70 lines
2.5 KiB
C++
70 lines
2.5 KiB
C++
// Copyright 2018 The Abseil Authors.
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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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// https://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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#include "absl/hash/internal/hash.h"
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namespace absl {
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ABSL_NAMESPACE_BEGIN
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namespace hash_internal {
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uint64_t MixingHashState::CombineLargeContiguousImpl32(
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uint64_t state, const unsigned char* first, size_t len) {
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while (len >= PiecewiseChunkSize()) {
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state = Mix(state,
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hash_internal::CityHash32(reinterpret_cast<const char*>(first),
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PiecewiseChunkSize()));
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len -= PiecewiseChunkSize();
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first += PiecewiseChunkSize();
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}
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// Handle the remainder.
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return CombineContiguousImpl(state, first, len,
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std::integral_constant<int, 4>{});
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}
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uint64_t MixingHashState::CombineLargeContiguousImpl64(
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uint64_t state, const unsigned char* first, size_t len) {
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while (len >= PiecewiseChunkSize()) {
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state = Mix(state, Hash64(first, PiecewiseChunkSize()));
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len -= PiecewiseChunkSize();
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first += PiecewiseChunkSize();
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}
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// Handle the remainder.
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return CombineContiguousImpl(state, first, len,
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std::integral_constant<int, 8>{});
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}
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ABSL_CONST_INIT const void* const MixingHashState::kSeed = &kSeed;
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// The salt array used by LowLevelHash. This array is NOT the mechanism used to
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// make absl::Hash non-deterministic between program invocations. See `Seed()`
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// for that mechanism.
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//
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// Any random values are fine. These values are just digits from the decimal
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// part of pi.
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// https://en.wikipedia.org/wiki/Nothing-up-my-sleeve_number
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constexpr uint64_t kHashSalt[5] = {
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uint64_t{0x243F6A8885A308D3}, uint64_t{0x13198A2E03707344},
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uint64_t{0xA4093822299F31D0}, uint64_t{0x082EFA98EC4E6C89},
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uint64_t{0x452821E638D01377},
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};
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uint64_t MixingHashState::LowLevelHashImpl(const unsigned char* data,
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size_t len) {
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return LowLevelHash(data, len, Seed(), kHashSalt);
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}
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} // namespace hash_internal
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ABSL_NAMESPACE_END
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} // namespace absl
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