pipe_server_ravelled

#!/usr/bin/python3
#+
# DBussy example -- demonstrate how to pass file descriptors
# over D-Bus. This is the server side, which receives requests
# 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. See the accompanying
# pipe_client script for an example of how to communicate with
# this server.
#
# 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 signal
import dbussy as dbus
from dbussy import \
    DBUS
import ravel

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

#+
# Interface
#-

pipes = {}
  # created pipes, indexed by object path

@ravel.interface(ravel.INTERFACE.SERVER, name = my_iface_name)
class PipeServer :

    @ravel.method \
      (
        name = "get",
        in_signature = "b",
        out_signature = "h",
        path_keyword = "path",
        arg_keys = ("writing",),
        result_keyword = "result",
      )
    def handle_get(self, path, writing, result) :
        if path not in pipes :
            sys.stderr.write("Create pipes for %s\n" % repr(path)) # debug
            read_side, write_side = os.pipe()
            pipes[path] = (read_side, write_side)
        #end if
        result[0] = pipes[path][writing]
    #end handle_get

#end PipeServer

signal.signal(signal.SIGINT, signal.SIG_DFL) # abort without raising KeyboardInterrupt on CTRL/C

bus = ravel.session_bus()
bus.attach_asyncio()
bus.request_name(bus_name = my_bus_name, flags = DBUS.NAME_FLAG_DO_NOT_QUEUE)
bus.register \
  (
    path = "/",
    fallback = True,
    interface = PipeServer()
  )
bus.loop.run_forever()