tor-browser

metrics.cc (5342B)

---

// Copyright (c) 2011-2017 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 "metrics.h"

#include "head.h"
#include "maxp.h"

// OpenType horizontal and vertical common header format
// http://www.microsoft.com/typography/otspec/hhea.htm
// http://www.microsoft.com/typography/otspec/vhea.htm

namespace ots {

bool OpenTypeMetricsHeader::Parse(const uint8_t *data, size_t length) {
 Buffer table(data, length);

 // Skip already read version.
 if (!table.Skip(4)) {
   return false;
 }

 if (!table.ReadS16(&this->ascent) ||
     !table.ReadS16(&this->descent) ||
     !table.ReadS16(&this->linegap) ||
     !table.ReadU16(&this->adv_width_max) ||
     !table.ReadS16(&this->min_sb1) ||
     !table.ReadS16(&this->min_sb2) ||
     !table.ReadS16(&this->max_extent) ||
     !table.ReadS16(&this->caret_slope_rise) ||
     !table.ReadS16(&this->caret_slope_run) ||
     !table.ReadS16(&this->caret_offset)) {
   return Error("Failed to read table");
 }

 if (this->ascent < 0) {
   Warning("Negative ascent, setting to 0: %d", this->ascent);
   this->ascent = 0;
 }
 if (this->linegap < 0) {
   Warning("Negative linegap, setting to: %d", this->linegap);
   this->linegap = 0;
 }

 OpenTypeHEAD *head = static_cast<OpenTypeHEAD*>(
     GetFont()->GetTypedTable(OTS_TAG_HEAD));
 if (!head) {
   return Error("Missing head font table");
 }

 // if the font is non-slanted, caret_offset should be zero.
 if (!(head->mac_style & 2) &&
     (this->caret_offset != 0)) {
   Warning("Non-zero caretOffset but head.macStyle italic bit is not set, setting to caretOffset to 0: %d", this->caret_offset);
   this->caret_offset = 0;
 }

 // skip the reserved bytes
 if (!table.Skip(8)) {
   return Error("Failed to read reserved bytes");
 }

 int16_t data_format;
 if (!table.ReadS16(&data_format)) {
   return Error("Failed to read metricDataFormat");
 }
 if (data_format) {
   return Error("Unsupported metricDataFormat: %d", data_format);
 }

 if (!table.ReadU16(&this->num_metrics)) {
   return Error("Failed to read number of metrics");
 }

 OpenTypeMAXP *maxp = static_cast<OpenTypeMAXP*>(
     GetFont()->GetTypedTable(OTS_TAG_MAXP));
 if (!maxp) {
   return Error("Missing maxp font table");
 }

 if (this->num_metrics > maxp->num_glyphs) {
   return Error("Bad number of metrics %d", this->num_metrics);
 }

 return true;
}

bool OpenTypeMetricsHeader::Serialize(OTSStream *out) {
 if (!out->WriteU32(this->version) ||
     !out->WriteS16(this->ascent) ||
     !out->WriteS16(this->descent) ||
     !out->WriteS16(this->linegap) ||
     !out->WriteU16(this->adv_width_max) ||
     !out->WriteS16(this->min_sb1) ||
     !out->WriteS16(this->min_sb2) ||
     !out->WriteS16(this->max_extent) ||
     !out->WriteS16(this->caret_slope_rise) ||
     !out->WriteS16(this->caret_slope_run) ||
     !out->WriteS16(this->caret_offset) ||
     !out->WriteR64(0) ||  // reserved
     !out->WriteS16(0) ||  // metric data format
     !out->WriteU16(this->num_metrics)) {
   return Error("Failed to write metrics");
 }

 return true;
}

bool OpenTypeMetricsTable::Parse(const uint8_t *data, size_t length) {
 Buffer table(data, length);

 // OpenTypeMetricsHeader is a superclass of both 'hhea' and 'vhea',
 // so the cast here is OK, whichever m_header_tag we have.
 OpenTypeMetricsHeader *header = static_cast<OpenTypeMetricsHeader*>(
     GetFont()->GetTypedTable(m_header_tag));
 if (!header) {
   return Error("Required %c%c%c%c table missing", OTS_UNTAG(m_header_tag));
 }
 // |num_metrics| is a uint16_t, so it's bounded < 65536. This limits that
 // amount of memory that we'll allocate for this to a sane amount.
 const unsigned num_metrics = header->num_metrics;

 OpenTypeMAXP *maxp = static_cast<OpenTypeMAXP*>(
     GetFont()->GetTypedTable(OTS_TAG_MAXP));
 if (!maxp) {
   return Error("Required maxp table missing");
 }
 if (num_metrics > maxp->num_glyphs) {
   return Error("Bad number of metrics %d", num_metrics);
 }
 if (!num_metrics) {
   return Error("No metrics!");
 }
 const unsigned num_sbs = maxp->num_glyphs - num_metrics;

 this->entries.reserve(num_metrics);
 for (unsigned i = 0; i < num_metrics; ++i) {
   uint16_t adv = 0;
   int16_t sb = 0;
   if (!table.ReadU16(&adv) || !table.ReadS16(&sb)) {
     return Error("Failed to read metric %d", i);
   }
   this->entries.push_back(std::make_pair(adv, sb));
 }

 this->sbs.reserve(num_sbs);
 for (unsigned i = 0; i < num_sbs; ++i) {
   int16_t sb;
   if (!table.ReadS16(&sb)) {
     // Some Japanese fonts (e.g., mona.ttf) fail this test.
     return Error("Failed to read side bearing %d", i + num_metrics);
   }
   this->sbs.push_back(sb);
 }

 return true;
}

bool OpenTypeMetricsTable::Serialize(OTSStream *out) {
 for (unsigned i = 0; i < this->entries.size(); ++i) {
   if (!out->WriteU16(this->entries[i].first) ||
       !out->WriteS16(this->entries[i].second)) {
     return Error("Failed to write metric %d", i);
   }
 }

 for (unsigned i = 0; i < this->sbs.size(); ++i) {
   if (!out->WriteS16(this->sbs[i])) {
     return Error("Failed to write side bearing %ld", i + this->entries.size());
   }
 }

 return true;
}

}  // namespace ots