1 // Copyright 2020 The Abseil Authors 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // https://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 // 15 // This file provides the Google-internal implementation of the Wyhash 16 // algorithm. 17 // 18 // Wyhash is a fast hash function for hash tables, the fastest we've currently 19 // (late 2020) found that passes the SMHasher tests. The algorithm relies on 20 // intrinsic 128-bit multiplication for speed. This is not meant to be secure - 21 // just fast. 22 23 #ifndef ABSL_HASH_INTERNAL_WYHASH_H_ 24 #define ABSL_HASH_INTERNAL_WYHASH_H_ 25 26 #include <stdint.h> 27 #include <stdlib.h> 28 29 #include "absl/base/config.h" 30 31 namespace absl { 32 ABSL_NAMESPACE_BEGIN 33 namespace hash_internal { 34 35 // Hash function for a byte array. A 64-bit seed and a set of five 64-bit 36 // integers are hashed into the result. 37 // 38 // To allow all hashable types (including string_view and Span) to depend on 39 // this algorithm, we keep the API low-level, with as few dependencies as 40 // possible. 41 uint64_t Wyhash(const void* data, size_t len, uint64_t seed, 42 const uint64_t salt[5]); 43 44 } // namespace hash_internal 45 ABSL_NAMESPACE_END 46 } // namespace absl 47 48 #endif // ABSL_HASH_INTERNAL_WYHASH_H_ 49