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Unified Diff: sdk/lib/html/html_common/jenkins_smi_hash.dart

Issue 18034021: Fixing analyzer warnings on overloading == but not get hashCode. (Closed) Base URL: https://dart.googlecode.com/svn/branches/bleeding_edge/dart
Patch Set: Created 7 years, 6 months ago
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Index: sdk/lib/html/html_common/jenkins_smi_hash.dart
diff --git a/sdk/lib/html/html_common/jenkins_smi_hash.dart b/sdk/lib/html/html_common/jenkins_smi_hash.dart
new file mode 100644
index 0000000000000000000000000000000000000000..cf5913f3e4f1704812d8547a653045a1798db923
--- /dev/null
+++ b/sdk/lib/html/html_common/jenkins_smi_hash.dart
@@ -0,0 +1,47 @@
+// Copyright (c) 2013, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+part of html_common;
+
+/**
+ * This is the [Jenkins hash function][1] but using masking to keep
+ * values in SMI range.
+ *
+ * [1]: http://en.wikipedia.org/wiki/Jenkins_hash_function
+ *
+ * Use:
+ * Hash each value with the hash of the previous value, then get the final
+ * hash by calling finish.
+ *
+ * var hash = 0;
+ * for (var value in values) {
+ * hash = JenkinsSmiHash.combine(hash, value.hashCode);
+ * }
+ * hash = JenkinsSmiHash.finish(hash);
+ */
+class JenkinsSmiHash {
+ // TODO: Bug 11617- This class should be optimized and standardized elsewhere.
+
+ static int combine(int hash, int value) {
+ hash = 0x1fffffff & (hash + value);
+ hash = 0x1fffffff & (hash + ((0x0007ffff & hash) << 10));
+ return hash ^ (hash >> 6);
+ }
+
+ static int finish(int hash) {
+ hash = 0x1fffffff & (hash + ((0x03ffffff & hash) << 3));
+ hash = hash ^ (hash >> 11);
+ return 0x1fffffff & (hash + ((0x00003fff & hash) << 15));
+ }
+
+ static int hash2(a, b) => JenkinsSmiHash.finish(
sra1 2013/06/28 22:25:02 Do you need the class name here?
blois 2013/06/28 22:35:37 Done.
+ JenkinsSmiHash.combine(
+ JenkinsSmiHash.combine(0, a), b));
+
+ static int hash4(a, b, c, d) => JenkinsSmiHash.finish(
+ JenkinsSmiHash.combine(
+ JenkinsSmiHash.combine(
+ JenkinsSmiHash.combine(
+ JenkinsSmiHash.combine(0, a), b), c), d));
+}

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