Add delim_encode and delim_read

- Add `StreamCommunicator` and `RawConnectionCommunicator`, read/write
messages with delim codec, with `IMuxedStream` and `IRawConnection`
respectively.
- Use it in `Multiselect` and `MultiselectClient`.

libp2p/protocol_muxer/multiselect.py

@@ -1,8 +1,7 @@
 from typing import Dict, Tuple
 
-from libp2p.typing import NegotiableTransport, StreamHandlerFn, TProtocol
+from libp2p.typing import StreamHandlerFn, TProtocol
 
-from .multiselect_communicator import MultiselectCommunicator
 from .multiselect_communicator_interface import IMultiselectCommunicator
 from .multiselect_muxer_interface import IMultiselectMuxer
 
@@ -31,7 +30,7 @@ class Multiselect(IMultiselectMuxer):
         self.handlers[protocol] = handler
 
     async def negotiate(
-        self, stream: NegotiableTransport
+        self, communicator: IMultiselectCommunicator
     ) -> Tuple[TProtocol, StreamHandlerFn]:
         """
         Negotiate performs protocol selection
@@ -39,8 +38,6 @@ class Multiselect(IMultiselectMuxer):
         :return: selected protocol name, handler function
         :raise Exception: negotiation failed exception
         """
-        # Create a communicator to handle all communication across the stream
-        communicator = MultiselectCommunicator(stream)
 
         # Perform handshake to ensure multiselect protocol IDs match
         await self.handshake(communicator)
@@ -48,7 +45,7 @@ class Multiselect(IMultiselectMuxer):
         # Read and respond to commands until a valid protocol ID is sent
         while True:
             # Read message
-            command = await communicator.read_stream_until_eof()
+            command = await communicator.read()
 
             # Command is ls or a protocol
             if command == "ls":
@@ -78,7 +75,7 @@ class Multiselect(IMultiselectMuxer):
         await communicator.write(MULTISELECT_PROTOCOL_ID)
 
         # Read in the protocol ID from other party
-        handshake_contents = await communicator.read_stream_until_eof()
+        handshake_contents = await communicator.read()
 
         # Confirm that the protocols are the same
         if not validate_handshake(handshake_contents):