| // Licensed to the Apache Software Foundation (ASF) under one |
| // or more contributor license agreements. See the NOTICE file |
| // distributed with this work for additional information |
| // regarding copyright ownership. The ASF licenses this file |
| // to you 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 |
| // |
| // http://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. |
| |
| // Copyright 2010 Google Inc. All Rights Reserved. |
| // Authors: gpike@google.com (Geoff Pike), jyrki@google.com (Jyrki Alakuijala) |
| // |
| // This file provides a few functions for hashing strings. On x86-64 |
| // hardware as of early 2010, CityHash64() is much faster than |
| // MurmurHash64(), and passes the quality-of-hash tests in |
| // ./hasheval/hasheval_test.cc, among others, with flying colors. The |
| // difference in speed can be a factor of two for strings of 50 to 64 |
| // bytes, and sometimes even more for cache-resident longer strings. |
| // |
| // CityHash128() is optimized for relatively long strings and returns |
| // a 128-bit hash. For strings more than about 2000 bytes it can be |
| // faster than CityHash64(). |
| // |
| // Functions in the CityHash family are not suitable for cryptography. |
| // |
| // By the way, for some hash functions, given strings a and b, the hash |
| // of a+b is easily derived from the hashes of a and b. This property |
| // doesn't hold for any hash functions in this file. |
| |
| #pragma once |
| |
| #include <cstddef> |
| #include <cstdint> |
| |
| // WARNING |
| // The implementation of cityhash in this file is somewhat different from Google's original version. |
| // For the same input, there will be different output results. |
| // Therefore, we should do not to use this special cityhash as possible as we can. |
| namespace doris::util_hash { |
| |
| uint64_t HashLen16(uint64_t u, uint64_t v); |
| |
| // Hash function for a byte array. |
| // The mapping may change from time to time. |
| uint64_t CityHash64(const char* buf, size_t len); |
| |
| // Hash function for a byte array. For convenience, a 64-bit seed is also |
| // hashed into the result. The mapping may change from time to time. |
| uint64_t CityHash64WithSeed(const char* buf, size_t len, uint64_t seed); |
| } // namespace doris::util_hash |
