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Side by Side Diff: sdk/lib/html/html_common/jenkins_smi_hash.dart

Issue 25808002: Move Rectangle and Point into dart:math. (Closed) Base URL: https://dart.googlecode.com/svn/branches/bleeding_edge/dart
Patch Set: Created 7 years, 2 months ago
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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
3 // BSD-style license that can be found in the LICENSE file.
4
5 part of html_common;
6
7 /**
8 * This is the [Jenkins hash function][1] but using masking to keep
9 * values in SMI range.
10 *
11 * [1]: http://en.wikipedia.org/wiki/Jenkins_hash_function
12 *
13 * Use:
14 * Hash each value with the hash of the previous value, then get the final
15 * hash by calling finish.
16 *
17 * var hash = 0;
18 * for (var value in values) {
19 * hash = JenkinsSmiHash.combine(hash, value.hashCode);
20 * }
21 * hash = JenkinsSmiHash.finish(hash);
22 */
23 class JenkinsSmiHash {
24 // TODO: Bug 11617- This class should be optimized and standardized elsewhere.
25
26 static int combine(int hash, int value) {
27 hash = 0x1fffffff & (hash + value);
28 hash = 0x1fffffff & (hash + ((0x0007ffff & hash) << 10));
29 return hash ^ (hash >> 6);
30 }
31
32 static int finish(int hash) {
33 hash = 0x1fffffff & (hash + ((0x03ffffff & hash) << 3));
34 hash = hash ^ (hash >> 11);
35 return 0x1fffffff & (hash + ((0x00003fff & hash) << 15));
36 }
37
38 static int hash2(a, b) => finish(combine(combine(0, a), b));
39
40 static int hash4(a, b, c, d) =>
41 finish(combine(combine(combine(combine(0, a), b), c), d));
42 }
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