remove Message objects + rewrite server startup

Change-Id: Ide72fb915c3ca93c74edadd8952853508e677de7
Reviewed-on: https://forge.frm2.tum.de/review/19199
Tested-by: JenkinsCodeReview <bjoern_pedersen@frm2.tum.de>
Reviewed-by: Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>

secop/protocol/interface/__init__.py

@@ -19,12 +19,47 @@
 #   Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>
 #
 # *****************************************************************************
-"""provide server interfaces to be used by clients"""
-from __future__ import absolute_import
 
-from .tcp import TCPServer
+import json
 
-INTERFACES = {'tcp': TCPServer, }
+EOL = b'\n'
+SPACE = b' '
 
-# for 'from protocol.interface import *' to only import the dict
-__ALL__ = ['INTERFACES']
+def encode_msg_frame(action, specifier=None, data=None):
+    """ encode a msg_tripel into an msg_frame, ready to be sent
+
+    action (and optional specifier) are unicode strings,
+    data may be an json-yfied python object"""
+    action = action.encode('utf-8')
+    if specifier is None:
+        # implicit: data is None
+        return b''.join((action, EOL))
+    specifier = specifier.encode('utf-8')
+    if data:
+        data = json.dumps(data).encode('utf-8')
+        return b''.join((action, SPACE, specifier, SPACE, data, EOL))
+    return b''.join((action, SPACE, specifier, EOL))
+
+
+def get_msg(_bytes):
+    """try to deframe the next msg in (binary) input
+    always return a tupel (msg, remaining_input)
+    msg may also be None
+    """
+    if EOL not in _bytes:
+        return None, _bytes
+    return _bytes.split(EOL, 1)
+
+
+def decode_msg(msg):
+    """decode the (binary) msg into a (unicode) msg_tripel"""
+    # check for leading/trailing CR and remove it
+    res = msg.split(b' ', 2)
+    action = res[0].decode('utf-8')
+    if len(res) == 1:
+        return action, None, None
+    specifier = res[1].decode('utf-8')
+    if len(res) == 2:
+        return action, specifier, None
+    data = json.loads(res[2].decode('utf-8'))
+    return action, specifier, data