132 lines
5 KiB
Python
132 lines
5 KiB
Python
"""Win32 compatibility utilities."""
|
|
|
|
#-----------------------------------------------------------------------------
|
|
# Copyright (C) PyZMQ Developers
|
|
# Distributed under the terms of the Modified BSD License.
|
|
#-----------------------------------------------------------------------------
|
|
|
|
import os
|
|
|
|
# No-op implementation for other platforms.
|
|
class _allow_interrupt(object):
|
|
"""Utility for fixing CTRL-C events on Windows.
|
|
|
|
On Windows, the Python interpreter intercepts CTRL-C events in order to
|
|
translate them into ``KeyboardInterrupt`` exceptions. It (presumably)
|
|
does this by setting a flag in its "console control handler" and
|
|
checking it later at a convenient location in the interpreter.
|
|
|
|
However, when the Python interpreter is blocked waiting for the ZMQ
|
|
poll operation to complete, it must wait for ZMQ's ``select()``
|
|
operation to complete before translating the CTRL-C event into the
|
|
``KeyboardInterrupt`` exception.
|
|
|
|
The only way to fix this seems to be to add our own "console control
|
|
handler" and perform some application-defined operation that will
|
|
unblock the ZMQ polling operation in order to force ZMQ to pass control
|
|
back to the Python interpreter.
|
|
|
|
This context manager performs all that Windows-y stuff, providing you
|
|
with a hook that is called when a CTRL-C event is intercepted. This
|
|
hook allows you to unblock your ZMQ poll operation immediately, which
|
|
will then result in the expected ``KeyboardInterrupt`` exception.
|
|
|
|
Without this context manager, your ZMQ-based application will not
|
|
respond normally to CTRL-C events on Windows. If a CTRL-C event occurs
|
|
while blocked on ZMQ socket polling, the translation to a
|
|
``KeyboardInterrupt`` exception will be delayed until the I/O completes
|
|
and control returns to the Python interpreter (this may never happen if
|
|
you use an infinite timeout).
|
|
|
|
A no-op implementation is provided on non-Win32 systems to avoid the
|
|
application from having to conditionally use it.
|
|
|
|
Example usage:
|
|
|
|
.. sourcecode:: python
|
|
|
|
def stop_my_application():
|
|
# ...
|
|
|
|
with allow_interrupt(stop_my_application):
|
|
# main polling loop.
|
|
|
|
In a typical ZMQ application, you would use the "self pipe trick" to
|
|
send message to a ``PAIR`` socket in order to interrupt your blocking
|
|
socket polling operation.
|
|
|
|
In a Tornado event loop, you can use the ``IOLoop.stop`` method to
|
|
unblock your I/O loop.
|
|
"""
|
|
|
|
def __init__(self, action=None):
|
|
"""Translate ``action`` into a CTRL-C handler.
|
|
|
|
``action`` is a callable that takes no arguments and returns no
|
|
value (returned value is ignored). It must *NEVER* raise an
|
|
exception.
|
|
|
|
If unspecified, a no-op will be used.
|
|
"""
|
|
self._init_action(action)
|
|
|
|
def _init_action(self, action):
|
|
pass
|
|
|
|
def __enter__(self):
|
|
return self
|
|
|
|
def __exit__(self, *args):
|
|
return
|
|
|
|
if os.name == 'nt':
|
|
from ctypes import WINFUNCTYPE, windll
|
|
from ctypes.wintypes import BOOL, DWORD
|
|
|
|
kernel32 = windll.LoadLibrary('kernel32')
|
|
|
|
# <http://msdn.microsoft.com/en-us/library/ms686016.aspx>
|
|
PHANDLER_ROUTINE = WINFUNCTYPE(BOOL, DWORD)
|
|
SetConsoleCtrlHandler = kernel32.SetConsoleCtrlHandler
|
|
SetConsoleCtrlHandler.argtypes = (PHANDLER_ROUTINE, BOOL)
|
|
SetConsoleCtrlHandler.restype = BOOL
|
|
|
|
class allow_interrupt(_allow_interrupt):
|
|
__doc__ = _allow_interrupt.__doc__
|
|
|
|
def _init_action(self, action):
|
|
if action is None:
|
|
action = lambda: None
|
|
self.action = action
|
|
@PHANDLER_ROUTINE
|
|
def handle(event):
|
|
if event == 0: # CTRL_C_EVENT
|
|
action()
|
|
# Typical C implementations would return 1 to indicate that
|
|
# the event was processed and other control handlers in the
|
|
# stack should not be executed. However, that would
|
|
# prevent the Python interpreter's handler from translating
|
|
# CTRL-C to a `KeyboardInterrupt` exception, so we pretend
|
|
# that we didn't handle it.
|
|
return 0
|
|
self.handle = handle
|
|
|
|
def __enter__(self):
|
|
"""Install the custom CTRL-C handler."""
|
|
result = SetConsoleCtrlHandler(self.handle, 1)
|
|
if result == 0:
|
|
# Have standard library automatically call `GetLastError()` and
|
|
# `FormatMessage()` into a nice exception object :-)
|
|
raise WindowsError()
|
|
|
|
def __exit__(self, *args):
|
|
"""Remove the custom CTRL-C handler."""
|
|
result = SetConsoleCtrlHandler(self.handle, 0)
|
|
if result == 0:
|
|
# Have standard library automatically call `GetLastError()` and
|
|
# `FormatMessage()` into a nice exception object :-)
|
|
raise WindowsError()
|
|
else:
|
|
class allow_interrupt(_allow_interrupt):
|
|
__doc__ = _allow_interrupt.__doc__
|
|
pass
|