// 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 MixingHashState::CombineLargeContiguousImpl32(

    uint64_t state, const unsigned char* first, size_t len) {

  while (len >= PiecewiseChunkSize()) {

    state = Mix(state,

                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 MixingHashState::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 MixingHashState::kSeed = &kSeed;

// The salt array used by LowLevelHash. 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 kHashSalt[5] = {

    uint64_t{0x243F6A8885A308D3}, uint64_t{0x13198A2E03707344},

    uint64_t{0xA4093822299F31D0}, uint64_t{0x082EFA98EC4E6C89},

    uint64_t{0x452821E638D01377},

};

uint64_t MixingHashState::LowLevelHashImpl(const unsigned char* data,

                                           size_t len) {

  return LowLevelHash(data, len, Seed(), kHashSalt);

}

}  // namespace hash_internal

ABSL_NAMESPACE_END

}  // namespace absl