michael@0: 
michael@0: expected = '1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,';
michael@0: function slice(a, b) {
michael@0:   return expected;
michael@0: }
michael@0: function f() {
michael@0:   var length = 4;
michael@0:   var index = 0;
michael@0:   function get3() {
michael@0:     if (length - index < 3)
michael@0:       return null;
michael@0:     return slice(index, ++index);
michael@0:   }
michael@0:   var bytes = null;
michael@0:   while (bytes = get3()) {  }
michael@0: }
michael@0: f();