third_party/ots/src/head.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 "head.h"
   6
   7 #include <cstring>
   8
   9 // head - Font Header
  10 // http://www.microsoft.com/typography/otspec/head.htm
  11
  12 #define TABLE_NAME "head"
  13
  14 namespace ots {
  15
  16 bool ots_head_parse(Font* font, const uint8_t *data, size_t length) {
  17   Buffer table(data, length);
  18   OpenTypeHEAD *head = new OpenTypeHEAD;
  19   font->head = head;
  20
  21   uint32_t version = 0;
  22   if (!table.ReadU32(&version) ||
  23       !table.ReadU32(&head->revision)) {
  24     return OTS_FAILURE_MSG("Failed to read head header");
  25   }
  26
  27   if (version >> 16 != 1) {
  28     return OTS_FAILURE_MSG("Bad head table version of %d", version);
  29   }
  30
  31   // Skip the checksum adjustment
  32   if (!table.Skip(4)) {
  33     return OTS_FAILURE_MSG("Failed to read checksum");
  34   }
  35
  36   uint32_t magic;
  37   if (!table.ReadU32(&magic) || magic != 0x5F0F3CF5) {
  38     return OTS_FAILURE_MSG("Failed to read font magic number");
  39   }
  40
  41   if (!table.ReadU16(&head->flags)) {
  42     return OTS_FAILURE_MSG("Failed to read head flags");
  43   }
  44
  45   // We allow bits 0..4, 11..13
  46   head->flags &= 0x381f;
  47
  48   if (!table.ReadU16(&head->ppem)) {
  49     return OTS_FAILURE_MSG("Failed to read pixels per em");
  50   }
  51
  52   // ppem must be in range
  53   if (head->ppem < 16 ||
  54       head->ppem > 16384) {
  55     return OTS_FAILURE_MSG("Bad ppm of %d", head->ppem);
  56   }
  57
  58   // ppem must be a power of two
  59 #if 0
  60   // We don't call ots_failure() for now since lots of TrueType fonts are
  61   // not following this rule. Putting OTS_WARNING here is too noisy.
  62   if ((head->ppem - 1) & head->ppem) {
  63     return OTS_FAILURE_MSG("ppm not a power of two: %d", head->ppem);
  64   }
  65 #endif
  66
  67   if (!table.ReadR64(&head->created) ||
  68       !table.ReadR64(&head->modified)) {
  69     return OTS_FAILURE_MSG("Can't read font dates");
  70   }
  71
  72   if (!table.ReadS16(&head->xmin) ||
  73       !table.ReadS16(&head->ymin) ||
  74       !table.ReadS16(&head->xmax) ||
  75       !table.ReadS16(&head->ymax)) {
  76     return OTS_FAILURE_MSG("Failed to read font bounding box");
  77   }
  78
  79   if (head->xmin > head->xmax) {
  80     return OTS_FAILURE_MSG("Bad x dimension in the font bounding box (%d, %d)", head->xmin, head->xmax);
  81   }
  82   if (head->ymin > head->ymax) {
  83     return OTS_FAILURE_MSG("Bad y dimension in the font bounding box (%d, %d)", head->ymin, head->ymax);
  84   }
  85
  86   if (!table.ReadU16(&head->mac_style)) {
  87     return OTS_FAILURE_MSG("Failed to read font style");
  88   }
  89
  90   // We allow bits 0..6
  91   head->mac_style &= 0x7f;
  92
  93   if (!table.ReadU16(&head->min_ppem)) {
  94     return OTS_FAILURE_MSG("Failed to read font minimum ppm");
  95   }
  96
  97   // We don't care about the font direction hint
  98   if (!table.Skip(2)) {
  99     return OTS_FAILURE_MSG("Failed to skip font direction hint");
 100   }
 101
 102   if (!table.ReadS16(&head->index_to_loc_format)) {
 103     return OTS_FAILURE_MSG("Failed to read index to loc format");
 104   }
 105   if (head->index_to_loc_format < 0 ||
 106       head->index_to_loc_format > 1) {
 107     return OTS_FAILURE_MSG("Bad index to loc format %d", head->index_to_loc_format);
 108   }
 109
 110   int16_t glyph_data_format;
 111   if (!table.ReadS16(&glyph_data_format) ||
 112       glyph_data_format) {
 113     return OTS_FAILURE_MSG("Failed to read glyph data format");
 114   }
 115
 116   return true;
 117 }
 118
 119 bool ots_head_should_serialise(Font *font) {
 120   return font->head != NULL;
 121 }
 122
 123 bool ots_head_serialise(OTSStream *out, Font *font) {
 124   const OpenTypeHEAD *head = font->head;
 125   if (!out->WriteU32(0x00010000) ||
 126       !out->WriteU32(head->revision) ||
 127       !out->WriteU32(0) ||  // check sum not filled in yet
 128       !out->WriteU32(0x5F0F3CF5) ||
 129       !out->WriteU16(head->flags) ||
 130       !out->WriteU16(head->ppem) ||
 131       !out->WriteR64(head->created) ||
 132       !out->WriteR64(head->modified) ||
 133       !out->WriteS16(head->xmin) ||
 134       !out->WriteS16(head->ymin) ||
 135       !out->WriteS16(head->xmax) ||
 136       !out->WriteS16(head->ymax) ||
 137       !out->WriteU16(head->mac_style) ||
 138       !out->WriteU16(head->min_ppem) ||
 139       !out->WriteS16(2) ||
 140       !out->WriteS16(head->index_to_loc_format) ||
 141       !out->WriteS16(0)) {
 142     return OTS_FAILURE_MSG("Failed to write head table");
 143   }
 144
 145   return true;
 146 }
 147
 148 void ots_head_reuse(Font *font, Font *other) {
 149   font->head = other->head;
 150   font->head_reused = true;
 151 }
 152
 153 void ots_head_free(Font *font) {
 154   delete font->head;
 155 }
 156
 157 }  // namespace
 158
 159 #undef TABLE_NAME