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Diffstat (limited to 'modules/woff2/src/normalize.cc')
| -rw-r--r-- | modules/woff2/src/normalize.cc | 322 |
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 000000000..b538b91a8 --- /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 |