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 #include <utils/JenkinsHash.h> 23 24 namespace android { 25 26 hash_t JenkinsHashWhiten(uint32_t hash) { 27 hash += (hash << 3); 28 hash ^= (hash >> 11); 29 hash += (hash << 15); 30 return hash; 31 } 32 33 uint32_t JenkinsHashMixBytes(uint32_t hash, const uint8_t* bytes, size_t size) { 34 hash = JenkinsHashMix(hash, (uint32_t)size); 35 size_t i; 36 for (i = 0; i < (size & -4); i += 4) { 37 uint32_t data = bytes[i] | (bytes[i+1] << 8) | (bytes[i+2] << 16) | (bytes[i+3] << 24); 38 hash = JenkinsHashMix(hash, data); 39 } 40 if (size & 3) { 41 uint32_t data = bytes[i]; 42 data |= ((size & 3) > 1) ? (bytes[i+1] << 8) : 0; 43 data |= ((size & 3) > 2) ? (bytes[i+2] << 16) : 0; 44 hash = JenkinsHashMix(hash, data); 45 } 46 return hash; 47 } 48 49 uint32_t JenkinsHashMixShorts(uint32_t hash, const uint16_t* shorts, size_t size) { 50 hash = JenkinsHashMix(hash, (uint32_t)size); 51 size_t i; 52 for (i = 0; i < (size & -2); i += 2) { 53 uint32_t data = shorts[i] | (shorts[i+1] << 16); 54 hash = JenkinsHashMix(hash, data); 55 } 56 if (size & 1) { 57 uint32_t data = shorts[i]; 58 hash = JenkinsHashMix(hash, data); 59 } 60 return hash; 61 } 62 63 } 64 65
