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LibCompress: Copy LZMA repetitions from the buffer in sequence

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This improves the decompression time of `clang-15.0.7.src.tar.xz` from
5.2 seconds down to about 2.7 seconds.
This commit is contained in:
Tim Schumacher 2023-04-04 19:50:17 +02:00 • committed by Tim Flynn
parent b88c58b94c
commit 7000ccf89f
1 changed files with 5 additions and 14 deletions
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19
Userland/Libraries/LibCompress/Lzma.cpp
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@ -520,22 +520,13 @@ ErrorOr<Bytes> LzmaDecompressor::read_some(Bytes bytes)
if (m_options.uncompressed_size.has_value() && m_options.uncompressed_size.value() < m_total_decoded_bytes + real_length)
return Error::from_string_literal("Tried to copy match beyond expected uncompressed file size");
while (real_length > 0) {
if (m_dictionary->empty_space() == 0) {
m_leftover_match_length = real_length;
break;
}
auto copied_length = TRY(m_dictionary->copy_from_seekback(current_repetition_offset(), real_length));
u8 byte;
auto read_bytes = TRY(m_dictionary->read_with_seekback({ &byte, sizeof(byte) }, current_repetition_offset()));
VERIFY(read_bytes.size() == sizeof(byte));
m_total_decoded_bytes += copied_length;
real_length -= copied_length;
auto written_bytes = m_dictionary->write({ &byte, sizeof(byte) });
VERIFY(written_bytes == sizeof(byte));
m_total_decoded_bytes++;
real_length--;
}
if (real_length > 0)
m_leftover_match_length = real_length;
return {};
};