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One note on defining _POSIX_C_SOURCE: while this feature test macro works to require certain behaviors on Linux, it works differently on *BSD platforms to REMOVE certain API calls that are not in the POSIX specification, such as vasprintf(3). Thus, defining it while depending upon vasprintf (and other extensions to the POSIX standard) to be defined is a recipe to ensure that Asterisk is only buildable on Linux. Hence, this define which was meant to INCREASE portability, effectively ensures the opposite. git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@214863 65c4cc65-6c06-0410-ace0-fbb531ad65f3
289 lines
8.3 KiB
C
289 lines
8.3 KiB
C
/*---------------------------------------------------------------------------*\
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$Id$
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NAME
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poll - select(2)-based poll() emulation function for BSD systems.
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SYNOPSIS
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#include "poll.h"
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struct pollfd
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{
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int fd;
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short events;
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short revents;
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}
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int poll (struct pollfd *pArray, unsigned long n_fds, int timeout)
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DESCRIPTION
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This file, and the accompanying "poll.h", implement the System V
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poll(2) system call for BSD systems (which typically do not provide
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poll()). Poll() provides a method for multiplexing input and output
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on multiple open file descriptors; in traditional BSD systems, that
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capability is provided by select(). While the semantics of select()
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differ from those of poll(), poll() can be readily emulated in terms
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of select() -- which is how this function is implemented.
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REFERENCES
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Stevens, W. Richard. Unix Network Programming. Prentice-Hall, 1990.
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NOTES
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1. This software requires an ANSI C compiler.
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LICENSE
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This software is released under the following license:
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Copyright (c) 1995-2002 Brian M. Clapper
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All rights reserved.
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Redistribution and use in source and binary forms are
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permitted provided that: (1) source distributions retain
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this entire copyright notice and comment; (2) modifications
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made to the software are prominently mentioned, and a copy
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of the original software (or a pointer to its location) are
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included; and (3) distributions including binaries display
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the following acknowledgement: "This product includes
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software developed by Brian M. Clapper <bmc@clapper.org>"
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in the documentation or other materials provided with the
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distribution. The name of the author may not be used to
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endorse or promote products derived from this software
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without specific prior written permission.
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THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS
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OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
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PARTICULAR PURPOSE.
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Effectively, this means you can do what you want with the software
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except remove this notice or take advantage of the author's name.
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If you modify the software and redistribute your modified version,
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you must indicate that your version is a modification of the
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original, and you must provide either a pointer to or a copy of the
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original.
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\*---------------------------------------------------------------------------*/
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/*---------------------------------------------------------------------------*\
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Includes
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\*---------------------------------------------------------------------------*/
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#include "asterisk.h"
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#include <unistd.h> /* standard Unix definitions */
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#include <sys/types.h> /* system types */
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#include <sys/time.h> /* time definitions */
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#include <assert.h> /* assertion macros */
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#include <string.h> /* string functions */
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#include "asterisk/poll-compat.h" /* this package */
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#ifdef AST_POLL_COMPAT
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#ifndef MAX
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#define MAX(a,b) a > b ? a : b
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#endif
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/*---------------------------------------------------------------------------*\
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Private Functions
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\*---------------------------------------------------------------------------*/
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static int map_poll_spec
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#if __STDC__ > 0
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(struct pollfd *pArray,
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unsigned long n_fds,
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fd_set *pReadSet,
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fd_set *pWriteSet,
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fd_set *pExceptSet)
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#else
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(pArray, n_fds, pReadSet, pWriteSet, pExceptSet)
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struct pollfd *pArray;
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unsigned long n_fds;
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fd_set *pReadSet;
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fd_set *pWriteSet;
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fd_set *pExceptSet;
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#endif
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{
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register unsigned long i; /* loop control */
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register struct pollfd *pCur; /* current array element */
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register int max_fd = -1; /* return value */
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/*!\note
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* Map the poll() structures into the file descriptor sets required
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* by select().
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*/
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for (i = 0, pCur = pArray; i < n_fds; i++, pCur++) {
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/* Skip any bad FDs in the array. */
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if (pCur->fd < 0)
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continue;
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if (pCur->events & POLLIN) {
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/* "Input Ready" notification desired. */
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FD_SET(pCur->fd, pReadSet);
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}
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if (pCur->events & POLLOUT) {
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/* "Output Possible" notification desired. */
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FD_SET(pCur->fd, pWriteSet);
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}
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if (pCur->events & POLLPRI) {
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/*!\note
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* "Exception Occurred" notification desired. (Exceptions
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* include out of band data.)
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*/
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FD_SET(pCur->fd, pExceptSet);
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}
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max_fd = MAX(max_fd, pCur->fd);
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}
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return max_fd;
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}
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static struct timeval *map_timeout
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#if __STDC__ > 0
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(int poll_timeout, struct timeval *pSelTimeout)
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#else
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(poll_timeout, pSelTimeout)
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int poll_timeout;
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struct timeval *pSelTimeout;
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#endif
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{
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struct timeval *pResult;
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/*!\note
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* Map the poll() timeout value into a select() timeout. The possible
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* values of the poll() timeout value, and their meanings, are:
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*
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* VALUE MEANING
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*
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* -1 wait indefinitely (until signal occurs)
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* 0 return immediately, don't block
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* >0 wait specified number of milliseconds
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*
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* select() uses a "struct timeval", which specifies the timeout in
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* seconds and microseconds, so the milliseconds value has to be mapped
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* accordingly.
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*/
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assert(pSelTimeout != (struct timeval *) NULL);
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switch (poll_timeout) {
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case -1:
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/*
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* A NULL timeout structure tells select() to wait indefinitely.
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*/
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pResult = (struct timeval *) NULL;
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break;
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case 0:
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/*
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* "Return immediately" (test) is specified by all zeros in
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* a timeval structure.
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*/
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pSelTimeout->tv_sec = 0;
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pSelTimeout->tv_usec = 0;
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pResult = pSelTimeout;
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break;
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default:
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/* Wait the specified number of milliseconds. */
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pSelTimeout->tv_sec = poll_timeout / 1000; /* get seconds */
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poll_timeout %= 1000; /* remove seconds */
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pSelTimeout->tv_usec = poll_timeout * 1000; /* get microseconds */
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pResult = pSelTimeout;
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break;
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}
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return pResult;
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}
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static void map_select_results
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#if __STDC__ > 0
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(struct pollfd *pArray,
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unsigned long n_fds,
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fd_set *pReadSet,
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fd_set *pWriteSet,
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fd_set *pExceptSet)
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#else
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(pArray, n_fds, pReadSet, pWriteSet, pExceptSet)
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struct pollfd *pArray;
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unsigned long n_fds;
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fd_set *pReadSet;
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fd_set *pWriteSet;
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fd_set *pExceptSet;
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#endif
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{
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register unsigned long i; /* loop control */
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register struct pollfd *pCur; /* current array element */
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for (i = 0, pCur = pArray; i < n_fds; i++, pCur++) {
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/* Skip any bad FDs in the array. */
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if (pCur->fd < 0) {
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continue;
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}
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/* Exception events take priority over input events. */
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pCur->revents = 0;
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if (FD_ISSET (pCur->fd, pExceptSet)) {
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pCur->revents |= POLLPRI;
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} else if (FD_ISSET (pCur->fd, pReadSet)) {
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pCur->revents |= POLLIN;
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}
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if (FD_ISSET (pCur->fd, pWriteSet)) {
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pCur->revents |= POLLOUT;
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}
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}
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return;
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}
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/*---------------------------------------------------------------------------*\
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Public Functions
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\*---------------------------------------------------------------------------*/
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int ast_internal_poll(struct pollfd *pArray, unsigned long n_fds, int timeout)
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{
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fd_set read_descs; /* input file descs */
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fd_set write_descs; /* output file descs */
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fd_set except_descs; /* exception descs */
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struct timeval stime; /* select() timeout value */
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int ready_descriptors; /* function result */
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int max_fd = 0; /* maximum fd value */
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struct timeval *pTimeout; /* actually passed */
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FD_ZERO (&read_descs);
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FD_ZERO (&write_descs);
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FD_ZERO (&except_descs);
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/* Map the poll() file descriptor list in the select() data structures. */
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if (pArray) {
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max_fd = map_poll_spec (pArray, n_fds,
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&read_descs, &write_descs, &except_descs);
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}
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/* Map the poll() timeout value in the select() timeout structure. */
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pTimeout = map_timeout(timeout, &stime);
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/* Make the select() call. */
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ready_descriptors = select(max_fd + 1, &read_descs, &write_descs,
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&except_descs, pTimeout);
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if (ready_descriptors >= 0) {
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map_select_results(pArray, n_fds, &read_descs, &write_descs, &except_descs);
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}
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return ready_descriptors;
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}
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#endif /* AST_POLL_COMPAT */
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