https://origsvn.digium.com/svn/asterisk/branches/1.4 ........ r140816 | russell | 2008-09-03 08:24:35 -0500 (Wed, 03 Sep 2008) | 4 lines Don't freak out if the poll emulation receives NULL for the pollfds array (closes issue #13307) Reported by: jcovert ........ git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@140817 65c4cc65-6c06-0410-ace0-fbb531ad65f3
298 lines
8.5 KiB
C
298 lines
8.5 KiB
C
/*---------------------------------------------------------------------------*\
|
||
$Id$
|
||
|
||
NAME
|
||
|
||
poll - select(2)-based poll() emulation function for BSD systems.
|
||
|
||
SYNOPSIS
|
||
#include "poll.h"
|
||
|
||
struct pollfd
|
||
{
|
||
int fd;
|
||
short events;
|
||
short revents;
|
||
}
|
||
|
||
int poll (struct pollfd *pArray, unsigned long n_fds, int timeout)
|
||
|
||
DESCRIPTION
|
||
|
||
This file, and the accompanying "poll.h", implement the System V
|
||
poll(2) system call for BSD systems (which typically do not provide
|
||
poll()). Poll() provides a method for multiplexing input and output
|
||
on multiple open file descriptors; in traditional BSD systems, that
|
||
capability is provided by select(). While the semantics of select()
|
||
differ from those of poll(), poll() can be readily emulated in terms
|
||
of select() -- which is how this function is implemented.
|
||
|
||
REFERENCES
|
||
Stevens, W. Richard. Unix Network Programming. Prentice-Hall, 1990.
|
||
|
||
NOTES
|
||
1. This software requires an ANSI C compiler.
|
||
|
||
LICENSE
|
||
|
||
This software is released under the following license:
|
||
|
||
Copyright (c) 1995-2002 Brian M. Clapper
|
||
All rights reserved.
|
||
|
||
Redistribution and use in source and binary forms are
|
||
permitted provided that: (1) source distributions retain
|
||
this entire copyright notice and comment; (2) modifications
|
||
made to the software are prominently mentioned, and a copy
|
||
of the original software (or a pointer to its location) are
|
||
included; and (3) distributions including binaries display
|
||
the following acknowledgement: "This product includes
|
||
software developed by Brian M. Clapper <bmc@clapper.org>"
|
||
in the documentation or other materials provided with the
|
||
distribution. The name of the author may not be used to
|
||
endorse or promote products derived from this software
|
||
without specific prior written permission.
|
||
|
||
THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS
|
||
OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE
|
||
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
|
||
PARTICULAR PURPOSE.
|
||
|
||
Effectively, this means you can do what you want with the software
|
||
except remove this notice or take advantage of the author's name.
|
||
If you modify the software and redistribute your modified version,
|
||
you must indicate that your version is a modification of the
|
||
original, and you must provide either a pointer to or a copy of the
|
||
original.
|
||
\*---------------------------------------------------------------------------*/
|
||
|
||
|
||
/*---------------------------------------------------------------------------*\
|
||
Includes
|
||
\*---------------------------------------------------------------------------*/
|
||
|
||
#include <unistd.h> /* standard Unix definitions */
|
||
#include <sys/types.h> /* system types */
|
||
#include <sys/time.h> /* time definitions */
|
||
#include <assert.h> /* assertion macros */
|
||
#include <string.h> /* string functions */
|
||
|
||
#include "asterisk/poll-compat.h" /* this package */
|
||
|
||
/*---------------------------------------------------------------------------*\
|
||
Macros
|
||
\*---------------------------------------------------------------------------*/
|
||
|
||
#ifndef MAX
|
||
#define MAX(a,b) ((a) > (b) ? (a) : (b))
|
||
#endif
|
||
|
||
|
||
/*---------------------------------------------------------------------------*\
|
||
Private Functions
|
||
\*---------------------------------------------------------------------------*/
|
||
|
||
static int map_poll_spec
|
||
#if __STDC__ > 0
|
||
(struct pollfd *pArray,
|
||
unsigned long n_fds,
|
||
fd_set *pReadSet,
|
||
fd_set *pWriteSet,
|
||
fd_set *pExceptSet)
|
||
#else
|
||
(pArray, n_fds, pReadSet, pWriteSet, pExceptSet)
|
||
struct pollfd *pArray;
|
||
unsigned long n_fds;
|
||
fd_set *pReadSet;
|
||
fd_set *pWriteSet;
|
||
fd_set *pExceptSet;
|
||
#endif
|
||
{
|
||
register unsigned long i; /* loop control */
|
||
register struct pollfd *pCur; /* current array element */
|
||
register int max_fd = -1; /* return value */
|
||
|
||
/*!\note
|
||
* Map the poll() structures into the file descriptor sets required
|
||
* by select().
|
||
*/
|
||
for (i = 0, pCur = pArray; i < n_fds; i++, pCur++) {
|
||
/* Skip any bad FDs in the array. */
|
||
|
||
if (pCur->fd < 0)
|
||
continue;
|
||
|
||
if (pCur->events & POLLIN) {
|
||
/* "Input Ready" notification desired. */
|
||
FD_SET(pCur->fd, pReadSet);
|
||
}
|
||
|
||
if (pCur->events & POLLOUT) {
|
||
/* "Output Possible" notification desired. */
|
||
FD_SET(pCur->fd, pWriteSet);
|
||
}
|
||
|
||
if (pCur->events & POLLPRI) {
|
||
/*!\note
|
||
* "Exception Occurred" notification desired. (Exceptions
|
||
* include out of band data.)
|
||
*/
|
||
FD_SET(pCur->fd, pExceptSet);
|
||
}
|
||
|
||
max_fd = MAX(max_fd, pCur->fd);
|
||
}
|
||
|
||
return max_fd;
|
||
}
|
||
|
||
static struct timeval *map_timeout
|
||
#if __STDC__ > 0
|
||
(int poll_timeout, struct timeval *pSelTimeout)
|
||
#else
|
||
(poll_timeout, pSelTimeout)
|
||
int poll_timeout;
|
||
struct timeval *pSelTimeout;
|
||
#endif
|
||
{
|
||
struct timeval *pResult;
|
||
|
||
/*!\note
|
||
* Map the poll() timeout value into a select() timeout. The possible
|
||
* values of the poll() timeout value, and their meanings, are:
|
||
*
|
||
* VALUE MEANING
|
||
*
|
||
* -1 wait indefinitely (until signal occurs)
|
||
* 0 return immediately, don't block
|
||
* >0 wait specified number of milliseconds
|
||
*
|
||
* select() uses a "struct timeval", which specifies the timeout in
|
||
* seconds and microseconds, so the milliseconds value has to be mapped
|
||
* accordingly.
|
||
*/
|
||
|
||
assert(pSelTimeout != (struct timeval *) NULL);
|
||
|
||
switch (poll_timeout) {
|
||
case -1:
|
||
/*
|
||
* A NULL timeout structure tells select() to wait indefinitely.
|
||
*/
|
||
pResult = (struct timeval *) NULL;
|
||
break;
|
||
|
||
case 0:
|
||
/*
|
||
* "Return immediately" (test) is specified by all zeros in
|
||
* a timeval structure.
|
||
*/
|
||
pSelTimeout->tv_sec = 0;
|
||
pSelTimeout->tv_usec = 0;
|
||
pResult = pSelTimeout;
|
||
break;
|
||
|
||
default:
|
||
/* Wait the specified number of milliseconds. */
|
||
pSelTimeout->tv_sec = poll_timeout / 1000; /* get seconds */
|
||
poll_timeout %= 1000; /* remove seconds */
|
||
pSelTimeout->tv_usec = poll_timeout * 1000; /* get microseconds */
|
||
pResult = pSelTimeout;
|
||
break;
|
||
}
|
||
|
||
return pResult;
|
||
}
|
||
|
||
static void map_select_results
|
||
#if __STDC__ > 0
|
||
(struct pollfd *pArray,
|
||
unsigned long n_fds,
|
||
fd_set *pReadSet,
|
||
fd_set *pWriteSet,
|
||
fd_set *pExceptSet)
|
||
#else
|
||
(pArray, n_fds, pReadSet, pWriteSet, pExceptSet)
|
||
struct pollfd *pArray;
|
||
unsigned long n_fds;
|
||
fd_set *pReadSet;
|
||
fd_set *pWriteSet;
|
||
fd_set *pExceptSet;
|
||
#endif
|
||
{
|
||
register unsigned long i; /* loop control */
|
||
register struct pollfd *pCur; /* current array element */
|
||
|
||
for (i = 0, pCur = pArray; i < n_fds; i++, pCur++) {
|
||
/* Skip any bad FDs in the array. */
|
||
|
||
if (pCur->fd < 0) {
|
||
continue;
|
||
}
|
||
|
||
/* Exception events take priority over input events. */
|
||
|
||
pCur->revents = 0;
|
||
if (FD_ISSET (pCur->fd, pExceptSet)) {
|
||
pCur->revents |= POLLPRI;
|
||
} else if (FD_ISSET (pCur->fd, pReadSet)) {
|
||
pCur->revents |= POLLIN;
|
||
}
|
||
|
||
if (FD_ISSET (pCur->fd, pWriteSet)) {
|
||
pCur->revents |= POLLOUT;
|
||
}
|
||
}
|
||
|
||
return;
|
||
}
|
||
|
||
/*---------------------------------------------------------------------------*\
|
||
Public Functions
|
||
\*---------------------------------------------------------------------------*/
|
||
|
||
int poll
|
||
|
||
#if __STDC__ > 0
|
||
(struct pollfd *pArray, unsigned long n_fds, int timeout)
|
||
#else
|
||
(pArray, n_fds, timeout)
|
||
struct pollfd *pArray;
|
||
unsigned long n_fds;
|
||
int timeout;
|
||
#endif
|
||
|
||
{
|
||
fd_set read_descs; /* input file descs */
|
||
fd_set write_descs; /* output file descs */
|
||
fd_set except_descs; /* exception descs */
|
||
struct timeval stime; /* select() timeout value */
|
||
int ready_descriptors; /* function result */
|
||
int max_fd = 0; /* maximum fd value */
|
||
struct timeval *pTimeout; /* actually passed */
|
||
|
||
FD_ZERO (&read_descs);
|
||
FD_ZERO (&write_descs);
|
||
FD_ZERO (&except_descs);
|
||
|
||
/* Map the poll() file descriptor list in the select() data structures. */
|
||
|
||
if (pArray) {
|
||
max_fd = map_poll_spec (pArray, n_fds,
|
||
&read_descs, &write_descs, &except_descs);
|
||
}
|
||
|
||
/* Map the poll() timeout value in the select() timeout structure. */
|
||
pTimeout = map_timeout(timeout, &stime);
|
||
|
||
/* Make the select() call. */
|
||
ready_descriptors = select(max_fd + 1, &read_descs, &write_descs,
|
||
&except_descs, pTimeout);
|
||
|
||
if (ready_descriptors >= 0) {
|
||
map_select_results(pArray, n_fds, &read_descs, &write_descs, &except_descs);
|
||
}
|
||
|
||
return ready_descriptors;
|
||
}
|