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// Copyright 2010 Google Inc. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Casting between integers and compound CRC types.
#ifndef CRCUTIL_CRC_CASTS_H_
#define CRCUTIL_CRC_CASTS_H_
#include "base_types.h" // uint8, uint64
#include "platform.h" // __forceinline
namespace crcutil {
// Downcasts a value of (oftentimes larger) Crc type to (smaller base integer)
// Result type, enabling specialized downcasts implemented by "large integer"
// classes (e.g. uint128_sse2).
template<typename Crc, typename Result>
__forceinline Result Downcast(const Crc &x) {
return static_cast<Result>(x);
}
// Extracts 8 least significant bits from a value of Crc type.
#define TO_BYTE(x) Downcast<Crc, uint8>(x)
// Converts a pair of uint64 bit values into single value of CRC type.
// It is caller's responsibility to ensure that the input is correct.
template<typename Crc>
__forceinline Crc CrcFromUint64(uint64 lo, uint64 hi = 0) {
if (sizeof(Crc) <= sizeof(lo)) {
return static_cast<Crc>(lo);
} else {
// static_cast to keep compiler happy.
Crc result = static_cast<Crc>(hi);
result = SHIFT_LEFT_SAFE(result, 8 * sizeof(lo));
result ^= lo;
return result;
}
}
// Converts Crc value to a pair of uint64 values.
template<typename Crc>
__forceinline void Uint64FromCrc(const Crc &crc,
uint64 *lo, uint64 *hi = NULL) {
if (sizeof(*lo) >= sizeof(crc)) {
*lo = Downcast<Crc, uint64>(crc);
if (hi != NULL) {
*hi = 0;
}
} else {
*lo = Downcast<Crc, uint64>(crc);
*hi = Downcast<Crc, uint64>(SHIFT_RIGHT_SAFE(crc, 8 * sizeof(lo)));
}
}
} // namespace crcutil
#endif // CRCUTIL_CRC_CASTS_H_
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