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/* Copyright 2013 Google Inc. All Rights Reserved.
Distributed under MIT 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 = num_glyphs ? &glyf_table->buffer[0] : NULL;
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;
}
StoreLoca(index_fmt, glyf_offset, &loca_offset, loca_dst);
glyf_table->buffer.resize(glyf_offset);
glyf_table->data = glyf_offset ? &glyf_table->buffer[0] : NULL;
glyf_table->length = glyf_offset;
loca_table->data = loca_offset ? &loca_table->buffer[0] : NULL;
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, table->length);
if (PREDICT_FALSE(sz > table->length)) {
memset(buf + table->length, 0, sz - table->length);
}
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