tor-browser

The Tor Browser
git clone https://git.dasho.dev/tor-browser.git
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loca.cc (2834B)

      1 // Copyright (c) 2009-2017 The OTS 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 "loca.h"
      6 
      7 #include "head.h"
      8 #include "maxp.h"
      9 
     10 // loca - Index to Location
     11 // http://www.microsoft.com/typography/otspec/loca.htm
     12 
     13 namespace ots {
     14 
     15 bool OpenTypeLOCA::Parse(const uint8_t *data, size_t length) {
     16  Buffer table(data, length);
     17 
     18  // We can't do anything useful in validating this data except to ensure that
     19  // the values are monotonically increasing.
     20 
     21  OpenTypeMAXP *maxp = static_cast<OpenTypeMAXP*>(
     22      GetFont()->GetTypedTable(OTS_TAG_MAXP));
     23  OpenTypeHEAD *head = static_cast<OpenTypeHEAD*>(
     24      GetFont()->GetTypedTable(OTS_TAG_HEAD));
     25  if (!maxp || !head) {
     26    return Error("Required maxp or head tables are missing");
     27  }
     28 
     29  const unsigned num_glyphs = maxp->num_glyphs;
     30  unsigned last_offset = 0;
     31  this->offsets.resize(num_glyphs + 1);
     32  // maxp->num_glyphs is uint16_t, thus the addition never overflows.
     33 
     34  if (head->index_to_loc_format == 0) {
     35    // Note that the <= here (and below) is correct. There is one more offset
     36    // than the number of glyphs in order to give the length of the final
     37    // glyph.
     38    for (unsigned i = 0; i <= num_glyphs; ++i) {
     39      uint16_t offset = 0;
     40      if (!table.ReadU16(&offset)) {
     41        return Error("Failed to read offset for glyph %d", i);
     42      }
     43      if (offset < last_offset) {
     44        return Error("Out of order offset %d < %d for glyph %d", offset, last_offset, i);
     45      }
     46      last_offset = offset;
     47      this->offsets[i] = offset * 2;
     48    }
     49  } else {
     50    for (unsigned i = 0; i <= num_glyphs; ++i) {
     51      uint32_t offset = 0;
     52      if (!table.ReadU32(&offset)) {
     53        return Error("Failed to read offset for glyph %d", i);
     54      }
     55      if (offset < last_offset) {
     56        return Error("Out of order offset %d < %d for glyph %d", offset, last_offset, i);
     57      }
     58      last_offset = offset;
     59      this->offsets[i] = offset;
     60    }
     61  }
     62 
     63  return true;
     64 }
     65 
     66 bool OpenTypeLOCA::Serialize(OTSStream *out) {
     67  OpenTypeHEAD *head = static_cast<OpenTypeHEAD*>(
     68      GetFont()->GetTypedTable(OTS_TAG_HEAD));
     69 
     70  if (!head) {
     71    return Error("Required head table is missing");
     72  }
     73 
     74  if (head->index_to_loc_format == 0) {
     75    for (unsigned i = 0; i < this->offsets.size(); ++i) {
     76      const uint16_t offset = static_cast<uint16_t>(this->offsets[i] >> 1);
     77      if ((offset != (this->offsets[i] >> 1)) ||
     78          !out->WriteU16(offset)) {
     79        return Error("Failed to write glyph offset for glyph %d", i);
     80      }
     81    }
     82  } else {
     83    for (unsigned i = 0; i < this->offsets.size(); ++i) {
     84      if (!out->WriteU32(this->offsets[i])) {
     85        return Error("Failed to write glyph offset for glyph %d", i);
     86      }
     87    }
     88  }
     89 
     90  return true;
     91 }
     92 
     93 }  // namespace ots