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/*
* Copyright (c) 2020, the SerenityOS developers.
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/Span.h>
#include <AK/Types.h>
#include <AK/Vector.h>
#include <LibCompress/Deflate.h>
#include <LibCompress/Zlib.h>
namespace Compress {
Optional<Zlib> Zlib::try_create(ReadonlyBytes data)
{
if (data.size() < 6)
return {}; // header + footer size is 6
Zlib zlib { data };
u8 compression_info = data.at(0);
u8 flags = data.at(1);
zlib.m_compression_method = compression_info & 0xF;
zlib.m_compression_info = (compression_info >> 4) & 0xF;
zlib.m_check_bits = flags & 0xF;
zlib.m_has_dictionary = (flags >> 5) & 0x1;
zlib.m_compression_level = (flags >> 6) & 0x3;
if (zlib.m_compression_method != 8 || zlib.m_compression_info > 7)
return {}; // non-deflate compression
if (zlib.m_has_dictionary)
return {}; // we dont support pre-defined dictionaries
if ((compression_info * 256 + flags) % 31 != 0)
return {}; // error correction code doesn't match
zlib.m_data_bytes = data.slice(2, data.size() - 2 - 4);
return zlib;
}
Zlib::Zlib(const ReadonlyBytes& data)
: m_input_data(data)
{
}
Optional<ByteBuffer> Zlib::decompress()
{
return DeflateDecompressor::decompress_all(m_data_bytes);
}
Optional<ByteBuffer> Zlib::decompress_all(ReadonlyBytes bytes)
{
auto zlib = try_create(bytes);
if (!zlib.has_value())
return {};
return zlib->decompress();
}
u32 Zlib::checksum()
{
if (!m_checksum) {
auto bytes = m_input_data.slice(m_input_data.size() - 4, 4);
m_checksum = bytes.at(0) << 24 | bytes.at(1) << 16 | bytes.at(2) << 8 || bytes.at(3);
}
return m_checksum;
}
}
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