| // 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. |
| |
| #ifndef KUDU_UTIL_HASH_UTIL_H |
| #define KUDU_UTIL_HASH_UTIL_H |
| |
| #include <stdint.h> |
| |
| #include "kudu/gutil/port.h" |
| |
| namespace kudu { |
| |
| /// Utility class to compute hash values. |
| class HashUtil { |
| public: |
| |
| static const uint64_t MURMUR_PRIME = 0xc6a4a7935bd1e995; |
| static const int MURMUR_R = 47; |
| |
| /// Murmur2 hash implementation returning 64-bit hashes. |
| ATTRIBUTE_NO_SANITIZE_INTEGER |
| static uint64_t MurmurHash2_64(const void* input, int len, uint64_t seed) { |
| uint64_t h = seed ^ (len * MURMUR_PRIME); |
| |
| const uint64_t* data = reinterpret_cast<const uint64_t*>(input); |
| const uint64_t* end = data + (len / sizeof(uint64_t)); |
| |
| while (data != end) { |
| uint64_t k = *data++; |
| k *= MURMUR_PRIME; |
| k ^= k >> MURMUR_R; |
| k *= MURMUR_PRIME; |
| h ^= k; |
| h *= MURMUR_PRIME; |
| } |
| |
| const uint8_t* data2 = reinterpret_cast<const uint8_t*>(data); |
| switch (len & 7) { |
| case 7: h ^= static_cast<uint64_t>(data2[6]) << 48; |
| case 6: h ^= static_cast<uint64_t>(data2[5]) << 40; |
| case 5: h ^= static_cast<uint64_t>(data2[4]) << 32; |
| case 4: h ^= static_cast<uint64_t>(data2[3]) << 24; |
| case 3: h ^= static_cast<uint64_t>(data2[2]) << 16; |
| case 2: h ^= static_cast<uint64_t>(data2[1]) << 8; |
| case 1: h ^= static_cast<uint64_t>(data2[0]); |
| h *= MURMUR_PRIME; |
| } |
| |
| h ^= h >> MURMUR_R; |
| h *= MURMUR_PRIME; |
| h ^= h >> MURMUR_R; |
| return h; |
| } |
| }; |
| |
| } // namespace kudu |
| #endif |