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1 // Copyright (c) 2013, the Dart project authors. Please see the AUTHORS file | 1 // Copyright (c) 2013, the Dart project authors. Please see the AUTHORS file |
2 // for details. All rights reserved. Use of this source code is governed by a | 2 // for details. All rights reserved. Use of this source code is governed by a |
3 // BSD-style license that can be found in the LICENSE file. | 3 // BSD-style license that can be found in the LICENSE file. |
4 part of dart.math; | 4 |
| 5 part of html_common; |
5 | 6 |
6 /** | 7 /** |
7 * This is the [Jenkins hash function][1] but using masking to keep | 8 * This is the [Jenkins hash function][1] but using masking to keep |
8 * values in SMI range. | 9 * values in SMI range. |
9 * | 10 * |
10 * [1]: http://en.wikipedia.org/wiki/Jenkins_hash_function | 11 * [1]: http://en.wikipedia.org/wiki/Jenkins_hash_function |
11 * | 12 * |
12 * Use: | 13 * Use: |
13 * Hash each value with the hash of the previous value, then get the final | 14 * Hash each value with the hash of the previous value, then get the final |
14 * hash by calling finish. | 15 * hash by calling finish. |
15 * | 16 * |
16 * var hash = 0; | 17 * var hash = 0; |
17 * for (var value in values) { | 18 * for (var value in values) { |
18 * hash = JenkinsSmiHash.combine(hash, value.hashCode); | 19 * hash = JenkinsSmiHash.combine(hash, value.hashCode); |
19 * } | 20 * } |
20 * hash = JenkinsSmiHash.finish(hash); | 21 * hash = JenkinsSmiHash.finish(hash); |
21 */ | 22 */ |
22 class _JenkinsSmiHash { | 23 class JenkinsSmiHash { |
23 // TODO(11617): This class should be optimized and standardized elsewhere. | 24 // TODO: Bug 11617- This class should be optimized and standardized elsewhere. |
24 | 25 |
25 static int combine(int hash, int value) { | 26 static int combine(int hash, int value) { |
26 hash = 0x1fffffff & (hash + value); | 27 hash = 0x1fffffff & (hash + value); |
27 hash = 0x1fffffff & (hash + ((0x0007ffff & hash) << 10)); | 28 hash = 0x1fffffff & (hash + ((0x0007ffff & hash) << 10)); |
28 return hash ^ (hash >> 6); | 29 return hash ^ (hash >> 6); |
29 } | 30 } |
30 | 31 |
31 static int finish(int hash) { | 32 static int finish(int hash) { |
32 hash = 0x1fffffff & (hash + ((0x03ffffff & hash) << 3)); | 33 hash = 0x1fffffff & (hash + ((0x03ffffff & hash) << 3)); |
33 hash = hash ^ (hash >> 11); | 34 hash = hash ^ (hash >> 11); |
34 return 0x1fffffff & (hash + ((0x00003fff & hash) << 15)); | 35 return 0x1fffffff & (hash + ((0x00003fff & hash) << 15)); |
35 } | 36 } |
36 | 37 |
37 static int hash2(a, b) => finish(combine(combine(0, a), b)); | 38 static int hash2(a, b) => finish(combine(combine(0, a), b)); |
38 | 39 |
39 static int hash4(a, b, c, d) => | 40 static int hash4(a, b, c, d) => |
40 finish(combine(combine(combine(combine(0, a), b), c), d)); | 41 finish(combine(combine(combine(combine(0, a), b), c), d)); |
41 } | 42 } |
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