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https://github.com/claunia/findcrcs.git
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69 lines
2.2 KiB
C++
69 lines
2.2 KiB
C++
// Copyright 2010 Google Inc. All rights reserved.
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//
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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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// Casting between integers and compound CRC types.
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#ifndef CRCUTIL_CRC_CASTS_H_
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#define CRCUTIL_CRC_CASTS_H_
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#include "base_types.h" // uint8, uint64
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#include "platform.h" // __forceinline
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namespace crcutil {
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// Downcasts a value of (oftentimes larger) Crc type to (smaller base integer)
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// Result type, enabling specialized downcasts implemented by "large integer"
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// classes (e.g. uint128_sse2).
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template<typename Crc, typename Result>
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__forceinline Result Downcast(const Crc &x) {
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return static_cast<Result>(x);
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}
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// Extracts 8 least significant bits from a value of Crc type.
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#define TO_BYTE(x) Downcast<Crc, uint8>(x)
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// Converts a pair of uint64 bit values into single value of CRC type.
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// It is caller's responsibility to ensure that the input is correct.
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template<typename Crc>
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__forceinline Crc CrcFromUint64(uint64 lo, uint64 hi = 0) {
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if (sizeof(Crc) <= sizeof(lo)) {
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return static_cast<Crc>(lo);
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} else {
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// static_cast to keep compiler happy.
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Crc result = static_cast<Crc>(hi);
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result = SHIFT_LEFT_SAFE(result, 8 * sizeof(lo));
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result ^= lo;
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return result;
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}
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}
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// Converts Crc value to a pair of uint64 values.
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template<typename Crc>
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__forceinline void Uint64FromCrc(const Crc &crc,
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uint64 *lo, uint64 *hi = NULL) {
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if (sizeof(*lo) >= sizeof(crc)) {
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*lo = Downcast<Crc, uint64>(crc);
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if (hi != NULL) {
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*hi = 0;
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}
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} else {
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*lo = Downcast<Crc, uint64>(crc);
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*hi = Downcast<Crc, uint64>(SHIFT_RIGHT_SAFE(crc, 8 * sizeof(lo)));
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}
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}
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} // namespace crcutil
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#endif // CRCUTIL_CRC_CASTS_H_
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