diff options
Diffstat (limited to 'modules/woff2/src/woff2_dec.cc')
| -rw-r--r-- | modules/woff2/src/woff2_dec.cc | 1327 |
1 files changed, 1327 insertions, 0 deletions
diff --git a/modules/woff2/src/woff2_dec.cc b/modules/woff2/src/woff2_dec.cc new file mode 100644 index 000000000..97b869fe6 --- /dev/null +++ b/modules/woff2/src/woff2_dec.cc @@ -0,0 +1,1327 @@ +// Copyright 2014 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. +// +// Library for converting WOFF2 format font files to their TTF versions. + +#include "./woff2_dec.h" + +#include <stdlib.h> +#include <algorithm> +#include <complex> +#include <cstring> +#include <limits> +#include <string> +#include <vector> +#include <map> +#include <memory> +#include <utility> + +#include "mozilla/UniquePtr.h" +namespace std +{ + using mozilla::DefaultDelete; + using mozilla::UniquePtr; + #define default_delete DefaultDelete + #define unique_ptr UniquePtr +} + +#include "./decode.h" +#include "./buffer.h" +#include "./port.h" +#include "./round.h" +#include "./store_bytes.h" +#include "./table_tags.h" +#include "./variable_length.h" +#include "./woff2_common.h" + +namespace woff2 { + +namespace { + +using std::string; +using std::vector; + + +// simple glyph flags +const int kGlyfOnCurve = 1 << 0; +const int kGlyfXShort = 1 << 1; +const int kGlyfYShort = 1 << 2; +const int kGlyfRepeat = 1 << 3; +const int kGlyfThisXIsSame = 1 << 4; +const int kGlyfThisYIsSame = 1 << 5; + +// composite glyph flags +// See CompositeGlyph.java in sfntly for full definitions +const int FLAG_ARG_1_AND_2_ARE_WORDS = 1 << 0; +const int FLAG_WE_HAVE_A_SCALE = 1 << 3; +const int FLAG_MORE_COMPONENTS = 1 << 5; +const int FLAG_WE_HAVE_AN_X_AND_Y_SCALE = 1 << 6; +const int FLAG_WE_HAVE_A_TWO_BY_TWO = 1 << 7; +const int FLAG_WE_HAVE_INSTRUCTIONS = 1 << 8; + +const size_t kCheckSumAdjustmentOffset = 8; + +const size_t kEndPtsOfContoursOffset = 10; +const size_t kCompositeGlyphBegin = 10; + +// 98% of Google Fonts have no glyph above 5k bytes +// Largest glyph ever observed was 72k bytes +const size_t kDefaultGlyphBuf = 5120; + +// Over 14k test fonts the max compression ratio seen to date was ~20. +// >100 suggests you wrote a bad uncompressed size. +const float kMaxPlausibleCompressionRatio = 100.0; + +// metadata for a TTC font entry +struct TtcFont { + uint32_t flavor; + uint32_t dst_offset; + uint32_t header_checksum; + std::vector<uint16_t> table_indices; +}; + +struct WOFF2Header { + uint32_t flavor; + uint32_t header_version; + uint16_t num_tables; + uint64_t compressed_offset; + uint32_t compressed_length; + uint32_t uncompressed_size; + std::vector<Table> tables; // num_tables unique tables + std::vector<TtcFont> ttc_fonts; // metadata to help rebuild font +}; + +/** + * Accumulates data we may need to reconstruct a single font. One per font + * created for a TTC. + */ +struct WOFF2FontInfo { + uint16_t num_glyphs; + uint16_t index_format; + uint16_t num_hmetrics; + std::vector<int16_t> x_mins; + std::map<uint32_t, uint32_t> table_entry_by_tag; +}; + +// Accumulates metadata as we rebuild the font +struct RebuildMetadata { + uint32_t header_checksum; // set by WriteHeaders + std::vector<WOFF2FontInfo> font_infos; + // checksums for tables that have been written. + // (tag, src_offset) => checksum. Need both because 0-length loca. + std::map<std::pair<uint32_t, uint32_t>, uint32_t> checksums; +}; + +int WithSign(int flag, int baseval) { + // Precondition: 0 <= baseval < 65536 (to avoid integer overflow) + return (flag & 1) ? baseval : -baseval; +} + +bool TripletDecode(const uint8_t* flags_in, const uint8_t* in, size_t in_size, + unsigned int n_points, Point* result, size_t* in_bytes_consumed) { + int x = 0; + int y = 0; + + if (PREDICT_FALSE(n_points > in_size)) { + return FONT_COMPRESSION_FAILURE(); + } + unsigned int triplet_index = 0; + + for (unsigned int i = 0; i < n_points; ++i) { + uint8_t flag = flags_in[i]; + bool on_curve = !(flag >> 7); + flag &= 0x7f; + unsigned int n_data_bytes; + if (flag < 84) { + n_data_bytes = 1; + } else if (flag < 120) { + n_data_bytes = 2; + } else if (flag < 124) { + n_data_bytes = 3; + } else { + n_data_bytes = 4; + } + if (PREDICT_FALSE(triplet_index + n_data_bytes > in_size || + triplet_index + n_data_bytes < triplet_index)) { + return FONT_COMPRESSION_FAILURE(); + } + int dx, dy; + if (flag < 10) { + dx = 0; + dy = WithSign(flag, ((flag & 14) << 7) + in[triplet_index]); + } else if (flag < 20) { + dx = WithSign(flag, (((flag - 10) & 14) << 7) + in[triplet_index]); + dy = 0; + } else if (flag < 84) { + int b0 = flag - 20; + int b1 = in[triplet_index]; + dx = WithSign(flag, 1 + (b0 & 0x30) + (b1 >> 4)); + dy = WithSign(flag >> 1, 1 + ((b0 & 0x0c) << 2) + (b1 & 0x0f)); + } else if (flag < 120) { + int b0 = flag - 84; + dx = WithSign(flag, 1 + ((b0 / 12) << 8) + in[triplet_index]); + dy = WithSign(flag >> 1, + 1 + (((b0 % 12) >> 2) << 8) + in[triplet_index + 1]); + } else if (flag < 124) { + int b2 = in[triplet_index + 1]; + dx = WithSign(flag, (in[triplet_index] << 4) + (b2 >> 4)); + dy = WithSign(flag >> 1, ((b2 & 0x0f) << 8) + in[triplet_index + 2]); + } else { + dx = WithSign(flag, (in[triplet_index] << 8) + in[triplet_index + 1]); + dy = WithSign(flag >> 1, + (in[triplet_index + 2] << 8) + in[triplet_index + 3]); + } + triplet_index += n_data_bytes; + // Possible overflow but coordinate values are not security sensitive + x += dx; + y += dy; + *result++ = {x, y, on_curve}; + } + *in_bytes_consumed = triplet_index; + return true; +} + +// This function stores just the point data. On entry, dst points to the +// beginning of a simple glyph. Returns true on success. +bool StorePoints(unsigned int n_points, const Point* points, + unsigned int n_contours, unsigned int instruction_length, + uint8_t* dst, size_t dst_size, size_t* glyph_size) { + // I believe that n_contours < 65536, in which case this is safe. However, a + // comment and/or an assert would be good. + unsigned int flag_offset = kEndPtsOfContoursOffset + 2 * n_contours + 2 + + instruction_length; + int last_flag = -1; + int repeat_count = 0; + int last_x = 0; + int last_y = 0; + unsigned int x_bytes = 0; + unsigned int y_bytes = 0; + + for (unsigned int i = 0; i < n_points; ++i) { + const Point& point = points[i]; + int flag = point.on_curve ? kGlyfOnCurve : 0; + int dx = point.x - last_x; + int dy = point.y - last_y; + if (dx == 0) { + flag |= kGlyfThisXIsSame; + } else if (dx > -256 && dx < 256) { + flag |= kGlyfXShort | (dx > 0 ? kGlyfThisXIsSame : 0); + x_bytes += 1; + } else { + x_bytes += 2; + } + if (dy == 0) { + flag |= kGlyfThisYIsSame; + } else if (dy > -256 && dy < 256) { + flag |= kGlyfYShort | (dy > 0 ? kGlyfThisYIsSame : 0); + y_bytes += 1; + } else { + y_bytes += 2; + } + + if (flag == last_flag && repeat_count != 255) { + dst[flag_offset - 1] |= kGlyfRepeat; + repeat_count++; + } else { + if (repeat_count != 0) { + if (PREDICT_FALSE(flag_offset >= dst_size)) { + return FONT_COMPRESSION_FAILURE(); + } + dst[flag_offset++] = repeat_count; + } + if (PREDICT_FALSE(flag_offset >= dst_size)) { + return FONT_COMPRESSION_FAILURE(); + } + dst[flag_offset++] = flag; + repeat_count = 0; + } + last_x = point.x; + last_y = point.y; + last_flag = flag; + } + + if (repeat_count != 0) { + if (PREDICT_FALSE(flag_offset >= dst_size)) { + return FONT_COMPRESSION_FAILURE(); + } + dst[flag_offset++] = repeat_count; + } + unsigned int xy_bytes = x_bytes + y_bytes; + if (PREDICT_FALSE(xy_bytes < x_bytes || + flag_offset + xy_bytes < flag_offset || + flag_offset + xy_bytes > dst_size)) { + return FONT_COMPRESSION_FAILURE(); + } + + int x_offset = flag_offset; + int y_offset = flag_offset + x_bytes; + last_x = 0; + last_y = 0; + for (unsigned int i = 0; i < n_points; ++i) { + int dx = points[i].x - last_x; + if (dx == 0) { + // pass + } else if (dx > -256 && dx < 256) { + dst[x_offset++] = std::abs(dx); + } else { + // will always fit for valid input, but overflow is harmless + x_offset = Store16(dst, x_offset, dx); + } + last_x += dx; + int dy = points[i].y - last_y; + if (dy == 0) { + // pass + } else if (dy > -256 && dy < 256) { + dst[y_offset++] = std::abs(dy); + } else { + y_offset = Store16(dst, y_offset, dy); + } + last_y += dy; + } + *glyph_size = y_offset; + return true; +} + +// Compute the bounding box of the coordinates, and store into a glyf buffer. +// A precondition is that there are at least 10 bytes available. +// dst should point to the beginning of a 'glyf' record. +void ComputeBbox(unsigned int n_points, const Point* points, uint8_t* dst) { + int x_min = 0; + int y_min = 0; + int x_max = 0; + int y_max = 0; + + if (n_points > 0) { + x_min = points[0].x; + x_max = points[0].x; + y_min = points[0].y; + y_max = points[0].y; + } + for (unsigned int i = 1; i < n_points; ++i) { + int x = points[i].x; + int y = points[i].y; + x_min = std::min(x, x_min); + x_max = std::max(x, x_max); + y_min = std::min(y, y_min); + y_max = std::max(y, y_max); + } + size_t offset = 2; + offset = Store16(dst, offset, x_min); + offset = Store16(dst, offset, y_min); + offset = Store16(dst, offset, x_max); + offset = Store16(dst, offset, y_max); +} + + +bool SizeOfComposite(Buffer composite_stream, size_t* size, + bool* have_instructions) { + size_t start_offset = composite_stream.offset(); + bool we_have_instructions = false; + + uint16_t flags = FLAG_MORE_COMPONENTS; + while (flags & FLAG_MORE_COMPONENTS) { + if (PREDICT_FALSE(!composite_stream.ReadU16(&flags))) { + return FONT_COMPRESSION_FAILURE(); + } + we_have_instructions |= (flags & FLAG_WE_HAVE_INSTRUCTIONS) != 0; + size_t arg_size = 2; // glyph index + if (flags & FLAG_ARG_1_AND_2_ARE_WORDS) { + arg_size += 4; + } else { + arg_size += 2; + } + if (flags & FLAG_WE_HAVE_A_SCALE) { + arg_size += 2; + } else if (flags & FLAG_WE_HAVE_AN_X_AND_Y_SCALE) { + arg_size += 4; + } else if (flags & FLAG_WE_HAVE_A_TWO_BY_TWO) { + arg_size += 8; + } + if (PREDICT_FALSE(!composite_stream.Skip(arg_size))) { + return FONT_COMPRESSION_FAILURE(); + } + } + + *size = composite_stream.offset() - start_offset; + *have_instructions = we_have_instructions; + + return true; +} + +bool Pad4(WOFF2Out* out) { + uint8_t zeroes[] = {0, 0, 0}; + if (PREDICT_FALSE(out->Size() + 3 < out->Size())) { + return FONT_COMPRESSION_FAILURE(); + } + uint32_t pad_bytes = Round4(out->Size()) - out->Size(); + if (pad_bytes > 0) { + if (PREDICT_FALSE(!out->Write(&zeroes, pad_bytes))) { + return FONT_COMPRESSION_FAILURE(); + } + } + return true; +} + +// Build TrueType loca table +bool StoreLoca(const std::vector<uint32_t>& loca_values, int index_format, + uint32_t* checksum, WOFF2Out* out) { + // TODO(user) figure out what index format to use based on whether max + // offset fits into uint16_t or not + const uint64_t loca_size = loca_values.size(); + const uint64_t offset_size = index_format ? 4 : 2; + if (PREDICT_FALSE((loca_size << 2) >> 2 != loca_size)) { + return FONT_COMPRESSION_FAILURE(); + } + std::vector<uint8_t> loca_content(loca_size * offset_size); + uint8_t* dst = &loca_content[0]; + size_t offset = 0; + for (size_t i = 0; i < loca_values.size(); ++i) { + uint32_t value = loca_values[i]; + if (index_format) { + offset = StoreU32(dst, offset, value); + } else { + offset = Store16(dst, offset, value >> 1); + } + } + *checksum = ComputeULongSum(&loca_content[0], loca_content.size()); + if (PREDICT_FALSE(!out->Write(&loca_content[0], loca_content.size()))) { + return FONT_COMPRESSION_FAILURE(); + } + return true; +} + +// Reconstruct entire glyf table based on transformed original +bool ReconstructGlyf(const uint8_t* data, Table* glyf_table, + uint32_t* glyf_checksum, Table * loca_table, + uint32_t* loca_checksum, WOFF2FontInfo* info, + WOFF2Out* out) { + static const int kNumSubStreams = 7; + Buffer file(data, glyf_table->transform_length); + uint32_t version; + std::vector<std::pair<const uint8_t*, size_t> > substreams(kNumSubStreams); + const size_t glyf_start = out->Size(); + + if (PREDICT_FALSE(!file.ReadU32(&version))) { + return FONT_COMPRESSION_FAILURE(); + } + if (PREDICT_FALSE(!file.ReadU16(&info->num_glyphs) || + !file.ReadU16(&info->index_format))) { + return FONT_COMPRESSION_FAILURE(); + } + + unsigned int offset = (2 + kNumSubStreams) * 4; + if (PREDICT_FALSE(offset > glyf_table->transform_length)) { + return FONT_COMPRESSION_FAILURE(); + } + // Invariant from here on: data_size >= offset + for (int i = 0; i < kNumSubStreams; ++i) { + uint32_t substream_size; + if (PREDICT_FALSE(!file.ReadU32(&substream_size))) { + return FONT_COMPRESSION_FAILURE(); + } + if (PREDICT_FALSE(substream_size > glyf_table->transform_length - offset)) { + return FONT_COMPRESSION_FAILURE(); + } + substreams[i] = std::make_pair(data + offset, substream_size); + offset += substream_size; + } + Buffer n_contour_stream(substreams[0].first, substreams[0].second); + Buffer n_points_stream(substreams[1].first, substreams[1].second); + Buffer flag_stream(substreams[2].first, substreams[2].second); + Buffer glyph_stream(substreams[3].first, substreams[3].second); + Buffer composite_stream(substreams[4].first, substreams[4].second); + Buffer bbox_stream(substreams[5].first, substreams[5].second); + Buffer instruction_stream(substreams[6].first, substreams[6].second); + + std::vector<uint32_t> loca_values(info->num_glyphs + 1); + std::vector<unsigned int> n_points_vec; + std::unique_ptr<Point[]> points; + size_t points_size = 0; + const uint8_t* bbox_bitmap = bbox_stream.buffer(); + // Safe because num_glyphs is bounded + unsigned int bitmap_length = ((info->num_glyphs + 31) >> 5) << 2; + if (!bbox_stream.Skip(bitmap_length)) { + return FONT_COMPRESSION_FAILURE(); + } + + // Temp buffer for glyph's. + size_t glyph_buf_size = kDefaultGlyphBuf; + std::unique_ptr<uint8_t[]> glyph_buf(new uint8_t[glyph_buf_size]); + + info->x_mins.resize(info->num_glyphs); + for (unsigned int i = 0; i < info->num_glyphs; ++i) { + size_t glyph_size = 0; + uint16_t n_contours = 0; + bool have_bbox = false; + if (bbox_bitmap[i >> 3] & (0x80 >> (i & 7))) { + have_bbox = true; + } + if (PREDICT_FALSE(!n_contour_stream.ReadU16(&n_contours))) { + return FONT_COMPRESSION_FAILURE(); + } + + if (n_contours == 0xffff) { + // composite glyph + bool have_instructions = false; + unsigned int instruction_size = 0; + if (PREDICT_FALSE(!have_bbox)) { + // composite glyphs must have an explicit bbox + return FONT_COMPRESSION_FAILURE(); + } + + size_t composite_size; + if (PREDICT_FALSE(!SizeOfComposite(composite_stream, &composite_size, + &have_instructions))) { + return FONT_COMPRESSION_FAILURE(); + } + if (have_instructions) { + if (PREDICT_FALSE(!Read255UShort(&glyph_stream, &instruction_size))) { + return FONT_COMPRESSION_FAILURE(); + } + } + + size_t size_needed = 12 + composite_size + instruction_size; + if (PREDICT_FALSE(glyph_buf_size < size_needed)) { + glyph_buf.reset(new uint8_t[size_needed]); + glyph_buf_size = size_needed; + } + + glyph_size = Store16(glyph_buf.get(), glyph_size, n_contours); + if (PREDICT_FALSE(!bbox_stream.Read(glyph_buf.get() + glyph_size, 8))) { + return FONT_COMPRESSION_FAILURE(); + } + glyph_size += 8; + + if (PREDICT_FALSE(!composite_stream.Read(glyph_buf.get() + glyph_size, + composite_size))) { + return FONT_COMPRESSION_FAILURE(); + } + glyph_size += composite_size; + if (have_instructions) { + glyph_size = Store16(glyph_buf.get(), glyph_size, instruction_size); + if (PREDICT_FALSE(!instruction_stream.Read(glyph_buf.get() + glyph_size, + instruction_size))) { + return FONT_COMPRESSION_FAILURE(); + } + glyph_size += instruction_size; + } + } else if (n_contours > 0) { + // simple glyph + n_points_vec.clear(); + unsigned int total_n_points = 0; + unsigned int n_points_contour; + for (unsigned int j = 0; j < n_contours; ++j) { + if (PREDICT_FALSE( + !Read255UShort(&n_points_stream, &n_points_contour))) { + return FONT_COMPRESSION_FAILURE(); + } + n_points_vec.push_back(n_points_contour); + if (PREDICT_FALSE(total_n_points + n_points_contour < total_n_points)) { + return FONT_COMPRESSION_FAILURE(); + } + total_n_points += n_points_contour; + } + unsigned int flag_size = total_n_points; + if (PREDICT_FALSE( + flag_size > flag_stream.length() - flag_stream.offset())) { + return FONT_COMPRESSION_FAILURE(); + } + const uint8_t* flags_buf = flag_stream.buffer() + flag_stream.offset(); + const uint8_t* triplet_buf = glyph_stream.buffer() + + glyph_stream.offset(); + size_t triplet_size = glyph_stream.length() - glyph_stream.offset(); + size_t triplet_bytes_consumed = 0; + if (points_size < total_n_points) { + points_size = total_n_points; + points.reset(new Point[points_size]); + } + if (PREDICT_FALSE(!TripletDecode(flags_buf, triplet_buf, triplet_size, + total_n_points, points.get(), &triplet_bytes_consumed))) { + return FONT_COMPRESSION_FAILURE(); + } + if (PREDICT_FALSE(!flag_stream.Skip(flag_size))) { + return FONT_COMPRESSION_FAILURE(); + } + if (PREDICT_FALSE(!glyph_stream.Skip(triplet_bytes_consumed))) { + return FONT_COMPRESSION_FAILURE(); + } + unsigned int instruction_size; + if (PREDICT_FALSE(!Read255UShort(&glyph_stream, &instruction_size))) { + return FONT_COMPRESSION_FAILURE(); + } + + if (PREDICT_FALSE(total_n_points >= (1 << 27) + || instruction_size >= (1 << 30))) { + return FONT_COMPRESSION_FAILURE(); + } + size_t size_needed = 12 + 2 * n_contours + 5 * total_n_points + + instruction_size; + if (PREDICT_FALSE(glyph_buf_size < size_needed)) { + glyph_buf.reset(new uint8_t[size_needed]); + glyph_buf_size = size_needed; + } + + glyph_size = Store16(glyph_buf.get(), glyph_size, n_contours); + if (have_bbox) { + if (PREDICT_FALSE(!bbox_stream.Read(glyph_buf.get() + glyph_size, 8))) { + return FONT_COMPRESSION_FAILURE(); + } + } else { + ComputeBbox(total_n_points, points.get(), glyph_buf.get()); + } + glyph_size = kEndPtsOfContoursOffset; + int end_point = -1; + for (unsigned int contour_ix = 0; contour_ix < n_contours; ++contour_ix) { + end_point += n_points_vec[contour_ix]; + if (PREDICT_FALSE(end_point >= 65536)) { + return FONT_COMPRESSION_FAILURE(); + } + glyph_size = Store16(glyph_buf.get(), glyph_size, end_point); + } + + glyph_size = Store16(glyph_buf.get(), glyph_size, instruction_size); + if (PREDICT_FALSE(!instruction_stream.Read(glyph_buf.get() + glyph_size, + instruction_size))) { + return FONT_COMPRESSION_FAILURE(); + } + glyph_size += instruction_size; + + if (PREDICT_FALSE(!StorePoints(total_n_points, points.get(), n_contours, + instruction_size, glyph_buf.get(), glyph_buf_size, &glyph_size))) { + return FONT_COMPRESSION_FAILURE(); + } + } + + loca_values[i] = out->Size() - glyf_start; + if (PREDICT_FALSE(!out->Write(glyph_buf.get(), glyph_size))) { + return FONT_COMPRESSION_FAILURE(); + } + + // TODO(user) Old code aligned glyphs ... but do we actually need to? + if (PREDICT_FALSE(!Pad4(out))) { + return FONT_COMPRESSION_FAILURE(); + } + + *glyf_checksum += ComputeULongSum(glyph_buf.get(), glyph_size); + + // We may need x_min to reconstruct 'hmtx' + if (n_contours > 0) { + Buffer x_min_buf(glyph_buf.get() + 2, 2); + if (PREDICT_FALSE(!x_min_buf.ReadS16(&info->x_mins[i]))) { + return FONT_COMPRESSION_FAILURE(); + } + } + } + + // glyf_table dst_offset was set by ReconstructFont + glyf_table->dst_length = out->Size() - glyf_table->dst_offset; + loca_table->dst_offset = out->Size(); + // loca[n] will be equal the length of the glyph data ('glyf') table + loca_values[info->num_glyphs] = glyf_table->dst_length; + if (PREDICT_FALSE(!StoreLoca(loca_values, info->index_format, loca_checksum, + out))) { + return FONT_COMPRESSION_FAILURE(); + } + loca_table->dst_length = out->Size() - loca_table->dst_offset; + + return true; +} + +Table* FindTable(std::vector<Table*>* tables, uint32_t tag) { + for (Table* table : *tables) { + if (table->tag == tag) { + return table; + } + } + return NULL; +} + +// Get numberOfHMetrics, https://www.microsoft.com/typography/otspec/hhea.htm +bool ReadNumHMetrics(const uint8_t* data, size_t data_size, + uint16_t* num_hmetrics) { + // Skip 34 to reach 'hhea' numberOfHMetrics + Buffer buffer(data, data_size); + if (PREDICT_FALSE(!buffer.Skip(34) || !buffer.ReadU16(num_hmetrics))) { + return FONT_COMPRESSION_FAILURE(); + } + return true; +} + +// http://dev.w3.org/webfonts/WOFF2/spec/Overview.html#hmtx_table_format +bool ReconstructTransformedHmtx(const uint8_t* transformed_buf, + size_t transformed_size, + uint16_t num_glyphs, + uint16_t num_hmetrics, + const std::vector<int16_t>& x_mins, + uint32_t* checksum, + WOFF2Out* out) { + Buffer hmtx_buff_in(transformed_buf, transformed_size); + + uint8_t hmtx_flags; + if (PREDICT_FALSE(!hmtx_buff_in.ReadU8(&hmtx_flags))) { + return FONT_COMPRESSION_FAILURE(); + } + + std::vector<uint16_t> advance_widths; + std::vector<int16_t> lsbs; + bool has_proportional_lsbs = (hmtx_flags & 1) == 0; + bool has_monospace_lsbs = (hmtx_flags & 2) == 0; + + // you say you transformed but there is little evidence of it + if (has_proportional_lsbs && has_monospace_lsbs) { + return FONT_COMPRESSION_FAILURE(); + } + + assert(x_mins.size() == num_glyphs); + + // num_glyphs 0 is OK if there is no 'glyf' but cannot then xform 'hmtx'. + if (PREDICT_FALSE(num_hmetrics > num_glyphs)) { + return FONT_COMPRESSION_FAILURE(); + } + + // https://www.microsoft.com/typography/otspec/hmtx.htm + // "...only one entry need be in the array, but that entry is required." + if (PREDICT_FALSE(num_hmetrics < 1)) { + return FONT_COMPRESSION_FAILURE(); + } + + for (uint16_t i = 0; i < num_hmetrics; i++) { + uint16_t advance_width; + if (PREDICT_FALSE(!hmtx_buff_in.ReadU16(&advance_width))) { + return FONT_COMPRESSION_FAILURE(); + } + advance_widths.push_back(advance_width); + } + + for (uint16_t i = 0; i < num_hmetrics; i++) { + int16_t lsb; + if (has_proportional_lsbs) { + if (PREDICT_FALSE(!hmtx_buff_in.ReadS16(&lsb))) { + return FONT_COMPRESSION_FAILURE(); + } + } else { + lsb = x_mins[i]; + } + lsbs.push_back(lsb); + } + + for (uint16_t i = num_hmetrics; i < num_glyphs; i++) { + int16_t lsb; + if (has_monospace_lsbs) { + if (PREDICT_FALSE(!hmtx_buff_in.ReadS16(&lsb))) { + return FONT_COMPRESSION_FAILURE(); + } + } else { + lsb = x_mins[i]; + } + lsbs.push_back(lsb); + } + + // bake me a shiny new hmtx table + uint32_t hmtx_output_size = 2 * num_glyphs + 2 * num_hmetrics; + std::vector<uint8_t> hmtx_table(hmtx_output_size); + uint8_t* dst = &hmtx_table[0]; + size_t dst_offset = 0; + for (uint32_t i = 0; i < num_glyphs; i++) { + if (i < num_hmetrics) { + Store16(advance_widths[i], &dst_offset, dst); + } + Store16(lsbs[i], &dst_offset, dst); + } + + *checksum = ComputeULongSum(&hmtx_table[0], hmtx_output_size); + if (PREDICT_FALSE(!out->Write(&hmtx_table[0], hmtx_output_size))) { + return FONT_COMPRESSION_FAILURE(); + } + + return true; +} + +bool Woff2Uncompress(uint8_t* dst_buf, size_t dst_size, + const uint8_t* src_buf, size_t src_size) { + size_t uncompressed_size = dst_size; + int ok = BrotliDecompressBuffer(src_size, src_buf, + &uncompressed_size, dst_buf); + if (PREDICT_FALSE(!ok || uncompressed_size != dst_size)) { + return FONT_COMPRESSION_FAILURE(); + } + return true; +} + +bool ReadTableDirectory(Buffer* file, std::vector<Table>* tables, + size_t num_tables) { + uint32_t src_offset = 0; + for (size_t i = 0; i < num_tables; ++i) { + Table* table = &(*tables)[i]; + uint8_t flag_byte; + if (PREDICT_FALSE(!file->ReadU8(&flag_byte))) { + return FONT_COMPRESSION_FAILURE(); + } + uint32_t tag; + if ((flag_byte & 0x3f) == 0x3f) { + if (PREDICT_FALSE(!file->ReadU32(&tag))) { + return FONT_COMPRESSION_FAILURE(); + } + } else { + tag = kKnownTags[flag_byte & 0x3f]; + } + uint32_t flags = 0; + uint8_t xform_version = (flag_byte >> 6) & 0x03; + + // 0 means xform for glyph/loca, non-0 for others + if (tag == kGlyfTableTag || tag == kLocaTableTag) { + if (xform_version == 0) { + flags |= kWoff2FlagsTransform; + } + } else if (xform_version != 0) { + flags |= kWoff2FlagsTransform; + } + flags |= xform_version; + + uint32_t dst_length; + if (PREDICT_FALSE(!ReadBase128(file, &dst_length))) { + return FONT_COMPRESSION_FAILURE(); + } + uint32_t transform_length = dst_length; + if ((flags & kWoff2FlagsTransform) != 0) { + if (PREDICT_FALSE(!ReadBase128(file, &transform_length))) { + return FONT_COMPRESSION_FAILURE(); + } + if (PREDICT_FALSE(tag == kLocaTableTag && transform_length)) { + return FONT_COMPRESSION_FAILURE(); + } + } + if (PREDICT_FALSE(src_offset + transform_length < src_offset)) { + return FONT_COMPRESSION_FAILURE(); + } + table->src_offset = src_offset; + table->src_length = transform_length; + src_offset += transform_length; + + table->tag = tag; + table->flags = flags; + table->transform_length = transform_length; + table->dst_length = dst_length; + } + return true; +} + +// Writes a single Offset Table entry +size_t StoreOffsetTable(uint8_t* result, size_t offset, uint32_t flavor, + uint16_t num_tables) { + offset = StoreU32(result, offset, flavor); // sfnt version + offset = Store16(result, offset, num_tables); // num_tables + unsigned max_pow2 = 0; + while (1u << (max_pow2 + 1) <= num_tables) { + max_pow2++; + } + const uint16_t output_search_range = (1u << max_pow2) << 4; + offset = Store16(result, offset, output_search_range); // searchRange + offset = Store16(result, offset, max_pow2); // entrySelector + // rangeShift + offset = Store16(result, offset, (num_tables << 4) - output_search_range); + return offset; +} + +size_t StoreTableEntry(uint8_t* result, uint32_t offset, uint32_t tag) { + offset = StoreU32(result, offset, tag); + offset = StoreU32(result, offset, 0); + offset = StoreU32(result, offset, 0); + offset = StoreU32(result, offset, 0); + return offset; +} + +// First table goes after all the headers, table directory, etc +uint64_t ComputeOffsetToFirstTable(const WOFF2Header& hdr) { + uint64_t offset = kSfntHeaderSize + + kSfntEntrySize * static_cast<uint64_t>(hdr.num_tables); + if (hdr.header_version) { + offset = CollectionHeaderSize(hdr.header_version, hdr.ttc_fonts.size()) + + kSfntHeaderSize * hdr.ttc_fonts.size(); + for (const auto& ttc_font : hdr.ttc_fonts) { + offset += kSfntEntrySize * ttc_font.table_indices.size(); + } + } + return offset; +} + +std::vector<Table*> Tables(WOFF2Header* hdr, size_t font_index) { + std::vector<Table*> tables; + if (PREDICT_FALSE(hdr->header_version)) { + for (auto index : hdr->ttc_fonts[font_index].table_indices) { + tables.push_back(&hdr->tables[index]); + } + } else { + for (auto& table : hdr->tables) { + tables.push_back(&table); + } + } + return tables; +} + +// Offset tables assumed to have been written in with 0's initially. +// WOFF2Header isn't const so we can use [] instead of at() (which upsets FF) +bool ReconstructFont(uint8_t* transformed_buf, + const uint32_t transformed_buf_size, + RebuildMetadata* metadata, + WOFF2Header* hdr, + size_t font_index, + WOFF2Out* out) { + size_t dest_offset = out->Size(); + uint8_t table_entry[12]; + WOFF2FontInfo* info = &metadata->font_infos[font_index]; + std::vector<Table*> tables = Tables(hdr, font_index); + + // 'glyf' without 'loca' doesn't make sense + if (PREDICT_FALSE(static_cast<bool>(FindTable(&tables, kGlyfTableTag)) != + static_cast<bool>(FindTable(&tables, kLocaTableTag)))) { + return FONT_COMPRESSION_FAILURE(); + } + + uint32_t font_checksum = metadata->header_checksum; + if (hdr->header_version) { + font_checksum = hdr->ttc_fonts[font_index].header_checksum; + } + + uint32_t loca_checksum = 0; + for (size_t i = 0; i < tables.size(); i++) { + Table& table = *tables[i]; + + std::pair<uint32_t, uint32_t> checksum_key = {table.tag, table.src_offset}; + bool reused = metadata->checksums.find(checksum_key) + != metadata->checksums.end(); + if (PREDICT_FALSE(font_index == 0 && reused)) { + return FONT_COMPRESSION_FAILURE(); + } + + // TODO(user) a collection with optimized hmtx that reused glyf/loca + // would fail. We don't optimize hmtx for collections yet. + if (PREDICT_FALSE(static_cast<uint64_t>(table.src_offset + table.src_length) + > transformed_buf_size)) { + return FONT_COMPRESSION_FAILURE(); + } + + if (table.tag == kHheaTableTag) { + if (!ReadNumHMetrics(transformed_buf + table.src_offset, + table.src_length, &info->num_hmetrics)) { + return FONT_COMPRESSION_FAILURE(); + } + } + + uint32_t checksum = 0; + if (!reused) { + if ((table.flags & kWoff2FlagsTransform) != kWoff2FlagsTransform) { + if (table.tag == kHeadTableTag) { + if (PREDICT_FALSE(table.src_length < 12)) { + return FONT_COMPRESSION_FAILURE(); + } + // checkSumAdjustment = 0 + StoreU32(transformed_buf + table.src_offset, 8, 0); + } + table.dst_offset = dest_offset; + checksum = ComputeULongSum(transformed_buf + table.src_offset, + table.src_length); + if (PREDICT_FALSE(!out->Write(transformed_buf + table.src_offset, + table.src_length))) { + return FONT_COMPRESSION_FAILURE(); + } + } else { + if (table.tag == kGlyfTableTag) { + table.dst_offset = dest_offset; + + Table* loca_table = FindTable(&tables, kLocaTableTag); + if (PREDICT_FALSE(!ReconstructGlyf(transformed_buf + table.src_offset, + &table, &checksum, loca_table, &loca_checksum, info, out))) { + return FONT_COMPRESSION_FAILURE(); + } + } else if (table.tag == kLocaTableTag) { + // All the work was done by ReconstructGlyf. We already know checksum. + checksum = loca_checksum; + } else if (table.tag == kHmtxTableTag) { + table.dst_offset = dest_offset; + // Tables are sorted so all the info we need has been gathered. + if (PREDICT_FALSE(!ReconstructTransformedHmtx( + transformed_buf + table.src_offset, table.src_length, + info->num_glyphs, info->num_hmetrics, info->x_mins, &checksum, + out))) { + return FONT_COMPRESSION_FAILURE(); + } + } else { + return FONT_COMPRESSION_FAILURE(); // transform unknown + } + } + metadata->checksums[checksum_key] = checksum; + } else { + checksum = metadata->checksums[checksum_key]; + } + font_checksum += checksum; + + // update the table entry with real values. + StoreU32(table_entry, 0, checksum); + StoreU32(table_entry, 4, table.dst_offset); + StoreU32(table_entry, 8, table.dst_length); + if (PREDICT_FALSE(!out->Write(table_entry, + info->table_entry_by_tag[table.tag] + 4, 12))) { + return FONT_COMPRESSION_FAILURE(); + } + + // We replaced 0's. Update overall checksum. + font_checksum += ComputeULongSum(table_entry, 12); + + if (PREDICT_FALSE(!Pad4(out))) { + return FONT_COMPRESSION_FAILURE(); + } + + if (PREDICT_FALSE(static_cast<uint64_t>(table.dst_offset + table.dst_length) + > out->Size())) { + return FONT_COMPRESSION_FAILURE(); + } + dest_offset = out->Size(); + } + + // Update 'head' checkSumAdjustment. We already set it to 0 and summed font. + Table* head_table = FindTable(&tables, kHeadTableTag); + if (head_table) { + if (PREDICT_FALSE(head_table->dst_length < 12)) { + return FONT_COMPRESSION_FAILURE(); + } + uint8_t checksum_adjustment[4]; + StoreU32(checksum_adjustment, 0, 0xB1B0AFBA - font_checksum); + if (PREDICT_FALSE(!out->Write(checksum_adjustment, + head_table->dst_offset + 8, 4))) { + return FONT_COMPRESSION_FAILURE(); + } + } + + return true; +} + +bool ReadWOFF2Header(const uint8_t* data, size_t length, WOFF2Header* hdr) { + Buffer file(data, length); + + uint32_t signature; + if (PREDICT_FALSE(!file.ReadU32(&signature) || signature != kWoff2Signature || + !file.ReadU32(&hdr->flavor))) { + return FONT_COMPRESSION_FAILURE(); + } + + // TODO(user): Should call IsValidVersionTag() here. + + uint32_t reported_length; + if (PREDICT_FALSE( + !file.ReadU32(&reported_length) || length != reported_length)) { + return FONT_COMPRESSION_FAILURE(); + } + if (PREDICT_FALSE(!file.ReadU16(&hdr->num_tables) || !hdr->num_tables)) { + return FONT_COMPRESSION_FAILURE(); + } + + // We don't care about these fields of the header: + // uint16_t reserved + // uint32_t total_sfnt_size, we don't believe this, will compute later + if (PREDICT_FALSE(!file.Skip(6))) { + return FONT_COMPRESSION_FAILURE(); + } + if (PREDICT_FALSE(!file.ReadU32(&hdr->compressed_length))) { + return FONT_COMPRESSION_FAILURE(); + } + // We don't care about these fields of the header: + // uint16_t major_version, minor_version + if (PREDICT_FALSE(!file.Skip(2 * 2))) { + return FONT_COMPRESSION_FAILURE(); + } + uint32_t meta_offset; + uint32_t meta_length; + uint32_t meta_length_orig; + if (PREDICT_FALSE(!file.ReadU32(&meta_offset) || + !file.ReadU32(&meta_length) || + !file.ReadU32(&meta_length_orig))) { + return FONT_COMPRESSION_FAILURE(); + } + if (meta_offset) { + if (PREDICT_FALSE( + meta_offset >= length || length - meta_offset < meta_length)) { + return FONT_COMPRESSION_FAILURE(); + } + } + uint32_t priv_offset; + uint32_t priv_length; + if (PREDICT_FALSE(!file.ReadU32(&priv_offset) || + !file.ReadU32(&priv_length))) { + return FONT_COMPRESSION_FAILURE(); + } + if (priv_offset) { + if (PREDICT_FALSE( + priv_offset >= length || length - priv_offset < priv_length)) { + return FONT_COMPRESSION_FAILURE(); + } + } + hdr->tables.resize(hdr->num_tables); + if (PREDICT_FALSE(!ReadTableDirectory( + &file, &hdr->tables, hdr->num_tables))) { + return FONT_COMPRESSION_FAILURE(); + } + + // Before we sort for output the last table end is the uncompressed size. + Table& last_table = hdr->tables.back(); + hdr->uncompressed_size = last_table.src_offset + last_table.src_length; + if (PREDICT_FALSE(hdr->uncompressed_size < last_table.src_offset)) { + return FONT_COMPRESSION_FAILURE(); + } + + hdr->header_version = 0; + + if (hdr->flavor == kTtcFontFlavor) { + if (PREDICT_FALSE(!file.ReadU32(&hdr->header_version))) { + return FONT_COMPRESSION_FAILURE(); + } + if (PREDICT_FALSE(hdr->header_version != 0x00010000 + && hdr->header_version != 0x00020000)) { + return FONT_COMPRESSION_FAILURE(); + } + uint32_t num_fonts; + if (PREDICT_FALSE(!Read255UShort(&file, &num_fonts) || !num_fonts)) { + return FONT_COMPRESSION_FAILURE(); + } + hdr->ttc_fonts.resize(num_fonts); + + for (uint32_t i = 0; i < num_fonts; i++) { + TtcFont& ttc_font = hdr->ttc_fonts[i]; + uint32_t num_tables; + if (PREDICT_FALSE(!Read255UShort(&file, &num_tables) || !num_tables)) { + return FONT_COMPRESSION_FAILURE(); + } + if (PREDICT_FALSE(!file.ReadU32(&ttc_font.flavor))) { + return FONT_COMPRESSION_FAILURE(); + } + + ttc_font.table_indices.resize(num_tables); + + const Table* glyf_table = NULL; + const Table* loca_table = NULL; + + for (uint32_t j = 0; j < num_tables; j++) { + unsigned int table_idx; + if (PREDICT_FALSE(!Read255UShort(&file, &table_idx)) || + table_idx >= hdr->tables.size()) { + return FONT_COMPRESSION_FAILURE(); + } + ttc_font.table_indices[j] = table_idx; + + const Table& table = hdr->tables[table_idx]; + if (table.tag == kLocaTableTag) { + loca_table = &table; + } + if (table.tag == kGlyfTableTag) { + glyf_table = &table; + } + + } + + if (PREDICT_FALSE((glyf_table == NULL) != (loca_table == NULL))) { +#ifdef FONT_COMPRESSION_BIN + fprintf(stderr, "Cannot have just one of glyf/loca\n"); +#endif + return FONT_COMPRESSION_FAILURE(); + } + } + } + + const uint64_t first_table_offset = ComputeOffsetToFirstTable(*hdr); + + hdr->compressed_offset = file.offset(); + if (PREDICT_FALSE(hdr->compressed_offset > + std::numeric_limits<uint32_t>::max())) { + return FONT_COMPRESSION_FAILURE(); + } + uint64_t src_offset = Round4(hdr->compressed_offset + hdr->compressed_length); + uint64_t dst_offset = first_table_offset; + + + if (PREDICT_FALSE(src_offset > length)) { +#ifdef FONT_COMPRESSION_BIN + fprintf(stderr, "offset fail; src_offset %" PRIu64 " length %lu " + "dst_offset %" PRIu64 "\n", + src_offset, length, dst_offset); +#endif + return FONT_COMPRESSION_FAILURE(); + } + if (meta_offset) { + if (PREDICT_FALSE(src_offset != meta_offset)) { + return FONT_COMPRESSION_FAILURE(); + } + src_offset = Round4(meta_offset + meta_length); + if (PREDICT_FALSE(src_offset > std::numeric_limits<uint32_t>::max())) { + return FONT_COMPRESSION_FAILURE(); + } + } + + if (priv_offset) { + if (PREDICT_FALSE(src_offset != priv_offset)) { + return FONT_COMPRESSION_FAILURE(); + } + src_offset = Round4(priv_offset + priv_length); + if (PREDICT_FALSE(src_offset > std::numeric_limits<uint32_t>::max())) { + return FONT_COMPRESSION_FAILURE(); + } + } + + if (PREDICT_FALSE(src_offset != Round4(length))) { + return FONT_COMPRESSION_FAILURE(); + } + + return true; +} + +// Write everything before the actual table data +bool WriteHeaders(const uint8_t* data, size_t length, RebuildMetadata* metadata, + WOFF2Header* hdr, WOFF2Out* out) { + std::vector<uint8_t> output(ComputeOffsetToFirstTable(*hdr), 0); + + // Re-order tables in output (OTSpec) order + std::vector<Table> sorted_tables(hdr->tables); + if (hdr->header_version) { + // collection; we have to sort the table offset vector in each font + for (auto& ttc_font : hdr->ttc_fonts) { + std::map<uint32_t, uint16_t> sorted_index_by_tag; + for (auto table_index : ttc_font.table_indices) { + sorted_index_by_tag[hdr->tables[table_index].tag] = table_index; + } + uint16_t index = 0; + for (auto& i : sorted_index_by_tag) { + ttc_font.table_indices[index++] = i.second; + } + } + } else { + // non-collection; we can just sort the tables + std::sort(sorted_tables.begin(), sorted_tables.end()); + } + + // Start building the font + uint8_t* result = &output[0]; + size_t offset = 0; + if (hdr->header_version) { + // TTC header + offset = StoreU32(result, offset, hdr->flavor); // TAG TTCTag + offset = StoreU32(result, offset, hdr->header_version); // FIXED Version + offset = StoreU32(result, offset, hdr->ttc_fonts.size()); // ULONG numFonts + // Space for ULONG OffsetTable[numFonts] (zeroed initially) + size_t offset_table = offset; // keep start of offset table for later + for (size_t i = 0; i < hdr->ttc_fonts.size(); i++) { + offset = StoreU32(result, offset, 0); // will fill real values in later + } + // space for DSIG fields for header v2 + if (hdr->header_version == 0x00020000) { + offset = StoreU32(result, offset, 0); // ULONG ulDsigTag + offset = StoreU32(result, offset, 0); // ULONG ulDsigLength + offset = StoreU32(result, offset, 0); // ULONG ulDsigOffset + } + + // write Offset Tables and store the location of each in TTC Header + metadata->font_infos.resize(hdr->ttc_fonts.size()); + for (size_t i = 0; i < hdr->ttc_fonts.size(); i++) { + TtcFont& ttc_font = hdr->ttc_fonts[i]; + + // write Offset Table location into TTC Header + offset_table = StoreU32(result, offset_table, offset); + + // write the actual offset table so our header doesn't lie + ttc_font.dst_offset = offset; + offset = StoreOffsetTable(result, offset, ttc_font.flavor, + ttc_font.table_indices.size()); + + for (const auto table_index : ttc_font.table_indices) { + uint32_t tag = hdr->tables[table_index].tag; + metadata->font_infos[i].table_entry_by_tag[tag] = offset; + offset = StoreTableEntry(result, offset, tag); + } + + ttc_font.header_checksum = ComputeULongSum(&output[ttc_font.dst_offset], + offset - ttc_font.dst_offset); + } + } else { + metadata->font_infos.resize(1); + offset = StoreOffsetTable(result, offset, hdr->flavor, hdr->num_tables); + for (uint16_t i = 0; i < hdr->num_tables; ++i) { + metadata->font_infos[0].table_entry_by_tag[sorted_tables[i].tag] = offset; + offset = StoreTableEntry(result, offset, sorted_tables[i].tag); + } + } + + if (PREDICT_FALSE(!out->Write(&output[0], output.size()))) { + return FONT_COMPRESSION_FAILURE(); + } + metadata->header_checksum = ComputeULongSum(&output[0], output.size()); + return true; +} + +} // namespace + +size_t ComputeWOFF2FinalSize(const uint8_t* data, size_t length) { + Buffer file(data, length); + uint32_t total_length; + + if (!file.Skip(16) || + !file.ReadU32(&total_length)) { + return 0; + } + return total_length; +} + +bool ConvertWOFF2ToTTF(uint8_t *result, size_t result_length, + const uint8_t *data, size_t length) { + WOFF2MemoryOut out(result, result_length); + return ConvertWOFF2ToTTF(data, length, &out); +} + +bool ConvertWOFF2ToTTF(const uint8_t* data, size_t length, + WOFF2Out* out) { + RebuildMetadata metadata; + WOFF2Header hdr; + if (!ReadWOFF2Header(data, length, &hdr)) { + return FONT_COMPRESSION_FAILURE(); + } + + if (!WriteHeaders(data, length, &metadata, &hdr, out)) { + return FONT_COMPRESSION_FAILURE(); + } + + const float compression_ratio = (float) hdr.uncompressed_size / length; + if (compression_ratio > kMaxPlausibleCompressionRatio) { +#ifdef FONT_COMPRESSION_BIN + fprintf(stderr, "Implausible compression ratio %.01f\n", compression_ratio); +#endif + return FONT_COMPRESSION_FAILURE(); + } + + const uint8_t* src_buf = data + hdr.compressed_offset; + std::vector<uint8_t> uncompressed_buf(hdr.uncompressed_size); + if (PREDICT_FALSE(!Woff2Uncompress(&uncompressed_buf[0], + hdr.uncompressed_size, src_buf, + hdr.compressed_length))) { + return FONT_COMPRESSION_FAILURE(); + } + + for (size_t i = 0; i < metadata.font_infos.size(); i++) { + if (PREDICT_FALSE(!ReconstructFont(&uncompressed_buf[0], + hdr.uncompressed_size, + &metadata, &hdr, i, out))) { + return FONT_COMPRESSION_FAILURE(); + } + } + + return true; +} + +} // namespace woff2 |