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https://github.com/RGBCube/serenity
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6bd880c404
CRC32 table is generated at compile-time and put into a static variable in the header file. This can be moved to be a function instead of a class, be moved to the `.cpp` file` and generated as an array instead of a class which only implements `operator[]`.
47 lines
901 B
C++
47 lines
901 B
C++
/*
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* Copyright (c) 2020-2022, the SerenityOS developers.
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/Array.h>
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#include <AK/Span.h>
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#include <AK/Types.h>
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#include <LibCrypto/Checksum/CRC32.h>
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namespace Crypto::Checksum {
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static constexpr auto generate_table()
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{
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Array<u32, 256> data {};
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for (auto i = 0u; i < data.size(); i++) {
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u32 value = i;
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for (auto j = 0; j < 8; j++) {
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if (value & 1) {
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value = 0xEDB88320 ^ (value >> 1);
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} else {
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value = value >> 1;
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}
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}
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data[i] = value;
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}
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return data;
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}
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static constexpr auto table = generate_table();
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void CRC32::update(ReadonlyBytes data)
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{
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for (size_t i = 0; i < data.size(); i++) {
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m_state = table[(m_state ^ data.at(i)) & 0xFF] ^ (m_state >> 8);
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}
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};
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u32 CRC32::digest()
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{
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return ~m_state;
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}
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}
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