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Diffstat (limited to 'third_party/abseil-cpp/absl/hash/internal/low_level_hash.h')
-rw-r--r-- | third_party/abseil-cpp/absl/hash/internal/low_level_hash.h | 50 |
1 files changed, 50 insertions, 0 deletions
diff --git a/third_party/abseil-cpp/absl/hash/internal/low_level_hash.h b/third_party/abseil-cpp/absl/hash/internal/low_level_hash.h new file mode 100644 index 0000000000..439968aa98 --- /dev/null +++ b/third_party/abseil-cpp/absl/hash/internal/low_level_hash.h @@ -0,0 +1,50 @@ +// Copyright 2020 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. +// +// This file provides the Google-internal implementation of LowLevelHash. +// +// LowLevelHash is a fast hash function for hash tables, the fastest we've +// currently (late 2020) found that passes the SMHasher tests. The algorithm +// relies on intrinsic 128-bit multiplication for speed. This is not meant to be +// secure - just fast. +// +// It is closely based on a version of wyhash, but does not maintain or +// guarantee future compatibility with it. + +#ifndef ABSL_HASH_INTERNAL_LOW_LEVEL_HASH_H_ +#define ABSL_HASH_INTERNAL_LOW_LEVEL_HASH_H_ + +#include <stdint.h> +#include <stdlib.h> + +#include "absl/base/config.h" + +namespace absl { +ABSL_NAMESPACE_BEGIN +namespace hash_internal { + +// Hash function for a byte array. A 64-bit seed and a set of five 64-bit +// integers are hashed into the result. +// +// To allow all hashable types (including string_view and Span) to depend on +// this algorithm, we keep the API low-level, with as few dependencies as +// possible. +uint64_t LowLevelHash(const void* data, size_t len, uint64_t seed, + const uint64_t salt[5]); + +} // namespace hash_internal +ABSL_NAMESPACE_END +} // namespace absl + +#endif // ABSL_HASH_INTERNAL_LOW_LEVEL_HASH_H_ |