twisted_kqueue.py

# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.

"""
A kqueue()/kevent() based implementation of the Twisted main loop.

To install the event loop (and you should do this before any connections,
listeners or connectors are added)::

    | import twisted_kqueue
    | twisted_kqueue.install()

This reactor only works on FreeBSD and requires Python 2.6+
"""

import errno, sys

from zope.interface import implements

from select import kqueue, kevent
from select import KQ_FILTER_READ, KQ_FILTER_WRITE, KQ_EV_ADD, KQ_EV_DELETE

from twisted.internet.interfaces import IReactorFDSet

from twisted.python import log, failure
from twisted.internet import main, posixbase


class KQueueReactor(posixbase.PosixReactorBase):
    """
    A reactor that uses kqueue(2)/kevent(2).

    @ivar _kq: A L{kqueue} which will be used to check for I/O readiness.

    @ivar _selectables: A dictionary mapping integer file descriptors to
        instances of L{FileDescriptor} which have been registered with the
        reactor.  All L{FileDescriptors} which are currently receiving read or
        write readiness notifications will be present as values in this
        dictionary.

    @ivar _reads: A dictionary mapping integer file descriptors to arbitrary
        values (this is essentially a set).  Keys in this dictionary will be
        registered with C{_kq} for read readiness notifications which will be
        dispatched to the corresponding L{FileDescriptor} instances in
        C{_selectables}.

    @ivar _writes: A dictionary mapping integer file descriptors to arbitrary
        values (this is essentially a set).  Keys in this dictionary will be
        registered with C{_kq} for write readiness notifications which will be
        dispatched to the corresponding L{FileDescriptor} instances in
        C{_selectables}.
    """
    implements(IReactorFDSet)

    def __init__(self):
        """
        Initialize kqueue object, file descriptor tracking dictionaries, and the
        base class.
        """
        self._kq = kqueue()
        self._reads = {}
        self._writes = {}
        self._selectables = {}
        posixbase.PosixReactorBase.__init__(self)


    def _updateRegistration(self, *args):
        self._kq.control([kevent(*args)], 0, 0)

    def addReader(self, reader):
        """Add a FileDescriptor for notification of data available to read.
        """
        fd = reader.fileno()
        if fd not in self._reads:
            self._selectables[fd] = reader
            self._reads[fd] = 1
            self._updateRegistration(fd, KQ_FILTER_READ, KQ_EV_ADD)

    def addWriter(self, writer):
        """Add a FileDescriptor for notification of data available to write.
        """
        fd = writer.fileno()
        if fd not in self._writes:
            self._selectables[fd] = writer
            self._writes[fd] = 1
            self._updateRegistration(fd, KQ_FILTER_WRITE, KQ_EV_ADD)

    def removeReader(self, reader):
        """Remove a Selectable for notification of data available to read.
        """
        fd = reader.fileno()
        if fd in self._reads:
            del self._reads[fd]
            if fd not in self._writes:
                del self._selectables[fd]
            self._updateRegistration(fd, KQ_FILTER_READ, KQ_EV_DELETE)

    def removeWriter(self, writer):
        """Remove a Selectable for notification of data available to write.
        """
        fd = writer.fileno()
        if fd in self._writes:
            del self._writes[fd]
            if fd not in self._reads:
                del self._selectables[fd]
            self._updateRegistration(fd, KQ_FILTER_WRITE, KQ_EV_DELETE)

    def removeAll(self):
        """
        Remove all selectables, and return a list of them.
        """
        return self._removeAll(
            [self._selectables[fd] for fd in self._reads],
            [self._selectables[fd] for fd in self._writes])


    def getReaders(self):
        return [self._selectables[fd] for fd in self._reads]


    def getWriters(self):
        return [self._selectables[fd] for fd in self._writes]


    def doKEvent(self, timeout):
        """Poll the kqueue for new events."""
        try:
            l = self._kq.control([], len(self._selectables), timeout)
        except OSError, e:
            if e[0] == errno.EINTR:
                return
            else:
                raise
        _drdw = self._doWriteOrRead
        for event in l:
            why = None
            fd, filter = event.ident, event.filter
            try:
                selectable = self._selectables[fd]
            except KeyError:
                # Handles the infrequent case where one selectable's
                # handler disconnects another.
                continue
            log.callWithLogger(selectable, _drdw, selectable, fd, filter)

    def _doWriteOrRead(self, selectable, fd, filter):
        try:
            if filter == KQ_FILTER_READ:
                why = selectable.doRead()
            if filter == KQ_FILTER_WRITE:
                why = selectable.doWrite()
            if not selectable.fileno() == fd:
                why = main.CONNECTION_LOST
        except:
            why = sys.exc_info()[1]
            log.deferr()

        if why:
            self.removeReader(selectable)
            self.removeWriter(selectable)
            selectable.connectionLost(failure.Failure(why))

    doIteration = doKEvent


def install():
    k = KQueueReactor()
    main.installReactor(k)


__all__ = ["KQueueReactor", "install"]