more convenient bufferreader

lib/bufferreader.js

@@ -1,10 +1,15 @@
 var BN = require('./bn');
 
-var BufferReader = function BufferReader(obj) {
+var BufferReader = function BufferReader(buf) {
   if (!(this instanceof BufferReader))
-    return new BufferReader(obj);
-  if (obj)
+    return new BufferReader(buf);
+  if (Buffer.isBuffer(buf)) {
+    this.set({buf: buf});
+  }
+  else if (buf) {
+    var obj = buf;
     this.set(obj);
+  }
 };
 
 BufferReader.prototype.set = function(obj) {

test/bufferreader.js

@@ -7,6 +7,15 @@ describe('BufferReader', function() {
   it('should make a new BufferReader', function() {
     var br = new BufferReader();
     should.exist(br);
+    br = BufferReader();
+    should.exist(br);
+  });
+
+  it('should create a new bufferreader with a buffer', function() {
+    var buf = new Buffer(0);
+    var br = new BufferReader(buf);
+    should.exist(br);
+    Buffer.isBuffer(br.buf).should.equal(true);
   });
 
   describe('#set', function() {