Source

cpython-withatomic / Modules / selectmodule.c

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/***********************************************************
Copyright 1991-1995 by Stichting Mathematisch Centrum, Amsterdam,
The Netherlands.

                        All Rights Reserved

Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted,
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in
supporting documentation, and that the names of Stichting Mathematisch
Centrum or CWI or Corporation for National Research Initiatives or
CNRI not be used in advertising or publicity pertaining to
distribution of the software without specific, written prior
permission.

While CWI is the initial source for this software, a modified version
is made available by the Corporation for National Research Initiatives
(CNRI) at the Internet address ftp://ftp.python.org.

STICHTING MATHEMATISCH CENTRUM AND CNRI DISCLAIM ALL WARRANTIES WITH
REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH
CENTRUM OR CNRI BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL
DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
PERFORMANCE OF THIS SOFTWARE.

******************************************************************/

/* 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.
   Under BeOS, we suffer the same dichotomy as Win32; sockets can be anything
   >= 0.
*/

#include "Python.h"

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

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

#ifndef DONT_HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif

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

#ifdef MS_WINDOWS
#include <winsock.h>
#else
#ifdef __BEOS__
#include <net/socket.h>
#define SOCKET int
#else
#include "myselect.h" /* Also includes mytime.h */
#define SOCKET int
#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(fd2obj)
	pylist fd2obj[FD_SETSIZE + 3];
{
	int i;
	for (i = 0; i < FD_SETSIZE + 3 && 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
list2set(list, set, fd2obj)
	PyObject *list;
	fd_set *set;
	pylist fd2obj[FD_SETSIZE + 3];
{
	int i;
	int max = -1;
	int index = 0;
	int len = PyList_Size(list);
	PyObject* o = NULL;

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

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

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

		Py_INCREF(o);

		if (PyInt_Check(o)) {
			v = PyInt_AsLong(o);
		}
		else if ((meth = PyObject_GetAttrString(o, "fileno")) != NULL)
		{
			PyObject *fno = PyEval_CallObject(meth, NULL);
			Py_DECREF(meth);
			if (fno == NULL)
				goto finally;

                        if (!PyInt_Check(fno)) {
				PyErr_SetString(PyExc_TypeError,
                                       "fileno method returned a non-integer");
				Py_DECREF(fno);
				goto finally;
                        }
                        v = PyInt_AsLong(fno);
			Py_DECREF(fno);
		}
		else {
			PyErr_SetString(PyExc_TypeError,
			"argument must be an int, or have a fileno() method.");
			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;
	}
	return max+1;

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

/* returns NULL and sets the Python exception if an error occurred */
static PyObject *
set2list(set, fd2obj)
	fd_set *set;
	pylist fd2obj[FD_SETSIZE + 3];
{
	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;
}

    
static PyObject *
select_select(self, args)
	PyObject *self;
	PyObject *args;
{
#ifdef MS_WINDOWS
	/* This would be an awful lot of stack space on Windows! */
	pylist *rfd2obj, *wfd2obj, *efd2obj;
#else
	pylist rfd2obj[FD_SETSIZE + 3];
	pylist wfd2obj[FD_SETSIZE + 3];
	pylist efd2obj[FD_SETSIZE + 3];
#endif
	PyObject *ifdlist, *ofdlist, *efdlist;
	PyObject *ret = NULL;
	PyObject *tout = Py_None;
	fd_set ifdset, ofdset, efdset;
	double timeout;
	struct timeval tv, *tvp;
	int seconds;
	int imax, omax, emax, max;
	int n;

	/* convert arguments */
	if (!PyArg_ParseTuple(args, "OOO|O:select",
			      &ifdlist, &ofdlist, &efdlist, &tout))
		return NULL;

	if (tout == Py_None)
		tvp = (struct timeval *)0;
	else if (!PyArg_Parse(tout, "d", &timeout)) {
		PyErr_SetString(PyExc_TypeError,
				"timeout must be a float or None");
		return NULL;
	}
	else {
		seconds = (int)timeout;
		timeout = timeout - (double)seconds;
		tv.tv_sec = seconds;
		tv.tv_usec = (int)(timeout*1000000.0);
		tvp = &tv;
	}

	/* sanity check first three arguments */
	if (!PyList_Check(ifdlist) ||
	    !PyList_Check(ofdlist) ||
	    !PyList_Check(efdlist))
	{
		PyErr_SetString(PyExc_TypeError,
				"arguments 1-3 must be lists");
		return NULL;
	}

#ifdef MS_WINDOWS
	/* Allocate memory for the lists */
	rfd2obj = PyMem_NEW(pylist, FD_SETSIZE + 3);
	wfd2obj = PyMem_NEW(pylist, FD_SETSIZE + 3);
	efd2obj = PyMem_NEW(pylist, FD_SETSIZE + 3);
	if (rfd2obj == NULL || wfd2obj == NULL || efd2obj == NULL) {
		PyMem_XDEL(rfd2obj);
		PyMem_XDEL(wfd2obj);
		PyMem_XDEL(efd2obj);
		return NULL;
	}
#endif
	/* Convert lists to fd_sets, and get maximum fd number
	 * propagates the Python exception set in list2set()
	 */
	rfd2obj[0].sentinel = -1;
	wfd2obj[0].sentinel = -1;
	efd2obj[0].sentinel = -1;
	if ((imax=list2set(ifdlist, &ifdset, rfd2obj)) < 0) 
		goto finally;
	if ((omax=list2set(ofdlist, &ofdset, wfd2obj)) < 0) 
		goto finally;
	if ((emax=list2set(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

	if (n < 0) {
		PyErr_SetFromErrno(SelectError);
	}
	else if (n == 0) {
                /* optimization */
		ifdlist = PyList_New(0);
		if (ifdlist) {
			ret = Py_BuildValue("OOO", 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 = Py_BuildValue("OOO", ifdlist, ofdlist, efdlist);

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

static char 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 lists 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, only sockets are supported; on Unix, all file descriptors.";


static PyMethodDef select_methods[] = {
    {"select",	select_select, 1, select_doc},
    {0,  	0},			     /* sentinel */
};

static char module_doc[] =
"This module supports asynchronous I/O on multiple file descriptors.\n\
\n\
*** IMPORTANT NOTICE ***\n\
On Windows, only sockets are supported; on Unix, all file descriptors.";

DL_EXPORT(void)
initselect()
{
	PyObject *m, *d;
	m = Py_InitModule3("select", select_methods, module_doc);
	d = PyModule_GetDict(m);
	SelectError = PyErr_NewException("select.error", NULL, NULL);
	PyDict_SetItemString(d, "error", SelectError);
}