cpython/Modules/selectmodule.c

/***********************************************************
Copyright 1991-1995 by Stichting Mathematisch Centrum, Amsterdam,
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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>

#ifdef MS_WINDOWS
#include <winsock.h>
#else
#include "myselect.h" /* Also includes mytime.h */
#define SOCKET int
#endif

static PyObject *SelectError;

typedef struct {	/* list of Python objects and their file descriptor */
	PyObject *obj;
	SOCKET fd;
} pylist;

/* 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, len, index, max = -1;
	PyObject *o, *fno;
	PyObject *meth;
	SOCKET v;

	index = 0;
	fd2obj[0].obj = (PyObject*)0;	     /* set list to zero size */
    
	FD_ZERO(set);
	len = PyList_Size(list);
	for (i=0; i<len; i++)  {
		o = PyList_GetItem(list, i);
		if (PyInt_Check(o)) {
			v = PyInt_AsLong(o);
		}
		else if ((meth = PyObject_GetAttrString(o, "fileno")) != NULL)
		{
			fno = PyEval_CallObject(meth, NULL);
			Py_DECREF(meth);
			if (fno == NULL)
				return -1;
                        if (!PyInt_Check(fno)) {
                            PyErr_SetString(PyExc_TypeError,
                                       "fileno method returned a non-integer");
                            Py_DECREF(fno);
                            return -1;
                        }
                        v = PyInt_AsLong(fno);
			Py_DECREF(fno);
		}
		else {
			PyErr_SetString(PyExc_TypeError,
			  "argument must be an int, or have a fileno() method."
				);
			return -1;
		}
#ifdef _MSC_VER
		max = 0;	/* not used for Win32 */
#else
		if (v < 0 || v >= FD_SETSIZE) {
			PyErr_SetString(
				PyExc_ValueError,
				"filedescriptor out of range in select()");
			return -1;
		}
		if (v > max)
			max = v;
#endif
		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()");
			return -1;
		}
		fd2obj[index].obj = o;
		fd2obj[index].fd = v;
		fd2obj[++index].obj = (PyObject *)0; /* sentinel */
	}
	return max+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 j, num=0;
	PyObject *list, *o;
	SOCKET fd;

	for (j=0; fd2obj[j].obj; j++)
		if (FD_ISSET(fd2obj[j].fd, set))
			num++;

	list = PyList_New(num);
	if (!list)
		return NULL;

	num = 0;
	for (j=0; fd2obj[j].obj; 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()");
				return NULL;
			}
#endif
			o = fd2obj[j].obj;
			Py_INCREF(o);
			if (PyList_SetItem(list, num, o) < 0) {
				Py_DECREF(list);
				return NULL;
			}
			num++;
		}
	}
	return list;
}
    
static PyObject *
select_select(self, args)
	PyObject *self;
	PyObject *args;
{
	pylist rfd2obj[FD_SETSIZE + 3];
	pylist wfd2obj[FD_SETSIZE + 3];
	pylist efd2obj[FD_SETSIZE + 3];
	PyObject *ifdlist, *ofdlist, *efdlist;
	PyObject *ret;
	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 must be float or None",
			      &timeout))
		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;
	}

	/* Convert lists to fd_sets, and get maximum fd number
	 * propagates the Python exception set in list2set()
	 */
	if ((imax=list2set(ifdlist, &ifdset, rfd2obj)) < 0) 
		return NULL;
	if ((omax=list2set(ofdlist, &ofdset, wfd2obj)) < 0) 
		return NULL;
	if ((emax=list2set(efdlist, &efdset, efd2obj)) < 0) 
		return NULL;
	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);
		return NULL;
	}

	if (n == 0) {			     /* Speedup hack */
		ifdlist = PyList_New(0);
		if (!ifdlist)
			return NULL;
		ret = Py_BuildValue("OOO", ifdlist, ifdlist, ifdlist);
		Py_XDECREF(ifdlist);
		return ret;
	}

	/* 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);
	return ret;
}


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


void
initselect()
{
	PyObject *m, *d;
	m = Py_InitModule("select", select_methods);
	d = PyModule_GetDict(m);
	SelectError = PyString_FromString("select.error");
	PyDict_SetItemString(d, "error", SelectError);
	if (PyErr_Occurred())
		Py_FatalError("Cannot initialize select module");
}