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Kevin P. Fleming authored
git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@7221 65c4cc65-6c06-0410-ace0-fbb531ad65f3
Kevin P. Fleming authoredgit-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@7221 65c4cc65-6c06-0410-ace0-fbb531ad65f3
poll.c 8.78 KiB
/*---------------------------------------------------------------------------*\
$Id$
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 */
/*
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)
{
/* "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;
/*
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; /* maximum fd value */
struct timeval *pTimeout; /* actually passed */
FD_ZERO (&read_descs);
FD_ZERO (&write_descs); FD_ZERO (&except_descs);
assert (pArray != (struct pollfd *) NULL);
/* Map the poll() file descriptor list in the select() data structures. */
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;
}