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LibCompress: Implement support for multiple concatenated XZ streams

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This commit is contained in:
Tim Schumacher 2023-03-30 13:16:40 +02:00 • committed by Andreas Kling
parent 00332c9b7d
commit 726963edc7
3 changed files with 62 additions and 13 deletions
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56
Userland/Libraries/LibCompress/Xz.cpp
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@ -177,14 +177,61 @@ XzDecompressor::XzDecompressor(NonnullOwnPtr<CountingStream> stream)
ErrorOr<Bytes> XzDecompressor::read_some(Bytes bytes)
{
if (m_found_stream_footer)
if (m_found_last_stream_footer)
return bytes.trim(0);
if (!m_stream_flags.has_value()) {
auto stream_header = TRY(m_stream->read_value<XzStreamHeader>());
// This assumes that we can just read the Stream Header into memory as-is. Check that this still holds up for good measure.
static_assert(AK::Traits<XzStreamHeader>::is_trivially_serializable());
XzStreamHeader stream_header {};
Bytes stream_header_bytes { &stream_header, sizeof(stream_header) };
if (m_found_first_stream_header) {
// 2.2. Stream Padding:
// "Stream Padding MUST contain only null bytes. To preserve the
// four-byte alignment of consecutive Streams, the size of Stream
// Padding MUST be a multiple of four bytes. Empty Stream Padding
// is allowed. If these requirements are not met, the decoder MUST
// indicate an error."
VERIFY(m_stream->read_bytes() % 4 == 0);
while (true) {
// Read the first byte until we either get a non-null byte or reach EOF.
auto byte_or_error = m_stream->read_value<u8>();
if (byte_or_error.is_error() && m_stream->is_eof())
break;
auto byte = TRY(byte_or_error);
if (byte != 0) {
stream_header_bytes[0] = byte;
stream_header_bytes = stream_header_bytes.slice(1);
break;
}
}
// If we aren't at EOF we already read the potential first byte of the header, so we need to subtract that.
auto end_of_padding_offset = m_stream->read_bytes();
if (!m_stream->is_eof())
end_of_padding_offset -= 1;
if (end_of_padding_offset % 4 != 0)
return Error::from_string_literal("XZ Stream Padding is not aligned to 4 bytes");
if (m_stream->is_eof()) {
m_found_last_stream_footer = true;
return bytes.trim(0);
}
}
TRY(m_stream->read_until_filled(stream_header_bytes));
TRY(stream_header.validate());
m_stream_flags = stream_header.flags;
m_found_first_stream_header = true;
}
if (!m_current_block_stream.has_value() || (*m_current_block_stream)->is_eof()) {
@ -335,7 +382,8 @@ ErrorOr<Bytes> XzDecompressor::read_some(Bytes bytes)
if (Bytes { &*m_stream_flags, sizeof(XzStreamFlags) } != Bytes { &stream_footer.flags, sizeof(stream_footer.flags) })
return Error::from_string_literal("XZ stream header flags don't match the stream footer");
m_found_stream_footer = true;
// Another XZ Stream might follow, so we just unset the current information and continue on the next read.
m_stream_flags.clear();
return bytes.trim(0);
}
@ -462,7 +510,7 @@ ErrorOr<size_t> XzDecompressor::write_some(ReadonlyBytes)
bool XzDecompressor::is_eof() const
{
return m_found_stream_footer;
return m_found_last_stream_footer;
}
bool XzDecompressor::is_open() const