poll.c

linux下traceroute的实现

/*
    Copyright (c)  2006, 2007		Dmitry Butskoy
					<[e-mail]>
    License:  GPL v2 or any later

    See COPYING for the status of this software.
*/

#include <stdlib.h>
#include <unistd.h>
#include <sys/poll.h>
#include <errno.h>

#include "traceroute.h"


static struct pollfd *pfd = NULL;
static unsigned int num_polls = 0;


void add_poll (int fd, int events) {
	int i;

	for (i = 0; i < num_polls && pfd[i].fd > 0; i++) ;

	if (i == num_polls) {
	    pfd = realloc (pfd, ++num_polls * sizeof (*pfd));
	    if (!pfd)  error ("realloc");
	}

	pfd[i].fd = fd;
	pfd[i].events = events;
}


void del_poll (int fd) {
	int i;

	for (i = 0; i < num_polls && pfd[i].fd != fd; i++) ;

	if (i < num_polls)  pfd[i].fd = -1;    /*  or just zero it...  */
}


static int cleanup_polls (void) {
	int i;

	for (i = 0; i < num_polls && pfd[i].fd > 0; i++) ;

	if (i < num_polls) {	/*  a hole have found   */
	    int j;

	    for (j = i + 1; j < num_polls; j++) {
		if (pfd[j].fd > 0) {
		    pfd[i++] = pfd[j];
		    pfd[j].fd = -1;
		}
	    }
	}

	return i;
}


void do_poll (double timeout, void (*callback) (int fd, int revents)) {
	int nfds, n, i;

	nfds = cleanup_polls ();

	if (!nfds)  return;

	n = poll (pfd, nfds, timeout * 1000);
	if (n < 0) {
	    if (errno == EINTR)  return;
	    error ("poll");
	}

	for (i = 0; n && i < num_polls; i++) {
	    if (pfd[i].revents) {
		callback (pfd[i].fd, pfd[i].revents);
		n--;
	    }
	}

	return;
}