# gevent

# Source code for gevent._interfaces

    # -*- coding: utf-8 -*-
    # Copyright (c) 2018 gevent contributors. See LICENSE for details.
    """
    Interfaces gevent uses that don't belong any one place.

    This is not a public module, these interfaces are not
    currently exposed to the public, they mostly exist for
    documentation and testing purposes.

    .. versionadded:: 1.3b2

    """
    from __future__ import absolute_import
    from __future__ import division
    from __future__ import print_function

    import sys

    from gevent._util import Interface
    from gevent._util import Attribute

    # pylint:disable=no-method-argument, unused-argument, no-self-argument

    __all__ = [
        'ILoop',
        'IWatcher',
    ]

    class ILoop(Interface):
        """
        The common interface expected for all event loops.

        .. caution::
           This is an internal, low-level interface. It may change
           between minor versions of gevent.

        .. rubric:: Watchers

        The methods that create event loop watchers are `io`, `timer`,
        `signal`, `idle`, `prepare`, `check`, `fork`, `async_`, `child`,
        `stat`. These all return various types of :class:`IWatcher`.

        All of those methods have one or two common arguments. *ref* is a
        boolean saying whether the event loop is allowed to exit even if
        this watcher is still started. *priority* is event loop specific.
        """

        default = Attribute("Boolean indicating whether this is the default loop")

        approx_timer_resolution = Attribute(
            "Floating point number of seconds giving (approximately) the minimum "
            "resolution of a timer (and hence the minimun value the sleep can sleep for). "
            "On libuv, this is fixed by the library, but on libev it is just a guess "
            "and the actual value is system dependent."
        )

        def run(nowait=False, once=False):
            """
            Run the event loop.

            This is usually called automatically by the hub greenlet, but
            in special cases (when the hub is *not* running) you can use
            this to control how the event loop runs (for example, to integrate
            it with another event loop).
            """

        def now():
            """
            now() -> float

            Return the loop's notion of the current time.

            This may not necessarily be related to :func:`time.time` (it
            may have a different starting point), but it must be expressed
            in fractional seconds (the same *units* used by :func:`time.time`).
            """

        def update_now():
            """
            Update the loop's notion of the current time.

            .. versionadded:: 1.3
               In the past, this available as ``update``. This is still available as
               an alias but will be removed in the future.
            """

        def destroy():
            """
            Clean up resources used by this loop.

            If you create loops
            (especially loops that are not the default) you *should* call
            this method when you are done with the loop.

            .. caution::

                As an implementation note, the libev C loop implementation has a
                finalizer (``__del__``) that destroys the object, but the libuv
                and libev CFFI implementations do not. The C implementation may change.

            """

        def io(fd, events, ref=True, priority=None):
            """
            Create and return a new IO watcher for the given *fd*.

            *events* is a bitmask specifying which events to watch
            for. 1 means read, and 2 means write.
            """

        def timer(after, repeat=0.0, ref=True, priority=None):
            """
            Create and return a timer watcher that will fire after *after* seconds.

            If *repeat* is given, the timer will continue to fire every *repeat* seconds.
            """

        def signal(signum, ref=True, priority=None):
            """
            Create and return a signal watcher for the signal *signum*,
            one of the constants defined in :mod:`signal`.

            This is platform and event loop specific.
            """

        def idle(ref=True, priority=None):
            """
            Create and return a watcher that fires when the event loop is idle.
            """

        def prepare(ref=True, priority=None):
            """
            Create and return a watcher that fires before the event loop
            polls for IO.

            .. caution:: This method is not supported by libuv.
            """

        def check(ref=True, priority=None):
            """
            Create and return a watcher that fires after the event loop
            polls for IO.
            """

        def fork(ref=True, priority=None):
            """
            Create a watcher that fires when the process forks.

            Availability: POSIX
            """

        def async_(ref=True, priority=None):
            """
            Create a watcher that fires when triggered, possibly
            from another thread.

            .. versionchanged:: 1.3
               This was previously just named ``async``; for compatibility
               with Python 3.7 where ``async`` is a keyword it was renamed.
               On older versions of Python the old name is still around, but
               it will be removed in the future.
            """

        if sys.platform != "win32":

            def child(pid, trace=0, ref=True):
                """
                Create a watcher that fires for events on the child with process ID *pid*.

                This is platform specific and not available on Windows.
                """

        def stat(path, interval=0.0, ref=True, priority=None):
            """
            Create a watcher that monitors the filesystem item at *path*.

            If the operating system doesn't support event notifications
            from the filesystem, poll for changes every *interval* seconds.
            """

        def run_callback(func, *args):
            """
            Run the *func* passing it *args* at the next opportune moment.

            This is a way of handing control to the event loop and deferring
            an action.
            """

    class IWatcher(Interface):
        """
        An event loop watcher.

        These objects call their *callback* function when the event
        loop detects the event has happened.

        .. important:: You *must* call :meth:`close` when you are
           done with this object to avoid leaking native resources.
        """

        def start(callback, *args, **kwargs):
            """
            Have the event loop begin watching for this event.

            When the event is detected, *callback* will be called with
            *args*.

            .. caution::

                Not all watchers accept ``**kwargs``,
                and some watchers define special meanings for certain keyword args.
            """

        def stop():
            """
            Have the event loop stop watching this event.

            In the future you may call :meth:`start` to begin watching
            again.
            """

        def close():
            """
            Dispose of any native resources associated with the watcher.

            If we were active, stop.

            Attempting to operate on this object after calling close is
            undefined. You should dispose of any references you have to it
            after calling this method.
            """