add set function to Base58

lib/base58.js

@@ -1,9 +1,15 @@
 var bs58 = require('bs58');
 
-var Base58 = function Base58(buf) {
+var Base58 = function Base58(obj) {
   if (!(this instanceof Base58))
-    return new Base58(buf);
-  this.buf = buf;
+    return new Base58(obj);
+  if (obj)
+    this.set(obj);
+};
+
+Base58.prototype.set = function(obj) {
+  this.buf = obj.buf || this.buf || undefined;
+  return this;
 };
 
 Base58.encode = function(buf) {

test/test.base58.js

@@ -15,6 +15,14 @@ describe('Base58', function() {
     should.exist(b58);
   });
 
+  describe('#set', function() {
+    
+    it('should set a blank buffer', function() {
+      Base58().set({buf: new Buffer([])});
+    });
+
+  });
+
   describe('@encode', function() {
 
     it('should encode the buffer accurately', function() {
@@ -67,7 +75,7 @@ describe('Base58', function() {
   describe('#toBuffer', function() {
 
     it('should return the buffer', function() {
-      var b58 = Base58(buf);
+      var b58 = Base58({buf: buf});
       b58.buf.toString('hex').should.equal(buf.toString('hex'));
     });
 
@@ -76,7 +84,7 @@ describe('Base58', function() {
   describe('#toString', function() {
 
     it('should return the buffer', function() {
-      var b58 = Base58(buf);
+      var b58 = Base58({buf: buf});
       b58.toString().should.equal(enc);
     });