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Diffstat (limited to 'libutils/JenkinsHash.cpp')
-rw-r--r-- | libutils/JenkinsHash.cpp | 64 |
1 files changed, 64 insertions, 0 deletions
diff --git a/libutils/JenkinsHash.cpp b/libutils/JenkinsHash.cpp new file mode 100644 index 000000000..52c9bb7df --- /dev/null +++ b/libutils/JenkinsHash.cpp | |||
@@ -0,0 +1,64 @@ | |||
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 | |||