 9,
 GPOS_TYPE_RESERVED = 10
};

// The maximum format number for anchor tables.
const uint16_t kMaxAnchorFormat = 3;

// Shared Tables: ValueRecord, Anchor Table, and MarkArray

size_t CalcValueRecordSize(const uint16_t value_format) {
 size_t size = 0;
 for (unsigned i = 0; i < 8; ++i) {
   if ((value_format >> i) & 0x1) {
     size += 2;
   }
 }

 return size;
}

bool ParseValueRecord(const ots::Font *font,
                     ots::Buffer* subtable,
                     const uint16_t value_format) {
 const uint8_t *data = subtable->buffer();
 const size_t length = subtable->length();

 // 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_MSG("Failed to read value reacord component");
     }
   }
 }

 // 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_MSG("Failed to read value record offset");
     }
     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_MSG("Value record offset too high %d >= %ld", offset, length);
       }
       if (!ots::ParseDeviceTable(font, data + offset, length - offset)) {
         return OTS_FAILURE_MSG("Failed to parse device table in value record");
       }
     }
   }
 }
 return true;
}

bool ParseAnchorTable(const ots::Font *font,
                     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_MSG("Faled to read anchor table");
 }

 if (format == 0 || format > kMaxAnchorFormat) {
   return OTS_FAILURE_MSG("Bad Anchor table format %d", format);
 }

 // 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_MSG("Failed to read anchor point in format 2 Anchor Table");
   }
 } 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_MSG("Failed to read device table offsets in format 3 anchor table");
   }
   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_MSG("Bad x device table offset %d", offset_x_device);
     }
     if (!ots::ParseDeviceTable(font, data + offset_x_device,
                                length - offset_x_device)) {
       return OTS_FAILURE_MSG("Failed to parse device table in anchor table");
     }
   }
   if (offset_y_device) {
     if (offset_y_device < format_end || offset_y_device >= length) {
       return OTS_FAILURE_MSG("Bad y device table offset %d", offset_y_device);
     }
     if (!ots::ParseDeviceTable(font, data + offset_y_device,
                                length - offset_y_device)) {
       return OTS_FAILURE_MSG("Failed to parse device table in anchor table");
     }
   }
 }
 return true;
}

bool ParseMarkArrayTable(const ots::Font *font,
                        const uint8_t *data, const size_t length) {
 ots::Buffer subtable(data, length);

 uint16_t mark_count = 0;
 if (!subtable.ReadU16(&mark_count)) {
   return OTS_FAILURE_MSG("Can't read mark table length");
 }

 // MarkRecord consists of 4-bytes.
 const unsigned mark_records_end = 4 * static_cast<unsigned>(mark_count) + 2;
 if (mark_records_end > std::numeric_limits<uint16_t>::max()) {
   return OTS_FAILURE_MSG("Bad mark table length");
 }
 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_MSG("Can't read mark table %d", i);
   }
   // |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_MSG("Bad mark anchor offset %d for mark table %d", offset_mark_anchor, i);
   }
   if (!ParseAnchorTable(font, data + offset_mark_anchor,
                         length - offset_mark_anchor)) {
     return OTS_FAILURE_MSG("Faled to parse anchor table for mark table %d", i);
   }
 }

 return true;
}

bool ParsePairSetTable(const ots::Font *font,
                      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_MSG("Failed to read pair set table structure");
 }
 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_MSG("Failed to read glyph in pair value record %d", i);
   }
   if (glyph_id >= num_glyphs) {
     return OTS_FAILURE_MSG("glyph id %d too high >= %d", glyph_id, num_glyphs);
   }
   if (!ParseValueRecord(font, &subtable, value_format1)) {
     return OTS_FAILURE_MSG("Failed to parse value record in format 1 pair set table");
   }
   if (!ParseValueRecord(font, &subtable, value_format2)) {
     return OTS_FAILURE_MSG("Failed to parse value record in format 2 pair set table");
   }
 }
 return true;
}

bool ParsePairPosFormat1(const ots::Font *font,
                        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_MSG("Failed to read pair pos table structure");
 }

 uint16_t pair_set_count = 0;
 if (!subtable.ReadU16(&pair_set_count)) {
   return OTS_FAILURE_MSG("Failed to read pair pos set count");
 }

 const unsigned pair_pos_end = 2 * static_cast<unsigned>(pair_set_count) + 10;
 if (pair_pos_end > std::numeric_limits<uint16_t>::max()) {
   return OTS_FAILURE_MSG("Bad pair set length %d", pair_pos_end);
 }
 for (unsigned i = 0; i < pair_set_count; ++i) {
   uint16_t pair_set_offset = 0;
   if (!subtable.ReadU16(&pair_set_offset)) {
     return OTS_FAILURE_MSG("Failed to read pair set offset for pair set %d", i);
   }
   if (pair_set_offset < pair_pos_end || pair_set_offset >= length) {
     return OTS_FAILURE_MSG("Bad pair set offset %d for pair set %d", pair_set_offset, i);
   }
   // Check pair set tables
   if (!ParsePairSetTable(font, data + pair_set_offset, length - pair_set_offset,
                          value_format1, value_format2,
                          num_glyphs)) {
     return OTS_FAILURE_MSG("Failed to parse pair set table %d", i);
   }
 }

 return true;
}

bool ParsePairPosFormat2(const ots::Font *font,
                        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_MSG("Failed to read pair pos format 2 structure");
 }

 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_MSG("Failed to read pair pos format 2 data");
 }

 size_t value_record1_size = CalcValueRecordSize(value_format1);
 size_t value_record2_size = CalcValueRecordSize(value_format2);
 size_t value_records_size = size_t(class1_count) * size_t(class2_count) *
   (value_record1_size + value_record2_size);

 // Check the validity of class definition offsets.
 if (offset_class_def1 < subtable.offset() + value_records_size ||
     offset_class_def2 < subtable.offset() + value_records_size ||
     offset_class_def1 >= length || offset_class_def2 >= length) {
   return OTS_FAILURE_MSG("Bad ParsePairPosFormat2 class definition offsets %d or %d", offset_class_def1, offset_class_def2);
 }

 // Check class 1 records.
 if (value_record1_size || value_record2_size) {
   for (unsigned i = 0; i < class1_count; ++i) {
     // Check class 2 records.
     for (unsigned j = 0; j < class2_count; ++j) {
       if (value_format1 && value_record2_size &&
           !ParseValueRecord(font, &subtable, value_format1)) {
         return OTS_FAILURE_MSG("Failed to parse value record 1 %d and %d", j, i);
       }
       if (value_format2 && value_record2_size &&
           !ParseValueRecord(font, &subtable, value_format2)) {
         return OTS_FAILURE_MSG("Falied to parse value record 2 %d and %d", j, i);
       }
     }
   }
 }

 // Check class definition tables.
 if (!ots::ParseClassDefTable(font, data + offset_class_def1,
                              length - offset_class_def1,
                              num_glyphs, ots::kMaxClassDefValue)) {
   return OTS_FAILURE_MSG("Failed to parse class definition table 1");
 }
 if (!ots::ParseClassDefTable(font, data + offset_class_def2,
                              length - offset_class_def2,
                              num_glyphs, ots::kMaxClassDefValue)) {
   return OTS_FAILURE_MSG("Failed to parse class definition table 2");
 }

 return true;
}

bool ParseAnchorArrayTable(const ots::Font *font,
                          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_MSG("Can't read anchor array length");
 }

 const unsigned anchor_array_end = 2 * static_cast<unsigned>(record_count) *
     static_cast<unsigned>(class_count) + 2;
 if (anchor_array_end > std::numeric_limits<uint16_t>::max()) {
   return OTS_FAILURE_MSG("Bad end of anchor array %d", anchor_array_end);
 }
 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_MSG("Can't read anchor array record offset for class %d and record %d", j, i);
     }
     // |offset_record| could be NULL.
     if (offset_record) {
       if (offset_record < anchor_array_end || offset_record >= length) {
         return OTS_FAILURE_MSG("Bad record offset %d in class %d, record %d", offset_record, j, i);
       }
       if (!ParseAnchorTable(font, data + offset_record,
                             length - offset_record)) {
         return OTS_FAILURE_MSG("Failed to parse anchor table for class %d, record %d", j, i);
       }
     }
   }
 }
 return true;
}

bool ParseLigatureArrayTable(const ots::Font *font,
                            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_MSG("Failed to read ligature count");
 }
 for (unsigned i = 0; i < ligature_count; ++i) {
   uint16_t offset_ligature_attach = 0;
   if (!subtable.ReadU16(&offset_ligature_attach)) {
     return OTS_FAILURE_MSG("Can't read ligature offset %d", i);
   }
   if (offset_ligature_attach < 2 || offset_ligature_attach >= length) {
     return OTS_FAILURE_MSG("Bad ligature attachment offset %d in ligature %d", offset_ligature_attach, i);
   }
   if (!ParseAnchorArrayTable(font, data + offset_ligature_attach,
                              length - offset_ligature_attach, class_count)) {
     return OTS_FAILURE_MSG("Failed to parse anchor table for ligature %d", i);
   }
 }
 return true;
}

// Common parser for Lookup Type 4, 5 and 6.
bool ParseMarkToAttachmentSubtables(const ots::Font *font,
                                   const uint8_t *data, const size_t length,
                                   const GPOS_TYPE type) {
 ots::Buffer subtable(data, length);

 ots::OpenTypeMAXP *maxp = static_cast<ots::OpenTypeMAXP*>(
     font->GetTypedTable(OTS_TAG_MAXP));
 if (!maxp) {
   return OTS_FAILURE_MSG("Required maxp table missing");
 }

 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_MSG("Failed to read mark attachment subtable header");
 }

 if (format != 1) {
   return OTS_FAILURE_MSG("bad mark attachment subtable format %d", format);
 }

 const unsigned header_end = static_cast<unsigned>(subtable.offset());
 if (header_end > std::numeric_limits<uint16_t>::max()) {
   return OTS_FAILURE_MSG("Bad mark attachment subtable size ending at %d", header_end);
 }
 if (offset_coverage1 < header_end || offset_coverage1 >= length) {
   return OTS_FAILURE_MSG("Bad coverage 1 offset %d", offset_coverage1);
 }
 if (!ots::ParseCoverageTable(font, data + offset_coverage1,
                              length - offset_coverage1,
                              maxp->num_glyphs)) {
   return OTS_FAILURE_MSG("Failed to parse converge 1 table");
 }
 if (offset_coverage2 < header_end || offset_coverage2 >= length) {
   return OTS_FAILURE_MSG("Bad coverage 2 offset %d", offset_coverage2);
 }
 if (!ots::ParseCoverageTable(font, data + offset_coverage2,
                              length - offset_coverage2,
                              maxp->num_glyphs)) {
   return OTS_FAILURE_MSG("Failed to parse coverage table 2");
 }

 if (offset_mark_array < header_end || offset_mark_array >= length) {
   return OTS_FAILURE_MSG("Bad mark array offset %d", offset_mark_array);
 }
 if (!ParseMarkArrayTable(font, data + offset_mark_array,
                          length - offset_mark_array)) {
   return OTS_FAILURE_MSG("Failed to parse mark array");
 }

 if (offset_type_specific_array < header_end ||
     offset_type_specific_array >= length) {
   return OTS_FAILURE_MSG("Bad type specific array offset %d", offset_type_specific_array);
 }
 if (type == GPOS_TYPE_MARK_TO_BASE_ATTACHMENT ||
     type == GPOS_TYPE_MARK_TO_MARK_ATTACHMENT) {
   if (!ParseAnchorArrayTable(font, data + offset_type_specific_array,
                              length - offset_type_specific_array,
                              class_count)) {
     return OTS_FAILURE_MSG("Failed to parse anchor array");
   }
 } else if (type == GPOS_TYPE_MARK_TO_LIGATURE_ATTACHMENT) {
   if (!ParseLigatureArrayTable(font, data + offset_type_specific_array,
                                length - offset_type_specific_array,
                                class_count)) {
     return OTS_FAILURE_MSG("Failed to parse ligature array");
   }
 } else {
   return OTS_FAILURE_MSG("Bad attachment type %d", type);
 }

 return true;
}

}  // namespace

namespace ots {

// Lookup Type 1:
// Single Adjustment Positioning Subtable
bool OpenTypeGPOS::ParseSingleAdjustment(const uint8_t *data,
                                        const size_t length) {
 Font* font = GetFont();
 Buffer subtable(data, length);

 OpenTypeMAXP *maxp = static_cast<OpenTypeMAXP*>(
     font->GetTypedTable(OTS_TAG_MAXP));
 if (!maxp) {
   return Error("Required maxp table missing");
 }

 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 Error("Can't read single adjustment information");
 }

 if (format == 1) {
   // Format 1 exactly one value record.
   if (!ParseValueRecord(font, &subtable, value_format)) {
     return Error("Failed to parse format 1 single adjustment table");
   }
 } else if (format == 2) {
   uint16_t value_count = 0;
   if (!subtable.ReadU16(&value_count)) {
     return Error("Failed to parse format 2 single adjustment table");
   }
   for (unsigned i = 0; i < value_count; ++i) {
     if (!ParseValueRecord(font, &subtable, value_format)) {
       return Error("Failed to parse value record %d in format 2 single adjustment table", i);
     }
   }
 } else {
   return Error("Bad format %d in single adjustment table", format);
 }

 if (offset_coverage < subtable.offset() || offset_coverage >= length) {
   return Error("Bad coverage offset %d in single adjustment table", offset_coverage);
 }

 if (!ots::ParseCoverageTable(font, data + offset_coverage,
                              length - offset_coverage,
                              maxp->num_glyphs)) {
   return Error("Failed to parse coverage table in single adjustment table");
 }

 return true;
}

// Lookup Type 2:
// Pair Adjustment Positioning Subtable
bool OpenTypeGPOS::ParsePairAdjustment(const uint8_t *data,
                                      const size_t length) {
 Font* font = GetFont();
 Buffer subtable(data, length);

 OpenTypeMAXP *maxp = static_cast<OpenTypeMAXP*>(
     font->GetTypedTable(OTS_TAG_MAXP));
 if (!maxp) {
   return Error("Required maxp table missing");
 }

 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 Error("Failed to read pair adjustment structure");
 }

 if (format == 1) {
   if (!ParsePairPosFormat1(font, data, length, value_format1, value_format2,
                            maxp->num_glyphs)) {
     return Error("Failed to parse pair pos format 1");
   }
 } else if (format == 2) {
   if (!ParsePairPosFormat2(font, data, length, value_format1, value_format2,
                            maxp->num_glyphs)) {
     return Error("Failed to parse pair format 2");
   }
 } else {
   return Error("Bad pos pair format %d", format);
 }

 if (offset_coverage < subtable.offset() || offset_coverage >= length) {
   return Error("Bad pair pos offset coverage %d", offset_coverage);
 }
 if (!ots::ParseCoverageTable(font, data + offset_coverage,
                              length - offset_coverage,
                              maxp->num_glyphs)) {
   return Error("Failed to parse coverage table");
 }

 return true;
}

// Lookup Type 3
// Cursive Attachment Positioning Subtable
bool OpenTypeGPOS::ParseCursiveAttachment(const uint8_t *data,
                                         const size_t length) {
 Font* font = GetFont();
 Buffer subtable(data, length);

 OpenTypeMAXP *maxp = static_cast<OpenTypeMAXP*>(
     font->GetTypedTable(OTS_TAG_MAXP));
 if (!maxp) {
   return Error("Required maxp table missing");
 }

 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 Error("Failed to read cursive attachment structure");
 }

 if (format != 1) {
   return Error("Bad cursive attachment format %d", format);
 }

 // Check entry exit records.
 const unsigned entry_exit_records_end =
     2 * static_cast<unsigned>(entry_exit_count) + 6;
 if (entry_exit_records_end > std::numeric_limits<uint16_t>::max()) {
   return Error("Bad entry exit record end %d", entry_exit_records_end);
 }
 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 Error("Can't read entry exit record %d", i);
   }
   // These offsets could be NULL.
   if (offset_entry_anchor) {
     if (offset_entry_anchor < entry_exit_records_end ||
         offset_entry_anchor >= length) {
       return Error("Bad entry anchor offset %d in entry exit record %d", offset_entry_anchor, i);
     }
     if (!ParseAnchorTable(font, data + offset_entry_anchor,
                           length - offset_entry_anchor)) {
       return Error("Failed to parse entry anchor table in entry exit record %d", i);
     }
   }
   if (offset_exit_anchor) {
     if (offset_exit_anchor < entry_exit_records_end ||
        offset_exit_anchor >= length) {
       return Error("Bad exit anchor offset %d in entry exit record %d", offset_exit_anchor, i);
     }
     if (!ParseAnchorTable(font, data + offset_exit_anchor,
                           length - offset_exit_anchor)) {
       return Error("Failed to parse exit anchor table in entry exit record %d", i);
     }
   }
 }

 if (offset_coverage < subtable.offset() || offset_coverage >= length) {
   return Error("Bad coverage offset in cursive attachment %d", offset_coverage);
 }
 if (!ots::ParseCoverageTable(font, data + offset_coverage,
                              length - offset_coverage,
                              maxp->num_glyphs)) {
   return Error("Failed to parse coverage table in cursive attachment");
 }

 return true;
}

// Lookup Type 4:
// MarkToBase Attachment Positioning Subtable
bool OpenTypeGPOS::ParseMarkToBaseAttachment(const uint8_t *data,
                                            const size_t length) {
 return ParseMarkToAttachmentSubtables(GetFont(), data, length,
                                       GPOS_TYPE_MARK_TO_BASE_ATTACHMENT);
}

// Lookup Type 5:
// MarkToLigature Attachment Positioning Subtable
bool OpenTypeGPOS::ParseMarkToLigatureAttachment(const uint8_t *data,
                                                const size_t length) {
 return ParseMarkToAttachmentSubtables(GetFont(), data, length,
                                       GPOS_TYPE_MARK_TO_LIGATURE_ATTACHMENT);
}

// Lookup Type 6:
// MarkToMark Attachment Positioning Subtable
bool OpenTypeGPOS::ParseMarkToMarkAttachment(const uint8_t *data,
                                            const size_t length) {
 return ParseMarkToAttachmentSubtables(GetFont(), data, length,
                                       GPOS_TYPE_MARK_TO_MARK_ATTACHMENT);
}

// Lookup Type 7:
// Contextual Positioning Subtables
// OpenTypeLayoutTable::ParseContextSubtable()

// Lookup Type 8:
// Chaining Contexual Positioning Subtable
// OpenTypeLayoutTable::ParseChainingContextSubtable()

// Lookup Type 9:
// Extension Positioning
// OpenTypeLayoutTable::ParseExtensionSubtable


bool OpenTypeGPOS::ValidLookupSubtableType(const uint16_t lookup_type,
                                          bool extension) const {
 if (extension && lookup_type == GPOS_TYPE_EXTENSION_POSITIONING)
   return false;
 return lookup_type >= GPOS_TYPE_SINGLE_ADJUSTMENT && lookup_type < GPOS_TYPE_RESERVED;
}

bool OpenTypeGPOS::ParseLookupSubtable(const uint8_t *data, const size_t length,
                                      const uint16_t lookup_type) {
 switch (lookup_type) {
   case GPOS_TYPE_SINGLE_ADJUSTMENT:
     return ParseSingleAdjustment(data, length);
   case GPOS_TYPE_PAIR_ADJUSTMENT:
     return ParsePairAdjustment(data, length);
   case GPOS_TYPE_CURSIVE_ATTACHMENT:
     return ParseCursiveAttachment(data, length);
   case GPOS_TYPE_MARK_TO_BASE_ATTACHMENT:
     return ParseMarkToBaseAttachment(data, length);
   case GPOS_TYPE_MARK_TO_LIGATURE_ATTACHMENT:
     return ParseMarkToLigatureAttachment(data, length);
   case GPOS_TYPE_MARK_TO_MARK_ATTACHMENT:
     return ParseMarkToMarkAttachment(data, length);
   case GPOS_TYPE_CONTEXT_POSITIONING:
     return ParseContextSubtable(data, length);
   case GPOS_TYPE_CHAINED_CONTEXT_POSITIONING:
     return ParseChainingContextSubtable(data, length);
   case GPOS_TYPE_EXTENSION_POSITIONING:
     return ParseExtensionSubtable(data, length);
 }
 return false;
}

}  // namespace ots

#undef TABLE_NAME