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#include "XZStream.h"
#include <algorithm>
#include "mozilla/Assertions.h"
#include "Logging.h"
// LZMA dictionary size, should have a minimum size for the given compression
// rate, see XZ Utils docs for details.
static const uint32_t kDictSize = 1 << 24;
static const size_t kFooterSize = 12;
// Parses a variable-length integer (VLI),
// see http://tukaani.org/xz/xz-file-format.txt for details.
static size_t
ParseVarLenInt(const uint8_t* aBuf, size_t aBufSize, uint64_t* aValue)
{
if (!aBufSize) {
return 0;
}
aBufSize = std::min(9u, aBufSize);
*aValue = aBuf[0] & 0x7F;
size_t i = 0;
while (aBuf[i++] & 0x80) {
if (i >= aBufSize || aBuf[i] == 0x0) {
return 0;
}
*aValue |= static_cast<uint64_t>(aBuf[i] & 0x7F) << (i * 7);
}
return i;
}
/* static */ bool
XZStream::IsXZ(const void* aBuf, size_t aBufSize)
{
static const uint8_t kXzMagic[] = {0xfd, '7', 'z', 'X', 'Z', 0x0};
MOZ_ASSERT(aBuf);
return aBufSize > sizeof(kXzMagic) &&
!memcmp(reinterpret_cast<const void*>(kXzMagic), aBuf, sizeof(kXzMagic));
}
XZStream::XZStream(const void* aInBuf, size_t aInSize)
: mInBuf(static_cast<const uint8_t*>(aInBuf))
, mUncompSize(0)
, mDec(nullptr)
{
mBuffers.in = mInBuf;
mBuffers.in_pos = 0;
mBuffers.in_size = aInSize;
}
XZStream::~XZStream()
{
xz_dec_end(mDec);
}
bool
XZStream::Init()
{
#ifdef XZ_USE_CRC64
xz_crc64_init();
#endif
xz_crc32_init();
mDec = xz_dec_init(XZ_DYNALLOC, kDictSize);
if (!mDec) {
return false;
}
mUncompSize = ParseUncompressedSize();
return true;
}
size_t
XZStream::Decode(void* aOutBuf, size_t aOutSize)
{
if (!mDec) {
return 0;
}
mBuffers.out = static_cast<uint8_t*>(aOutBuf);
mBuffers.out_pos = 0;
mBuffers.out_size = aOutSize;
while (mBuffers.in_pos < mBuffers.in_size &&
mBuffers.out_pos < mBuffers.out_size) {
const xz_ret ret = xz_dec_run(mDec, &mBuffers);
switch (ret) {
case XZ_STREAM_END:
// Stream ended, the next loop iteration should terminate.
MOZ_ASSERT(mBuffers.in_pos == mBuffers.in_size);
[[fallthrough]];
#ifdef XZ_DEC_ANY_CHECK
case XZ_UNSUPPORTED_CHECK:
// Ignore unsupported check.
[[fallthrough]];
#endif
case XZ_OK:
// Chunk decoded, proceed.
break;
case XZ_MEM_ERROR:
ERROR("XZ decoding: memory allocation failed");
return 0;
case XZ_MEMLIMIT_ERROR:
ERROR("XZ decoding: memory usage limit reached");
return 0;
case XZ_FORMAT_ERROR:
ERROR("XZ decoding: invalid stream format");
return 0;
case XZ_OPTIONS_ERROR:
ERROR("XZ decoding: unsupported header options");
return 0;
case XZ_DATA_ERROR:
[[fallthrough]];
case XZ_BUF_ERROR:
ERROR("XZ decoding: corrupt input stream");
return 0;
default:
MOZ_ASSERT_UNREACHABLE("XZ decoding: unknown error condition");
return 0;
}
}
return mBuffers.out_pos;
}
size_t
XZStream::RemainingInput() const
{
return mBuffers.in_size - mBuffers.in_pos;
}
size_t
XZStream::Size() const
{
return mBuffers.in_size;
}
size_t
XZStream::UncompressedSize() const
{
return mUncompSize;
}
size_t
XZStream::ParseIndexSize() const
{
static const uint8_t kFooterMagic[] = {'Y', 'Z'};
const uint8_t* footer = mInBuf + mBuffers.in_size - kFooterSize;
// The magic bytes are at the end of the footer.
if (memcmp(reinterpret_cast<const void*>(kFooterMagic),
footer + kFooterSize - sizeof(kFooterMagic),
sizeof(kFooterMagic))) {
// Not a valid footer at stream end.
return 0;
}
// Backward size is a 32 bit LE integer field positioned after the 32 bit CRC32
// code. It encodes the index size as a multiple of 4 bytes with a minimum
// size of 4 bytes.
const uint32_t backwardSize = *(footer + 4);
return (backwardSize + 1) * 4;
}
size_t
XZStream::ParseUncompressedSize() const
{
static const uint8_t kIndexIndicator[] = {0x0};
const size_t indexSize = ParseIndexSize();
if (!indexSize) {
return 0;
}
// The footer follows directly the index, so we can use it as a reference.
const uint8_t* end = mInBuf + mBuffers.in_size;
const uint8_t* index = end - kFooterSize - indexSize;
// The index consists of a one byte indicator followed by a VLI field for the
// number of records (1 expected) followed by a list of records. One record
// contains a VLI field for unpadded size followed by a VLI field for
// uncompressed size.
if (memcmp(reinterpret_cast<const void*>(kIndexIndicator),
index, sizeof(kIndexIndicator))) {
// Not a valid index.
return 0;
}
index += sizeof(kIndexIndicator);
uint64_t numRecords = 0;
index += ParseVarLenInt(index, end - index, &numRecords);
if (!numRecords) {
return 0;
}
uint64_t unpaddedSize = 0;
index += ParseVarLenInt(index, end - index, &unpaddedSize);
if (!unpaddedSize) {
return 0;
}
uint64_t uncompressedSize = 0;
index += ParseVarLenInt(index, end - index, &uncompressedSize);
return uncompressedSize;
}
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