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