Implement String.hashCode.

dart/frog/leg/lib/js_helper.dart

 // Copyright (c) 2012, 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.
 
 #library('js_helper');
 
 #import('coreimpl.dart');
 
 #source('date_helper.dart');
 #source('regexp_helper.dart');
@@ skipping 341 matching lines @@
     return value;
   }
 }
 
 builtin$charCodeAt$1(var receiver, int index) {
   checkNull(receiver);
   if (receiver is String) {
     if (index is !num) throw new IllegalArgumentException(index);
     if (index < 0) throw new IndexOutOfRangeException(index);
     if (index >= receiver.length) throw new IndexOutOfRangeException(index);
-    return JS("string", @"$0.charCodeAt($1)", receiver, index);
+    return JS("int", @"$0.charCodeAt($1)", receiver, index);
   } else {
     return UNINTERCEPTED(receiver.charCodeAt(index));
   }
 }
 
 builtin$isEmpty$0(receiver) {
   checkNull(receiver);
   if (receiver is String || isJsArray(receiver)) {
     return JS("bool", @"$0.length === 0", receiver);
   }
@@ skipping 800 matching lines @@
 
   static num pow(num value, num exponent) {
     checkNum(value);
     checkNum(exponent);
     return JS("num", @"Math.pow($0, $1)", value, exponent);
   }
 
   static double random() => JS("double", @"Math.random()");
 }
 
+/**
+ * This is the [Jenkins hash function][1], but always using XOR

[kasperl, 2012/02/28 13:58:42]

Update comment to match reality.

[ahe, 2012/02/28 17:26:10]

Done.

+ * instead of addition to keep the hash value in 32bit. This was
+ * inspired by jmesserly's work in Frog.
+ *
+ * [1]: http://en.wikipedia.org/wiki/Jenkins_hash_function
+ */
 builtin$hashCode$0(receiver) {
-  if (receiver is num) return receiver & 0x1FFFFFFF;
-  if (receiver is String) {
-    throw 'String.hashCode is not implemented';
+  if (receiver is num) return JS('int', @'$0 & 0x1FFFFFFF', receiver);

[Lasse Reichstein Nielsen, 2012/02/28 14:12:16]

That's a somewhat bad hash for doubles (specifically fractions are all the
same).

[ahe, 2012/02/28 17:26:10]

What do you suggest I use instead?

+  if (receiver is !String) return UNINTERCEPTED(receiver.hashCode());

[Lasse Reichstein Nielsen, 2012/02/28 14:12:16]

What about arrays and booleans?

[ahe, 2012/02/28 17:26:10]

I checked, neither List nor bool are hashable.

+  int hash = 0;
+  int length = JS('int', @'$0.length', receiver);
+  for (int i = 0; i < length; i++) {
+    hash = 0x1fffffff & (hash + JS('int', @'$0.charCodeAt($1)', receiver, i));
+    hash = 0x1fffffff & (hash + JS("int", @"$0 << $1", 0x0007ffff & hash, 10));
+    hash ^= hash >> 6;
   }
-  if (isJsArray(receiver)) {
-    throw 'List.hashCode is not implemented';
-  }
-  return UNINTERCEPTED(receiver.hashCode());
+  hash = 0x1fffffff & (hash + JS("int", @"$0 << $1", 0x03ffffff & hash, 3));
+  hash ^= hash >> 11;
+  return 0x1fffffff & (hash + JS("int", @"$0 << $1", 0x00003fff & hash, 15));
 }
 
 // TODO(ahe): Dynamic may be overridden.
 builtin$get$dynamic(receiver) => receiver;
 
 /**
  * Called by generated code to capture the stacktrace before throwing
  * an exception.
  */
 captureStackTrace(ex) {
@@ skipping 61 matching lines @@
       }
     }
   } else if (JS('bool', @'$0 instanceof RangeError', ex)) {
     var message = JS('String', @'$0.message', ex);
     if (message.contains('call stack')) {
       return new StackOverflowException();
     }
   }
   return ex;
 }