third_party/ots/src/gasp.cc

   1 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "gasp.h"
   6
   7 // gasp - Grid-fitting And Scan-conversion Procedure
   8 // http://www.microsoft.com/typography/otspec/gasp.htm
   9
  10 #define TABLE_NAME "gasp"
  11
  12 #define DROP_THIS_TABLE(...) \
  13   do { \
  14     OTS_FAILURE_MSG_(font->file, TABLE_NAME ": " __VA_ARGS__); \
  15     OTS_FAILURE_MSG("Table discarded"); \
  16     delete font->gasp; \
  17     font->gasp = 0; \
  18   } while (0)
  19
  20 namespace ots {
  21
  22 bool ots_gasp_parse(Font *font, const uint8_t *data, size_t length) {
  23   Buffer table(data, length);
  24
  25   OpenTypeGASP *gasp = new OpenTypeGASP;
  26   font->gasp = gasp;
  27
  28   uint16_t num_ranges = 0;
  29   if (!table.ReadU16(&gasp->version) ||
  30       !table.ReadU16(&num_ranges)) {
  31     return OTS_FAILURE_MSG("Failed to read table header");
  32   }
  33
  34   if (gasp->version > 1) {
  35     // Lots of Linux fonts have bad version numbers...
  36     DROP_THIS_TABLE("bad version: %u", gasp->version);
  37     return true;
  38   }
  39
  40   if (num_ranges == 0) {
  41     DROP_THIS_TABLE("num_ranges is zero");
  42     return true;
  43   }
  44
  45   gasp->gasp_ranges.reserve(num_ranges);
  46   for (unsigned i = 0; i < num_ranges; ++i) {
  47     uint16_t max_ppem = 0;
  48     uint16_t behavior = 0;
  49     if (!table.ReadU16(&max_ppem) ||
  50         !table.ReadU16(&behavior)) {
  51       return OTS_FAILURE_MSG("Failed to read subrange %d", i);
  52     }
  53     if ((i > 0) && (gasp->gasp_ranges[i - 1].first >= max_ppem)) {
  54       // The records in the gaspRange[] array must be sorted in order of
  55       // increasing rangeMaxPPEM value.
  56       DROP_THIS_TABLE("ranges are not sorted");
  57       return true;
  58     }
  59     if ((i == num_ranges - 1u) &&  // never underflow.
  60         (max_ppem != 0xffffu)) {
  61       DROP_THIS_TABLE("The last record should be 0xFFFF as a sentinel value "
  62                   "for rangeMaxPPEM");
  63       return true;
  64     }
  65
  66     if (behavior >> 8) {
  67       OTS_WARNING("undefined bits are used: %x", behavior);
  68       // mask undefined bits.
  69       behavior &= 0x000fu;
  70     }
  71
  72     if (gasp->version == 0 && (behavior >> 2) != 0) {
  73       OTS_WARNING("changed the version number to 1");
  74       gasp->version = 1;
  75     }
  76
  77     gasp->gasp_ranges.push_back(std::make_pair(max_ppem, behavior));
  78   }
  79
  80   return true;
  81 }
  82
  83 bool ots_gasp_should_serialise(Font *font) {
  84   return font->gasp != NULL;
  85 }
  86
  87 bool ots_gasp_serialise(OTSStream *out, Font *font) {
  88   const OpenTypeGASP *gasp = font->gasp;
  89
  90   const uint16_t num_ranges = static_cast<uint16_t>(gasp->gasp_ranges.size());
  91   if (num_ranges != gasp->gasp_ranges.size() ||
  92       !out->WriteU16(gasp->version) ||
  93       !out->WriteU16(num_ranges)) {
  94     return OTS_FAILURE_MSG("failed to write gasp header");
  95   }
  96
  97   for (uint16_t i = 0; i < num_ranges; ++i) {
  98     if (!out->WriteU16(gasp->gasp_ranges[i].first) ||
  99         !out->WriteU16(gasp->gasp_ranges[i].second)) {
 100       return OTS_FAILURE_MSG("Failed to write gasp subtable %d", i);
 101     }
 102   }
 103
 104   return true;
 105 }
 106
 107 void ots_gasp_reuse(Font *font, Font *other) {
 108   font->gasp = other->gasp;
 109   font->gasp_reused = true;
 110 }
 111
 112 void ots_gasp_free(Font *font) {
 113   delete font->gasp;
 114 }
 115
 116 }  // namespace ots
 117
 118 #undef TABLE_NAME
 119 #undef DROP_THIS_TABLE