Improve unpack_message with multiple versions

Reuse unpack_message method from v0x01.common.utils and v0x04.common.utils
Fix kytos#344

pyof/utils.py

@@ -3,11 +3,12 @@
 This package was moved from kytos/of_core for the purpose of creating a generic
 method to perform package unpack independent of the OpenFlow version.
 """
-from pyof import v0x01, v0x04
+from pyof.v0x01.common.utils import Header0x01, unpack_message_v0x01
+from pyof.v0x04.common.utils import unpack_message as unpack_message_v0x04
 from pyof.foundation.exceptions import UnpackException
 
-PYOF_VERSION_LIBS = {0x01: v0x01,
-                     0x04: v0x04}
+PYOF_UNPACK_MESSAGE = {0x01: unpack_message_v0x01,
+                       0x04: unpack_message_v0x04}
 
 
 def validate_packet(packet):
@@ -45,23 +46,15 @@ def unpack(packet):
 
     """
     validate_packet(packet)
-
     version = packet[0]
+
     try:
-        pyof_lib = PYOF_VERSION_LIBS[version]
+        unpack_message = PYOF_UNPACK_MESSAGE[version]
     except KeyError:
         raise UnpackException('Version not supported')
 
     try:
-        header = pyof_lib.common.header.Header()
-        header.unpack(packet[:header.get_size()])
-        message = pyof_lib.common.utils.new_message_from_header(header)
-
-        binary_data = packet[header.get_size():]
-        binary_data_size = header.length - header.get_size()
-
-        if binary_data and len(binary_data) == binary_data_size:
-            message.unpack(binary_data)
-        return message
+        message = unpack_message(packet)
     except (UnpackException, ValueError) as exception:
         raise UnpackException(exception)
+    return message

pyof/v0x04/common/utils.py

@@ -166,7 +166,15 @@ def new_message_from_header(header):
 
 
 def unpack_message(buffer):
-    """Unpack the whole buffer, including header pack."""
+    """Unpack the whole buffer, including header pack.
+
+    Args:
+        buffer (bytes): Bytes representation of a openflow message.
+
+    Returns:
+        object: Instance of openflow message.
+
+    """
     hdr_size = Header().get_size()
     hdr_buff, msg_buff = buffer[:hdr_size], buffer[hdr_size:]
     header = Header()