poll.c

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/*---------------------------------------------------------------------------*\
 $Id$

 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 <[email protected]>"
 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 "asterisk.h"

#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 <errno.h>

#include "asterisk/utils.h" /* this package */
#include "asterisk/poll-compat.h" /* this package */

unsigned int ast_FD_SETSIZE = FD_SETSIZE;

#ifndef MAX
#define MAX(a,b) a > b ? a : b
#endif

/*---------------------------------------------------------------------------*\
 Private Functions
\*---------------------------------------------------------------------------*/

#if defined(AST_POLL_COMPAT)
static int map_poll_spec(struct pollfd *pArray, unsigned long n_fds,
 ast_fdset *pReadSet, ast_fdset *pWriteSet, ast_fdset *pExceptSet)
{
 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) {
 /*!\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;
}

#ifdef AST_POLL_COMPAT
static struct timeval *map_timeout(int poll_timeout, struct timeval *pSelTimeout)
{
 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 != 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;
}
#endif /* AST_POLL_COMPAT */

static void map_select_results(struct pollfd *pArray, unsigned long n_fds,
 ast_fdset *pReadSet, ast_fdset *pWriteSet, ast_fdset *pExceptSet)
{
 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, (fd_set *) pExceptSet)) {
 pCur->revents |= POLLPRI;
 } else if (FD_ISSET(pCur->fd, (fd_set *) pReadSet)) {
 pCur->revents |= POLLIN;
 }

 if (FD_ISSET(pCur->fd, (fd_set *) pWriteSet)) {
 pCur->revents |= POLLOUT;
 }
 }

 return;
}
#endif /* defined(AST_POLL_COMPAT) || !defined(HAVE_PPOLL) */

/*---------------------------------------------------------------------------*\
 Public Functions
\*---------------------------------------------------------------------------*/
#ifdef AST_POLL_COMPAT
int ast_internal_poll(struct pollfd *pArray, unsigned long n_fds, int timeout)
{
 ast_fdset read_descs; /* input file descs */
 ast_fdset write_descs; /* output file descs */
 ast_fdset 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 */
 int save_errno;

 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 = ast_select(max_fd + 1, &read_descs, &write_descs,
 &except_descs, pTimeout);
 save_errno = errno;

 if (ready_descriptors >= 0) {
 map_select_results (pArray, n_fds,
 &read_descs, &write_descs, &except_descs);
 }

 errno = save_errno;
 return ready_descriptors;
}
#endif /* AST_POLL_COMPAT */

int ast_poll2(struct pollfd *pArray, unsigned long n_fds, struct timeval *tv)
{
#if !defined(AST_POLL_COMPAT)
 struct timeval start = ast_tvnow();
#if defined(HAVE_PPOLL)
 struct timespec ts = { tv ? tv->tv_sec : 0, tv ? tv->tv_usec * 1000 : 0 };
 int res = ppoll(pArray, n_fds, tv ? &ts : NULL, NULL);
#else
 int res = poll(pArray, n_fds, tv ? tv->tv_sec * 1000 + tv->tv_usec / 1000 : -1);
#endif
 struct timeval after = ast_tvnow();
 if (res > 0 && tv && ast_tvdiff_ms(ast_tvadd(*tv, start), after) > 0) {
 *tv = ast_tvsub(*tv, ast_tvsub(after, start));
 } else if (res > 0 && tv) {
 *tv = ast_tv(0, 0);
 }
 return res;
#else
 ast_fdset read_descs, write_descs, except_descs;
 int ready_descriptors, max_fd = 0;

 FD_ZERO(&read_descs);
 FD_ZERO(&write_descs);
 FD_ZERO(&except_descs);

 if (pArray) {
 max_fd = map_poll_spec(pArray, n_fds, &read_descs, &write_descs, &except_descs);
 }

 ready_descriptors = ast_select(max_fd + 1, &read_descs, &write_descs, &except_descs, tv);

 if (ready_descriptors >= 0) {
 map_select_results(pArray, n_fds, &read_descs, &write_descs, &except_descs);
 }

 return ready_descriptors;
#endif
}