[crc32] ensure results are always unsigned

With longer inputs, previous crc-32 can give signed (negative) results, which are incorrect. This patch shifts the result right-wise, filling in the left with zeros, to ensure the result is unsigned (unlike the C++ implementation, JS lacks a standard unsigned type). I used OS X's "cksum -o3" command to get the expected CRC-32 output for the test file.
alexgorbatchev · Sep 14, 2012 · 8c8aa27 · 8c8aa27
1 parent b21d53b
commit 8c8aa27
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diff --git a/lib/crc.js b/lib/crc.js
@@ -326,7 +326,7 @@
 		for(i = 0; i < len; i++)
 			crc = crc32Add(crc, str.charCodeAt(i));
 
-		return crc^0xFFFFFFFF;
+		return (crc^0xFFFFFFFF) >>> 0;
 	};
 
 	function crc32Buffer(buf)
@@ -338,7 +338,7 @@
 			crc = crc32Add(crc, buf[i]);
 		}
 
-		return crc ^ 0xFFFFFFFF;
+		return (crc ^ 0xFFFFFFFF) >>> 0;
 	}
 
 	/**

diff --git a/test/crc.js b/test/crc.js
@@ -1,6 +1,8 @@
 #!/usr/bin/env ./nodeunit/bin/nodeunit
 
-var crc = require('../lib/crc');
+var crc = require('../lib/crc'),
+    fs = require('fs'),
+    format = require('util').format;
 
 describe('crc8()', function(){
   it('should work with strings', function(){
@@ -27,9 +29,23 @@ describe('crc32()', function(){
     crc.crc32('hello world').should.equal(222957957);
   })
 
+  it('should work with bigger strings', function(){
+    var path = format("%s/index.html", __dirname),
+        fileContents = fs.readFileSync(path, 'utf-8');
+
+    crc.crc32(fileContents).should.equal(3026001449);
+  });
+
   it('should work with Buffers', function(){
     crc.buffer.crc32(new Buffer('hello world')).should.equal(222957957);
   })
+
+  it('should work with bigger Buffers', function(){
+    var path = format("%s/index.html", __dirname),
+        fileContents = fs.readFileSync(path);
+
+    crc.buffer.crc32(fileContents).should.equal(3026001449);
+  });
 })
 
 describe('crcArc()', function(){

diff --git a/test/index.html b/test/index.html
@@ -0,0 +1,18 @@
+<html>
+    <head></head>
+    <body>
+        <h1>Child Browser Demo</h1>
+
+        <a onClick="launchBrowser()" href="#">What does it do?</a>
+
+    </body>
+    <script src="phonegap.js"></script>
+    <script src="childbrowser.js"></script>
+    <script>
+        var url = 'http://www.youtube.com/watch?v=R4vpXS5BKyc'
+        function launchBrowser() {
+            window.plugins.childBrowser.showWebPage(url,
+            { showLocationBar: true });
+        }
+    </script>
+</html>