sha3 method signature

lib/abi.js

@@ -140,7 +140,6 @@ var toAbiInput = function (json, methodName, params) {
         return;
     }
 
-    bytes = "0x" + padLeft(index.toString(16), 2);
     var method = json[index];
 
     for (var i = 0; i < method.inputs.length; i++) {
@@ -259,7 +258,20 @@ var outputParser = function (json) {
     return parser;
 };
 
+var methodSignature = function (json, name) {
+    var method = json[findMethodIndex(json, name)];
+    var result = name + '(';
+    var inputTypes = method.inputs.map(function (inp) {
+        return inp.type;
+    });
+    result += inputTypes.join(',');
+    result += ')';
+
+    return web3.sha3(result);
+};
+
 module.exports = {
     inputParser: inputParser,
-    outputParser: outputParser
+    outputParser: outputParser,
+    methodSignature: methodSignature
 };