punycode: Test for integer overflow

lib/punycode.js

@@ -28,6 +28,7 @@ var SKEW = 38;
 var DAMP = 700; // initial bias scaler
 var INITIAL_N = 128;
 var INITIAL_BIAS = 72;
+var MAX_INTEGER = Math.pow(2, 53);
 
 function adapt_bias(delta, n_points, is_first) {
   // scale back, then increase delta
@@ -151,7 +152,7 @@ function encode(input) {
     for (var i = 0; i < len; ++i) {
       var c = input[i];
       if (c < n) {
-        if (++delta == 0) {
+        if (++delta == MAX_INTEGER) {
           throw new Error('Delta overflow.');
         }
       }