poll.c

UNIX下perl实现代码

/*
 * poll.c
 *
 * Copyright (c) 1997-8 Graham Barr <[e-mail]>. All rights reserved.
 * This program is free software; you can redistribute it and/or
 * modify it under the same terms as Perl itself.
 *
 * For systems that do not have the poll() system call (for example Linux
 * kernels < v2.1.23) try to emulate it as closely as possible using select()
 *
 */

#include "EXTERN.h"
#include "perl.h"
#include "poll.h"
#ifdef I_SYS_TIME
# include <sys/time.h>
#endif
#ifdef I_TIME
# include <time.h>
#endif
#include <sys/types.h>
#if defined(HAS_SOCKET) && !defined(VMS) /* VMS handles sockets via vmsish.h */
#  include <sys/socket.h>
#endif
#include <sys/stat.h>
#include <errno.h>

#ifdef HAS_SELECT
#ifdef I_SYS_SELECT
#include <sys/select.h>
#endif
#endif

#ifdef EMULATE_POLL_WITH_SELECT

# define POLL_CAN_READ	(POLLIN | POLLRDNORM )
# define POLL_CAN_WRITE	(POLLOUT | POLLWRNORM | POLLWRBAND )
# define POLL_HAS_EXCP	(POLLRDBAND | POLLPRI )

# define POLL_EVENTS_MASK (POLL_CAN_READ | POLL_CAN_WRITE | POLL_HAS_EXCP)

int
poll(struct pollfd *fds, unsigned long nfds, int timeout)
{
    int i,err;
    fd_set rfd,wfd,efd,ifd;
    struct timeval timebuf;
    struct timeval *tbuf = (struct timeval *)0;
    int n = 0;
    int count;

    FD_ZERO(&ifd);

again:

    FD_ZERO(&rfd);
    FD_ZERO(&wfd);
    FD_ZERO(&efd);

    for(i = 0 ; i < nfds ; i++) {
	int events = fds[i].events;
	int fd = fds[i].fd;

	fds[i].revents = 0;

	if(fd < 0 || FD_ISSET(fd, &ifd))
	    continue;

	if(fd > n)
	    n = fd;

	if(events & POLL_CAN_READ)
	    FD_SET(fd, &rfd);

	if(events & POLL_CAN_WRITE)
	    FD_SET(fd, &wfd);

	if(events & POLL_HAS_EXCP)
	    FD_SET(fd, &efd);
    }

    if(timeout >= 0) {
	timebuf.tv_sec = timeout / 1000;
	timebuf.tv_usec = (timeout % 1000) * 1000;
	tbuf = &timebuf;
    }

    err = select(n+1,&rfd,&wfd,&efd,tbuf);

    if(err < 0) {
#ifdef HAS_FSTAT
	if(errno == EBADF) {
	    for(i = 0 ; i < nfds ; i++) {
		struct stat buf;
		if((fstat(fds[i].fd,&buf) < 0) && (errno == EBADF)) {
		    FD_SET(fds[i].fd, &ifd);
		    goto again;
		}
	    }
	}
#endif /* HAS_FSTAT */
	return err;
    }

    count = 0;

    for(i = 0 ; i < nfds ; i++) {
	int revents = (fds[i].events & POLL_EVENTS_MASK);
	int fd = fds[i].fd;

	if(fd < 0)
	    continue;

	if(FD_ISSET(fd, &ifd))
	    revents = POLLNVAL;
	else {
	    if(!FD_ISSET(fd, &rfd))
	        revents &= ~POLL_CAN_READ;

	    if(!FD_ISSET(fd, &wfd))
	        revents &= ~POLL_CAN_WRITE;

	    if(!FD_ISSET(fd, &efd))
	        revents &= ~POLL_HAS_EXCP;
	}

	if((fds[i].revents = revents) != 0)
	    count++;
    }

    return count; 
}

#endif /* EMULATE_POLL_WITH_SELECT */