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