diff options
Diffstat (limited to 'gfx/2d/SFNTData.cpp')
| -rw-r--r-- | gfx/2d/SFNTData.cpp | 193 |
1 files changed, 193 insertions, 0 deletions
diff --git a/gfx/2d/SFNTData.cpp b/gfx/2d/SFNTData.cpp new file mode 100644 index 0000000000..b81163b02b --- /dev/null +++ b/gfx/2d/SFNTData.cpp @@ -0,0 +1,193 @@ +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ +/* vim: set ts=8 sts=2 et sw=2 tw=80: */ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +#include "SFNTData.h" + +#include <algorithm> +#include <numeric> + +#include "BigEndianInts.h" +#include "Logging.h" +#include "mozilla/HashFunctions.h" +#include "mozilla/Span.h" + +namespace mozilla { +namespace gfx { + +#define TRUETYPE_TAG(a, b, c, d) ((a) << 24 | (b) << 16 | (c) << 8 | (d)) + +#pragma pack(push, 1) + +struct TTCHeader { + BigEndianUint32 ttcTag; // Always 'ttcf' + BigEndianUint32 version; // Fixed, 0x00010000 + BigEndianUint32 numFonts; +}; + +struct OffsetTable { + BigEndianUint32 sfntVersion; // Fixed, 0x00010000 for version 1.0. + BigEndianUint16 numTables; + BigEndianUint16 searchRange; // (Maximum power of 2 <= numTables) x 16. + BigEndianUint16 entrySelector; // Log2(maximum power of 2 <= numTables). + BigEndianUint16 rangeShift; // NumTables x 16-searchRange. +}; + +struct TableDirEntry { + BigEndianUint32 tag; // 4 -byte identifier. + BigEndianUint32 checkSum; // CheckSum for this table. + BigEndianUint32 offset; // Offset from beginning of TrueType font file. + BigEndianUint32 length; // Length of this table. + + friend bool operator<(const TableDirEntry& lhs, const uint32_t aTag) { + return lhs.tag < aTag; + } +}; + +#pragma pack(pop) + +class SFNTData::Font { + public: + Font(const OffsetTable* aOffsetTable, const uint8_t* aFontData, + uint32_t aDataLength) + : mFontData(aFontData), + mFirstDirEntry( + reinterpret_cast<const TableDirEntry*>(aOffsetTable + 1)), + mEndOfDirEntries(mFirstDirEntry + aOffsetTable->numTables), + mDataLength(aDataLength) {} + + Span<const uint8_t> GetHeadTableBytes() const { + const TableDirEntry* dirEntry = + GetDirEntry(TRUETYPE_TAG('h', 'e', 'a', 'd')); + if (!dirEntry) { + gfxWarning() << "Head table entry not found."; + return {}; + } + + return {mFontData + dirEntry->offset, dirEntry->length}; + } + + private: + const TableDirEntry* GetDirEntry(const uint32_t aTag) const { + const TableDirEntry* foundDirEntry = + std::lower_bound(mFirstDirEntry, mEndOfDirEntries, aTag); + + if (foundDirEntry == mEndOfDirEntries || foundDirEntry->tag != aTag) { + gfxWarning() << "Font data does not contain tag."; + return nullptr; + } + + if (mDataLength < (foundDirEntry->offset + foundDirEntry->length)) { + gfxWarning() << "Font data too short to contain table."; + return nullptr; + } + + return foundDirEntry; + } + + const uint8_t* mFontData; + const TableDirEntry* mFirstDirEntry; + const TableDirEntry* mEndOfDirEntries; + uint32_t mDataLength; +}; + +/* static */ +UniquePtr<SFNTData> SFNTData::Create(const uint8_t* aFontData, + uint32_t aDataLength) { + MOZ_ASSERT(aFontData); + + // Check to see if this is a font collection. + if (aDataLength < sizeof(TTCHeader)) { + gfxWarning() << "Font data too short."; + return nullptr; + } + + const TTCHeader* ttcHeader = reinterpret_cast<const TTCHeader*>(aFontData); + if (ttcHeader->ttcTag == TRUETYPE_TAG('t', 't', 'c', 'f')) { + uint32_t numFonts = ttcHeader->numFonts; + if (aDataLength < + sizeof(TTCHeader) + (numFonts * sizeof(BigEndianUint32))) { + gfxWarning() << "Font data too short to contain full TTC Header."; + return nullptr; + } + + UniquePtr<SFNTData> sfntData(new SFNTData); + const BigEndianUint32* offset = + reinterpret_cast<const BigEndianUint32*>(aFontData + sizeof(TTCHeader)); + const BigEndianUint32* endOfOffsets = offset + numFonts; + while (offset != endOfOffsets) { + if (!sfntData->AddFont(aFontData, aDataLength, *offset)) { + return nullptr; + } + ++offset; + } + + return sfntData; + } + + UniquePtr<SFNTData> sfntData(new SFNTData); + if (!sfntData->AddFont(aFontData, aDataLength, 0)) { + return nullptr; + } + + return sfntData; +} + +/* static */ +uint64_t SFNTData::GetUniqueKey(const uint8_t* aFontData, uint32_t aDataLength, + uint32_t aVarDataSize, const void* aVarData) { + uint64_t hash = 0; + UniquePtr<SFNTData> sfntData = SFNTData::Create(aFontData, aDataLength); + if (sfntData) { + hash = sfntData->HashHeadTables(); + } else { + gfxWarning() << "Failed to create SFNTData from data, hashing whole font."; + hash = HashBytes(aFontData, aDataLength); + } + + if (aVarDataSize) { + hash = AddToHash(hash, HashBytes(aVarData, aVarDataSize)); + } + + return hash << 32 | aDataLength; +} + +SFNTData::~SFNTData() { + for (size_t i = 0; i < mFonts.length(); ++i) { + delete mFonts[i]; + } +} + +bool SFNTData::AddFont(const uint8_t* aFontData, uint32_t aDataLength, + uint32_t aOffset) { + uint32_t remainingLength = aDataLength - aOffset; + if (remainingLength < sizeof(OffsetTable)) { + gfxWarning() << "Font data too short to contain OffsetTable " << aOffset; + return false; + } + + const OffsetTable* offsetTable = + reinterpret_cast<const OffsetTable*>(aFontData + aOffset); + if (remainingLength < + sizeof(OffsetTable) + (offsetTable->numTables * sizeof(TableDirEntry))) { + gfxWarning() << "Font data too short to contain tables."; + return false; + } + + return mFonts.append(new Font(offsetTable, aFontData, aDataLength)); +} + +uint32_t SFNTData::HashHeadTables() { + uint32_t headTableHash = std::accumulate( + mFonts.begin(), mFonts.end(), 0U, [](uint32_t hash, Font* font) { + Span<const uint8_t> headBytes = font->GetHeadTableBytes(); + return AddToHash(hash, HashBytes(headBytes.data(), headBytes.size())); + }); + + return headTableHash; +} + +} // namespace gfx +} // namespace mozilla |