third_party/woff2/src/font.cc

   1 // Copyright 2013 Google Inc. All Rights Reserved.
   2 //
   3 // Licensed under the Apache License, Version 2.0 (the "License");
   4 // you may not use this file except in compliance with the License.
   5 // You may obtain a copy of the License at
   6 //
   7 // http://www.apache.org/licenses/LICENSE-2.0
   8 //
   9 // Unless required by applicable law or agreed to in writing, software
  10 // distributed under the License is distributed on an "AS IS" BASIS,
  11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12 // See the License for the specific language governing permissions and
  13 // limitations under the License.
  14 //
  15 // Font management utilities
  16
  17 #include "./font.h"
  18
  19 #include <algorithm>
  20
  21 #include "./buffer.h"
  22 #include "./port.h"
  23 #include "./store_bytes.h"
  24 #include "./table_tags.h"
  25
  26 namespace woff2 {
  27
  28 Font::Table* Font::FindTable(uint32_t tag) {
  29   std::map<uint32_t, Font::Table>::iterator it = tables.find(tag);
  30   return it == tables.end() ? 0 : &it->second;
  31 }
  32
  33 const Font::Table* Font::FindTable(uint32_t tag) const {
  34   std::map<uint32_t, Font::Table>::const_iterator it = tables.find(tag);
  35   return it == tables.end() ? 0 : &it->second;
  36 }
  37
  38 bool ReadFont(const uint8_t* data, size_t len, Font* font) {
  39   Buffer file(data, len);
  40
  41   // We don't care about the search_range, entry_selector and range_shift
  42   // fields, they will always be computed upon writing the font.
  43   if (!file.ReadU32(&font->flavor) ||
  44       !file.ReadU16(&font->num_tables) ||
  45       !file.Skip(6)) {
  46     return FONT_COMPRESSION_FAILURE();
  47   }
  48
  49   std::map<uint32_t, uint32_t> intervals;
  50   for (uint16_t i = 0; i < font->num_tables; ++i) {
  51     Font::Table table;
  52     if (!file.ReadU32(&table.tag) ||
  53         !file.ReadU32(&table.checksum) ||
  54         !file.ReadU32(&table.offset) ||
  55         !file.ReadU32(&table.length)) {
  56       return FONT_COMPRESSION_FAILURE();
  57     }
  58     if ((table.offset & 3) != 0 ||
  59         table.length > len ||
  60         len - table.length < table.offset) {
  61       return FONT_COMPRESSION_FAILURE();
  62     }
  63     intervals[table.offset] = table.length;
  64     table.data = data + table.offset;
  65     if (font->tables.find(table.tag) != font->tables.end()) {
  66       return FONT_COMPRESSION_FAILURE();
  67     }
  68     font->tables[table.tag] = table;
  69   }
  70
  71   // Check that tables are non-overlapping.
  72   uint32_t last_offset = 12UL + 16UL * font->num_tables;
  73   for (const auto& i : intervals) {
  74     if (i.first < last_offset || i.first + i.second < i.first) {
  75       return FONT_COMPRESSION_FAILURE();
  76     }
  77     last_offset = i.first + i.second;
  78   }
  79   return true;
  80 }
  81
  82 size_t FontFileSize(const Font& font) {
  83   size_t max_offset = 12ULL + 16ULL * font.num_tables;
  84   for (const auto& i : font.tables) {
  85     const Font::Table& table = i.second;
  86     size_t padding_size = (4 - (table.length & 3)) & 3;
  87     size_t end_offset = (padding_size + table.offset) + table.length;
  88     max_offset = std::max(max_offset, end_offset);
  89   }
  90   return max_offset;
  91 }
  92
  93 bool WriteFont(const Font& font, uint8_t* dst, size_t dst_size) {
  94   if (dst_size < 12ULL + 16ULL * font.num_tables) {
  95     return FONT_COMPRESSION_FAILURE();
  96   }
  97   size_t offset = 0;
  98   StoreU32(font.flavor, &offset, dst);
  99   Store16(font.num_tables, &offset, dst);
 100   uint16_t max_pow2 = font.num_tables ? Log2Floor(font.num_tables) : 0;
 101   uint16_t search_range = max_pow2 ? 1 << (max_pow2 + 4) : 0;
 102   uint16_t range_shift = (font.num_tables << 4) - search_range;
 103   Store16(search_range, &offset, dst);
 104   Store16(max_pow2, &offset, dst);
 105   Store16(range_shift, &offset, dst);
 106   for (const auto& i : font.tables) {
 107     const Font::Table& table = i.second;
 108     StoreU32(table.tag, &offset, dst);
 109     StoreU32(table.checksum, &offset, dst);
 110     StoreU32(table.offset, &offset, dst);
 111     StoreU32(table.length, &offset, dst);
 112     if (table.offset + table.length < table.offset ||
 113         dst_size < table.offset + table.length) {
 114       return FONT_COMPRESSION_FAILURE();
 115     }
 116     memcpy(dst + table.offset, table.data, table.length);
 117     size_t padding_size = (4 - (table.length & 3)) & 3;
 118     if (table.offset + table.length + padding_size < padding_size ||
 119         dst_size < table.offset + table.length + padding_size) {
 120       return FONT_COMPRESSION_FAILURE();
 121     }
 122     memset(dst + table.offset + table.length, 0, padding_size);
 123   }
 124   return true;
 125 }
 126
 127 int NumGlyphs(const Font& font) {
 128   const Font::Table* head_table = font.FindTable(kHeadTableTag);
 129   const Font::Table* loca_table = font.FindTable(kLocaTableTag);
 130   if (head_table == NULL || loca_table == NULL || head_table->length < 52) {
 131     return 0;
 132   }
 133   int index_fmt = IndexFormat(font);
 134   int num_glyphs = (loca_table->length / (index_fmt == 0 ? 2 : 4)) - 1;
 135   return num_glyphs;
 136 }
 137
 138 int IndexFormat(const Font& font) {
 139   const Font::Table* head_table = font.FindTable(kHeadTableTag);
 140   if (head_table == NULL) {
 141     return 0;
 142   }
 143   return head_table->data[51];
 144 }
 145
 146 bool GetGlyphData(const Font& font, int glyph_index,
 147                   const uint8_t** glyph_data, size_t* glyph_size) {
 148   if (glyph_index < 0) {
 149     return FONT_COMPRESSION_FAILURE();
 150   }
 151   const Font::Table* head_table = font.FindTable(kHeadTableTag);
 152   const Font::Table* loca_table = font.FindTable(kLocaTableTag);
 153   const Font::Table* glyf_table = font.FindTable(kGlyfTableTag);
 154   if (head_table == NULL || loca_table == NULL || glyf_table == NULL ||
 155       head_table->length < 52) {
 156     return FONT_COMPRESSION_FAILURE();
 157   }
 158
 159   int index_fmt = IndexFormat(font);
 160
 161   Buffer loca_buf(loca_table->data, loca_table->length);
 162   if (index_fmt == 0) {
 163     uint16_t offset1, offset2;
 164     if (!loca_buf.Skip(2 * glyph_index) ||
 165         !loca_buf.ReadU16(&offset1) ||
 166         !loca_buf.ReadU16(&offset2) ||
 167         offset2 < offset1 ||
 168         2 * offset2 > glyf_table->length) {
 169       return FONT_COMPRESSION_FAILURE();
 170     }
 171     *glyph_data = glyf_table->data + 2 * offset1;
 172     *glyph_size = 2 * (offset2 - offset1);
 173   } else {
 174     uint32_t offset1, offset2;
 175     if (!loca_buf.Skip(4 * glyph_index) ||
 176         !loca_buf.ReadU32(&offset1) ||
 177         !loca_buf.ReadU32(&offset2) ||
 178         offset2 < offset1 ||
 179         offset2 > glyf_table->length) {
 180       return FONT_COMPRESSION_FAILURE();
 181     }
 182     *glyph_data = glyf_table->data + offset1;
 183     *glyph_size = offset2 - offset1;
 184   }
 185   return true;
 186 }
 187
 188 bool RemoveDigitalSignature(Font* font) {
 189   std::map<uint32_t, Font::Table>::iterator it =
 190       font->tables.find(kDsigTableTag);
 191   if (it != font->tables.end()) {
 192     font->tables.erase(it);
 193     font->num_tables = font->tables.size();
 194   }
 195   return true;
 196 }
 197
 198 } // namespace woff2