Merge pull request #1408 from parrt/ghosthope-master

Javascript performance improvement (hash function)

contributors.txt

@@ -119,3 +119,4 @@ YYYY/MM/DD, github id, Full name, email
 2016/11/06, janyou, Janyou, janyou.antlr@outlook.com
 2016/11/20, marcohu, Marco Hunsicker, antlr@hunsicker.de
 2016/09/02, lygav, Vladimir (Vladi) Lyga, lyvladi@gmail.com
+2016/09/23, ghosthope, Dmitry Shakhtanov, sudstrike@gmail.com

runtime/JavaScript/src/antlr4/Utils.js

@@ -2,18 +2,63 @@ function arrayToString(a) {
 	return "[" + a.join(", ") + "]";
 }
 
-String.prototype.hashCode = function(s) {
-	var hash = 0;
-	if (this.length === 0) {
-		return hash;
-	}
-	for (var i = 0; i < this.length; i++) {
-		var character = this.charCodeAt(i);
-		hash = ((hash << 5) - hash) + character;
-		hash = hash & hash; // Convert to 32bit integer
-	}
-	return hash;
-};
+    String.prototype.seed = String.prototype.seed || Math.round(Math.random() * Math.pow(2, 32));;
+
+    String.prototype.hashCode = function () {
+        var remainder, bytes, h1, h1b, c1, c1b, c2, c2b, k1, i,
+            key = this.toString();
+
+        remainder = key.length & 3; // key.length % 4
+        bytes = key.length - remainder;
+        h1 = String.prototype.seed;
+        c1 = 0xcc9e2d51;
+        c2 = 0x1b873593;
+        i = 0;
+
+        while (i < bytes) {
+            k1 =
+                ((key.charCodeAt(i) & 0xff)) |
+                ((key.charCodeAt(++i) & 0xff) << 8) |
+                ((key.charCodeAt(++i) & 0xff) << 16) |
+                ((key.charCodeAt(++i) & 0xff) << 24);
+            ++i;
+
+            k1 = ((((k1 & 0xffff) * c1) + ((((k1 >>> 16) * c1) & 0xffff) << 16))) & 0xffffffff;
+            k1 = (k1 << 15) | (k1 >>> 17);
+            k1 = ((((k1 & 0xffff) * c2) + ((((k1 >>> 16) * c2) & 0xffff) << 16))) & 0xffffffff;
+
+            h1 ^= k1;
+            h1 = (h1 << 13) | (h1 >>> 19);
+            h1b = ((((h1 & 0xffff) * 5) + ((((h1 >>> 16) * 5) & 0xffff) << 16))) & 0xffffffff;
+            h1 = (((h1b & 0xffff) + 0x6b64) + ((((h1b >>> 16) + 0xe654) & 0xffff) << 16));
+        }
+
+        k1 = 0;
+
+        switch (remainder) {
+            case 3:
+                k1 ^= (key.charCodeAt(i + 2) & 0xff) << 16;
+            case 2:
+                k1 ^= (key.charCodeAt(i + 1) & 0xff) << 8;
+            case 1:
+                k1 ^= (key.charCodeAt(i) & 0xff);
+
+                k1 = (((k1 & 0xffff) * c1) + ((((k1 >>> 16) * c1) & 0xffff) << 16)) & 0xffffffff;
+                k1 = (k1 << 15) | (k1 >>> 17);
+                k1 = (((k1 & 0xffff) * c2) + ((((k1 >>> 16) * c2) & 0xffff) << 16)) & 0xffffffff;
+                h1 ^= k1;
+        }
+
+        h1 ^= key.length;
+
+        h1 ^= h1 >>> 16;
+        h1 = (((h1 & 0xffff) * 0x85ebca6b) + ((((h1 >>> 16) * 0x85ebca6b) & 0xffff) << 16)) & 0xffffffff;
+        h1 ^= h1 >>> 13;
+        h1 = ((((h1 & 0xffff) * 0xc2b2ae35) + ((((h1 >>> 16) * 0xc2b2ae35) & 0xffff) << 16))) & 0xffffffff;
+        h1 ^= h1 >>> 16;
+
+        return h1 >>> 0;
+    };
 
 function standardEqualsFunction(a,b) {
 	return a.equals(b);