Abseil Common Libraries (C++) (grcp 依赖)
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70 lines
2.6 KiB
70 lines
2.6 KiB
// 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 HashState::CombineLargeContiguousImpl32(uint64_t state, |
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const unsigned char* first, |
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size_t len) { |
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while (len >= PiecewiseChunkSize()) { |
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state = |
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Mix(state, absl::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 HashState::CombineLargeContiguousImpl64(uint64_t state, |
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const unsigned char* first, |
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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 HashState::kSeed = &kSeed; |
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// The salt array used by Wyhash. This array is NOT the mechanism used to make |
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// absl::Hash non-deterministic between program invocations. See `Seed()` for |
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// 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 kWyhashSalt[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 HashState::WyhashImpl(const unsigned char* data, size_t len) { |
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return Wyhash(data, len, Seed(), kWyhashSalt); |
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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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