michael@0: /*
michael@0:  * Copyright 2011 Google Inc.
michael@0:  *
michael@0:  * Use of this source code is governed by a BSD-style license that can be
michael@0:  * found in the LICENSE file.
michael@0:  */
michael@0: 
michael@0: #include "SkEndian.h"
michael@0: #include "SkFontStream.h"
michael@0: #include "SkStream.h"
michael@0: 
michael@0: struct SkSFNTHeader {
michael@0:     uint32_t    fVersion;
michael@0:     uint16_t    fNumTables;
michael@0:     uint16_t    fSearchRange;
michael@0:     uint16_t    fEntrySelector;
michael@0:     uint16_t    fRangeShift;
michael@0: };
michael@0: 
michael@0: struct SkTTCFHeader {
michael@0:     uint32_t    fTag;
michael@0:     uint32_t    fVersion;
michael@0:     uint32_t    fNumOffsets;
michael@0:     uint32_t    fOffset0;   // the first of N (fNumOffsets)
michael@0: };
michael@0: 
michael@0: union SkSharedTTHeader {
michael@0:     SkSFNTHeader    fSingle;
michael@0:     SkTTCFHeader    fCollection;
michael@0: };
michael@0: 
michael@0: struct SkSFNTDirEntry {
michael@0:     uint32_t    fTag;
michael@0:     uint32_t    fChecksum;
michael@0:     uint32_t    fOffset;
michael@0:     uint32_t    fLength;
michael@0: };
michael@0: 
michael@0: static bool read(SkStream* stream, void* buffer, size_t amount) {
michael@0:     return stream->read(buffer, amount) == amount;
michael@0: }
michael@0: 
michael@0: static bool skip(SkStream* stream, size_t amount) {
michael@0:     return stream->skip(amount) == amount;
michael@0: }
michael@0: 
michael@0: /** Return the number of tables, or if this is a TTC (collection), return the
michael@0:     number of tables in the first element of the collection. In either case,
michael@0:     if offsetToDir is not-null, set it to the offset to the beginning of the
michael@0:     table headers (SkSFNTDirEntry), relative to the start of the stream.
michael@0: 
michael@0:     On an error, return 0 for number of tables, and ignore offsetToDir
michael@0:  */
michael@0: static int count_tables(SkStream* stream, int ttcIndex, size_t* offsetToDir) {
michael@0:     SkASSERT(ttcIndex >= 0);
michael@0: 
michael@0:     SkAutoSMalloc<1024> storage(sizeof(SkSharedTTHeader));
michael@0:     SkSharedTTHeader* header = (SkSharedTTHeader*)storage.get();
michael@0: 
michael@0:     if (!read(stream, header, sizeof(SkSharedTTHeader))) {
michael@0:         return 0;
michael@0:     }
michael@0: 
michael@0:     // by default, SkSFNTHeader is at the start of the stream
michael@0:     size_t offset = 0;
michael@0: 
michael@0:     // if we're really a collection, the first 4-bytes will be 'ttcf'
michael@0:     uint32_t tag = SkEndian_SwapBE32(header->fCollection.fTag);
michael@0:     if (SkSetFourByteTag('t', 't', 'c', 'f') == tag) {
michael@0:         unsigned count = SkEndian_SwapBE32(header->fCollection.fNumOffsets);
michael@0:         if ((unsigned)ttcIndex >= count) {
michael@0:             return 0;
michael@0:         }
michael@0: 
michael@0:         if (ttcIndex > 0) { // need to read more of the shared header
michael@0:             stream->rewind();
michael@0:             size_t amount = sizeof(SkSharedTTHeader) + ttcIndex * sizeof(uint32_t);
michael@0:             header = (SkSharedTTHeader*)storage.reset(amount);
michael@0:             if (!read(stream, header, amount)) {
michael@0:                 return 0;
michael@0:             }
michael@0:         }
michael@0:         // this is the offset to the local SkSFNTHeader
michael@0:         offset = SkEndian_SwapBE32((&header->fCollection.fOffset0)[ttcIndex]);
michael@0:         stream->rewind();
michael@0:         if (!skip(stream, offset)) {
michael@0:             return 0;
michael@0:         }
michael@0:         if (!read(stream, header, sizeof(SkSFNTHeader))) {
michael@0:             return 0;
michael@0:         }
michael@0:     }
michael@0: 
michael@0:     if (offsetToDir) {
michael@0:         // add the size of the header, so we will point to the DirEntries
michael@0:         *offsetToDir = offset + sizeof(SkSFNTHeader);
michael@0:     }
michael@0:     return SkEndian_SwapBE16(header->fSingle.fNumTables);
michael@0: }
michael@0: 
michael@0: ///////////////////////////////////////////////////////////////////////////////
michael@0: 
michael@0: struct SfntHeader {
michael@0:     SfntHeader() : fCount(0), fDir(NULL) {}
michael@0:     ~SfntHeader() { sk_free(fDir); }
michael@0: 
michael@0:     /** If it returns true, then fCount and fDir are properly initialized.
michael@0:         Note: fDir will point to the raw array of SkSFNTDirEntry values,
michael@0:         meaning they will still be in the file's native endianness (BE).
michael@0: 
michael@0:         fDir will be automatically freed when this object is destroyed
michael@0:      */
michael@0:     bool init(SkStream* stream, int ttcIndex) {
michael@0:         stream->rewind();
michael@0: 
michael@0:         size_t offsetToDir;
michael@0:         fCount = count_tables(stream, ttcIndex, &offsetToDir);
michael@0:         if (0 == fCount) {
michael@0:             return false;
michael@0:         }
michael@0: 
michael@0:         stream->rewind();
michael@0:         if (!skip(stream, offsetToDir)) {
michael@0:             return false;
michael@0:         }
michael@0: 
michael@0:         size_t size = fCount * sizeof(SkSFNTDirEntry);
michael@0:         fDir = reinterpret_cast<SkSFNTDirEntry*>(sk_malloc_throw(size));
michael@0:         return read(stream, fDir, size);
michael@0:     }
michael@0: 
michael@0:     int             fCount;
michael@0:     SkSFNTDirEntry* fDir;
michael@0: };
michael@0: 
michael@0: ///////////////////////////////////////////////////////////////////////////////
michael@0: 
michael@0: int SkFontStream::CountTTCEntries(SkStream* stream) {
michael@0:     stream->rewind();
michael@0: 
michael@0:     SkSharedTTHeader shared;
michael@0:     if (!read(stream, &shared, sizeof(shared))) {
michael@0:         return 0;
michael@0:     }
michael@0: 
michael@0:     // if we're really a collection, the first 4-bytes will be 'ttcf'
michael@0:     uint32_t tag = SkEndian_SwapBE32(shared.fCollection.fTag);
michael@0:     if (SkSetFourByteTag('t', 't', 'c', 'f') == tag) {
michael@0:         return SkEndian_SwapBE32(shared.fCollection.fNumOffsets);
michael@0:     } else {
michael@0:         return 1;   // normal 'sfnt' has 1 dir entry
michael@0:     }
michael@0: }
michael@0: 
michael@0: int SkFontStream::GetTableTags(SkStream* stream, int ttcIndex,
michael@0:                                SkFontTableTag tags[]) {
michael@0:     SfntHeader  header;
michael@0:     if (!header.init(stream, ttcIndex)) {
michael@0:         return 0;
michael@0:     }
michael@0: 
michael@0:     if (tags) {
michael@0:         for (int i = 0; i < header.fCount; i++) {
michael@0:             tags[i] = SkEndian_SwapBE32(header.fDir[i].fTag);
michael@0:         }
michael@0:     }
michael@0:     return header.fCount;
michael@0: }
michael@0: 
michael@0: size_t SkFontStream::GetTableData(SkStream* stream, int ttcIndex,
michael@0:                                   SkFontTableTag tag,
michael@0:                                   size_t offset, size_t length, void* data) {
michael@0:     SfntHeader  header;
michael@0:     if (!header.init(stream, ttcIndex)) {
michael@0:         return 0;
michael@0:     }
michael@0: 
michael@0:     for (int i = 0; i < header.fCount; i++) {
michael@0:         if (SkEndian_SwapBE32(header.fDir[i].fTag) == tag) {
michael@0:             size_t realOffset = SkEndian_SwapBE32(header.fDir[i].fOffset);
michael@0:             size_t realLength = SkEndian_SwapBE32(header.fDir[i].fLength);
michael@0:             // now sanity check the caller's offset/length
michael@0:             if (offset >= realLength) {
michael@0:                 return 0;
michael@0:             }
michael@0:             // if the caller is trusting the length from the file, then a
michael@0:             // hostile file might choose a value which would overflow offset +
michael@0:             // length.
michael@0:             if (offset + length < offset) {
michael@0:                 return 0;
michael@0:             }
michael@0:             if (length > realLength - offset) {
michael@0:                 length = realLength - offset;
michael@0:             }
michael@0:             if (data) {
michael@0:                 // skip the stream to the part of the table we want to copy from
michael@0:                 stream->rewind();
michael@0:                 size_t bytesToSkip = realOffset + offset;
michael@0:                 if (!skip(stream, bytesToSkip)) {
michael@0:                     return 0;
michael@0:                 }
michael@0:                 if (!read(stream, data, length)) {
michael@0:                     return 0;
michael@0:                 }
michael@0:             }
michael@0:             return length;
michael@0:         }
michael@0:     }
michael@0:     return 0;
michael@0: }