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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 
JenkinsHashWhiten(uint32_t hash)26 hash_t JenkinsHashWhiten(uint32_t hash) {
27     hash += (hash << 3);
28     hash ^= (hash >> 11);
29     hash += (hash << 15);
30     return hash;
31 }
32 
JenkinsHashMixBytes(uint32_t hash,const uint8_t * bytes,size_t size)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 
JenkinsHashMixShorts(uint32_t hash,const uint16_t * shorts,size_t size)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