1 /* 2 * Copyright (C) 2012 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 /* Implementation of Jenkins one-at-a-time hash function. These choices are 18 * optimized for code size and portability, rather than raw speed. But speed 19 * should still be quite good. 20 **/ 21 22 #ifndef ANDROID_JENKINS_HASH_H 23 #define ANDROID_JENKINS_HASH_H 24 25 #include <utils/TypeHelpers.h> 26 27 namespace android { 28 29 /* The Jenkins hash of a sequence of 32 bit words A, B, C is: 30 * Whiten(Mix(Mix(Mix(0, A), B), C)) */ 31 JenkinsHashMix(uint32_t hash,uint32_t data)32 inline uint32_t JenkinsHashMix(uint32_t hash, uint32_t data) { 33 hash += data; 34 hash += (hash << 10); 35 hash ^= (hash >> 6); 36 return hash; 37 } 38 39 hash_t JenkinsHashWhiten(uint32_t hash); 40 41 /* Helpful utility functions for hashing data in 32 bit chunks */ 42 uint32_t JenkinsHashMixBytes(uint32_t hash, const uint8_t* bytes, size_t size); 43 44 uint32_t JenkinsHashMixShorts(uint32_t hash, const uint16_t* shorts, size_t size); 45 46 } 47 48 #endif // ANDROID_JENKINS_HASH_H 49