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