third_party/ots/src/loca.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 "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 #define TABLE_NAME "loca"
  14
  15 namespace ots {
  16
  17 bool ots_loca_parse(OpenTypeFile *file, const uint8_t *data, size_t length) {
  18   Buffer table(data, length);
  19
  20   // We can't do anything useful in validating this data except to ensure that
  21   // the values are monotonically increasing.
  22
  23   OpenTypeLOCA *loca = new OpenTypeLOCA;
  24   file->loca = loca;
  25
  26   if (!file->maxp || !file->head) {
  27     return OTS_FAILURE_MSG("maxp or head tables missing from font, needed by loca");
  28   }
  29
  30   const unsigned num_glyphs = file->maxp->num_glyphs;
  31   unsigned last_offset = 0;
  32   loca->offsets.resize(num_glyphs + 1);
  33   // maxp->num_glyphs is uint16_t, thus the addition never overflows.
  34
  35   if (file->head->index_to_loc_format == 0) {
  36     // Note that the <= here (and below) is correct. There is one more offset
  37     // than the number of glyphs in order to give the length of the final
  38     // glyph.
  39     for (unsigned i = 0; i <= num_glyphs; ++i) {
  40       uint16_t offset = 0;
  41       if (!table.ReadU16(&offset)) {
  42         return OTS_FAILURE_MSG("Failed to read offset for glyph %d", i);
  43       }
  44       if (offset < last_offset) {
  45         return OTS_FAILURE_MSG("Out of order offset %d < %d for glyph %d", offset, last_offset, i);
  46       }
  47       last_offset = offset;
  48       loca->offsets[i] = offset * 2;
  49     }
  50   } else {
  51     for (unsigned i = 0; i <= num_glyphs; ++i) {
  52       uint32_t offset = 0;
  53       if (!table.ReadU32(&offset)) {
  54         return OTS_FAILURE_MSG("Failed to read offset for glyph %d", i);
  55       }
  56       if (offset < last_offset) {
  57         return OTS_FAILURE_MSG("Out of order offset %d < %d for glyph %d", offset, last_offset, i);
  58       }
  59       last_offset = offset;
  60       loca->offsets[i] = offset;
  61     }
  62   }
  63
  64   return true;
  65 }
  66
  67 bool ots_loca_should_serialise(OpenTypeFile *file) {
  68   return file->loca != NULL;
  69 }
  70
  71 bool ots_loca_serialise(OTSStream *out, OpenTypeFile *file) {
  72   const OpenTypeLOCA *loca = file->loca;
  73   const OpenTypeHEAD *head = file->head;
  74
  75   if (!head) {
  76     return OTS_FAILURE_MSG("Missing head table in font needed by loca");
  77   }
  78
  79   if (head->index_to_loc_format == 0) {
  80     for (unsigned i = 0; i < loca->offsets.size(); ++i) {
  81       const uint16_t offset = static_cast<uint16_t>(loca->offsets[i] >> 1);
  82       if ((offset != (loca->offsets[i] >> 1)) ||
  83           !out->WriteU16(offset)) {
  84         return OTS_FAILURE_MSG("Failed to write glyph offset for glyph %d", i);
  85       }
  86     }
  87   } else {
  88     for (unsigned i = 0; i < loca->offsets.size(); ++i) {
  89       if (!out->WriteU32(loca->offsets[i])) {
  90         return OTS_FAILURE_MSG("Failed to write glyph offset for glyph %d", i);
  91       }
  92     }
  93   }
  94
  95   return true;
  96 }
  97
  98 void ots_loca_free(OpenTypeFile *file) {
  99   delete file->loca;
 100 }
 101
 102 }  // namespace ots
 103
 104 #undef TABLE_NAME