cpython/Modules/selectmodule.c

/* select - Module containing unix select(2) call.
   Under Unix, the file descriptors are small integers.
   Under Win32, select only exists for sockets, and sockets may
   have any value except INVALID_SOCKET.
*/

#include "Python.h"
#include <structmember.h>

#ifdef __APPLE__
    /* Perform runtime testing for a broken poll on OSX to make it easier
     * to use the same binary on multiple releases of the OS.
     */
#undef HAVE_BROKEN_POLL
#endif

/* Windows #defines FD_SETSIZE to 64 if FD_SETSIZE isn't already defined.
   64 is too small (too many people have bumped into that limit).
   Here we boost it.
   Users who want even more than the boosted limit should #define
   FD_SETSIZE higher before this; e.g., via compiler /D switch.
*/
#if defined(MS_WINDOWS) && !defined(FD_SETSIZE)
#define FD_SETSIZE 512
#endif 

#if defined(HAVE_POLL_H)
#include <poll.h>
#elif defined(HAVE_SYS_POLL_H)
#include <sys/poll.h>
#endif

#ifdef __sgi
/* This is missing from unistd.h */
extern void bzero(void *, int);
#endif

#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif

#if defined(PYOS_OS2) && !defined(PYCC_GCC)
#include <sys/time.h>
#include <utils.h>
#endif

#ifdef MS_WINDOWS
#  define WIN32_LEAN_AND_MEAN
#  include <winsock.h>
#else
#  define SOCKET int
#  if defined(__VMS)
#    include <socket.h>
#  endif
#endif

static PyObject *SelectError;

/* list of Python objects and their file descriptor */
typedef struct {
	PyObject *obj;			     /* owned reference */
	SOCKET fd;
	int sentinel;			     /* -1 == sentinel */
} pylist;

static void
reap_obj(pylist fd2obj[FD_SETSIZE + 1])
{
	int i;
	for (i = 0; i < FD_SETSIZE + 1 && fd2obj[i].sentinel >= 0; i++) {
		Py_XDECREF(fd2obj[i].obj);
		fd2obj[i].obj = NULL;
	}
	fd2obj[0].sentinel = -1;
}


/* returns -1 and sets the Python exception if an error occurred, otherwise
   returns a number >= 0
*/
static int
seq2set(PyObject *seq, fd_set *set, pylist fd2obj[FD_SETSIZE + 1])
{
	int i;
	int max = -1;
	int index = 0;
        int len = -1;
        PyObject* fast_seq = NULL;
	PyObject* o = NULL;

	fd2obj[0].obj = (PyObject*)0;	     /* set list to zero size */
	FD_ZERO(set);

        fast_seq=PySequence_Fast(seq, "arguments 1-3 must be sequences");
        if (!fast_seq)
            return -1;

        len = PySequence_Fast_GET_SIZE(fast_seq);

	for (i = 0; i < len; i++)  {
		SOCKET v;

		/* any intervening fileno() calls could decr this refcnt */
		if (!(o = PySequence_Fast_GET_ITEM(fast_seq, i)))
                    return -1;

		Py_INCREF(o);
		v = PyObject_AsFileDescriptor( o );
		if (v == -1) goto finally;

#if defined(_MSC_VER)
		max = 0;		     /* not used for Win32 */
#else  /* !_MSC_VER */
		if (v < 0 || v >= FD_SETSIZE) {
			PyErr_SetString(PyExc_ValueError,
				    "filedescriptor out of range in select()");
			goto finally;
		}
		if (v > max)
			max = v;
#endif /* _MSC_VER */
		FD_SET(v, set);

		/* add object and its file descriptor to the list */
		if (index >= FD_SETSIZE) {
			PyErr_SetString(PyExc_ValueError,
				      "too many file descriptors in select()");
			goto finally;
		}
		fd2obj[index].obj = o;
		fd2obj[index].fd = v;
		fd2obj[index].sentinel = 0;
		fd2obj[++index].sentinel = -1;
	}
        Py_DECREF(fast_seq);
	return max+1;

  finally:
	Py_XDECREF(o);
        Py_DECREF(fast_seq);
	return -1;
}

/* returns NULL and sets the Python exception if an error occurred */
static PyObject *
set2list(fd_set *set, pylist fd2obj[FD_SETSIZE + 1])
{
	int i, j, count=0;
	PyObject *list, *o;
	SOCKET fd;

	for (j = 0; fd2obj[j].sentinel >= 0; j++) {
		if (FD_ISSET(fd2obj[j].fd, set))
			count++;
	}
	list = PyList_New(count);
	if (!list)
		return NULL;

	i = 0;
	for (j = 0; fd2obj[j].sentinel >= 0; j++) {
		fd = fd2obj[j].fd;
		if (FD_ISSET(fd, set)) {
#ifndef _MSC_VER
			if (fd > FD_SETSIZE) {
				PyErr_SetString(PyExc_SystemError,
			   "filedescriptor out of range returned in select()");
				goto finally;
			}
#endif
			o = fd2obj[j].obj;
			fd2obj[j].obj = NULL;
			/* transfer ownership */
			if (PyList_SetItem(list, i, o) < 0)
				goto finally;

			i++;
		}
	}
	return list;
  finally:
	Py_DECREF(list);
	return NULL;
}

#undef SELECT_USES_HEAP
#if FD_SETSIZE > 1024
#define SELECT_USES_HEAP
#endif /* FD_SETSIZE > 1024 */

static PyObject *
select_select(PyObject *self, PyObject *args)
{
#ifdef SELECT_USES_HEAP
	pylist *rfd2obj, *wfd2obj, *efd2obj;
#else  /* !SELECT_USES_HEAP */
	/* XXX: All this should probably be implemented as follows:
	 * - find the highest descriptor we're interested in
	 * - add one
	 * - that's the size
	 * See: Stevens, APitUE, $12.5.1
	 */
	pylist rfd2obj[FD_SETSIZE + 1];
	pylist wfd2obj[FD_SETSIZE + 1];
	pylist efd2obj[FD_SETSIZE + 1];
#endif /* SELECT_USES_HEAP */
	PyObject *ifdlist, *ofdlist, *efdlist;
	PyObject *ret = NULL;
	PyObject *tout = Py_None;
	fd_set ifdset, ofdset, efdset;
	double timeout;
	struct timeval tv, *tvp;
	long seconds;
	int imax, omax, emax, max;
	int n;

	/* convert arguments */
	if (!PyArg_UnpackTuple(args, "select", 3, 4,
			      &ifdlist, &ofdlist, &efdlist, &tout))
		return NULL;

	if (tout == Py_None)
		tvp = (struct timeval *)0;
	else if (!PyNumber_Check(tout)) {
		PyErr_SetString(PyExc_TypeError,
				"timeout must be a float or None");
		return NULL;
	}
	else {
		timeout = PyFloat_AsDouble(tout);
		if (timeout == -1 && PyErr_Occurred())
			return NULL;
		if (timeout > (double)LONG_MAX) {
			PyErr_SetString(PyExc_OverflowError,
					"timeout period too long");
			return NULL;
		}
		seconds = (long)timeout;
		timeout = timeout - (double)seconds;
		tv.tv_sec = seconds;
		tv.tv_usec = (long)(timeout * 1E6);
		tvp = &tv;
	}


#ifdef SELECT_USES_HEAP
	/* Allocate memory for the lists */
	rfd2obj = PyMem_NEW(pylist, FD_SETSIZE + 1);
	wfd2obj = PyMem_NEW(pylist, FD_SETSIZE + 1);
	efd2obj = PyMem_NEW(pylist, FD_SETSIZE + 1);
	if (rfd2obj == NULL || wfd2obj == NULL || efd2obj == NULL) {
		if (rfd2obj) PyMem_DEL(rfd2obj);
		if (wfd2obj) PyMem_DEL(wfd2obj);
		if (efd2obj) PyMem_DEL(efd2obj);
		return PyErr_NoMemory();
	}
#endif /* SELECT_USES_HEAP */
	/* Convert sequences to fd_sets, and get maximum fd number
	 * propagates the Python exception set in seq2set()
	 */
	rfd2obj[0].sentinel = -1;
	wfd2obj[0].sentinel = -1;
	efd2obj[0].sentinel = -1;
	if ((imax=seq2set(ifdlist, &ifdset, rfd2obj)) < 0) 
		goto finally;
	if ((omax=seq2set(ofdlist, &ofdset, wfd2obj)) < 0) 
		goto finally;
	if ((emax=seq2set(efdlist, &efdset, efd2obj)) < 0) 
		goto finally;
	max = imax;
	if (omax > max) max = omax;
	if (emax > max) max = emax;

	Py_BEGIN_ALLOW_THREADS
	n = select(max, &ifdset, &ofdset, &efdset, tvp);
	Py_END_ALLOW_THREADS

#ifdef MS_WINDOWS
	if (n == SOCKET_ERROR) {
		PyErr_SetExcFromWindowsErr(SelectError, WSAGetLastError());
	}
#else
	if (n < 0) {
		PyErr_SetFromErrno(SelectError);
	}
#endif
	else if (n == 0) {
                /* optimization */
		ifdlist = PyList_New(0);
		if (ifdlist) {
			ret = PyTuple_Pack(3, ifdlist, ifdlist, ifdlist);
			Py_DECREF(ifdlist);
		}
	}
	else {
		/* any of these three calls can raise an exception.  it's more
		   convenient to test for this after all three calls... but
		   is that acceptable?
		*/
		ifdlist = set2list(&ifdset, rfd2obj);
		ofdlist = set2list(&ofdset, wfd2obj);
		efdlist = set2list(&efdset, efd2obj);
		if (PyErr_Occurred())
			ret = NULL;
		else
			ret = PyTuple_Pack(3, ifdlist, ofdlist, efdlist);

		Py_DECREF(ifdlist);
		Py_DECREF(ofdlist);
		Py_DECREF(efdlist);
	}
	
  finally:
	reap_obj(rfd2obj);
	reap_obj(wfd2obj);
	reap_obj(efd2obj);
#ifdef SELECT_USES_HEAP
	PyMem_DEL(rfd2obj);
	PyMem_DEL(wfd2obj);
	PyMem_DEL(efd2obj);
#endif /* SELECT_USES_HEAP */
	return ret;
}

#if defined(HAVE_POLL) && !defined(HAVE_BROKEN_POLL)
/* 
 * poll() support
 */

typedef struct {
	PyObject_HEAD
	PyObject *dict;
	int ufd_uptodate; 
	int ufd_len;
        struct pollfd *ufds;
} pollObject;

static PyTypeObject poll_Type;

/* Update the malloc'ed array of pollfds to match the dictionary 
   contained within a pollObject.  Return 1 on success, 0 on an error.
*/

static int
update_ufd_array(pollObject *self)
{
	Py_ssize_t i, pos;
	PyObject *key, *value;
        struct pollfd *old_ufds = self->ufds;

	self->ufd_len = PyDict_Size(self->dict);
	PyMem_RESIZE(self->ufds, struct pollfd, self->ufd_len);
	if (self->ufds == NULL) {
                self->ufds = old_ufds;
		PyErr_NoMemory();
		return 0;
	}

	i = pos = 0;
	while (PyDict_Next(self->dict, &pos, &key, &value)) {
		self->ufds[i].fd = PyLong_AsLong(key);
		self->ufds[i].events = (short)PyLong_AsLong(value);
		i++;
	}
	self->ufd_uptodate = 1;
	return 1;
}

PyDoc_STRVAR(poll_register_doc,
"register(fd [, eventmask] ) -> None\n\n\
Register a file descriptor with the polling object.\n\
fd -- either an integer, or an object with a fileno() method returning an\n\
      int.\n\
events -- an optional bitmask describing the type of events to check for");

static PyObject *
poll_register(pollObject *self, PyObject *args) 
{
	PyObject *o, *key, *value;
	int fd, events = POLLIN | POLLPRI | POLLOUT;
	int err;

	if (!PyArg_ParseTuple(args, "O|i:register", &o, &events)) {
		return NULL;
	}
  
	fd = PyObject_AsFileDescriptor(o);
	if (fd == -1) return NULL;

	/* Add entry to the internal dictionary: the key is the 
	   file descriptor, and the value is the event mask. */
	key = PyLong_FromLong(fd);
	if (key == NULL)
		return NULL;
	value = PyLong_FromLong(events);
	if (value == NULL) {
		Py_DECREF(key);
		return NULL;
	}
	err = PyDict_SetItem(self->dict, key, value);
	Py_DECREF(key);
	Py_DECREF(value);
	if (err < 0)
		return NULL;

	self->ufd_uptodate = 0;

	Py_INCREF(Py_None);
	return Py_None;
}

PyDoc_STRVAR(poll_modify_doc,
"modify(fd, eventmask) -> None\n\n\
Modify an already registered file descriptor.\n\
fd -- either an integer, or an object with a fileno() method returning an\n\
      int.\n\
events -- an optional bitmask describing the type of events to check for");

static PyObject *
poll_modify(pollObject *self, PyObject *args)
{
	PyObject *o, *key, *value;
	int fd, events;
	int err;

	if (!PyArg_ParseTuple(args, "Oi:modify", &o, &events)) {
		return NULL;
	}
  
	fd = PyObject_AsFileDescriptor(o);
	if (fd == -1) return NULL;

	/* Modify registered fd */
	key = PyLong_FromLong(fd);
	if (key == NULL)
		return NULL;
	if (PyDict_GetItem(self->dict, key) == NULL) {
		errno = ENOENT;
		PyErr_SetFromErrno(PyExc_IOError);
		return NULL;
	}
	value = PyLong_FromLong(events);
	if (value == NULL) {
		Py_DECREF(key);
		return NULL;
	}
	err = PyDict_SetItem(self->dict, key, value);
	Py_DECREF(key);
	Py_DECREF(value);
	if (err < 0)
		return NULL;

	self->ufd_uptodate = 0;

	Py_INCREF(Py_None);
	return Py_None;
}


PyDoc_STRVAR(poll_unregister_doc,
"unregister(fd) -> None\n\n\
Remove a file descriptor being tracked by the polling object.");

static PyObject *
poll_unregister(pollObject *self, PyObject *o) 
{
	PyObject *key;
	int fd;

	fd = PyObject_AsFileDescriptor( o );
	if (fd == -1) 
		return NULL;

	/* Check whether the fd is already in the array */
	key = PyLong_FromLong(fd);
	if (key == NULL) 
		return NULL;

	if (PyDict_DelItem(self->dict, key) == -1) {
		Py_DECREF(key);
		/* This will simply raise the KeyError set by PyDict_DelItem
		   if the file descriptor isn't registered. */
		return NULL;
	}

	Py_DECREF(key);
	self->ufd_uptodate = 0;

	Py_INCREF(Py_None);
	return Py_None;
}

PyDoc_STRVAR(poll_poll_doc,
"poll( [timeout] ) -> list of (fd, event) 2-tuples\n\n\
Polls the set of registered file descriptors, returning a list containing \n\
any descriptors that have events or errors to report.");

static PyObject *
poll_poll(pollObject *self, PyObject *args) 
{
	PyObject *result_list = NULL, *tout = NULL;
	int timeout = 0, poll_result, i, j;
	PyObject *value = NULL, *num = NULL;

	if (!PyArg_UnpackTuple(args, "poll", 0, 1, &tout)) {
		return NULL;
	}

	/* Check values for timeout */
	if (tout == NULL || tout == Py_None)
		timeout = -1;
	else if (!PyNumber_Check(tout)) {
		PyErr_SetString(PyExc_TypeError,
				"timeout must be an integer or None");
		return NULL;
	}
	else {
		tout = PyNumber_Long(tout);
		if (!tout)
			return NULL;
		timeout = PyLong_AsLong(tout);
		Py_DECREF(tout);
		if (timeout == -1 && PyErr_Occurred())
			return NULL;
	}

	/* Ensure the ufd array is up to date */
	if (!self->ufd_uptodate) 
		if (update_ufd_array(self) == 0)
			return NULL;

	/* call poll() */
	Py_BEGIN_ALLOW_THREADS
	poll_result = poll(self->ufds, self->ufd_len, timeout);
	Py_END_ALLOW_THREADS
 
	if (poll_result < 0) {
		PyErr_SetFromErrno(SelectError);
		return NULL;
	} 
       
	/* build the result list */
  
	result_list = PyList_New(poll_result);
	if (!result_list) 
		return NULL;
	else {
		for (i = 0, j = 0; j < poll_result; j++) {
 			/* skip to the next fired descriptor */
 			while (!self->ufds[i].revents) {
 				i++;
 			}
			/* if we hit a NULL return, set value to NULL
			   and break out of loop; code at end will
			   clean up result_list */
			value = PyTuple_New(2);
			if (value == NULL)
				goto error;
			num = PyLong_FromLong(self->ufds[i].fd);
			if (num == NULL) {
				Py_DECREF(value);
				goto error;
			}
			PyTuple_SET_ITEM(value, 0, num);

			/* The &0xffff is a workaround for AIX.  'revents'
			   is a 16-bit short, and IBM assigned POLLNVAL
			   to be 0x8000, so the conversion to int results
			   in a negative number. See SF bug #923315. */
			num = PyLong_FromLong(self->ufds[i].revents & 0xffff);
			if (num == NULL) {
				Py_DECREF(value);
				goto error;
			}
			PyTuple_SET_ITEM(value, 1, num);
 			if ((PyList_SetItem(result_list, j, value)) == -1) {
				Py_DECREF(value);
				goto error;
 			}
 			i++;
 		}
 	}
 	return result_list;

  error:
	Py_DECREF(result_list);
	return NULL;
}

static PyMethodDef poll_methods[] = {
	{"register",	(PyCFunction)poll_register,	
	 METH_VARARGS,  poll_register_doc},
	{"modify",	(PyCFunction)poll_modify,
	 METH_VARARGS,  poll_modify_doc},
	{"unregister",	(PyCFunction)poll_unregister,
	 METH_O,        poll_unregister_doc},
	{"poll",	(PyCFunction)poll_poll,	
	 METH_VARARGS,  poll_poll_doc},
	{NULL,		NULL}		/* sentinel */
};

static pollObject *
newPollObject(void)
{
        pollObject *self;
	self = PyObject_New(pollObject, &poll_Type);
	if (self == NULL)
		return NULL;
	/* ufd_uptodate is a Boolean, denoting whether the 
	   array pointed to by ufds matches the contents of the dictionary. */
	self->ufd_uptodate = 0;
	self->ufds = NULL;
	self->dict = PyDict_New();
	if (self->dict == NULL) {
		Py_DECREF(self);
		return NULL;
	}
	return self;
}

static void
poll_dealloc(pollObject *self)
{
	if (self->ufds != NULL)
		PyMem_DEL(self->ufds);
	Py_XDECREF(self->dict);
  	PyObject_Del(self);
}

static PyTypeObject poll_Type = {
	/* The ob_type field must be initialized in the module init function
	 * to be portable to Windows without using C++. */
	PyVarObject_HEAD_INIT(NULL, 0)
	"select.poll",		/*tp_name*/
	sizeof(pollObject),	/*tp_basicsize*/
	0,			/*tp_itemsize*/
	/* methods */
	(destructor)poll_dealloc, /*tp_dealloc*/
	0,			/*tp_print*/
	0,			/*tp_getattr*/
	0,                      /*tp_setattr*/
	0,			/*tp_reserved*/
	0,			/*tp_repr*/
	0,			/*tp_as_number*/
	0,			/*tp_as_sequence*/
	0,			/*tp_as_mapping*/
	0,			/*tp_hash*/
	0,			/*tp_call*/
	0,			/*tp_str*/
	0,			/*tp_getattro*/
	0,			/*tp_setattro*/
	0,			/*tp_as_buffer*/
	Py_TPFLAGS_DEFAULT,	/*tp_flags*/
	0,			/*tp_doc*/
	0,			/*tp_traverse*/
	0,			/*tp_clear*/
	0,			/*tp_richcompare*/
	0,			/*tp_weaklistoffset*/
	0,			/*tp_iter*/
	0,			/*tp_iternext*/
	poll_methods,		/*tp_methods*/
};

PyDoc_STRVAR(poll_doc,
"Returns a polling object, which supports registering and\n\
unregistering file descriptors, and then polling them for I/O events.");

static PyObject *
select_poll(PyObject *self, PyObject *unused)
{
	return (PyObject *)newPollObject();
}

#ifdef __APPLE__
/* 
 * On some systems poll() sets errno on invalid file descriptors. We test
 * for this at runtime because this bug may be fixed or introduced between
 * OS releases.
 */
static int select_have_broken_poll(void)
{
	int poll_test;
	int filedes[2];

	struct pollfd poll_struct = { 0, POLLIN|POLLPRI|POLLOUT, 0 };

	/* Create a file descriptor to make invalid */
	if (pipe(filedes) < 0) {
		return 1;
	}
	poll_struct.fd = filedes[0];
	close(filedes[0]);
	close(filedes[1]);
	poll_test = poll(&poll_struct, 1, 0);
	if (poll_test < 0) {
		return 1;
	} else if (poll_test == 0 && poll_struct.revents != POLLNVAL) {
		return 1;
	}
	return 0;
}
#endif /* __APPLE__ */

#endif /* HAVE_POLL */

#ifdef HAVE_EPOLL
/* **************************************************************************
 *                      epoll interface for Linux 2.6
 *
 * Written by Christian Heimes
 * Inspired by Twisted's _epoll.pyx and select.poll()
 */

#ifdef HAVE_SYS_EPOLL_H
#include <sys/epoll.h>
#endif

typedef struct {
	PyObject_HEAD
	SOCKET epfd;			/* epoll control file descriptor */
} pyEpoll_Object;

static PyTypeObject pyEpoll_Type;
#define pyepoll_CHECK(op) (PyObject_TypeCheck((op), &pyEpoll_Type))

static PyObject *
pyepoll_err_closed(void)
{
	PyErr_SetString(PyExc_ValueError, "I/O operation on closed epoll fd");
	return NULL;
}

static int
pyepoll_internal_close(pyEpoll_Object *self)
{
	int save_errno = 0;
	if (self->epfd >= 0) {
		int epfd = self->epfd;
		self->epfd = -1;
		Py_BEGIN_ALLOW_THREADS
		if (close(epfd) < 0)
			save_errno = errno;
		Py_END_ALLOW_THREADS
	}
	return save_errno;
}

static PyObject *
newPyEpoll_Object(PyTypeObject *type, int sizehint, SOCKET fd)
{
	pyEpoll_Object *self;
	
	if (sizehint == -1) {
		sizehint = FD_SETSIZE-1;
	}
	else if (sizehint < 1) {
		PyErr_Format(PyExc_ValueError,
			     "sizehint must be greater zero, got %d",
			     sizehint);
		return NULL;
	}

	assert(type != NULL && type->tp_alloc != NULL);
	self = (pyEpoll_Object *) type->tp_alloc(type, 0);
	if (self == NULL)
		return NULL;

	if (fd == -1) {
		Py_BEGIN_ALLOW_THREADS
		self->epfd = epoll_create(sizehint);
		Py_END_ALLOW_THREADS
	}
	else {
		self->epfd = fd;
	}
	if (self->epfd < 0) {
		Py_DECREF(self);
		PyErr_SetFromErrno(PyExc_IOError);
		return NULL;
	}
	return (PyObject *)self;
}


static PyObject *
pyepoll_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
	int sizehint = -1;
	static char *kwlist[] = {"sizehint", NULL};

	if (!PyArg_ParseTupleAndKeywords(args, kwds, "|i:epoll", kwlist,
					 &sizehint))
		return NULL;

	return newPyEpoll_Object(type, sizehint, -1);
}


static void
pyepoll_dealloc(pyEpoll_Object *self)
{
	(void)pyepoll_internal_close(self);
	Py_TYPE(self)->tp_free(self);
}

static PyObject*
pyepoll_close(pyEpoll_Object *self)
{
	errno = pyepoll_internal_close(self);
	if (errno < 0) {
		PyErr_SetFromErrno(PyExc_IOError);
		return NULL;
	}
	Py_RETURN_NONE;
}

PyDoc_STRVAR(pyepoll_close_doc,
"close() -> None\n\
\n\
Close the epoll control file descriptor. Further operations on the epoll\n\
object will raise an exception.");

static PyObject*
pyepoll_get_closed(pyEpoll_Object *self)
{
	if (self->epfd < 0)
		Py_RETURN_TRUE;
	else
		Py_RETURN_FALSE;
}

static PyObject*
pyepoll_fileno(pyEpoll_Object *self)
{
	if (self->epfd < 0)
		return pyepoll_err_closed();
	return PyLong_FromLong(self->epfd);
}

PyDoc_STRVAR(pyepoll_fileno_doc,
"fileno() -> int\n\
\n\
Return the epoll control file descriptor.");

static PyObject*
pyepoll_fromfd(PyObject *cls, PyObject *args)
{
	SOCKET fd;

	if (!PyArg_ParseTuple(args, "i:fromfd", &fd))
		return NULL;

	return newPyEpoll_Object((PyTypeObject*)cls, -1, fd);
}

PyDoc_STRVAR(pyepoll_fromfd_doc,
"fromfd(fd) -> epoll\n\
\n\
Create an epoll object from a given control fd.");

static PyObject *
pyepoll_internal_ctl(int epfd, int op, PyObject *pfd, unsigned int events)
{
	struct epoll_event ev;
	int result;
	int fd;

	if (epfd < 0)
		return pyepoll_err_closed();

	fd = PyObject_AsFileDescriptor(pfd);
	if (fd == -1) {
		return NULL;
	}

	switch(op) {
	    case EPOLL_CTL_ADD:
	    case EPOLL_CTL_MOD:
		ev.events = events;
		ev.data.fd = fd;
		Py_BEGIN_ALLOW_THREADS
		result = epoll_ctl(epfd, op, fd, &ev);
		Py_END_ALLOW_THREADS
		break;
	    case EPOLL_CTL_DEL:
		/* In kernel versions before 2.6.9, the EPOLL_CTL_DEL
		 * operation required a non-NULL pointer in event, even
		 * though this argument is ignored. */
		Py_BEGIN_ALLOW_THREADS
		result = epoll_ctl(epfd, op, fd, &ev);
		if (errno == EBADF) {
			/* fd already closed */
			result = 0;
			errno = 0;
		}
		Py_END_ALLOW_THREADS
		break;
	    default:
		result = -1;
		errno = EINVAL;
	}

	if (result < 0) {
		PyErr_SetFromErrno(PyExc_IOError);
		return NULL;
	}
	Py_RETURN_NONE;
}

static PyObject *
pyepoll_register(pyEpoll_Object *self, PyObject *args, PyObject *kwds)
{
	PyObject *pfd;
	unsigned int events = EPOLLIN | EPOLLOUT | EPOLLPRI;
	static char *kwlist[] = {"fd", "eventmask", NULL};

	if (!PyArg_ParseTupleAndKeywords(args, kwds, "O|I:register", kwlist,
					 &pfd, &events)) {
		return NULL;
	}

	return pyepoll_internal_ctl(self->epfd, EPOLL_CTL_ADD, pfd, events);
}

PyDoc_STRVAR(pyepoll_register_doc,
"register(fd[, eventmask]) -> bool\n\
\n\
Registers a new fd or modifies an already registered fd. register() returns\n\
True if a new fd was registered or False if the event mask for fd was modified.\n\
fd is the target file descriptor of the operation.\n\
events is a bit set composed of the various EPOLL constants; the default\n\
is EPOLL_IN | EPOLL_OUT | EPOLL_PRI.\n\
\n\
The epoll interface supports all file descriptors that support poll.");

static PyObject *
pyepoll_modify(pyEpoll_Object *self, PyObject *args, PyObject *kwds)
{
	PyObject *pfd;
	unsigned int events;
	static char *kwlist[] = {"fd", "eventmask", NULL};

	if (!PyArg_ParseTupleAndKeywords(args, kwds, "OI:modify", kwlist,
					 &pfd, &events)) {
		return NULL;
	}

	return pyepoll_internal_ctl(self->epfd, EPOLL_CTL_MOD, pfd, events);
}

PyDoc_STRVAR(pyepoll_modify_doc,
"modify(fd, eventmask) -> None\n\
\n\
fd is the target file descriptor of the operation\n\
events is a bit set composed of the various EPOLL constants");

static PyObject *
pyepoll_unregister(pyEpoll_Object *self, PyObject *args, PyObject *kwds)
{
	PyObject *pfd;
	static char *kwlist[] = {"fd", NULL};

	if (!PyArg_ParseTupleAndKeywords(args, kwds, "O:unregister", kwlist,
					 &pfd)) {
		return NULL;
	}

	return pyepoll_internal_ctl(self->epfd, EPOLL_CTL_DEL, pfd, 0);
}

PyDoc_STRVAR(pyepoll_unregister_doc,
"unregister(fd) -> None\n\
\n\
fd is the target file descriptor of the operation.");

static PyObject *
pyepoll_poll(pyEpoll_Object *self, PyObject *args, PyObject *kwds)
{
	double dtimeout = -1.;
	int timeout;
	int maxevents = -1;
	int nfds, i;
	PyObject *elist = NULL, *etuple = NULL;
	struct epoll_event *evs = NULL;
	static char *kwlist[] = {"timeout", "maxevents", NULL};

	if (self->epfd < 0)
		return pyepoll_err_closed();

	if (!PyArg_ParseTupleAndKeywords(args, kwds, "|di:poll", kwlist,
					 &dtimeout, &maxevents)) {
		return NULL;
	}

	if (dtimeout < 0) {
		timeout = -1;
	}
	else if (dtimeout * 1000.0 > INT_MAX) {
		PyErr_SetString(PyExc_OverflowError,
				"timeout is too large");
		return NULL;
	}
	else {
		timeout = (int)(dtimeout * 1000.0);
	}

	if (maxevents == -1) {
		maxevents = FD_SETSIZE-1;
	}
	else if (maxevents < 1) {
		PyErr_Format(PyExc_ValueError,
			     "maxevents must be greater than 0, got %d",
			     maxevents);
		return NULL;
	}

	evs = PyMem_New(struct epoll_event, maxevents);
	if (evs == NULL) {
		Py_DECREF(self);
		PyErr_NoMemory();
		return NULL;
	}

	Py_BEGIN_ALLOW_THREADS
	nfds = epoll_wait(self->epfd, evs, maxevents, timeout);
	Py_END_ALLOW_THREADS
	if (nfds < 0) {
		PyErr_SetFromErrno(PyExc_IOError);
		goto error;
	}

	elist = PyList_New(nfds);
	if (elist == NULL) {
		goto error;
	}

	for (i = 0; i < nfds; i++) {
		etuple = Py_BuildValue("iI", evs[i].data.fd, evs[i].events);
		if (etuple == NULL) {
			Py_CLEAR(elist);
			goto error;
		}
		PyList_SET_ITEM(elist, i, etuple);
	}

    error:
	PyMem_Free(evs);
	return elist;
}

PyDoc_STRVAR(pyepoll_poll_doc,
"poll([timeout=-1[, maxevents=-1]]) -> [(fd, events), (...)]\n\
\n\
Wait for events on the epoll file descriptor for a maximum time of timeout\n\
in seconds (as float). -1 makes poll wait indefinitely.\n\
Up to maxevents are returned to the caller.");

static PyMethodDef pyepoll_methods[] = {
	{"fromfd",	(PyCFunction)pyepoll_fromfd,
	 METH_VARARGS | METH_CLASS, pyepoll_fromfd_doc},
	{"close",	(PyCFunction)pyepoll_close,	METH_NOARGS,
	 pyepoll_close_doc},
	{"fileno",	(PyCFunction)pyepoll_fileno,	METH_NOARGS,
	 pyepoll_fileno_doc},
	{"modify",	(PyCFunction)pyepoll_modify,
	 METH_VARARGS | METH_KEYWORDS,	pyepoll_modify_doc},
	{"register",	(PyCFunction)pyepoll_register,
	 METH_VARARGS | METH_KEYWORDS,	pyepoll_register_doc},
	{"unregister",	(PyCFunction)pyepoll_unregister,
	 METH_VARARGS | METH_KEYWORDS,	pyepoll_unregister_doc},
	{"poll",	(PyCFunction)pyepoll_poll,
	 METH_VARARGS | METH_KEYWORDS,	pyepoll_poll_doc},
	{NULL,	NULL},
};

static PyGetSetDef pyepoll_getsetlist[] = {
	{"closed", (getter)pyepoll_get_closed, NULL,
	 "True if the epoll handler is closed"},
	{0},
};

PyDoc_STRVAR(pyepoll_doc,
"select.epoll([sizehint=-1])\n\
\n\
Returns an epolling object\n\
\n\
sizehint must be a positive integer or -1 for the default size. The\n\
sizehint is used to optimize internal data structures. It doesn't limit\n\
the maximum number of monitored events.");

static PyTypeObject pyEpoll_Type = {
	PyVarObject_HEAD_INIT(NULL, 0)
	"select.epoll",					/* tp_name */
	sizeof(pyEpoll_Object),				/* tp_basicsize */
	0,						/* tp_itemsize */
	(destructor)pyepoll_dealloc,			/* tp_dealloc */
	0,						/* tp_print */
	0,						/* tp_getattr */
	0,						/* tp_setattr */
	0,						/* tp_reserved */
	0,						/* tp_repr */
	0,						/* tp_as_number */
	0,						/* tp_as_sequence */
	0,						/* tp_as_mapping */
	0,						/* tp_hash */
	0,              				/* tp_call */
	0,						/* tp_str */
	PyObject_GenericGetAttr,			/* tp_getattro */
	0,						/* tp_setattro */
	0,						/* tp_as_buffer */
	Py_TPFLAGS_DEFAULT,				/* tp_flags */
	pyepoll_doc,					/* tp_doc */
	0,						/* tp_traverse */
	0,						/* tp_clear */
	0,						/* tp_richcompare */
	0,						/* tp_weaklistoffset */
	0,						/* tp_iter */
	0,						/* tp_iternext */
	pyepoll_methods,				/* tp_methods */
	0,						/* tp_members */
	pyepoll_getsetlist,				/* tp_getset */
	0,						/* tp_base */
	0,						/* tp_dict */
	0,						/* tp_descr_get */
	0,						/* tp_descr_set */
	0,						/* tp_dictoffset */
	0,						/* tp_init */
	0,						/* tp_alloc */
	pyepoll_new,					/* tp_new */
	0,						/* tp_free */
};

#endif /* HAVE_EPOLL */

#ifdef HAVE_KQUEUE
/* **************************************************************************
 *                      kqueue interface for BSD
 *
 * Copyright (c) 2000 Doug White, 2006 James Knight, 2007 Christian Heimes
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#ifdef HAVE_SYS_EVENT_H
#include <sys/event.h>
#endif

PyDoc_STRVAR(kqueue_event_doc,
"kevent(ident, filter=KQ_FILTER_READ, flags=KQ_EV_ADD, fflags=0, data=0, udata=0)\n\
\n\
This object is the equivalent of the struct kevent for the C API.\n\
\n\
See the kqueue manpage for more detailed information about the meaning\n\
of the arguments.\n\
\n\
One minor note: while you might hope that udata could store a\n\
reference to a python object, it cannot, because it is impossible to\n\
keep a proper reference count of the object once it's passed into the\n\
kernel. Therefore, I have restricted it to only storing an integer.  I\n\
recommend ignoring it and simply using the 'ident' field to key off\n\
of. You could also set up a dictionary on the python side to store a\n\
udata->object mapping.");

typedef struct {
	PyObject_HEAD
	struct kevent e;
} kqueue_event_Object;

static PyTypeObject kqueue_event_Type;

#define kqueue_event_Check(op) (PyObject_TypeCheck((op), &kqueue_event_Type))

typedef struct {
	PyObject_HEAD
	SOCKET kqfd;		/* kqueue control fd */
} kqueue_queue_Object;

static PyTypeObject kqueue_queue_Type;

#define kqueue_queue_Check(op) (PyObject_TypeCheck((op), &kqueue_queue_Type))

#if (SIZEOF_UINTPTR_T != SIZEOF_VOID_P)
#   error uintptr_t does not match void *!
#elif (SIZEOF_UINTPTR_T == SIZEOF_LONG_LONG)
#   define T_UINTPTRT         T_ULONGLONG
#   define T_INTPTRT          T_LONGLONG
#   define PyLong_AsUintptr_t PyLong_AsUnsignedLongLong
#   define UINTPTRT_FMT_UNIT  "K"
#   define INTPTRT_FMT_UNIT   "L"
#elif (SIZEOF_UINTPTR_T == SIZEOF_LONG)
#   define T_UINTPTRT         T_ULONG
#   define T_INTPTRT          T_LONG
#   define PyLong_AsUintptr_t PyLong_AsUnsignedLong
#   define UINTPTRT_FMT_UNIT  "k"
#   define INTPTRT_FMT_UNIT   "l"
#elif (SIZEOF_UINTPTR_T == SIZEOF_INT)
#   define T_UINTPTRT         T_UINT
#   define T_INTPTRT          T_INT
#   define PyLong_AsUintptr_t PyLong_AsUnsignedLong
#   define UINTPTRT_FMT_UNIT  "I"
#   define INTPTRT_FMT_UNIT   "i"
#else
#   error uintptr_t does not match int, long, or long long!
#endif

/* Unfortunately, we can't store python objects in udata, because
 * kevents in the kernel can be removed without warning, which would
 * forever lose the refcount on the object stored with it.
 */

#define KQ_OFF(x) offsetof(kqueue_event_Object, x)
static struct PyMemberDef kqueue_event_members[] = {
	{"ident",	T_UINTPTRT,	KQ_OFF(e.ident)},
	{"filter",	T_SHORT,	KQ_OFF(e.filter)},
	{"flags",	T_USHORT,	KQ_OFF(e.flags)},
	{"fflags",	T_UINT,		KQ_OFF(e.fflags)},
	{"data",	T_INTPTRT,	KQ_OFF(e.data)},
	{"udata",	T_UINTPTRT,	KQ_OFF(e.udata)},
	{NULL} /* Sentinel */
};
#undef KQ_OFF

static PyObject *

kqueue_event_repr(kqueue_event_Object *s)
{
	char buf[1024];
	PyOS_snprintf(
		buf, sizeof(buf),
		"<select.kevent ident=%zu filter=%d flags=0x%x fflags=0x%x "
		"data=0x%zd udata=%p>",
		(size_t)(s->e.ident), s->e.filter, s->e.flags,
		s->e.fflags, (Py_ssize_t)(s->e.data), s->e.udata);
	return PyUnicode_FromString(buf);
}

static int
kqueue_event_init(kqueue_event_Object *self, PyObject *args, PyObject *kwds)
{
	PyObject *pfd;
	static char *kwlist[] = {"ident", "filter", "flags", "fflags",
				 "data", "udata", NULL};
	static char *fmt = "O|hhi" INTPTRT_FMT_UNIT UINTPTRT_FMT_UNIT ":kevent";

	EV_SET(&(self->e), 0, EVFILT_READ, EV_ADD, 0, 0, 0); /* defaults */
	
	if (!PyArg_ParseTupleAndKeywords(args, kwds, fmt, kwlist,
		&pfd, &(self->e.filter), &(self->e.flags),
		&(self->e.fflags), &(self->e.data), &(self->e.udata))) {
		return -1;
	}

	if (PyLong_Check(pfd)) {
		self->e.ident = PyLong_AsUintptr_t(pfd);
	}
	else {
		self->e.ident = PyObject_AsFileDescriptor(pfd);
	}
	if (PyErr_Occurred()) {
		return -1;
	}
	return 0;
}

static PyObject *
kqueue_event_richcompare(kqueue_event_Object *s, kqueue_event_Object *o,
			 int op)
{
	Py_intptr_t result = 0;

	if (!kqueue_event_Check(o)) {
		if (op == Py_EQ || op == Py_NE) {
                	PyObject *res = op == Py_EQ ? Py_False : Py_True;
			Py_INCREF(res);
			return res;
		}
		PyErr_Format(PyExc_TypeError,
			"can't compare %.200s to %.200s",
			Py_TYPE(s)->tp_name, Py_TYPE(o)->tp_name);
		return NULL;
	}
	if (((result = s->e.ident - o->e.ident) == 0) &&
	    ((result = s->e.filter - o->e.filter) == 0) &&
	    ((result = s->e.flags - o->e.flags) == 0) &&
	    ((result = s->e.fflags - o->e.fflags) == 0) &&
	    ((result = s->e.data - o->e.data) == 0) &&
	    ((result = s->e.udata - o->e.udata) == 0)
	   ) {
		result = 0;
	}

	switch (op) {
	    case Py_EQ:
		result = (result == 0);
		break;
	    case Py_NE:
		result = (result != 0);
		break;
	    case Py_LE:
		result = (result <= 0);
		break;
	    case Py_GE:
		result = (result >= 0);
		break;
	    case Py_LT:
		result = (result < 0);
		break;
	    case Py_GT:
		result = (result > 0);
		break;
	}
	return PyBool_FromLong((long)result);
}

static PyTypeObject kqueue_event_Type = {
	PyVarObject_HEAD_INIT(NULL, 0)
	"select.kevent",				/* tp_name */
	sizeof(kqueue_event_Object),			/* tp_basicsize */
	0,						/* tp_itemsize */
	0,						/* tp_dealloc */
	0,						/* tp_print */
	0,						/* tp_getattr */
	0,						/* tp_setattr */
	0,						/* tp_reserved */
	(reprfunc)kqueue_event_repr,			/* tp_repr */
	0,						/* tp_as_number */
	0,						/* tp_as_sequence */
	0,						/* tp_as_mapping */
	0,						/* tp_hash */
	0,              				/* tp_call */
	0,						/* tp_str */
	0,						/* tp_getattro */
	0,						/* tp_setattro */
	0,						/* tp_as_buffer */
	Py_TPFLAGS_DEFAULT,				/* tp_flags */
	kqueue_event_doc,				/* tp_doc */
	0,						/* tp_traverse */
	0,						/* tp_clear */
	(richcmpfunc)kqueue_event_richcompare,		/* tp_richcompare */
	0,						/* tp_weaklistoffset */
	0,						/* tp_iter */
	0,						/* tp_iternext */
	0,						/* tp_methods */
	kqueue_event_members,				/* tp_members */
	0,						/* tp_getset */
	0,						/* tp_base */
	0,						/* tp_dict */
	0,						/* tp_descr_get */
	0,						/* tp_descr_set */
	0,						/* tp_dictoffset */
	(initproc)kqueue_event_init,			/* tp_init */
	0,						/* tp_alloc */
	0,						/* tp_new */
	0,						/* tp_free */
};

static PyObject *
kqueue_queue_err_closed(void)
{
	PyErr_SetString(PyExc_ValueError, "I/O operation on closed kqueue fd");
	return NULL;
}

static int
kqueue_queue_internal_close(kqueue_queue_Object *self)
{
	int save_errno = 0;
	if (self->kqfd >= 0) {
		int kqfd = self->kqfd;
		self->kqfd = -1;
		Py_BEGIN_ALLOW_THREADS
		if (close(kqfd) < 0)
			save_errno = errno;
		Py_END_ALLOW_THREADS
	}
	return save_errno;
}

static PyObject *
newKqueue_Object(PyTypeObject *type, SOCKET fd)
{
	kqueue_queue_Object *self;
	assert(type != NULL && type->tp_alloc != NULL);
	self = (kqueue_queue_Object *) type->tp_alloc(type, 0);
	if (self == NULL) {
		return NULL;
	}
	
	if (fd == -1) {
		Py_BEGIN_ALLOW_THREADS
		self->kqfd = kqueue();
		Py_END_ALLOW_THREADS
	}
	else {
		self->kqfd = fd;
	}
	if (self->kqfd < 0) {
		Py_DECREF(self);
		PyErr_SetFromErrno(PyExc_IOError);
		return NULL;
	}
	return (PyObject *)self;
}

static PyObject *
kqueue_queue_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{

	if ((args != NULL && PyObject_Size(args)) ||
			(kwds != NULL && PyObject_Size(kwds))) {
		PyErr_SetString(PyExc_ValueError,
				"select.kqueue doesn't accept arguments");
		return NULL;
	}

	return newKqueue_Object(type, -1);
}

static void
kqueue_queue_dealloc(kqueue_queue_Object *self)
{
	kqueue_queue_internal_close(self);
	Py_TYPE(self)->tp_free(self);
}

static PyObject*
kqueue_queue_close(kqueue_queue_Object *self)
{
	errno = kqueue_queue_internal_close(self);
	if (errno < 0) {
		PyErr_SetFromErrno(PyExc_IOError);
		return NULL;
	}
	Py_RETURN_NONE;
}

PyDoc_STRVAR(kqueue_queue_close_doc,
"close() -> None\n\
\n\
Close the kqueue control file descriptor. Further operations on the kqueue\n\
object will raise an exception.");

static PyObject*
kqueue_queue_get_closed(kqueue_queue_Object *self)
{
	if (self->kqfd < 0)
		Py_RETURN_TRUE;
	else
		Py_RETURN_FALSE;
}

static PyObject*
kqueue_queue_fileno(kqueue_queue_Object *self)
{
	if (self->kqfd < 0)
		return kqueue_queue_err_closed();
	return PyLong_FromLong(self->kqfd);
}

PyDoc_STRVAR(kqueue_queue_fileno_doc,
"fileno() -> int\n\
\n\
Return the kqueue control file descriptor.");

static PyObject*
kqueue_queue_fromfd(PyObject *cls, PyObject *args)
{
	SOCKET fd;

	if (!PyArg_ParseTuple(args, "i:fromfd", &fd))
		return NULL;

	return newKqueue_Object((PyTypeObject*)cls, fd);
}

PyDoc_STRVAR(kqueue_queue_fromfd_doc,
"fromfd(fd) -> kqueue\n\
\n\
Create a kqueue object from a given control fd.");

static PyObject *
kqueue_queue_control(kqueue_queue_Object *self, PyObject *args)
{
	int nevents = 0;
	int gotevents = 0;
	int nchanges = 0;
	int i = 0;
	PyObject *otimeout = NULL;
	PyObject *ch = NULL;
	PyObject *it = NULL, *ei = NULL;
	PyObject *result = NULL;
	struct kevent *evl = NULL;
	struct kevent *chl = NULL;
	struct timespec timeoutspec;
	struct timespec *ptimeoutspec;

	if (self->kqfd < 0)
		return kqueue_queue_err_closed();

	if (!PyArg_ParseTuple(args, "Oi|O:control", &ch, &nevents, &otimeout))
		return NULL;

	if (nevents < 0) {
		PyErr_Format(PyExc_ValueError,
			"Length of eventlist must be 0 or positive, got %d",
			nevents);
		return NULL;
	}

	if (otimeout == Py_None || otimeout == NULL) {
		ptimeoutspec = NULL;
	}
	else if (PyNumber_Check(otimeout)) {
		double timeout;
		long seconds;

		timeout = PyFloat_AsDouble(otimeout);
		if (timeout == -1 && PyErr_Occurred())
			return NULL;
		if (timeout > (double)LONG_MAX) {
			PyErr_SetString(PyExc_OverflowError,
					"timeout period too long");
			return NULL;
		}
		if (timeout < 0) {
			PyErr_SetString(PyExc_ValueError,
					"timeout must be positive or None");
			return NULL;
		}

		seconds = (long)timeout;
		timeout = timeout - (double)seconds;
		timeoutspec.tv_sec = seconds;
		timeoutspec.tv_nsec = (long)(timeout * 1E9);
		ptimeoutspec = &timeoutspec;
	}
	else {
		PyErr_Format(PyExc_TypeError,
			"timeout argument must be an number "
			"or None, got %.200s",
			Py_TYPE(otimeout)->tp_name);
		return NULL;
	}

	if (ch != NULL && ch != Py_None) {
		it = PyObject_GetIter(ch);
		if (it == NULL) {
			PyErr_SetString(PyExc_TypeError,
					"changelist is not iterable");
			return NULL;
		}
		nchanges = PyObject_Size(ch);
		if (nchanges < 0) {
			goto error;
		}

		chl = PyMem_New(struct kevent, nchanges);
		if (chl == NULL) {
			PyErr_NoMemory();
			goto error;
		}
		i = 0;
		while ((ei = PyIter_Next(it)) != NULL) {
			if (!kqueue_event_Check(ei)) {
				Py_DECREF(ei);
				PyErr_SetString(PyExc_TypeError,
					"changelist must be an iterable of "
				 	"select.kevent objects");
				goto error;
			} else {
				chl[i++] = ((kqueue_event_Object *)ei)->e;
			}
			Py_DECREF(ei);
		}
	}
	Py_CLEAR(it);

	/* event list */
	if (nevents) {
		evl = PyMem_New(struct kevent, nevents);
		if (evl == NULL) {
			PyErr_NoMemory();
			goto error;
		}
	}

	Py_BEGIN_ALLOW_THREADS
	gotevents = kevent(self->kqfd, chl, nchanges,
			   evl, nevents, ptimeoutspec);
	Py_END_ALLOW_THREADS

	if (gotevents == -1) {
		PyErr_SetFromErrno(PyExc_OSError);
		goto error;
	}

	result = PyList_New(gotevents);
	if (result == NULL) {
		goto error;
	}

	for (i = 0; i < gotevents; i++) {
		kqueue_event_Object *ch;

		ch = PyObject_New(kqueue_event_Object, &kqueue_event_Type);
		if (ch == NULL) {
			goto error;
		}
		ch->e = evl[i];
		PyList_SET_ITEM(result, i, (PyObject *)ch);
	}
	PyMem_Free(chl);
	PyMem_Free(evl);
	return result;

    error:
	PyMem_Free(chl);
	PyMem_Free(evl);
	Py_XDECREF(result);
	Py_XDECREF(it);
	return NULL;
}

PyDoc_STRVAR(kqueue_queue_control_doc,
"control(changelist, max_events[, timeout=None]) -> eventlist\n\
\n\
Calls the kernel kevent function.\n\
- changelist must be a list of kevent objects describing the changes\n\
  to be made to the kernel's watch list or None.\n\
- max_events lets you specify the maximum number of events that the\n\
  kernel will return.\n\
- timeout is the maximum time to wait in seconds, or else None,\n\
  to wait forever. timeout accepts floats for smaller timeouts, too.");


static PyMethodDef kqueue_queue_methods[] = {
	{"fromfd",	(PyCFunction)kqueue_queue_fromfd,
	 METH_VARARGS | METH_CLASS, kqueue_queue_fromfd_doc},
	{"close",	(PyCFunction)kqueue_queue_close,	METH_NOARGS,
	 kqueue_queue_close_doc},
	{"fileno",	(PyCFunction)kqueue_queue_fileno,	METH_NOARGS,
	 kqueue_queue_fileno_doc},
	{"control",	(PyCFunction)kqueue_queue_control,
	 METH_VARARGS ,	kqueue_queue_control_doc},
	{NULL,	NULL},
};

static PyGetSetDef kqueue_queue_getsetlist[] = {
	{"closed", (getter)kqueue_queue_get_closed, NULL,
	 "True if the kqueue handler is closed"},
	{0},
};

PyDoc_STRVAR(kqueue_queue_doc,
"Kqueue syscall wrapper.\n\
\n\
For example, to start watching a socket for input:\n\
>>> kq = kqueue()\n\
>>> sock = socket()\n\
>>> sock.connect((host, port))\n\
>>> kq.control([kevent(sock, KQ_FILTER_WRITE, KQ_EV_ADD)], 0)\n\
\n\
To wait one second for it to become writeable:\n\
>>> kq.control(None, 1, 1000)\n\
\n\
To stop listening:\n\
>>> kq.control([kevent(sock, KQ_FILTER_WRITE, KQ_EV_DELETE)], 0)");

static PyTypeObject kqueue_queue_Type = {
	PyVarObject_HEAD_INIT(NULL, 0)
	"select.kqueue",				/* tp_name */
	sizeof(kqueue_queue_Object),			/* tp_basicsize */
	0,						/* tp_itemsize */
	(destructor)kqueue_queue_dealloc,		/* tp_dealloc */
	0,						/* tp_print */
	0,						/* tp_getattr */
	0,						/* tp_setattr */
	0,						/* tp_reserved */
	0,						/* tp_repr */
	0,						/* tp_as_number */
	0,						/* tp_as_sequence */
	0,						/* tp_as_mapping */
	0,						/* tp_hash */
	0,              				/* tp_call */
	0,						/* tp_str */
	0,						/* tp_getattro */
	0,						/* tp_setattro */
	0,						/* tp_as_buffer */
	Py_TPFLAGS_DEFAULT,				/* tp_flags */
	kqueue_queue_doc,				/* tp_doc */
	0,						/* tp_traverse */
	0,						/* tp_clear */
	0,						/* tp_richcompare */
	0,						/* tp_weaklistoffset */
	0,						/* tp_iter */
	0,						/* tp_iternext */
	kqueue_queue_methods,				/* tp_methods */
	0,						/* tp_members */
	kqueue_queue_getsetlist,			/* tp_getset */
	0,						/* tp_base */
	0,						/* tp_dict */
	0,						/* tp_descr_get */
	0,						/* tp_descr_set */
	0,						/* tp_dictoffset */
	0,						/* tp_init */
	0,						/* tp_alloc */
	kqueue_queue_new,				/* tp_new */
	0,						/* tp_free */
};

#endif /* HAVE_KQUEUE */
/* ************************************************************************ */

PyDoc_STRVAR(select_doc,
"select(rlist, wlist, xlist[, timeout]) -> (rlist, wlist, xlist)\n\
\n\
Wait until one or more file descriptors are ready for some kind of I/O.\n\
The first three arguments are sequences of file descriptors to be waited for:\n\
rlist -- wait until ready for reading\n\
wlist -- wait until ready for writing\n\
xlist -- wait for an ``exceptional condition''\n\
If only one kind of condition is required, pass [] for the other lists.\n\
A file descriptor is either a socket or file object, or a small integer\n\
gotten from a fileno() method call on one of those.\n\
\n\
The optional 4th argument specifies a timeout in seconds; it may be\n\
a floating point number to specify fractions of seconds.  If it is absent\n\
or None, the call will never time out.\n\
\n\
The return value is a tuple of three lists corresponding to the first three\n\
arguments; each contains the subset of the corresponding file descriptors\n\
that are ready.\n\
\n\
*** IMPORTANT NOTICE ***\n\
On Windows and OpenVMS, only sockets are supported; on Unix, all file\n\
descriptors can be used.");

static PyMethodDef select_methods[] = {
	{"select",	select_select,	METH_VARARGS,	select_doc},
#ifdef HAVE_POLL
	{"poll",	select_poll,	METH_NOARGS,	poll_doc},
#endif /* HAVE_POLL */
	{0,  	0},	/* sentinel */
};

PyDoc_STRVAR(module_doc,
"This module supports asynchronous I/O on multiple file descriptors.\n\
\n\
*** IMPORTANT NOTICE ***\n\
On Windows and OpenVMS, only sockets are supported; on Unix, all file descriptors.");


static struct PyModuleDef selectmodule = {
	PyModuleDef_HEAD_INIT,
	"select",
	module_doc,
	-1,
	select_methods,
	NULL,
	NULL,
	NULL,
	NULL
};

PyMODINIT_FUNC
PyInit_select(void)
{
	PyObject *m;
	m = PyModule_Create(&selectmodule);
	if (m == NULL)
		return NULL;

	SelectError = PyErr_NewException("select.error", NULL, NULL);
	Py_INCREF(SelectError);
	PyModule_AddObject(m, "error", SelectError);

#ifdef PIPE_BUF
	PyModule_AddIntConstant(m, "PIPE_BUF", PIPE_BUF);
#endif

#if defined(HAVE_POLL)
#ifdef __APPLE__
	if (select_have_broken_poll()) {
		if (PyObject_DelAttrString(m, "poll") == -1) {
			PyErr_Clear();
		}
	} else {
#else
	{
#endif
		if (PyType_Ready(&poll_Type) < 0)
			return NULL;
		PyModule_AddIntConstant(m, "POLLIN", POLLIN);
		PyModule_AddIntConstant(m, "POLLPRI", POLLPRI);
		PyModule_AddIntConstant(m, "POLLOUT", POLLOUT);
		PyModule_AddIntConstant(m, "POLLERR", POLLERR);
		PyModule_AddIntConstant(m, "POLLHUP", POLLHUP);
		PyModule_AddIntConstant(m, "POLLNVAL", POLLNVAL);

#ifdef POLLRDNORM
		PyModule_AddIntConstant(m, "POLLRDNORM", POLLRDNORM);
#endif
#ifdef POLLRDBAND
		PyModule_AddIntConstant(m, "POLLRDBAND", POLLRDBAND);
#endif
#ifdef POLLWRNORM
		PyModule_AddIntConstant(m, "POLLWRNORM", POLLWRNORM);
#endif
#ifdef POLLWRBAND
		PyModule_AddIntConstant(m, "POLLWRBAND", POLLWRBAND);
#endif
#ifdef POLLMSG
		PyModule_AddIntConstant(m, "POLLMSG", POLLMSG);
#endif
	}
#endif /* HAVE_POLL */

#ifdef HAVE_EPOLL
	Py_TYPE(&pyEpoll_Type) = &PyType_Type;
	if (PyType_Ready(&pyEpoll_Type) < 0)
		return NULL;

	Py_INCREF(&pyEpoll_Type);
	PyModule_AddObject(m, "epoll", (PyObject *) &pyEpoll_Type);

	PyModule_AddIntConstant(m, "EPOLLIN", EPOLLIN);
	PyModule_AddIntConstant(m, "EPOLLOUT", EPOLLOUT);
	PyModule_AddIntConstant(m, "EPOLLPRI", EPOLLPRI);
	PyModule_AddIntConstant(m, "EPOLLERR", EPOLLERR);
	PyModule_AddIntConstant(m, "EPOLLHUP", EPOLLHUP);
	PyModule_AddIntConstant(m, "EPOLLET", EPOLLET);
#ifdef EPOLLONESHOT
	/* Kernel 2.6.2+ */
	PyModule_AddIntConstant(m, "EPOLLONESHOT", EPOLLONESHOT);
#endif
	/* PyModule_AddIntConstant(m, "EPOLL_RDHUP", EPOLLRDHUP); */
	PyModule_AddIntConstant(m, "EPOLLRDNORM", EPOLLRDNORM);
	PyModule_AddIntConstant(m, "EPOLLRDBAND", EPOLLRDBAND);
	PyModule_AddIntConstant(m, "EPOLLWRNORM", EPOLLWRNORM);
	PyModule_AddIntConstant(m, "EPOLLWRBAND", EPOLLWRBAND);
	PyModule_AddIntConstant(m, "EPOLLMSG", EPOLLMSG);
#endif /* HAVE_EPOLL */

#ifdef HAVE_KQUEUE
	kqueue_event_Type.tp_new = PyType_GenericNew;
	Py_TYPE(&kqueue_event_Type) = &PyType_Type;
	if(PyType_Ready(&kqueue_event_Type) < 0)
		return NULL;

	Py_INCREF(&kqueue_event_Type);
	PyModule_AddObject(m, "kevent", (PyObject *)&kqueue_event_Type);

	Py_TYPE(&kqueue_queue_Type) = &PyType_Type;
	if(PyType_Ready(&kqueue_queue_Type) < 0)
		return NULL;
	Py_INCREF(&kqueue_queue_Type);
	PyModule_AddObject(m, "kqueue", (PyObject *)&kqueue_queue_Type);
	
	/* event filters */
	PyModule_AddIntConstant(m, "KQ_FILTER_READ", EVFILT_READ);
	PyModule_AddIntConstant(m, "KQ_FILTER_WRITE", EVFILT_WRITE);
	PyModule_AddIntConstant(m, "KQ_FILTER_AIO", EVFILT_AIO);
	PyModule_AddIntConstant(m, "KQ_FILTER_VNODE", EVFILT_VNODE);
	PyModule_AddIntConstant(m, "KQ_FILTER_PROC", EVFILT_PROC);
#ifdef EVFILT_NETDEV
	PyModule_AddIntConstant(m, "KQ_FILTER_NETDEV", EVFILT_NETDEV);
#endif
	PyModule_AddIntConstant(m, "KQ_FILTER_SIGNAL", EVFILT_SIGNAL);
	PyModule_AddIntConstant(m, "KQ_FILTER_TIMER", EVFILT_TIMER);

	/* event flags */
	PyModule_AddIntConstant(m, "KQ_EV_ADD", EV_ADD);
	PyModule_AddIntConstant(m, "KQ_EV_DELETE", EV_DELETE);
	PyModule_AddIntConstant(m, "KQ_EV_ENABLE", EV_ENABLE);
	PyModule_AddIntConstant(m, "KQ_EV_DISABLE", EV_DISABLE);
	PyModule_AddIntConstant(m, "KQ_EV_ONESHOT", EV_ONESHOT);
	PyModule_AddIntConstant(m, "KQ_EV_CLEAR", EV_CLEAR);

	PyModule_AddIntConstant(m, "KQ_EV_SYSFLAGS", EV_SYSFLAGS);
	PyModule_AddIntConstant(m, "KQ_EV_FLAG1", EV_FLAG1);

	PyModule_AddIntConstant(m, "KQ_EV_EOF", EV_EOF);
	PyModule_AddIntConstant(m, "KQ_EV_ERROR", EV_ERROR);

	/* READ WRITE filter flag */
	PyModule_AddIntConstant(m, "KQ_NOTE_LOWAT", NOTE_LOWAT);
	
	/* VNODE filter flags  */
	PyModule_AddIntConstant(m, "KQ_NOTE_DELETE", NOTE_DELETE);
	PyModule_AddIntConstant(m, "KQ_NOTE_WRITE", NOTE_WRITE);
	PyModule_AddIntConstant(m, "KQ_NOTE_EXTEND", NOTE_EXTEND);
	PyModule_AddIntConstant(m, "KQ_NOTE_ATTRIB", NOTE_ATTRIB);
	PyModule_AddIntConstant(m, "KQ_NOTE_LINK", NOTE_LINK);
	PyModule_AddIntConstant(m, "KQ_NOTE_RENAME", NOTE_RENAME);
	PyModule_AddIntConstant(m, "KQ_NOTE_REVOKE", NOTE_REVOKE);

	/* PROC filter flags  */
	PyModule_AddIntConstant(m, "KQ_NOTE_EXIT", NOTE_EXIT);
	PyModule_AddIntConstant(m, "KQ_NOTE_FORK", NOTE_FORK);
	PyModule_AddIntConstant(m, "KQ_NOTE_EXEC", NOTE_EXEC);
	PyModule_AddIntConstant(m, "KQ_NOTE_PCTRLMASK", NOTE_PCTRLMASK);
	PyModule_AddIntConstant(m, "KQ_NOTE_PDATAMASK", NOTE_PDATAMASK);

	PyModule_AddIntConstant(m, "KQ_NOTE_TRACK", NOTE_TRACK);
	PyModule_AddIntConstant(m, "KQ_NOTE_CHILD", NOTE_CHILD);
	PyModule_AddIntConstant(m, "KQ_NOTE_TRACKERR", NOTE_TRACKERR);

	/* NETDEV filter flags */
#ifdef EVFILT_NETDEV
	PyModule_AddIntConstant(m, "KQ_NOTE_LINKUP", NOTE_LINKUP);
	PyModule_AddIntConstant(m, "KQ_NOTE_LINKDOWN", NOTE_LINKDOWN);
	PyModule_AddIntConstant(m, "KQ_NOTE_LINKINV", NOTE_LINKINV);
#endif

#endif /* HAVE_KQUEUE */
	return m;
}