BufferWriter uses provided buffer

hbmqtt/adapters.py

@@ -173,8 +173,8 @@ class BufferReader(ReaderAdapter):
     Byte Buffer reader adapter
     This adapter simply adapt reading a byte buffer.
     """
-    def __init__(self, data: bytes):
-        self._stream = io.BytesIO(data)
+    def __init__(self, buffer: bytes):
+        self._stream = io.BytesIO(buffer)
 
     @asyncio.coroutine
     def read(self, n=-1) -> bytes:
@@ -186,8 +186,8 @@ class BufferWriter(WriterAdapter):
     ByteBuffer writer adapter
     This adapter simply adapt writing to a byte buffer
     """
-    def __init__(self):
-        self._stream = io.BytesIO(b'')
+    def __init__(self, buffer=b''):
+        self._stream = io.BytesIO(buffer)
 
     def write(self, data):
         """
@@ -197,7 +197,7 @@ class BufferWriter(WriterAdapter):
 
     @asyncio.coroutine
     def drain(self):
-        self._stream = io.BytesIO(b'')
+        pass
 
     def get_buffer(self):
         return self._stream.getvalue()