121 lines
3.2 KiB
C++
121 lines
3.2 KiB
C++
/*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* Copyright 2011 Danny Robson <danny@nerdcruft.net>
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*/
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#include "./crc.hpp"
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#include "../debug.hpp"
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#include <array>
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using util::hash::crc;
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///////////////////////////////////////////////////////////////////////////////
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template <typename DigestT, DigestT Generator>
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const std::array<DigestT,256>
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crc<DigestT,Generator>::s_table = crc<DigestT,Generator>::table ();
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///////////////////////////////////////////////////////////////////////////////
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template <typename DigestT, DigestT Generator>
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crc<DigestT,Generator>::crc () noexcept
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{
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reset ();
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}
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//-----------------------------------------------------------------------------
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template <typename DigestT, DigestT Generator>
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void
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crc<DigestT,Generator>::reset (void) noexcept
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{
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m_digest = 0;
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m_digest = ~m_digest;
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}
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///////////////////////////////////////////////////////////////////////////////
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template <typename DigestT, DigestT Generator>
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void
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crc<DigestT,Generator>::update (const uint8_t *restrict first,
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const uint8_t *restrict last) noexcept
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{
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CHECK_LE (first, last);
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for (auto cursor = first; cursor != last; ++cursor) {
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m_digest = s_table[*cursor ^ (m_digest & 0xFF)] ^ (m_digest >> 8u);
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}
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}
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//-----------------------------------------------------------------------------
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template <typename DigestT, DigestT Generator>
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void
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crc<DigestT,Generator>::update (const void *restrict _data, size_t len) noexcept
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{
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auto data = reinterpret_cast<const uint8_t *restrict> (_data);
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return update(data, data + len);
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}
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//-----------------------------------------------------------------------------
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template <typename DigestT, DigestT Generator>
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void
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crc<DigestT,Generator>::finish (void)
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{
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;
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}
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//-----------------------------------------------------------------------------
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template <typename DigestT, DigestT Generator>
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DigestT
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crc<DigestT,Generator>::digest (void) const
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{
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return ~m_digest;
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}
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///////////////////////////////////////////////////////////////////////////////
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template <typename DigestT, DigestT Generator>
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std::array<DigestT,256>
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util::hash::crc<DigestT,Generator>::table (void)
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{
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auto gen = Generator;
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std::array<digest_t,256> value {};
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for (int i = 0; i < 256; ++i) {
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digest_t c = i;
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for (int k = 0; k < 8; ++k) {
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if (c & 1)
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c = gen ^ (c >> 1);
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else
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c >>= 1;
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}
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value[i] = c;
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}
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return value;
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};
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///////////////////////////////////////////////////////////////////////////////
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template class util::hash::crc<uint32_t, 0xEDB88320>; // png
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//template class util::hash::crc<uint32_t, 0X04C11DB7>; // ogg
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