pipe_client_ravelled

#!/usr/bin/python3
#+
# DBussy example -- demonstrate how to pass file descriptors
# over D-Bus. This is the client side, which sends requests
# to the server to create either a transmit or receive pipe
# matching a given key value. Two clients specifying the
# same key can then exchange messages over the pipe.
#
# Invoke this script as either
#
#     pipe_client_ravelled «path» write «message»
# or
#     pipe_client_ravelled «path» read
#
# The “write” form will open the write end of the pipe identified
# by «path», which must be a valid D-Bus object path, and write
# the given «message» text to it. The “read” form will open the read
# end of the pipe identified by «path», and read and display a
# message written to it.
#
# Copyright 2018 by Lawrence D'Oliveiro <ldo@geek-central.gen.nz>. This
# script is licensed CC0
# <https://creativecommons.org/publicdomain/zero/1.0/>; do with it
# what you will.
#-

import sys
import os
import getopt
import dbussy as dbus
from dbussy import \
    DBUS, \
    Introspection
import ravel

my_bus_name = "com.example.pipes"
my_iface_name = "com.example.pipes"

loop = dbus.get_event_loop()

#+
# Server proxy interface
#-

Server = ravel.def_proxy_interface \
  (
    ravel.INTERFACE.CLIENT,
    name = "Server",
    introspected =
        Introspection.Interface
          (
            name = my_iface_name,
            methods =
                (
                    Introspection.Interface.Method
                      (
                        name = "get",
                        args =
                            (
                                Introspection.Interface.Method.Arg
                                  (
                                    name = "writing",
                                    type = chr(DBUS.TYPE_BOOLEAN),
                                    direction = Introspection.DIRECTION.IN,
                                  ),
                                Introspection.Interface.Method.Arg
                                  (
                                    type = chr(DBUS.TYPE_UNIX_FD),
                                    direction = Introspection.DIRECTION.OUT,
                                  ),
                            ),
                      ),
                )
          ),
    is_async = True
  )

#+
# Mainline
#-

if len(sys.argv) not in (3, 4) :
    raise getopt.GetoptError("usage: %s «path» read|write [«message»]" % sys.argv[0])
#end if
path = sys.argv[1]
writing = {"read" : False, "write" : True}[sys.argv[2]]
if len(sys.argv) != 3 + writing :
    raise getopt.GetoptError("message arg required for write, not read")
#end if
if writing :
    message = sys.argv[3]
#end if

bus = ravel.session_bus()
bus.attach_asyncio(loop)
server = Server \
  (
    connection = bus.connection,
    dest = my_bus_name
  )

async def mainline() :
    global message
    pipe, = await server[path].get(writing = writing)
    if writing :
        os.write(pipe, message.encode())
    else :
        message = os.read(pipe, 80)
        sys.stdout.write("message: %s\n" % repr(message))
    #end if
    os.close(pipe)
#end mainline

loop.run_until_complete(mainline())