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LibCompress: Allow appending input streams to an existing LZMA decoder

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Tim Schumacher 2023-03-14 04:12:20 +01:00 • committed by Andreas Kling
parent 04f69de7f1
commit f4506a3a72
2 changed files with 43 additions and 15 deletions
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55
Userland/Libraries/LibCompress/Lzma.cpp
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@ -99,16 +99,6 @@ ErrorOr<NonnullOwnPtr<LzmaDecompressor>> LzmaDecompressor::create_from_container
ErrorOr<NonnullOwnPtr<LzmaDecompressor>> LzmaDecompressor::create_from_raw_stream(MaybeOwned<Stream> stream, LzmaDecompressorOptions const& options)
{
// "The LZMA Encoder always writes ZERO in initial byte of compressed stream.
// That scheme allows to simplify the code of the Range Encoder in the
// LZMA Encoder. If initial byte is not equal to ZERO, the LZMA Decoder must
// stop decoding and report error."
{
auto byte = TRY(stream->read_value<u8>());
if (byte != 0)
return Error::from_string_literal("Initial byte of data stream is not zero");
}
auto output_buffer = TRY(CircularBuffer::create_empty(options.dictionary_size));
// "The LZMA Decoder uses (1 << (lc + lp)) tables with CProb values, where each table contains 0x300 CProb values."
@ -116,11 +106,7 @@ ErrorOr<NonnullOwnPtr<LzmaDecompressor>> LzmaDecompressor::create_from_raw_strea
auto decompressor = TRY(adopt_nonnull_own_or_enomem(new (nothrow) LzmaDecompressor(move(stream), options, move(output_buffer), move(literal_probabilities))));
// Read the initial bytes into the range decoder.
for (size_t i = 0; i < 4; i++) {
auto byte = TRY(decompressor->m_stream->read_value<u8>());
decompressor->m_range_decoder_code = decompressor->m_range_decoder_code << 8 | byte;
}
TRY(decompressor->initialize_range_decoder());
return decompressor;
}
@ -149,6 +135,45 @@ LzmaDecompressor::LzmaDecompressor(MaybeOwned<Stream> stream, LzmaDecompressorOp
initialize_to_default_probability(m_is_rep0_long_probabilities);
}
ErrorOr<void> LzmaDecompressor::initialize_range_decoder()
{
// "The LZMA Encoder always writes ZERO in initial byte of compressed stream.
// That scheme allows to simplify the code of the Range Encoder in the
// LZMA Encoder. If initial byte is not equal to ZERO, the LZMA Decoder must
// stop decoding and report error."
{
auto byte = TRY(m_stream->read_value<u8>());
if (byte != 0)
return Error::from_string_literal("Initial byte of data stream is not zero");
}
// Read the initial bytes into the range decoder.
m_range_decoder_code = 0;
for (size_t i = 0; i < 4; i++) {
auto byte = TRY(m_stream->read_value<u8>());
m_range_decoder_code = m_range_decoder_code << 8 | byte;
}
m_range_decoder_range = 0xFFFFFFFF;
return {};
}
ErrorOr<void> LzmaDecompressor::append_input_stream(MaybeOwned<Stream> stream, Optional<u64> uncompressed_size)
{
m_stream = move(stream);
TRY(initialize_range_decoder());
if (m_options.uncompressed_size.has_value() != uncompressed_size.has_value())
return Error::from_string_literal("Appending LZMA streams with mismatching uncompressed size status");
if (uncompressed_size.has_value())
*m_options.uncompressed_size += *uncompressed_size;
return {};
}
ErrorOr<void> LzmaDecompressor::normalize_range_decoder()
{
// "The value of the "Range" variable before each bit decoding can not be smaller