cpython/Modules/selectmodule.c

/***********************************************************
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,
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/* 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"

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

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

#include <sys/types.h>

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

#ifdef MS_WINDOWS
#include <winsock.h>
#else
#include "myselect.h" /* Also includes mytime.h */
#define SOCKET int
#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;
		}
#ifdef _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",
			      &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.";

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);
}