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implicitfield
47146b00c9
Previously, there were two slightly different implementations of this in the Kernel and in LibCrypto. This patch removes those, and replaces them with an implementation that seeks to combine the best aspects of both while not being a drop-in replacement for either. Two new tests are also included.
42 lines
1.0 KiB
C++
42 lines
1.0 KiB
C++
/*
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* Copyright (c) 2025, 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/ByteReader.h>
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#include <AK/InternetChecksum.h>
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namespace AK {
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InternetChecksum::InternetChecksum(ReadonlyBytes bytes)
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{
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update(bytes);
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}
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void InternetChecksum::update(ReadonlyBytes bytes)
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{
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VERIFY(!m_uneven_payload);
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for (size_t i = 0; i < bytes.size() / sizeof(u16); ++i)
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m_state += ByteReader::load16(bytes.offset_pointer(i * sizeof(u16)));
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if (bytes.size() % 2 == 1) {
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m_state += bytes.last();
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m_uneven_payload = true;
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}
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}
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NetworkOrdered<u16> InternetChecksum::digest()
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{
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u32 output = m_state;
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// While there are any bits above the bottom 16...
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while (output >> 16)
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// Drop the top bits, and add the carries to the sum.
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output = (output & 0xFFFF) + (output >> 16);
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// Return the one's complement (this is already network-ordered, so we
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// bypass the constructor of that).
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return bit_cast<NetworkOrdered<u16>>(static_cast<u16>(~output));
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}
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}
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