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LibCompress: Implement GZip compression
This commit implements a stream compressor for the gzip specification (RFC 1952), which is essentially a thin wrapper around the DEFLATE compression format.
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02569bec11
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2 changed files with 94 additions and 25 deletions
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@ -1,5 +1,6 @@
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/*
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* Copyright (c) 2020, the SerenityOS developers.
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* Copyright (c) 2021, Idan Horowitz <idan.horowitz@gmail.com>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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@ -36,12 +37,12 @@ bool GzipDecompressor::is_likely_compressed(ReadonlyBytes bytes)
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return bytes.size() >= 2 && bytes[0] == gzip_magic_1 && bytes[1] == gzip_magic_2;
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}
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bool GzipDecompressor::BlockHeader::valid_magic_number() const
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bool BlockHeader::valid_magic_number() const
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{
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return identification_1 == gzip_magic_1 && identification_2 == gzip_magic_2;
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}
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bool GzipDecompressor::BlockHeader::supported_by_implementation() const
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bool BlockHeader::supported_by_implementation() const
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{
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if (compression_method != 0x08) {
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// RFC 1952 does not define any compression methods other than deflate.
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@ -187,4 +188,58 @@ Optional<ByteBuffer> GzipDecompressor::decompress_all(ReadonlyBytes bytes)
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bool GzipDecompressor::unreliable_eof() const { return m_eof; }
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GzipCompressor::GzipCompressor(OutputStream& stream)
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: m_output_stream(stream)
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{
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}
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GzipCompressor::~GzipCompressor()
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{
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}
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size_t GzipCompressor::write(ReadonlyBytes bytes)
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{
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BlockHeader header;
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header.identification_1 = 0x1f;
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header.identification_2 = 0x8b;
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header.compression_method = 0x08;
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header.flags = 0;
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header.modification_time = 0;
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header.extra_flags = 3; // DEFLATE sets 2 for maximum compression and 4 for minimum compression
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header.operating_system = 3; // unix
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m_output_stream << Bytes { &header, sizeof(header) };
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DeflateCompressor compressed_stream { m_output_stream };
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VERIFY(compressed_stream.write_or_error(bytes));
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compressed_stream.final_flush();
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Crypto::Checksum::CRC32 crc32;
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crc32.update(bytes);
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LittleEndian<u32> digest = crc32.digest();
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LittleEndian<u32> size = bytes.size();
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m_output_stream << digest << size;
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return bytes.size();
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}
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bool GzipCompressor::write_or_error(ReadonlyBytes bytes)
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{
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if (write(bytes) < bytes.size()) {
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set_fatal_error();
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return false;
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}
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return true;
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}
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Optional<ByteBuffer> GzipCompressor::compress_all(const ReadonlyBytes& bytes)
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{
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DuplexMemoryStream output_stream;
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GzipCompressor gzip_stream { output_stream };
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gzip_stream.write_or_error(bytes);
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if (gzip_stream.handle_any_error())
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return {};
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return output_stream.copy_into_contiguous_buffer();
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}
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}
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