tor-browser

vdmx.cc (5403B)

---

// 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 "vdmx.h"

#include <set>

// VDMX - Vertical Device Metrics
// http://www.microsoft.com/typography/otspec/vdmx.htm

namespace ots {

#define TABLE_NAME "VDMX"

bool OpenTypeVDMX::Parse(const uint8_t *data, size_t length) {
 Buffer table(data, length);
 ots::Font* font = this->GetFont();

 if (!table.ReadU16(&this->version) ||
     !table.ReadU16(&this->num_recs) ||
     !table.ReadU16(&this->num_ratios)) {
   return Drop("Failed to read table header");
 }

 if (this->version > 1) {
   return Drop("Unsupported table version: %u", this->version);
 }

 this->rat_ranges.reserve(this->num_ratios);
 for (unsigned i = 0; i < this->num_ratios; ++i) {
   OpenTypeVDMXRatioRecord rec;

   if (!table.ReadU8(&rec.charset) ||
       !table.ReadU8(&rec.x_ratio) ||
       !table.ReadU8(&rec.y_start_ratio) ||
       !table.ReadU8(&rec.y_end_ratio)) {
     return Drop("Failed to read RatioRange record %d", i);
   }

   if (rec.charset > 1) {
     return Drop("Unsupported character set: %u", rec.charset);
   }

   if (rec.y_start_ratio > rec.y_end_ratio) {
     return Drop("Bad y ratio");
   }

   // All values set to zero signal the default grouping to use;
   // if present, this must be the last Ratio group in the table.
   if ((i < this->num_ratios - 1u) &&
       (rec.x_ratio == 0) &&
       (rec.y_start_ratio == 0) &&
       (rec.y_end_ratio == 0)) {
     // workaround for fonts which have 2 or more {0, 0, 0} terminators.
     return Drop("Superfluous terminator found");
   }

   this->rat_ranges.push_back(rec);
 }

 this->offsets.reserve(this->num_ratios);
 const size_t current_offset = table.offset();
 std::set<uint16_t> unique_offsets;
 // current_offset is less than (2 bytes * 3) + (4 bytes * USHRT_MAX) = 256k.
 for (unsigned i = 0; i < this->num_ratios; ++i) {
   uint16_t offset;
   if (!table.ReadU16(&offset)) {
     return Drop("Failed to read ratio offset %d", i);
   }
   if (current_offset + offset >= length) {  // thus doesn't overflow.
     return Drop("Bad ratio offset %d for ration %d", offset, i);
   }

   this->offsets.push_back(offset);
   unique_offsets.insert(offset);
 }

 // Check that num_recs is sufficient to provide as many VDMXGroup records
 // as there are unique offsets; if not, update it (we'll return an error
 // below if they're not actually present).
 if (unique_offsets.size() > this->num_recs) {
   OTS_WARNING("increasing num_recs (%u is too small for %u unique offsets)",
               this->num_recs, unique_offsets.size());
   this->num_recs = unique_offsets.size();
 }

 this->groups.reserve(this->num_recs);
 for (unsigned i = 0; i < this->num_recs; ++i) {
   OpenTypeVDMXGroup group;
   if (!table.ReadU16(&group.recs) ||
       !table.ReadU8(&group.startsz) ||
       !table.ReadU8(&group.endsz)) {
     return Drop("Failed to read record header %d", i);
   }
   group.entries.reserve(group.recs);
   for (unsigned j = 0; j < group.recs; ++j) {
     OpenTypeVDMXVTable vt;
     if (!table.ReadU16(&vt.y_pel_height) ||
         !table.ReadS16(&vt.y_max) ||
         !table.ReadS16(&vt.y_min)) {
       return Drop("Failed to read record %d group %d", i, j);
     }
     if (vt.y_max < vt.y_min) {
       return Drop("bad y min/max");
     }

     // This table must appear in sorted order (sorted by yPelHeight),
     // but need not be continuous.
     if ((j != 0) && (group.entries[j - 1].y_pel_height >= vt.y_pel_height)) {
       return Drop("The table is not sorted");
     }

     group.entries.push_back(vt);
   }
   this->groups.push_back(group);
 }

 return true;
}

bool OpenTypeVDMX::ShouldSerialize() {
 return Table::ShouldSerialize() &&
        // this table is not for CFF fonts.
        GetFont()->GetTable(OTS_TAG_GLYF) != NULL;
}

bool OpenTypeVDMX::Serialize(OTSStream *out) {
 if (!out->WriteU16(this->version) ||
     !out->WriteU16(this->num_recs) ||
     !out->WriteU16(this->num_ratios)) {
   return Error("Failed to write table header");
 }

 for (unsigned i = 0; i < this->rat_ranges.size(); ++i) {
   const OpenTypeVDMXRatioRecord& rec = this->rat_ranges[i];
   if (!out->Write(&rec.charset, 1) ||
       !out->Write(&rec.x_ratio, 1) ||
       !out->Write(&rec.y_start_ratio, 1) ||
       !out->Write(&rec.y_end_ratio, 1)) {
     return Error("Failed to write RatioRange record %d", i);
   }
 }

 for (unsigned i = 0; i < this->offsets.size(); ++i) {
   if (!out->WriteU16(this->offsets[i])) {
     return Error("Failed to write ratio offset %d", i);
   }
 }

 for (unsigned i = 0; i < this->groups.size(); ++i) {
   const OpenTypeVDMXGroup& group = this->groups[i];
   if (!out->WriteU16(group.recs) ||
       !out->Write(&group.startsz, 1) ||
       !out->Write(&group.endsz, 1)) {
     return Error("Failed to write group %d", i);
   }
   for (unsigned j = 0; j < group.entries.size(); ++j) {
     const OpenTypeVDMXVTable& vt = group.entries[j];
     if (!out->WriteU16(vt.y_pel_height) ||
         !out->WriteS16(vt.y_max) ||
         !out->WriteS16(vt.y_min)) {
       return Error("Failed to write group %d entry %d", i, j);
     }
   }
 }

 return true;
}

#undef TABLE_NAME

}  // namespace ots