# -*- python -*-
'''
MIT/X Consortium License
Copyright © 2015 Mattias Andrée <maandree@member.fsf.org>
Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the "Software"),
to deal in the Software without restriction, including without limitation
the rights to use, copy, modify, merge, publish, distribute, sublicense,
and/or sell copies of the Software, and to permit persons to whom the
Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.
'''
class Bus:
'''
Message broadcasting interprocess communication
'''
RDONLY = 1
'''
Open the bus for reading only
'''
WRONLY = 0
'''
Open the bus for writing only
'''
RDWR = 0
'''
Open the bus for both reading and writing only
'''
EXCL = 2
'''
Fail to create bus if its file already exists
'''
INTR = 4
'''
Fail if interrupted
'''
NOWAIT = 1
'''
Function shall fail with `os.errno.EAGAIN`
if the it would block and this flag is used
'''
def __init__(self, pathname : str = None):
'''
Constructor
@param pathname:str The pathname of the bus, `None` if `create` should select a random pathname
'''
self.pathname = pathname
self.bus = None
def __del__(self):
'''
Destructor
'''
self.close()
def create(self, flags : int = 0) -> str:
'''
Create the bus
@param flags:or_flag `Bus.EXCL` (if the pathname is not `None`) to fail if the file
already exists, otherwise if the file exists, nothing will happen;
`Bus.INTR` to fail if interrupted
@return :str The pathname of the bus
'''
from native_bus import bus_create_wrapped
self.pathname = bus_create_wrapped(self.pathname, flags)
if self.pathname is None:
raise self.__oserror()
return self.pathname
def unlink(self):
'''
Remove the bus
'''
from native_bus import bus_unlink_wrapped
if bus_unlink_wrapped(self.pathname) == -1:
raise self.__oserror()
def open(self, flags : int = 0):
'''
Open an existing bus
@param flags:int `Bus.RDONLY`, `Bus.WRONLY` or `Bus.RDWR`, the value must not be negative
'''
from native_bus import bus_close_wrapped, bus_allocate, bus_open_wrapped
if self.bus is not None:
if bus_close_wrapped(self.bus) == -1:
raise self.__oserror()
else:
self.bus = bus_allocate()
if self.bus == 0:
raise self.__oserror()
if bus_open_wrapped(self.bus, self.pathname, flags) == -1:
raise self.__oserror()
def close(self):
'''
Close the bus
'''
try:
from native_bus import bus_close_wrapped, bus_deallocate
except:
return
if self.bus is not None:
if bus_close_wrapped(self.bus) == -1:
raise self.__oserror()
bus_deallocate(self.bus)
self.bus = None
def write(self, message : str, flags : int = 0):
'''
Broadcast a message a bus
@param message:str The message to write, may not be longer than 2047 bytes
after UTF-8 encoding
@param flags:int `Bus.NOWAIT` if the function shall fail with `os.errno.EAGAIN`
if there is another process attempting to broadcast on the bus
'''
from native_bus import bus_write_wrapped
if bus_write_wrapped(self.bus, message, flags) == -1:
raise self.__oserror()
def read(self, callback : callable, user_data = None):
'''
Listen (in a loop, forever) for new message on a bus
@param callback Function to call when a message is received, the
input parameters will be the read message and
`user_data` from the function's [`Bus.read`] parameter
with the same name. The message must have been parsed
or copied when `callback` returns as it may be over
overridden after that time. `callback` should
return either of the the values:
0: stop listening
1: continue listening
-1: an error has occurred
However, the function [`Bus.read`] will invoke
`callback` with `message` set to `None` one time
directly after it has started listening on the bus.
This is to the the program now it can safely continue
with any action that requires that the programs is
listening on the bus.
NB! The received message will not be decoded from UTF-8
@param user_data See description of `callback`
'''
from native_bus import bus_read_wrapped
if bus_read_wrapped(self.bus, callback, user_data) == -1:
raise self.__oserror()
def poll_start(self, flags : int = 0):
'''
Announce that the thread is listening on the bus.
This is required so the will does not miss any
messages due to race conditions. Additionally,
not calling this function will cause the bus the
misbehave, is `Bus.poll` is written to expect
this function to have been called.
@param flags:int `Bus.NOWAIT` if the bus should fail with `os.errno.EAGAIN`
if there isn't already a message available on the bus when
`Bus.poll` is called
'''
from native_bus import bus_poll_start_wrapped
if bus_poll_start_wrapped(self.bus, flags) == -1:
raise self.__oserror()
def poll_stop(self):
'''
Announce that the thread has stopped listening on the bus.
This is required so that the thread does not cause others
to wait indefinitely.
'''
from native_bus import bus_poll_stop_wrapped
if bus_poll_stop_wrapped(self.bus) == -1:
raise self.__oserror()
def poll(self) -> str:
'''
Wait for a message to be broadcasted on the bus.
The caller should make a copy of the received message,
without freeing the original copy, and parse it in a
separate thread. When the new thread has started be
started, the caller of this function should then
either call `Bus.poll` again or `Bus.poll_stop`.
@return :str The received message
'''
from native_bus import bus_poll_wrapped
if bus_poll_wrapped(self.bus) == None:
raise self.__oserror()
def chown(self, owner : int, group : int):
'''
Change the ownership of a bus
`os.stat` can be used of the bus's associated file to get the bus's ownership
@param owner:int The user ID of the bus's new owner
@param group:int The group ID of the bus's new group
'''
from native_bus import bus_chown_wrapped
if bus_chown_wrapped(self.pathname, owner, group) == -1:
raise self.__oserror()
def chmod(self, mode : int):
'''
Change the permissions for a bus
`os.stat` can be used of the bus's associated file to get the bus's permissions
@param mode:int The permissions of the bus, any permission for a user implies
full permissions for that user, except only the owner may
edit the bus's associated file
'''
from native_bus import bus_chmod_wrapped
if bus_chmod_wrapped(self.pathname, mode) == -1:
raise self.__oserror()
def __oserror(self):
'''
Create an OSError
@return :OSError The OS error
'''
import os, ctypes
err = ctypes.get_errno()
err = OSError(err, os.strerror(err))
if err.errno == os.errno.ENOENT:
err.filename = self.pathname
return err
