tor-browser

ots.cc (37970B)

---

// Copyright (c) 2009-2017 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 "ots.h"

#include <sys/types.h>
#include <zlib.h>

#include <algorithm>
#include <cstdlib>
#include <cstring>
#include <limits>
#include <map>
#include <vector>

#include "../RLBoxWOFF2Host.h"

// The OpenType Font File
// http://www.microsoft.com/typography/otspec/otff.htm

#include "avar.h"
#include "cff.h"
#include "cmap.h"
#include "colr.h"
#include "cpal.h"
#include "cvar.h"
#include "cvt.h"
#include "fpgm.h"
#include "fvar.h"
#include "gasp.h"
#include "gdef.h"
#include "glyf.h"
#include "gpos.h"
#include "gsub.h"
#include "gvar.h"
#include "hdmx.h"
#include "head.h"
#include "hhea.h"
#include "hmtx.h"
#include "hvar.h"
#include "kern.h"
#include "loca.h"
#include "ltsh.h"
#include "math_.h"
#include "maxp.h"
#include "mvar.h"
#include "name.h"
#include "os2.h"
#include "ots.h"
#include "post.h"
#include "prep.h"
#include "stat.h"
#include "vdmx.h"
#include "vhea.h"
#include "vmtx.h"
#include "vorg.h"
#include "vvar.h"

// Graphite tables
#ifdef OTS_GRAPHITE
#include "feat.h"
#include "glat.h"
#include "gloc.h"
#include "sile.h"
#include "silf.h"
#include "sill.h"
#endif

namespace ots {

struct Arena {
public:
 ~Arena() {
   for (auto& hunk : hunks_) {
     delete[] hunk;
   }
 }

 uint8_t* Allocate(size_t length) {
   uint8_t* p = new uint8_t[length];
   hunks_.push_back(p);
   return p;
 }

private:
 std::vector<uint8_t*> hunks_;
};

bool CheckTag(uint32_t tag_value) {
 for (unsigned i = 0; i < 4; ++i) {
   const uint32_t check = tag_value & 0xff;
   if (check < 32 || check > 126) {
     return false;  // non-ASCII character found.
   }
   tag_value >>= 8;
 }
 return true;
}

}; // namespace ots

namespace {

// ots_msg_tag emits the tag as hex if it is not valid, to avoid putting NUL or
// other non-printables into the message string.
static inline void ots_msg_tag(int level, const ots::FontFile* otf, const char* msg, uint32_t tag) {
 if (ots::CheckTag(tag)) {
   OTS_MESSAGE_(level, otf, "%c%c%c%c: %s", OTS_UNTAG(tag), msg);
 } else {
   OTS_MESSAGE_(level, otf, "<%08X>: %s", tag, msg);
 }
}

// Generate a message with or without a table tag, when 'header' is the FontFile pointer
#define OTS_FAILURE_MSG_TAG(msg_,tag_) (ots_msg_tag(0, header, msg_, tag_), false)
#define OTS_FAILURE_MSG_HDR(...)       OTS_FAILURE_MSG_(header, __VA_ARGS__)
#define OTS_WARNING_MSG_HDR(...)       OTS_WARNING_MSG_(header, __VA_ARGS__)


const struct {
 uint32_t tag;
 bool required;
} supported_tables[] = {
 { OTS_TAG_MAXP, true },
 { OTS_TAG_HEAD, true },
 { OTS_TAG_OS2,  true },
 { OTS_TAG_CMAP, true },
 { OTS_TAG_HHEA, true },
 { OTS_TAG_HMTX, true },
 { OTS_TAG_NAME, true },
 { OTS_TAG_POST, true },
 { OTS_TAG_LOCA, false },
 { OTS_TAG_GLYF, false },
 { OTS_TAG_CFF,  false },
 { OTS_TAG_VDMX, false },
 { OTS_TAG_HDMX, false },
 { OTS_TAG_GASP, false },
 { OTS_TAG_CVT,  false },
 { OTS_TAG_FPGM, false },
 { OTS_TAG_PREP, false },
 { OTS_TAG_LTSH, false },
 { OTS_TAG_VORG, false },
 { OTS_TAG_KERN, false },
 // We need to parse fvar table before other tables that may need to know
 // the number of variation axes (if any)
 { OTS_TAG_FVAR, false },
 { OTS_TAG_AVAR, false },
 { OTS_TAG_CVAR, false },
 { OTS_TAG_GVAR, false },
 { OTS_TAG_HVAR, false },
 { OTS_TAG_MVAR, false },
 { OTS_TAG_STAT, false },
 { OTS_TAG_VVAR, false },
 { OTS_TAG_CFF2, false },
 // Color font tables.
 // We need to parse CPAL before COLR so that the number of palette entries
 // is known; and these tables follow fvar because COLR may use variations.
 { OTS_TAG_CPAL, false },
 { OTS_TAG_COLR, false },
 // We need to parse GDEF table in advance of parsing GSUB/GPOS tables
 // because they could refer GDEF table.
 { OTS_TAG_GDEF, false },
 { OTS_TAG_GPOS, false },
 { OTS_TAG_GSUB, false },
 { OTS_TAG_VHEA, false },
 { OTS_TAG_VMTX, false },
 { OTS_TAG_MATH, false },
 // Graphite tables
#ifdef OTS_GRAPHITE
 { OTS_TAG_GLOC, false },
 { OTS_TAG_GLAT, false },
 { OTS_TAG_FEAT, false },
 { OTS_TAG_SILF, false },
 { OTS_TAG_SILE, false },
 { OTS_TAG_SILL, false },
#endif
 { 0, false },
};

bool ValidateVersionTag(ots::Font *font) {
 switch (font->version) {
   case 0x000010000:
   case OTS_TAG('O','T','T','O'):
     return true;
   case OTS_TAG('t','r','u','e'):
     font->version = 0x000010000;
     return true;
   default:
     return false;
 }
}

bool ProcessGeneric(ots::FontFile *header,
                   ots::Font *font,
                   uint32_t signature,
                   ots::OTSStream *output,
                   const uint8_t *data, size_t length,
                   const std::vector<ots::TableEntry>& tables,
                   ots::Buffer& file);

bool ProcessTTF(ots::FontFile *header,
               ots::Font *font,
               ots::OTSStream *output, const uint8_t *data, size_t length,
               uint32_t offset = 0) {
 ots::Buffer file(data + offset, length - offset);

 if (offset > length) {
   return OTS_FAILURE_MSG_HDR("offset beyond end of file");
 }

 // we disallow all files > 1GB in size for sanity.
 if (length > 1024 * 1024 * 1024) {
   return OTS_FAILURE_MSG_HDR("file exceeds 1GB");
 }

 if (!file.ReadU32(&font->version)) {
   return OTS_FAILURE_MSG_HDR("error reading sfntVersion");
 }
 if (!ValidateVersionTag(font)) {
   return OTS_FAILURE_MSG_HDR("invalid sfntVersion: %d", font->version);
 }

 if (!file.ReadU16(&font->num_tables) ||
     !file.ReadU16(&font->search_range) ||
     !file.ReadU16(&font->entry_selector) ||
     !file.ReadU16(&font->range_shift)) {
   return OTS_FAILURE_MSG_HDR("error reading table directory search header");
 }

 // search_range is (Maximum power of 2 <= numTables) x 16. Thus, to avoid
 // overflow num_tables is, at most, 2^16 / 16 = 2^12
 if (font->num_tables >= 4096 || font->num_tables < 1) {
   return OTS_FAILURE_MSG_HDR("excessive (or zero) number of tables");
 }

 unsigned max_pow2 = 0;
 while (1u << (max_pow2 + 1) <= font->num_tables) {
   max_pow2++;
 }
 const uint16_t expected_search_range = (1u << max_pow2) << 4;

 // Don't call ots_failure() here since ~25% of fonts (250+ fonts) in
 // http://www.princexml.com/fonts/ have unexpected search_range value.
 if (font->search_range != expected_search_range) {
   OTS_WARNING_MSG_HDR("bad table directory searchRange");
   font->search_range = expected_search_range;  // Fix the value.
 }

 // entry_selector is Log2(maximum power of 2 <= numTables)
 if (font->entry_selector != max_pow2) {
   OTS_WARNING_MSG_HDR("bad table directory entrySelector");
   font->entry_selector = max_pow2;  // Fix the value.
 }

 // range_shift is NumTables x 16-searchRange. We know that 16*num_tables
 // doesn't over flow because we range checked it above. Also, we know that
 // it's > font->search_range by construction of search_range.
 const uint16_t expected_range_shift =
     16 * font->num_tables - font->search_range;
 if (font->range_shift != expected_range_shift) {
   OTS_WARNING_MSG_HDR("bad table directory rangeShift");
   font->range_shift = expected_range_shift;  // the same as above.
 }

 // Next up is the list of tables.
 std::vector<ots::TableEntry> tables;

 for (unsigned i = 0; i < font->num_tables; ++i) {
   ots::TableEntry table;
   if (!file.ReadU32(&table.tag) ||
       !file.ReadU32(&table.chksum) ||
       !file.ReadU32(&table.offset) ||
       !file.ReadU32(&table.length)) {
     return OTS_FAILURE_MSG_HDR("error reading table directory");
   }

   table.uncompressed_length = table.length;
   tables.push_back(table);
 }

 return ProcessGeneric(header, font, font->version, output, data, length,
                       tables, file);
}

bool ProcessTTC(ots::FontFile *header,
               ots::OTSStream *output,
               const uint8_t *data,
               size_t length,
               uint32_t index) {
 ots::Buffer file(data, length);

 // we disallow all files > 1GB in size for sanity.
 if (length > 1024 * 1024 * 1024) {
   return OTS_FAILURE_MSG_HDR("file exceeds 1GB");
 }

 uint32_t ttc_tag;
 if (!file.ReadU32(&ttc_tag)) {
   return OTS_FAILURE_MSG_HDR("Error reading TTC tag");
 }
 if (ttc_tag != OTS_TAG('t','t','c','f')) {
   return OTS_FAILURE_MSG_HDR("Invalid TTC tag");
 }

 uint32_t ttc_version;
 if (!file.ReadU32(&ttc_version)) {
   return OTS_FAILURE_MSG_HDR("Error reading TTC version");
 }
 if (ttc_version != 0x00010000 && ttc_version != 0x00020000) {
   return OTS_FAILURE_MSG_HDR("Invalid TTC version");
 }

 uint32_t num_fonts;
 if (!file.ReadU32(&num_fonts)) {
   return OTS_FAILURE_MSG_HDR("Error reading number of TTC fonts");
 }
 // Limit the allowed number of subfonts to have same memory allocation.
 if (num_fonts > 0x10000) {
   return OTS_FAILURE_MSG_HDR("Too many fonts in TTC");
 }

 std::vector<uint32_t> offsets(num_fonts);
 for (unsigned i = 0; i < num_fonts; i++) {
   if (!file.ReadU32(&offsets[i])) {
     return OTS_FAILURE_MSG_HDR("Error reading offset to OffsetTable");
   }
 }

 if (ttc_version == 0x00020000) {
   // We don't care about these fields of the header:
   // uint32_t dsig_tag, dsig_length, dsig_offset
   if (!file.Skip(3 * 4)) {
     return OTS_FAILURE_MSG_HDR("Error reading DSIG offset and length in TTC font");
   }
 }

 if (index == static_cast<uint32_t>(-1)) {
   if (!output->WriteU32(ttc_tag) ||
       !output->WriteU32(0x00010000) ||
       !output->WriteU32(num_fonts) ||
       !output->Seek((3 + num_fonts) * 4)) {
     return OTS_FAILURE_MSG_HDR("Error writing output");
   }

   // Keep references to the fonts processed in the loop below, as we need
   // them for reused tables.
   std::vector<ots::Font> fonts(num_fonts, ots::Font(header));

   for (unsigned i = 0; i < num_fonts; i++) {
     uint32_t out_offset = output->Tell();
     if (!output->Seek((3 + i) * 4) ||
         !output->WriteU32(out_offset) ||
         !output->Seek(out_offset)) {
       return OTS_FAILURE_MSG_HDR("Error writing output");
     }
     if (!ProcessTTF(header, &fonts[i], output, data, length, offsets[i])) {
       return false;
     }
   }

   return true;
 } else {
   if (index >= num_fonts) {
     return OTS_FAILURE_MSG_HDR("Requested font index is bigger than the number of fonts in the TTC file");
   }

   ots::Font font(header);
   return ProcessTTF(header, &font, output, data, length, offsets[index]);
 }
}

bool ProcessWOFF(ots::FontFile *header,
                ots::Font *font,
                ots::OTSStream *output, const uint8_t *data, size_t length) {
 ots::Buffer file(data, length);

 // we disallow all files > 1GB in size for sanity.
 if (length > 1024 * 1024 * 1024) {
   return OTS_FAILURE_MSG_HDR("file exceeds 1GB");
 }

 uint32_t woff_tag;
 if (!file.ReadU32(&woff_tag)) {
   return OTS_FAILURE_MSG_HDR("error reading WOFF marker");
 }

 if (woff_tag != OTS_TAG('w','O','F','F')) {
   return OTS_FAILURE_MSG_HDR("invalid WOFF marker");
 }

 if (!file.ReadU32(&font->version)) {
   return OTS_FAILURE_MSG_HDR("error reading sfntVersion");
 }
 if (!ValidateVersionTag(font)) {
   return OTS_FAILURE_MSG_HDR("invalid sfntVersion: %d", font->version);
 }

 uint32_t reported_length;
 if (!file.ReadU32(&reported_length) || length != reported_length) {
   return OTS_FAILURE_MSG_HDR("incorrect file size in WOFF header");
 }

 if (!file.ReadU16(&font->num_tables) || !font->num_tables) {
   return OTS_FAILURE_MSG_HDR("error reading number of tables");
 }

 uint16_t reserved_value;
 if (!file.ReadU16(&reserved_value) || reserved_value) {
   return OTS_FAILURE_MSG_HDR("error in reserved field of WOFF header");
 }

 uint32_t reported_total_sfnt_size;
 if (!file.ReadU32(&reported_total_sfnt_size)) {
   return OTS_FAILURE_MSG_HDR("error reading total sfnt size");
 }

 // We don't care about these fields of the header:
 //   uint16_t major_version, minor_version
 if (!file.Skip(2 * 2)) {
   return OTS_FAILURE_MSG_HDR("Failed to read 'majorVersion' or 'minorVersion'");
 }

 // Checks metadata block size.
 uint32_t meta_offset;
 uint32_t meta_length;
 uint32_t meta_length_orig;
 if (!file.ReadU32(&meta_offset) ||
     !file.ReadU32(&meta_length) ||
     !file.ReadU32(&meta_length_orig)) {
   return OTS_FAILURE_MSG_HDR("Failed to read header metadata block fields");
 }
 if (meta_offset) {
   if (meta_offset >= length || length - meta_offset < meta_length) {
     return OTS_FAILURE_MSG_HDR("Invalid metadata block offset or length");
   }
 }

 // Checks private data block size.
 uint32_t priv_offset;
 uint32_t priv_length;
 if (!file.ReadU32(&priv_offset) ||
     !file.ReadU32(&priv_length)) {
   return OTS_FAILURE_MSG_HDR("Failed to read header private block fields");
 }
 if (priv_offset) {
   if (priv_offset >= length || length - priv_offset < priv_length) {
     return OTS_FAILURE_MSG_HDR("Invalid private block offset or length");
   }
 }

 // Next up is the list of tables.
 std::vector<ots::TableEntry> tables;

 uint32_t first_index = 0;
 uint32_t last_index = 0;
 // Size of sfnt header plus size of table records.
 uint64_t total_sfnt_size = 12 + 16 * font->num_tables;
 for (unsigned i = 0; i < font->num_tables; ++i) {
   ots::TableEntry table;
   if (!file.ReadU32(&table.tag) ||
       !file.ReadU32(&table.offset) ||
       !file.ReadU32(&table.length) ||
       !file.ReadU32(&table.uncompressed_length) ||
       !file.ReadU32(&table.chksum)) {
     return OTS_FAILURE_MSG_HDR("error reading table directory");
   }

   total_sfnt_size += ots::Round4(table.uncompressed_length);
   if (total_sfnt_size > std::numeric_limits<uint32_t>::max()) {
     return OTS_FAILURE_MSG_HDR("sfnt size overflow");
   }
   tables.push_back(table);
   if (i == 0 || tables[first_index].offset > table.offset)
     first_index = i;
   if (i == 0 || tables[last_index].offset < table.offset)
     last_index = i;
 }

 if (reported_total_sfnt_size != total_sfnt_size) {
   return OTS_FAILURE_MSG_HDR("uncompressed sfnt size mismatch");
 }

 // Table data must follow immediately after the header.
 if (tables[first_index].offset != ots::Round4(file.offset())) {
   return OTS_FAILURE_MSG_HDR("junk before tables in WOFF file");
 }

 if (tables[last_index].offset >= length ||
     length - tables[last_index].offset < tables[last_index].length) {
   return OTS_FAILURE_MSG_HDR("invalid table location/size");
 }
 // Blocks must follow immediately after the previous block.
 // (Except for padding with a maximum of three null bytes)
 uint64_t block_end = ots::Round4(
     static_cast<uint64_t>(tables[last_index].offset) +
     static_cast<uint64_t>(tables[last_index].length));
 if (block_end > std::numeric_limits<uint32_t>::max()) {
   return OTS_FAILURE_MSG_HDR("invalid table location/size");
 }
 if (meta_offset) {
   if (block_end != meta_offset) {
     return OTS_FAILURE_MSG_HDR("Invalid metadata block offset");
   }
   block_end = ots::Round4(static_cast<uint64_t>(meta_offset) +
                           static_cast<uint64_t>(meta_length));
   if (block_end > std::numeric_limits<uint32_t>::max()) {
     return OTS_FAILURE_MSG_HDR("Invalid metadata block length");
   }
 }
 if (priv_offset) {
   if (block_end != priv_offset) {
     return OTS_FAILURE_MSG_HDR("Invalid private block offset");
   }
   block_end = ots::Round4(static_cast<uint64_t>(priv_offset) +
                           static_cast<uint64_t>(priv_length));
   if (block_end > std::numeric_limits<uint32_t>::max()) {
     return OTS_FAILURE_MSG_HDR("Invalid private block length");
   }
 }
 if (block_end != ots::Round4(length)) {
   return OTS_FAILURE_MSG_HDR("File length mismatch (trailing junk?)");
 }

 return ProcessGeneric(header, font, woff_tag, output, data, length, tables, file);
}

bool ProcessWOFF2(ots::FontFile* header, ots::OTSStream* output,
                 const uint8_t* data, size_t length, uint32_t index) {
 return RLBoxProcessWOFF2(header, output, data, length, index, ProcessTTC, ProcessTTF);
}

ots::TableAction GetTableAction(const ots::FontFile *header, uint32_t tag) {
 ots::TableAction action = header->context->GetTableAction(tag);

 if (action == ots::TABLE_ACTION_DEFAULT) {
   action = ots::TABLE_ACTION_DROP;

   for (unsigned i = 0; ; ++i) {
     if (supported_tables[i].tag == 0) break;

     if (supported_tables[i].tag == tag) {
       action = ots::TABLE_ACTION_SANITIZE;
       break;
     }
   }
 }

 assert(action != ots::TABLE_ACTION_DEFAULT); // Should never return this.
 return action;
}

bool GetTableData(const uint8_t *data,
                 const ots::TableEntry& table,
                 ots::Arena &arena,
                 size_t *table_length,
                 const uint8_t **table_data) {
 if (table.uncompressed_length != table.length) {
   // Compressed table. Need to uncompress into memory first.
   *table_length = table.uncompressed_length;
   *table_data = arena.Allocate(*table_length);
   uLongf dest_len = *table_length;
   int r = uncompress((Bytef*) *table_data, &dest_len,
                      data + table.offset, table.length);
   if (r != Z_OK || dest_len != *table_length) {
     return false;
   }
 } else {
   // Uncompressed table. We can process directly from memory.
   *table_data = data + table.offset;
   *table_length = table.length;
 }

 return true;
}

bool ProcessGeneric(ots::FontFile *header,
                   ots::Font *font,
                   uint32_t signature,
                   ots::OTSStream *output,
                   const uint8_t *data, size_t length,
                   const std::vector<ots::TableEntry>& tables,
                   ots::Buffer& file) {
 const size_t data_offset = file.offset();

 uint32_t uncompressed_sum = 0;

 for (unsigned i = 0; i < font->num_tables; ++i) {
   // the tables must be sorted by tag (when taken as big-endian numbers).
   // This also remove the possibility of duplicate tables.
   if (i) {
     const uint32_t this_tag = tables[i].tag;
     const uint32_t prev_tag = tables[i - 1].tag;
     if (this_tag <= prev_tag) {
       OTS_WARNING_MSG_HDR("Table directory is not correctly ordered");
     }
   }

   // all tag names must be built from printable ASCII characters
   if (!ots::CheckTag(tables[i].tag)) {
     OTS_WARNING_MSG_HDR("Invalid table tag: 0x%X", tables[i].tag);
   }

   // tables must be 4-byte aligned
   if (tables[i].offset & 3) {
     return OTS_FAILURE_MSG_TAG("misaligned table", tables[i].tag);
   }

   // and must be within the file
   if (tables[i].offset < data_offset || tables[i].offset >= length) {
     return OTS_FAILURE_MSG_TAG("invalid table offset", tables[i].tag);
   }
   // disallow all tables with a zero length
   if (tables[i].length < 1) {
     // Note: malayalam.ttf has zero length CVT table...
     return OTS_FAILURE_MSG_TAG("zero-length table", tables[i].tag);
   }
   // disallow all tables with a length > 1GB
   if (tables[i].length > 1024 * 1024 * 1024) {
     return OTS_FAILURE_MSG_TAG("table length exceeds 1GB", tables[i].tag);
   }
   // disallow tables where the uncompressed size is < the compressed size.
   if (tables[i].uncompressed_length < tables[i].length) {
     return OTS_FAILURE_MSG_TAG("invalid compressed table", tables[i].tag);
   }
   if (tables[i].uncompressed_length > tables[i].length) {
     // We'll probably be decompressing this table.

     // disallow all tables which decompress to > OTS_MAX_DECOMPRESSED_TABLE_SIZE
     if (tables[i].uncompressed_length > OTS_MAX_DECOMPRESSED_TABLE_SIZE) {
       return OTS_FAILURE_MSG_HDR("%c%c%c%c: decompressed table length exceeds %gMB",
                                  OTS_UNTAG(tables[i].tag),
                                  OTS_MAX_DECOMPRESSED_TABLE_SIZE / (1024.0 * 1024.0));        
     }
     if (uncompressed_sum + tables[i].uncompressed_length < uncompressed_sum) {
       return OTS_FAILURE_MSG_TAG("overflow of decompressed sum", tables[i].tag);
     }

     uncompressed_sum += tables[i].uncompressed_length;
   }
   // since we required that the file be < 1GB in length, and that the table
   // length is < 1GB, the following addtion doesn't overflow
   uint32_t end_byte = tables[i].offset + tables[i].length;
   // Tables in the WOFF file must be aligned 4-byte boundary.
   if (signature == OTS_TAG('w','O','F','F')) {
       end_byte = ots::Round4(end_byte);
   }
   if (!end_byte || end_byte > length) {
     return OTS_FAILURE_MSG_TAG("table overruns end of file", tables[i].tag);
   }
 }

 // All decompressed tables decompressed must be <= OTS_MAX_DECOMPRESSED_FILE_SIZE.
 if (uncompressed_sum > OTS_MAX_DECOMPRESSED_FILE_SIZE) {
   return OTS_FAILURE_MSG_HDR("decompressed sum exceeds %gMB",
                              OTS_MAX_DECOMPRESSED_FILE_SIZE / (1024.0 * 1024.0));        
 }

 if (uncompressed_sum > output->size()) {
   return OTS_FAILURE_MSG_HDR("decompressed sum exceeds output size (%gMB)", output->size() / (1024.0 * 1024.0));
 }

 // check that the tables are not overlapping.
 std::vector<std::pair<uint32_t, uint8_t> > overlap_checker;
 for (unsigned i = 0; i < font->num_tables; ++i) {
   overlap_checker.push_back(
       std::make_pair(tables[i].offset, static_cast<uint8_t>(1) /* start */));
   overlap_checker.push_back(
       std::make_pair(tables[i].offset + tables[i].length,
                      static_cast<uint8_t>(0) /* end */));
 }
 std::sort(overlap_checker.begin(), overlap_checker.end());
 int overlap_count = 0;
 for (unsigned i = 0; i < overlap_checker.size(); ++i) {
   overlap_count += (overlap_checker[i].second ? 1 : -1);
   if (overlap_count > 1) {
     return OTS_FAILURE_MSG_HDR("overlapping tables");
   }
 }

 std::map<uint32_t, ots::TableEntry> table_map;
 for (unsigned i = 0; i < font->num_tables; ++i) {
   table_map[tables[i].tag] = tables[i];
 }

 ots::Arena arena;
 // Parse known tables first as we need to parse them in specific order.
 for (unsigned i = 0; ; ++i) {
   if (supported_tables[i].tag == 0) break;

   uint32_t tag = supported_tables[i].tag;
   const auto &it = table_map.find(tag);
   if (it == table_map.cend()) {
     if (supported_tables[i].required) {
       return OTS_FAILURE_MSG_TAG("missing required table", tag);
     }
   } else {
     if (!font->ParseTable(it->second, data, arena)) {
       return OTS_FAILURE_MSG_TAG("Failed to parse table", tag);
     }
   }
 }

 // Then parse any tables left.
 for (const auto &table_entry : tables) {
   if (!font->GetTable(table_entry.tag)) {
     if (!font->ParseTable(table_entry, data, arena)) {
       return OTS_FAILURE_MSG_TAG("Failed to parse table", table_entry.tag);
     }
   }
 }

#ifdef OTS_SYNTHESIZE_MISSING_GVAR
 // If there was an fvar table but no gvar, synthesize an empty gvar to avoid
 // issues with rasterizers (e.g. Core Text) that assume it must be present.
 if (font->GetTable(OTS_TAG_FVAR) && !font->GetTable(OTS_TAG_GVAR)) {
   ots::TableEntry table_entry{ OTS_TAG_GVAR, 0, 0, 0, 0 };
   const auto &it = font->file->tables.find(table_entry);
   if (it != font->file->tables.end()) {
     table_map[OTS_TAG_GVAR] = table_entry;
     font->AddTable(table_entry, it->second);
   } else {
     ots::OpenTypeGVAR *gvar = new ots::OpenTypeGVAR(font, OTS_TAG_GVAR);
     if (gvar->InitEmpty()) {
       table_map[OTS_TAG_GVAR] = table_entry;
       font->AddTable(table_entry, gvar);
     } else {
       delete gvar;
     }
   }
 }
#endif

 ots::Table *glyf = font->GetTable(OTS_TAG_GLYF);
 ots::Table *loca = font->GetTable(OTS_TAG_LOCA);
 ots::Table *cff  = font->GetTable(OTS_TAG_CFF);
 ots::Table *cff2 = font->GetTable(OTS_TAG_CFF2);
 ots::OpenTypeMAXP *maxp = static_cast<ots::OpenTypeMAXP*>(
   font->GetTypedTable(OTS_TAG_MAXP));

 if (glyf && loca) {
   if (font->version != 0x000010000) {
     OTS_WARNING_MSG_HDR("wrong sfntVersion for glyph data");
     font->version = 0x000010000;
   }
   if (!maxp->version_1) {
     return OTS_FAILURE_MSG_TAG("wrong maxp version for glyph data",
                                OTS_TAG_MAXP);
   }
   if (cff)
      cff->Drop("font contains both CFF and glyf/loca tables");
   if (cff2)
      cff2->Drop("font contains both CFF and glyf/loca tables");
 } else if (cff || cff2) {
   if (font->version != OTS_TAG('O','T','T','O')) {
     OTS_WARNING_MSG_HDR("wrong sfntVersion for glyph data");
     font->version = OTS_TAG('O','T','T','O');
   }
   if (glyf)
      glyf->Drop("font contains both CFF and glyf tables");
   if (loca)
      loca->Drop("font contains both CFF and loca tables");
   if (maxp->version_1) {
     OTS_WARNING_MSG_HDR("fixing incorrect maxp version for CFF font");
     maxp->version_1 = false;
   }
 } else if (font->GetTable(OTS_TAG('C','B','D','T')) &&
            font->GetTable(OTS_TAG('C','B','L','C'))) {
     // We don't sanitize bitmap tables, but don’t reject bitmap-only fonts if
     // we are asked to pass them thru.
 } else {
     return OTS_FAILURE_MSG_HDR("no supported glyph data table(s) present");
 }

 uint16_t num_output_tables = 0;
 for (const auto &it : table_map) {
   ots::Table *table = font->GetTable(it.first);
   if (table)
     num_output_tables++;
 }

 uint16_t max_pow2 = 0;
 while (1u << (max_pow2 + 1) <= num_output_tables) {
   max_pow2++;
 }
 const uint16_t output_search_range = (1u << max_pow2) << 4;

 // most of the errors here are highly unlikely - they'd only occur if the
 // output stream returns a failure, e.g. lack of space to write
 output->ResetChecksum();
 if (!output->WriteU32(font->version) ||
     !output->WriteU16(num_output_tables) ||
     !output->WriteU16(output_search_range) ||
     !output->WriteU16(max_pow2) ||
     !output->WriteU16((num_output_tables << 4) - output_search_range)) {
   return OTS_FAILURE_MSG_HDR("error writing output");
 }
 const uint32_t offset_table_chksum = output->chksum();

 const size_t table_record_offset = output->Tell();
 if (!output->Pad(16 * num_output_tables)) {
   return OTS_FAILURE_MSG_HDR("error writing output");
 }

 std::vector<ots::TableEntry> out_tables;

 size_t head_table_offset = 0;
 for (const auto &it : table_map) {
   uint32_t input_offset = it.second.offset;
   const auto &ot = header->table_entries.find(input_offset);
   if (ot != header->table_entries.end()) {
     ots::TableEntry out = ot->second;
     if (out.tag == OTS_TAG('h','e','a','d')) {
       head_table_offset = out.offset;
     }
     out_tables.push_back(out);
   } else {
     ots::TableEntry out;
     out.tag = it.first;
     out.offset = output->Tell();

     if (out.tag == OTS_TAG('h','e','a','d')) {
       head_table_offset = out.offset;
     }

     ots::Table *table = font->GetTable(out.tag);
     if (table) {
       output->ResetChecksum();
       if (!table->Serialize(output)) {
         return OTS_FAILURE_MSG_TAG("Failed to serialize table", out.tag);
       }

       const size_t end_offset = output->Tell();
       if (end_offset <= out.offset) {
         // paranoid check. |end_offset| is supposed to be greater than the offset,
         // as long as the Tell() interface is implemented correctly.
         return OTS_FAILURE_MSG_TAG("Table is empty or have -ve size", out.tag);
       }
       out.length = end_offset - out.offset;

       // align tables to four bytes
       if (!output->Pad((4 - (end_offset & 3)) % 4)) {
         return OTS_FAILURE_MSG_TAG("Failed to pad table to 4 bytes", out.tag);
       }
       out.chksum = output->chksum();
       out_tables.push_back(out);
       header->table_entries[input_offset] = out;
     }
   }
 }

 const size_t end_of_file = output->Tell();

 // Need to sort the output tables for inclusion in the file
 std::sort(out_tables.begin(), out_tables.end());
 if (!output->Seek(table_record_offset)) {
   return OTS_FAILURE_MSG_HDR("error writing output");
 }

 output->ResetChecksum();
 uint32_t tables_chksum = 0;
 for (unsigned i = 0; i < out_tables.size(); ++i) {
   if (!output->WriteU32(out_tables[i].tag) ||
       !output->WriteU32(out_tables[i].chksum) ||
       !output->WriteU32(out_tables[i].offset) ||
       !output->WriteU32(out_tables[i].length)) {
     return OTS_FAILURE_MSG_HDR("error writing output");
   }
   tables_chksum += out_tables[i].chksum;
 }
 const uint32_t table_record_chksum = output->chksum();

 // http://www.microsoft.com/typography/otspec/otff.htm
 const uint32_t file_chksum
     = offset_table_chksum + tables_chksum + table_record_chksum;
 const uint32_t chksum_magic = static_cast<uint32_t>(0xb1b0afba) - file_chksum;

 // seek into the 'head' table and write in the checksum magic value
 if (!head_table_offset) {
   return OTS_FAILURE_MSG_HDR("internal error!");
 }
 if (!output->Seek(head_table_offset + 8)) {
   return OTS_FAILURE_MSG_HDR("error writing output");
 }
 if (!output->WriteU32(chksum_magic)) {
   return OTS_FAILURE_MSG_HDR("error writing output");
 }

 if (!output->Seek(end_of_file)) {
   return OTS_FAILURE_MSG_HDR("error writing output");
 }

 return true;
}

bool IsGraphiteTag(uint32_t tag) {
 if (tag == OTS_TAG_FEAT ||
     tag == OTS_TAG_GLAT ||
     tag == OTS_TAG_GLOC ||
     tag == OTS_TAG_SILE ||
     tag == OTS_TAG_SILF ||
     tag == OTS_TAG_SILL) {
   return true;
 }
 return false;
}

bool IsVariationsTag(uint32_t tag) {
 if (tag == OTS_TAG_AVAR ||
     tag == OTS_TAG_CVAR ||
     tag == OTS_TAG_FVAR ||
     tag == OTS_TAG_GVAR ||
     tag == OTS_TAG_HVAR ||
     tag == OTS_TAG_MVAR ||
     tag == OTS_TAG_STAT ||
     tag == OTS_TAG_VVAR) {
   return true;
 }
 return false;
}

}  // namespace

namespace ots {

FontFile::~FontFile() {
 for (const auto& it : tables) {
   delete it.second;
 }
 tables.clear();
}

bool Font::ParseTable(const TableEntry& table_entry, const uint8_t* data,
                     Arena &arena) {
 uint32_t tag = table_entry.tag;
 TableAction action = GetTableAction(file, tag);
 if (action == TABLE_ACTION_DROP) {
   return true;
 }

 const auto &it = file->tables.find(table_entry);
 if (it != file->tables.end()) {
   m_tables[tag] = it->second;
   return true;
 }

 Table *table = NULL;
 bool ret = false;

 if (action == TABLE_ACTION_PASSTHRU) {
   table = new TablePassthru(this, tag);
 } else {
   switch (tag) {
     case OTS_TAG_AVAR: table = new OpenTypeAVAR(this, tag); break;
     case OTS_TAG_CFF:  table = new OpenTypeCFF(this,  tag); break;
     case OTS_TAG_CFF2: table = new OpenTypeCFF2(this, tag); break;
     case OTS_TAG_CMAP: table = new OpenTypeCMAP(this, tag); break;
     case OTS_TAG_COLR: table = new OpenTypeCOLR(this, tag); break;
     case OTS_TAG_CPAL: table = new OpenTypeCPAL(this, tag); break;
     case OTS_TAG_CVAR: table = new OpenTypeCVAR(this, tag); break;
     case OTS_TAG_CVT:  table = new OpenTypeCVT(this,  tag); break;
     case OTS_TAG_FPGM: table = new OpenTypeFPGM(this, tag); break;
     case OTS_TAG_FVAR: table = new OpenTypeFVAR(this, tag); break;
     case OTS_TAG_GASP: table = new OpenTypeGASP(this, tag); break;
     case OTS_TAG_GDEF: table = new OpenTypeGDEF(this, tag); break;
     case OTS_TAG_GLYF: table = new OpenTypeGLYF(this, tag); break;
     case OTS_TAG_GPOS: table = new OpenTypeGPOS(this, tag); break;
     case OTS_TAG_GSUB: table = new OpenTypeGSUB(this, tag); break;
     case OTS_TAG_GVAR: table = new OpenTypeGVAR(this, tag); break;
     case OTS_TAG_HDMX: table = new OpenTypeHDMX(this, tag); break;
     case OTS_TAG_HEAD: table = new OpenTypeHEAD(this, tag); break;
     case OTS_TAG_HHEA: table = new OpenTypeHHEA(this, tag); break;
     case OTS_TAG_HMTX: table = new OpenTypeHMTX(this, tag); break;
     case OTS_TAG_HVAR: table = new OpenTypeHVAR(this, tag); break;
     case OTS_TAG_KERN: table = new OpenTypeKERN(this, tag); break;
     case OTS_TAG_LOCA: table = new OpenTypeLOCA(this, tag); break;
     case OTS_TAG_LTSH: table = new OpenTypeLTSH(this, tag); break;
     case OTS_TAG_MATH: table = new OpenTypeMATH(this, tag); break;
     case OTS_TAG_MAXP: table = new OpenTypeMAXP(this, tag); break;
     case OTS_TAG_MVAR: table = new OpenTypeMVAR(this, tag); break;
     case OTS_TAG_NAME: table = new OpenTypeNAME(this, tag); break;
     case OTS_TAG_OS2:  table = new OpenTypeOS2(this,  tag); break;
     case OTS_TAG_POST: table = new OpenTypePOST(this, tag); break;
     case OTS_TAG_PREP: table = new OpenTypePREP(this, tag); break;
     case OTS_TAG_STAT: table = new OpenTypeSTAT(this, tag); break;
     case OTS_TAG_VDMX: table = new OpenTypeVDMX(this, tag); break;
     case OTS_TAG_VHEA: table = new OpenTypeVHEA(this, tag); break;
     case OTS_TAG_VMTX: table = new OpenTypeVMTX(this, tag); break;
     case OTS_TAG_VORG: table = new OpenTypeVORG(this, tag); break;
     case OTS_TAG_VVAR: table = new OpenTypeVVAR(this, tag); break;
     // Graphite tables
#ifdef OTS_GRAPHITE
     case OTS_TAG_FEAT: table = new OpenTypeFEAT(this, tag); break;
     case OTS_TAG_GLAT: table = new OpenTypeGLAT(this, tag); break;
     case OTS_TAG_GLOC: table = new OpenTypeGLOC(this, tag); break;
     case OTS_TAG_SILE: table = new OpenTypeSILE(this, tag); break;
     case OTS_TAG_SILF: table = new OpenTypeSILF(this, tag); break;
     case OTS_TAG_SILL: table = new OpenTypeSILL(this, tag); break;
#endif
     default: break;
   }
 }

 if (table) {
   const uint8_t* table_data;
   size_t table_length;

   ret = GetTableData(data, table_entry, arena, &table_length, &table_data);
   if (ret) {
     ret = table->Parse(table_data, table_length);
     if (ret)
       AddTable(table_entry, table);
     else if (action == TABLE_ACTION_SANITIZE_SOFT) {
       // We're dropping the table (having reported whatever errors we found),
       // but do not return failure, so that processing continues.
       delete table;
       ret = true;
     }
   }
 }

 if (!ret)
   delete table;

 return ret;
}

Table* Font::GetTable(uint32_t tag) const {
 const auto &it = m_tables.find(tag);
 if (it != m_tables.end() && it->second && it->second->ShouldSerialize())
   return it->second;
 return NULL;
}

Table* Font::GetTypedTable(uint32_t tag) const {
 Table* t = GetTable(tag);
 if (t && t->Type() == tag)
   return t;
 return NULL;
}

void Font::AddTable(TableEntry entry, Table* table) {
 // Attempting to add a duplicate table would be an error; this should only
 // be used to add a table that does not already exist.
 assert(m_tables.find(table->Tag()) == m_tables.end());
 m_tables[table->Tag()] = table;
 file->tables[entry] = table;
}

void Font::DropGraphite() {
 file->context->Message(0, "Dropping all Graphite tables");
 for (const std::pair<uint32_t, Table*> entry : m_tables) {
   if (IsGraphiteTag(entry.first)) {
     entry.second->Drop("Discarding Graphite table");
   }
 }
}

void Font::DropVariations() {
 file->context->Message(0, "Dropping all Variation tables");
 for (const std::pair<uint32_t, Table*> entry : m_tables) {
   if (IsVariationsTag(entry.first)) {
     entry.second->Drop("Discarding Variations table");
   }
 }
}

bool Table::ShouldSerialize() {
 return m_shouldSerialize;
}

void Table::Message(int level, const char *format, va_list va) {
 char msg[206] = { OTS_UNTAG(m_tag), ':', ' ' };
 std::vsnprintf(msg + 6, 200, format, va);
 m_font->file->context->Message(level, msg);
}

bool Table::Error(const char *format, ...) {
 va_list va;
 va_start(va, format);
 Message(0, format, va);
 va_end(va);

 return false;
}

bool Table::Warning(const char *format, ...) {
 va_list va;
 va_start(va, format);
 Message(1, format, va);
 va_end(va);

 return true;
}

bool Table::Drop(const char *format, ...) {
 m_shouldSerialize = false;

 va_list va;
 va_start(va, format);
 Message(0, format, va);
 m_font->file->context->Message(0, "Table discarded");
 va_end(va);

 return true;
}

bool Table::DropGraphite(const char *format, ...) {
 va_list va;
 va_start(va, format);
 Message(0, format, va);
 va_end(va);

 m_font->DropGraphite();
 if (IsGraphiteTag(m_tag))
     Drop("Discarding Graphite table");

 return true;
}

bool Table::DropVariations(const char *format, ...) {
 va_list va;
 va_start(va, format);
 Message(0, format, va);
 va_end(va);

 m_font->DropVariations();
 if (IsVariationsTag(m_tag))
     Drop("Discarding Variations table");

 return true;
}

bool TablePassthru::Parse(const uint8_t *data, size_t length) {
 m_data = data;
 m_length = length;
 return true;
}

bool TablePassthru::Serialize(OTSStream *out) {
   if (!out->Write(m_data, m_length)) {
   return Error("Failed to write table");
 }

 return true;
}

bool OTSContext::Process(OTSStream *output,
                        const uint8_t *data,
                        size_t length,
                        uint32_t index) {
 FontFile header;
 Font font(&header);
 header.context = this;

 if (length < 4) {
   return OTS_FAILURE_MSG_(&header, "file less than 4 bytes");
 }

 bool result;
 if (data[0] == 'w' && data[1] == 'O' && data[2] == 'F' && data[3] == 'F') {
   result = ProcessWOFF(&header, &font, output, data, length);
 } else if (data[0] == 'w' && data[1] == 'O' && data[2] == 'F' && data[3] == '2') {
   result = ProcessWOFF2(&header, output, data, length, index);
 } else if (data[0] == 't' && data[1] == 't' && data[2] == 'c' && data[3] == 'f') {
   result = ProcessTTC(&header, output, data, length, index);
 } else {
   result = ProcessTTF(&header, &font, output, data, length);
 }

 return result;
}

}  // namespace ots