py-libp2p/libp2p/protocol_muxer/multiselect.py
2019-01-10 20:45:03 +08:00

97 lines
3.2 KiB
Python

from .multiselect_muxer_interface import IMultiselectMuxer
from .multiselect_communicator import MultiselectCommunicator
MULTISELECT_PROTOCOL_ID = "/multistream/1.0.0"
PROTOCOL_NOT_FOUND_MSG = "na"
class Multiselect(IMultiselectMuxer):
"""
Multiselect module that is responsible for responding to
a multiselect client and deciding on
a specific protocol and handler pair to use for communication
"""
def __init__(self):
self.handlers = {}
def add_handler(self, protocol, handler):
"""
Store the handler with the given protocol
:param protocol: protocol name
:param handler: handler function
"""
self.handlers[protocol] = handler
async def negotiate(self, stream):
"""
Negotiate performs protocol selection
:param stream: stream to negotiate on
: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)
# Read and respond to commands until a valid protocol ID is sent
while True:
# Read message
command = await communicator.read_stream_until_eof()
# Command is ls or a protocol
if command == "ls":
# TODO: handle ls command
pass
else:
protocol = command
if protocol in self.handlers:
# Tell counterparty we have decided on a protocol
await communicator.write(protocol)
# Return the decided on protocol
return protocol, self.handlers[protocol]
# Tell counterparty this protocol was not found
await communicator.write(PROTOCOL_NOT_FOUND_MSG)
async def handshake(self, communicator):
"""
Perform handshake to agree on multiselect protocol
:param communicator: communicator to use
:raise Exception: error in handshake
"""
# TODO: Use format used by go repo for messages
# Send our MULTISELECT_PROTOCOL_ID to other party
await communicator.write(MULTISELECT_PROTOCOL_ID)
# Read in the protocol ID from other party
handshake_contents = await communicator.read_stream_until_eof()
# Confirm that the protocols are the same
if not validate_handshake(handshake_contents):
raise MultiselectError("multiselect protocol ID mismatch")
# Handshake succeeded if this point is reached
def validate_handshake(handshake_contents):
"""
Determine if handshake is valid and should be confirmed
:param handshake_contents: contents of handshake message
:return: true if handshake is complete, false otherwise
"""
# TODO: Modify this when format used by go repo for messages
# is added
return handshake_contents == MULTISELECT_PROTOCOL_ID
class MultiselectError(ValueError):
"""Raised when an error occurs in multiselect process"""