cs.packetstream 20211208

general purpose bidirectional packet stream connection

A general purpose bidirectional packet stream connection.

Latest release 20211208:

• Packet.eq: only test .rq_type if .is_request.
• Update tests for changes.

Class Packet(cs.binary.SimpleBinary,types.SimpleNamespace,cs.binary.AbstractBinary,cs.binary.BinaryMixin)

A protocol packet.

Method Packet.__str__(self)

pylint: disable=signature-differs

Method Packet.parse(bfr)

Parse a packet from a buffer.

Method Packet.transcribe(self)

Transcribe this packet.

Class PacketConnection

A bidirectional binary connection for exchanging requests and responses.

Method PacketConnection.__init__(self, recv, send, request_handler=None, name=None, packet_grace=None, tick=None)

Initialise the PacketConnection.

Parameters:

• recv: inbound binary stream. If this is an int it is taken to be an OS file descriptor, otherwise it should be a cs.buffer.CornuCopyBuffer or a file like object with a read1 or read method.
• send: outbound binary stream. If this is an int it is taken to be an OS file descriptor, otherwise it should be a file like object with .write(bytes) and .flush() methods. For a file descriptor sending is done via an os.dup() of the supplied descriptor, so the caller remains responsible for closing the original descriptor.
• packet_grace: default pause in the packet sending worker to allow another packet to be queued before flushing the output stream. Default: DEFAULT_PACKET_GRACEs. A value of 0 will flush immediately if the queue is empty.
• request_handler: an optional callable accepting (rq_type, flags, payload). The request_handler may return one of 5 values on success:
  • None: response will be 0 flags and an empty payload.
  • int: flags only. Response will be the flags and an empty payload.
  • bytes: payload only. Response will be 0 flags and the payload.
  • str: payload only. Response will be 0 flags and the str encoded as bytes using UTF-8.
  • (int, bytes): Specify flags and payload for response. An unsuccessful request should raise an exception, which will cause a failure response packet.
• tick: optional tick parameter, default None. If None, do nothing. If a Boolean, call tick_fd_2 if true, otherwise do nothing. Otherwise tick should be a callable accepting a byteslike value.

Method PacketConnection.do(self, *a, **kw)

Wrapper function to check that this instance is not closed.

Method PacketConnection.join(self)

Wait for the receive side of the connection to terminate.

Method PacketConnection.request(self, *a, **kw)

Wrapper function to check that this instance is not closed.

Method PacketConnection.shutdown(self, *a, **kw)

Shut down the PacketConnection, optionally blocking for outstanding requests.

Parameters: block: block for outstanding requests, default False.

Class Request_State(builtins.tuple)

RequestState(decode_response, result)

Property Request_State.decode_response

Alias for field number 0

Property Request_State.result

Alias for field number 1

Function tick_fd_2(bs)

A low level tick function to write a short binary tick to the standard error file descriptor.

This may be called by the send and receive workers to give an indication of activity type.

Release Log

Release 20211208:

• Packet.eq: only test .rq_type if .is_request.
• Update tests for changes.

Release 20210306:

• Port to new cs.binary.Binary* classes.
• Some refactors and small fixes.

Release 20191004:

• PacketConnection: new optional parameter packet_grace to tune the send delay for additional packets before a flush, default DEFAULT_PACKET_GRACE (0.01s), 0 for no delay.
• Add a crude packet level activity ticker.

Release 20190221: DISTINFO requirement updates.

Release 20181228: Initial PyPI release.