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/* Copyright 2014 Google Inc. All Rights Reserved.
Distributed under MIT license.
See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
*/
/* Library for converting WOFF2 format font files to their TTF versions. */
#include <woff2/decode.h>
#include <algorithm>
#include <complex>
#include <cstring>
#include <limits>
#include <string>
#include <vector>
#include <map>
#include <memory>
#include <stdlib.h>
#include <utility>
#include <brotli/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++] = 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++] = 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();
}
// https://dev.w3.org/webfonts/WOFF2/spec/#conform-mustRejectLoca
// dst_length here is origLength in the spec
uint32_t expected_loca_dst_length = (info->index_format ? 4 : 2)
* (static_cast<uint32_t>(info->num_glyphs) + 1);
if (PREDICT_FALSE(loca_table->dst_length != expected_loca_dst_length)) {
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();
}
} else {
// n_contours == 0; empty glyph. Must NOT have a bbox.
if (PREDICT_FALSE(have_bbox)) {
#ifdef FONT_COMPRESSION_BIN
fprintf(stderr, "Empty glyph has a bbox\n");
#endif
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;
// Bits 2-7 are reserved and MUST be zero.
if ((hmtx_flags & 0xFC) != 0) {
#ifdef FONT_COMPRESSION_BIN
fprintf(stderr, "Illegal hmtx flags; bits 2-7 must be 0\n");
#endif
return FONT_COMPRESSION_FAILURE();
}
// 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;
BrotliDecoderResult result = BrotliDecoderDecompress(
src_size, src_buf, &uncompressed_size, dst_buf);
if (PREDICT_FALSE(result != BROTLI_DECODER_RESULT_SUCCESS ||
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
const Table* glyf_table = FindTable(&tables, kGlyfTableTag);
const Table* loca_table = FindTable(&tables, kLocaTableTag);
if (PREDICT_FALSE(static_cast<bool>(glyf_table) !=
static_cast<bool>(loca_table))) {
#ifdef FONT_COMPRESSION_BIN
fprintf(stderr, "Cannot have just one of glyf/loca\n");
#endif
return FONT_COMPRESSION_FAILURE();
}
if (glyf_table != NULL) {
if (PREDICT_FALSE((glyf_table->flags & kWoff2FlagsTransform)
!= (loca_table->flags & kWoff2FlagsTransform))) {
#ifdef FONT_COMPRESSION_BIN
fprintf(stderr, "Cannot transform just one of glyf/loca\n");
#endif
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);
unsigned int glyf_idx = 0;
unsigned int loca_idx = 0;
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_idx = table_idx;
}
if (table.tag == kGlyfTableTag) {
glyf_idx = table_idx;
}
}
// if we have both glyf and loca make sure they are consecutive
// if we have just one we'll reject the font elsewhere
if (glyf_idx > 0 || loca_idx > 0) {
if (PREDICT_FALSE(glyf_idx > loca_idx || loca_idx - glyf_idx != 1)) {
#ifdef FONT_COMPRESSION_BIN
fprintf(stderr, "TTC font %d has non-consecutive glyf/loca\n", i);
#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(hdr.uncompressed_size < 1)) {
return FONT_COMPRESSION_FAILURE();
}
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