third_party/ots/src/vdmx.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 "vdmx.h"
   6
   7 // VDMX - Vertical Device Metrics
   8 // http://www.microsoft.com/typography/otspec/vdmx.htm
   9
  10 #define TABLE_NAME "VDMX"
  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->vdmx; \
  17     font->vdmx = 0; \
  18   } while (0)
  19
  20 namespace ots {
  21
  22 bool ots_vdmx_parse(Font *font, const uint8_t *data, size_t length) {
  23   Buffer table(data, length);
  24   font->vdmx = new OpenTypeVDMX;
  25   OpenTypeVDMX * const vdmx = font->vdmx;
  26
  27   if (!table.ReadU16(&vdmx->version) ||
  28       !table.ReadU16(&vdmx->num_recs) ||
  29       !table.ReadU16(&vdmx->num_ratios)) {
  30     return OTS_FAILURE_MSG("Failed to read table header");
  31   }
  32
  33   if (vdmx->version > 1) {
  34     DROP_THIS_TABLE("bad version: %u", vdmx->version);
  35     return true;  // continue transcoding
  36   }
  37
  38   vdmx->rat_ranges.reserve(vdmx->num_ratios);
  39   for (unsigned i = 0; i < vdmx->num_ratios; ++i) {
  40     OpenTypeVDMXRatioRecord rec;
  41
  42     if (!table.ReadU8(&rec.charset) ||
  43         !table.ReadU8(&rec.x_ratio) ||
  44         !table.ReadU8(&rec.y_start_ratio) ||
  45         !table.ReadU8(&rec.y_end_ratio)) {
  46       return OTS_FAILURE_MSG("Failed to read ratio header %d", i);
  47     }
  48
  49     if (rec.charset > 1) {
  50       DROP_THIS_TABLE("bad charset: %u", rec.charset);
  51       return true;
  52     }
  53
  54     if (rec.y_start_ratio > rec.y_end_ratio) {
  55       DROP_THIS_TABLE("bad y ratio");
  56       return true;
  57     }
  58
  59     // All values set to zero signal the default grouping to use;
  60     // if present, this must be the last Ratio group in the table.
  61     if ((i < vdmx->num_ratios - 1u) &&
  62         (rec.x_ratio == 0) &&
  63         (rec.y_start_ratio == 0) &&
  64         (rec.y_end_ratio == 0)) {
  65       // workaround for fonts which have 2 or more {0, 0, 0} terminators.
  66       DROP_THIS_TABLE("superfluous terminator found");
  67       return true;
  68     }
  69
  70     vdmx->rat_ranges.push_back(rec);
  71   }
  72
  73   vdmx->offsets.reserve(vdmx->num_ratios);
  74   const size_t current_offset = table.offset();
  75   // current_offset is less than (2 bytes * 3) + (4 bytes * USHRT_MAX) = 256k.
  76   for (unsigned i = 0; i < vdmx->num_ratios; ++i) {
  77     uint16_t offset;
  78     if (!table.ReadU16(&offset)) {
  79       return OTS_FAILURE_MSG("Failed to read ratio offset %d", i);
  80     }
  81     if (current_offset + offset >= length) {  // thus doesn't overflow.
  82       return OTS_FAILURE_MSG("Bad ratio offset %d for ration %d", offset, i);
  83     }
  84
  85     vdmx->offsets.push_back(offset);
  86   }
  87
  88   vdmx->groups.reserve(vdmx->num_recs);
  89   for (unsigned i = 0; i < vdmx->num_recs; ++i) {
  90     OpenTypeVDMXGroup group;
  91     if (!table.ReadU16(&group.recs) ||
  92         !table.ReadU8(&group.startsz) ||
  93         !table.ReadU8(&group.endsz)) {
  94       return OTS_FAILURE_MSG("Failed to read record header %d", i);
  95     }
  96     group.entries.reserve(group.recs);
  97     for (unsigned j = 0; j < group.recs; ++j) {
  98       OpenTypeVDMXVTable vt;
  99       if (!table.ReadU16(&vt.y_pel_height) ||
 100           !table.ReadS16(&vt.y_max) ||
 101           !table.ReadS16(&vt.y_min)) {
 102         return OTS_FAILURE_MSG("Failed to read reacord %d group %d", i, j);
 103       }
 104       if (vt.y_max < vt.y_min) {
 105         DROP_THIS_TABLE("bad y min/max");
 106         return true;
 107       }
 108
 109       // This table must appear in sorted order (sorted by yPelHeight),
 110       // but need not be continuous.
 111       if ((j != 0) && (group.entries[j - 1].y_pel_height >= vt.y_pel_height)) {
 112         DROP_THIS_TABLE("the table is not sorted");
 113         return true;
 114       }
 115
 116       group.entries.push_back(vt);
 117     }
 118     vdmx->groups.push_back(group);
 119   }
 120
 121   return true;
 122 }
 123
 124 bool ots_vdmx_should_serialise(Font *font) {
 125   if (!font->glyf) return false;  // this table is not for CFF fonts.
 126   return font->vdmx != NULL;
 127 }
 128
 129 bool ots_vdmx_serialise(OTSStream *out, Font *font) {
 130   OpenTypeVDMX * const vdmx = font->vdmx;
 131
 132   if (!out->WriteU16(vdmx->version) ||
 133       !out->WriteU16(vdmx->num_recs) ||
 134       !out->WriteU16(vdmx->num_ratios)) {
 135     return OTS_FAILURE_MSG("Failed to write table header");
 136   }
 137
 138   for (unsigned i = 0; i < vdmx->rat_ranges.size(); ++i) {
 139     const OpenTypeVDMXRatioRecord& rec = vdmx->rat_ranges[i];
 140     if (!out->Write(&rec.charset, 1) ||
 141         !out->Write(&rec.x_ratio, 1) ||
 142         !out->Write(&rec.y_start_ratio, 1) ||
 143         !out->Write(&rec.y_end_ratio, 1)) {
 144       return OTS_FAILURE_MSG("Failed to write ratio %d", i);
 145     }
 146   }
 147
 148   for (unsigned i = 0; i < vdmx->offsets.size(); ++i) {
 149     if (!out->WriteU16(vdmx->offsets[i])) {
 150       return OTS_FAILURE_MSG("Failed to write ratio offset %d", i);
 151     }
 152   }
 153
 154   for (unsigned i = 0; i < vdmx->groups.size(); ++i) {
 155     const OpenTypeVDMXGroup& group = vdmx->groups[i];
 156     if (!out->WriteU16(group.recs) ||
 157         !out->Write(&group.startsz, 1) ||
 158         !out->Write(&group.endsz, 1)) {
 159       return OTS_FAILURE_MSG("Failed to write group %d", i);
 160     }
 161     for (unsigned j = 0; j < group.entries.size(); ++j) {
 162       const OpenTypeVDMXVTable& vt = group.entries[j];
 163       if (!out->WriteU16(vt.y_pel_height) ||
 164           !out->WriteS16(vt.y_max) ||
 165           !out->WriteS16(vt.y_min)) {
 166         return OTS_FAILURE_MSG("Failed to write group %d entry %d", i, j);
 167       }
 168     }
 169   }
 170
 171   return true;
 172 }
 173
 174 void ots_vdmx_reuse(Font *font, Font *other) {
 175   font->vdmx = other->vdmx;
 176   font->vdmx_reused = true;
 177 }
 178
 179 void ots_vdmx_free(Font *font) {
 180   delete font->vdmx;
 181 }
 182
 183 }  // namespace ots
 184
 185 #undef TABLE_NAME
 186 #undef DROP_THIS_TABLE