1 files changed, 322 insertions, 0 deletions
diff --git a/modules/woff2/src/normalize.cc b/modules/woff2/src/normalize.cc
new file mode 100644
index 0000000000..b538b91a89
--- /dev/null
+++ b/modules/woff2/src/normalize.cc
@@ -0,0 +1,322 @@
+// Copyright 2013 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Glyph normalization
+
+#include "./normalize.h"
+
+#include <inttypes.h>
+#include <stddef.h>
+
+#include "./buffer.h"
+#include "./port.h"
+#include "./font.h"
+#include "./glyph.h"
+#include "./round.h"
+#include "./store_bytes.h"
+#include "./table_tags.h"
+#include "./woff2_common.h"
+
+namespace woff2 {
+
+namespace {
+
+void StoreLoca(int index_fmt, uint32_t value, size_t* offset, uint8_t* dst) {
+  if (index_fmt == 0) {
+    Store16(value >> 1, offset, dst);
+  } else {
+    StoreU32(value, offset, dst);
+  }
+}
+
+}  // namespace
+
+namespace {
+
+bool WriteNormalizedLoca(int index_fmt, int num_glyphs, Font* font) {
+  Font::Table* glyf_table = font->FindTable(kGlyfTableTag);
+  Font::Table* loca_table = font->FindTable(kLocaTableTag);
+
+  int glyph_sz = index_fmt == 0 ? 2 : 4;
+  loca_table->buffer.resize(Round4(num_glyphs + 1) * glyph_sz);
+  loca_table->length = (num_glyphs + 1) * glyph_sz;
+
+  uint8_t* glyf_dst = &glyf_table->buffer[0];
+  uint8_t* loca_dst = &loca_table->buffer[0];
+  uint32_t glyf_offset = 0;
+  size_t loca_offset = 0;
+
+  for (int i = 0; i < num_glyphs; ++i) {
+    StoreLoca(index_fmt, glyf_offset, &loca_offset, loca_dst);
+    Glyph glyph;
+    const uint8_t* glyph_data;
+    size_t glyph_size;
+    if (!GetGlyphData(*font, i, &glyph_data, &glyph_size) ||
+        (glyph_size > 0 && !ReadGlyph(glyph_data, glyph_size, &glyph))) {
+      return FONT_COMPRESSION_FAILURE();
+    }
+    size_t glyf_dst_size = glyf_table->buffer.size() - glyf_offset;
+    if (!StoreGlyph(glyph, glyf_dst + glyf_offset, &glyf_dst_size)) {
+      return FONT_COMPRESSION_FAILURE();
+    }
+    glyf_dst_size = Round4(glyf_dst_size);
+    if (glyf_dst_size > std::numeric_limits<uint32_t>::max() ||
+        glyf_offset + static_cast<uint32_t>(glyf_dst_size) < glyf_offset ||
+        (index_fmt == 0 && glyf_offset + glyf_dst_size >= (1UL << 17))) {
+      return FONT_COMPRESSION_FAILURE();
+    }
+    glyf_offset += glyf_dst_size;
+  }
+  if (glyf_offset == 0) {
+    return false;
+  }
+
+  StoreLoca(index_fmt, glyf_offset, &loca_offset, loca_dst);
+
+  glyf_table->buffer.resize(glyf_offset);
+  glyf_table->data = &glyf_table->buffer[0];
+  glyf_table->length = glyf_offset;
+  loca_table->data = &loca_table->buffer[0];
+
+  return true;
+}
+
+}  // namespace
+
+namespace {
+
+bool MakeEditableBuffer(Font* font, int tableTag) {
+  Font::Table* table = font->FindTable(tableTag);
+  if (table == NULL) {
+    return FONT_COMPRESSION_FAILURE();
+  }
+  if (table->IsReused()) {
+    return true;
+  }
+  int sz = Round4(table->length);
+  table->buffer.resize(sz);
+  uint8_t* buf = &table->buffer[0];
+  memcpy(buf, table->data, sz);
+  table->data = buf;
+  return true;
+}
+
+}  // namespace
+
+bool NormalizeGlyphs(Font* font) {
+  Font::Table* head_table = font->FindTable(kHeadTableTag);
+  Font::Table* glyf_table = font->FindTable(kGlyfTableTag);
+  Font::Table* loca_table = font->FindTable(kLocaTableTag);
+  if (head_table == NULL) {
+    return FONT_COMPRESSION_FAILURE();
+  }
+  // If you don't have glyf/loca this transform isn't very interesting
+  if (loca_table == NULL && glyf_table == NULL) {
+    return true;
+  }
+  // It would be best if you didn't have just one of glyf/loca
+  if ((glyf_table == NULL) != (loca_table == NULL)) {
+    return FONT_COMPRESSION_FAILURE();
+  }
+  // Must share neither or both loca & glyf
+  if (loca_table->IsReused() != glyf_table->IsReused()) {
+    return FONT_COMPRESSION_FAILURE();
+  }
+  if (loca_table->IsReused()) {
+    return true;
+  }
+
+  int index_fmt = head_table->data[51];
+  int num_glyphs = NumGlyphs(*font);
+
+  // We need to allocate a bit more than its original length for the normalized
+  // glyf table, since it can happen that the glyphs in the original table are
+  // 2-byte aligned, while in the normalized table they are 4-byte aligned.
+  // That gives a maximum of 2 bytes increase per glyph. However, there is no
+  // theoretical guarantee that the total size of the flags plus the coordinates
+  // is the smallest possible in the normalized version, so we have to allow
+  // some general overhead.
+  // TODO(user) Figure out some more precise upper bound on the size of
+  // the overhead.
+  size_t max_normalized_glyf_size = 1.1 * glyf_table->length + 2 * num_glyphs;
+
+  glyf_table->buffer.resize(max_normalized_glyf_size);
+
+  // if we can't write a loca using short's (index_fmt 0)
+  // try again using longs (index_fmt 1)
+  if (!WriteNormalizedLoca(index_fmt, num_glyphs, font)) {
+    if (index_fmt != 0) {
+      return FONT_COMPRESSION_FAILURE();
+    }
+
+    // Rewrite loca with 4-byte entries & update head to match
+    index_fmt = 1;
+    if (!WriteNormalizedLoca(index_fmt, num_glyphs, font)) {
+      return FONT_COMPRESSION_FAILURE();
+    }
+    head_table->buffer[51] = 1;
+  }
+
+  return true;
+}
+
+bool NormalizeOffsets(Font* font) {
+  uint32_t offset = 12 + 16 * font->num_tables;
+  for (auto tag : font->OutputOrderedTags()) {
+    auto& table = font->tables[tag];
+    table.offset = offset;
+    offset += Round4(table.length);
+  }
+  return true;
+}
+
+namespace {
+
+uint32_t ComputeHeaderChecksum(const Font& font) {
+  uint32_t checksum = font.flavor;
+  uint16_t max_pow2 = font.num_tables ? Log2Floor(font.num_tables) : 0;
+  uint16_t search_range = max_pow2 ? 1 << (max_pow2 + 4) : 0;
+  uint16_t range_shift = (font.num_tables << 4) - search_range;
+  checksum += (font.num_tables << 16 | search_range);
+  checksum += (max_pow2 << 16 | range_shift);
+  for (const auto& i : font.tables) {
+    const Font::Table* table = &i.second;
+    if (table->IsReused()) {
+      table = table->reuse_of;
+    }
+    checksum += table->tag;
+    checksum += table->checksum;
+    checksum += table->offset;
+    checksum += table->length;
+  }
+  return checksum;
+}
+
+}  // namespace
+
+bool FixChecksums(Font* font) {
+  Font::Table* head_table = font->FindTable(kHeadTableTag);
+  if (head_table == NULL) {
+    return FONT_COMPRESSION_FAILURE();
+  }
+  if (head_table->reuse_of != NULL) {
+    head_table = head_table->reuse_of;
+  }
+  if (head_table->length < 12) {
+    return FONT_COMPRESSION_FAILURE();
+  }
+
+  uint8_t* head_buf = &head_table->buffer[0];
+  size_t offset = 8;
+  StoreU32(0, &offset, head_buf);
+  uint32_t file_checksum = 0;
+  uint32_t head_checksum = 0;
+  for (auto& i : font->tables) {
+    Font::Table* table = &i.second;
+    if (table->IsReused()) {
+      table = table->reuse_of;
+    }
+    table->checksum = ComputeULongSum(table->data, table->length);
+    file_checksum += table->checksum;
+
+    if (table->tag == kHeadTableTag) {
+      head_checksum = table->checksum;
+    }
+  }
+
+  file_checksum += ComputeHeaderChecksum(*font);
+  offset = 8;
+  StoreU32(0xb1b0afba - file_checksum, &offset, head_buf);
+
+  return true;
+}
+
+namespace {
+bool MarkTransformed(Font* font) {
+  Font::Table* head_table = font->FindTable(kHeadTableTag);
+  if (head_table == NULL) {
+    return FONT_COMPRESSION_FAILURE();
+  }
+  if (head_table->reuse_of != NULL) {
+    head_table = head_table->reuse_of;
+  }
+  if (head_table->length < 17) {
+    return FONT_COMPRESSION_FAILURE();
+  }
+  // set bit 11 of head table 'flags' to indicate that font has undergone
+  // lossless modifying transform
+  int head_flags = head_table->data[16];
+  head_table->buffer[16] = head_flags | 0x08;
+  return true;
+}
+}  // namespace
+
+
+bool NormalizeWithoutFixingChecksums(Font* font) {
+  return (MakeEditableBuffer(font, kHeadTableTag) &&
+          RemoveDigitalSignature(font) &&
+          MarkTransformed(font) &&
+          NormalizeGlyphs(font) &&
+          NormalizeOffsets(font));
+}
+
+bool NormalizeFont(Font* font) {
+  return (NormalizeWithoutFixingChecksums(font) &&
+          FixChecksums(font));
+}
+
+bool NormalizeFontCollection(FontCollection* font_collection) {
+  if (font_collection->fonts.size() == 1) {
+    return NormalizeFont(&font_collection->fonts[0]);
+  }
+
+  uint32_t offset = CollectionHeaderSize(font_collection->header_version,
+    font_collection->fonts.size());
+  for (auto& font : font_collection->fonts) {
+    if (!NormalizeWithoutFixingChecksums(&font)) {
+#ifdef FONT_COMPRESSION_BIN
+      fprintf(stderr, "Font normalization failed.\n");
+#endif
+      return FONT_COMPRESSION_FAILURE();
+    }
+    offset += kSfntHeaderSize + kSfntEntrySize * font.num_tables;
+  }
+
+  // Start table offsets after TTC Header and Sfnt Headers
+  for (auto& font : font_collection->fonts) {
+    for (auto tag : font.OutputOrderedTags()) {
+      Font::Table& table = font.tables[tag];
+      if (table.IsReused()) {
+        table.offset = table.reuse_of->offset;
+      } else {
+        table.offset = offset;
+        offset += Round4(table.length);
+      }
+    }
+  }
+
+  // Now we can fix the checksums
+  for (auto& font : font_collection->fonts) {
+    if (!FixChecksums(&font)) {
+#ifdef FONT_COMPRESSION_BIN
+      fprintf(stderr, "Failed to fix checksums\n");
+#endif
+      return FONT_COMPRESSION_FAILURE();
+    }
+  }
+
+  return true;
+}
+
+} // namespace woff2