select.c

/*      $OpenBSD: select.c,v 1.2 2002/06/25 15:50:15 mickey Exp $       */

/*
 * Copyright 2000-2002 Niels Provos <provos@citi.umich.edu>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. 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 BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <sys/types.h>
#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#else
#include <sys/_time.h>
#endif
#ifdef HAVE_SYS_SELECT_H
#include <sys/select.h>
#endif
#include <sys/queue.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#ifdef CHECK_INVARIANTS
#include <assert.h>
#endif

#include "event.h"
#include "event-internal.h"
#include "evsignal.h"
#include "log.h"

#ifndef howmany
#define        howmany(x, y)   (((x)+((y)-1))/(y))
#endif

struct selectop {
        int event_fds;          /* Highest fd in fd set */
        int event_fdsz;
        fd_set *event_readset_in;
        fd_set *event_writeset_in;
        fd_set *event_readset_out;
        fd_set *event_writeset_out;
        struct event **event_r_by_fd;
        struct event **event_w_by_fd;
};

static void *select_init        (struct event_base *);
static int select_add           (void *, struct event *);
static int select_del           (void *, struct event *);
static int select_dispatch      (struct event_base *, void *, struct timeval *);
static void select_dealloc     (struct event_base *, void *);

const struct eventop selectops = {
        "select",
        select_init,
        select_add,
        select_del,
        select_dispatch,
        select_dealloc,
        0
};

static int select_resize(struct selectop *sop, int fdsz);

static void *
select_init(struct event_base *base)
{
        struct selectop *sop;

        /* Disable select when this environment variable is set */
        if (getenv("EVENT_NOSELECT"))
                return (NULL);

        if (!(sop = calloc(1, sizeof(struct selectop))))
                return (NULL);

        select_resize(sop, howmany(32 + 1, NFDBITS)*sizeof(fd_mask));

        evsignal_init(base);

        return (sop);
}

#ifdef CHECK_INVARIANTS
static void
check_selectop(struct selectop *sop)
{
        int i;
        for (i = 0; i <= sop->event_fds; ++i) {
                if (FD_ISSET(i, sop->event_readset_in)) {
                        assert(sop->event_r_by_fd[i]);
                        assert(sop->event_r_by_fd[i]->ev_events & EV_READ);
                        assert(sop->event_r_by_fd[i]->ev_fd == i);
                } else {
                        assert(! sop->event_r_by_fd[i]);
                }
                if (FD_ISSET(i, sop->event_writeset_in)) {
                        assert(sop->event_w_by_fd[i]);
                        assert(sop->event_w_by_fd[i]->ev_events & EV_WRITE);
                        assert(sop->event_w_by_fd[i]->ev_fd == i);
                } else {
                        assert(! sop->event_w_by_fd[i]);
                }
        }

}
#else
#define check_selectop(sop) do { (void) sop; } while (0)
#endif

static int
select_dispatch(struct event_base *base, void *arg, struct timeval *tv)
{
        int res, i, j;
        struct selectop *sop = arg;

        check_selectop(sop);

        memcpy(sop->event_readset_out, sop->event_readset_in,
               sop->event_fdsz);
        memcpy(sop->event_writeset_out, sop->event_writeset_in,
               sop->event_fdsz);

        res = select(sop->event_fds + 1, sop->event_readset_out,
            sop->event_writeset_out, NULL, tv);

        check_selectop(sop);

        if (res == -1) {
                if (errno != EINTR) {
                        event_warn("select");
                        return (-1);
                }

                evsignal_process(base);
                return (0);
        } else if (base->sig.evsignal_caught) {
                evsignal_process(base);
        }

        event_debug(("%s: select reports %d", __func__, res));

        check_selectop(sop);
        i = random() % (sop->event_fds+1);
        for (j = 0; j <= sop->event_fds; ++j) {
                struct event *r_ev = NULL, *w_ev = NULL;
                if (++i >= sop->event_fds+1)
                        i = 0;

                res = 0;
                if (FD_ISSET(i, sop->event_readset_out)) {
                        r_ev = sop->event_r_by_fd[i];
                        res |= EV_READ;
                }
                if (FD_ISSET(i, sop->event_writeset_out)) {
                        w_ev = sop->event_w_by_fd[i];
                        res |= EV_WRITE;
                }
                if (r_ev && (res & r_ev->ev_events)) {
                        event_active(r_ev, res & r_ev->ev_events, 1);
                }
                if (w_ev && w_ev != r_ev && (res & w_ev->ev_events)) {
                        event_active(w_ev, res & w_ev->ev_events, 1);
                }
        }
        check_selectop(sop);

        return (0);
}


static int
select_resize(struct selectop *sop, int fdsz)
{
        int n_events, n_events_old;

        fd_set *readset_in = NULL;
        fd_set *writeset_in = NULL;
        fd_set *readset_out = NULL;
        fd_set *writeset_out = NULL;
        struct event **r_by_fd = NULL;
        struct event **w_by_fd = NULL;

        n_events = (fdsz/sizeof(fd_mask)) * NFDBITS;
        n_events_old = (sop->event_fdsz/sizeof(fd_mask)) * NFDBITS;

        if (sop->event_readset_in)
                check_selectop(sop);

        if ((readset_in = realloc(sop->event_readset_in, fdsz)) == NULL)
                goto error;
        sop->event_readset_in = readset_in;
        if ((readset_out = realloc(sop->event_readset_out, fdsz)) == NULL)
                goto error;
        sop->event_readset_out = readset_out;
        if ((writeset_in = realloc(sop->event_writeset_in, fdsz)) == NULL)
                goto error;
        sop->event_writeset_in = writeset_in;
        if ((writeset_out = realloc(sop->event_writeset_out, fdsz)) == NULL)
                goto error;
        sop->event_writeset_out = writeset_out;
        if ((r_by_fd = realloc(sop->event_r_by_fd,
                 n_events*sizeof(struct event*))) == NULL)
                goto error;
        sop->event_r_by_fd = r_by_fd;
        if ((w_by_fd = realloc(sop->event_w_by_fd,
                 n_events * sizeof(struct event*))) == NULL)
                goto error;
        sop->event_w_by_fd = w_by_fd;

        memset((char *)sop->event_readset_in + sop->event_fdsz, 0,
            fdsz - sop->event_fdsz);
        memset((char *)sop->event_writeset_in + sop->event_fdsz, 0,
            fdsz - sop->event_fdsz);
        memset(sop->event_r_by_fd + n_events_old, 0,
            (n_events-n_events_old) * sizeof(struct event*));
        memset(sop->event_w_by_fd + n_events_old, 0,
            (n_events-n_events_old) * sizeof(struct event*));

        sop->event_fdsz = fdsz;
        check_selectop(sop);

        return (0);

 error:
        event_warn("malloc");
        return (-1);
}


static int
select_add(void *arg, struct event *ev)
{
        struct selectop *sop = arg;

        if (ev->ev_events & EV_SIGNAL)
                return (evsignal_add(ev));

        check_selectop(sop);
        /*
         * Keep track of the highest fd, so that we can calculate the size
         * of the fd_sets for select(2)
         */
        if (sop->event_fds < ev->ev_fd) {
                int fdsz = sop->event_fdsz;

                if (fdsz < sizeof(fd_mask))
                        fdsz = sizeof(fd_mask);

                while (fdsz <
                    (howmany(ev->ev_fd + 1, NFDBITS) * sizeof(fd_mask)))
                        fdsz *= 2;

                if (fdsz != sop->event_fdsz) {
                        if (select_resize(sop, fdsz)) {
                                check_selectop(sop);
                                return (-1);
                        }
                }

                sop->event_fds = ev->ev_fd;
        }

        if (ev->ev_events & EV_READ) {
                FD_SET(ev->ev_fd, sop->event_readset_in);
                sop->event_r_by_fd[ev->ev_fd] = ev;
        }
        if (ev->ev_events & EV_WRITE) {
                FD_SET(ev->ev_fd, sop->event_writeset_in);
                sop->event_w_by_fd[ev->ev_fd] = ev;
        }
        check_selectop(sop);

        return (0);
}

/*
 * Nothing to be done here.
 */

static int
select_del(void *arg, struct event *ev)
{
        struct selectop *sop = arg;

        check_selectop(sop);
        if (ev->ev_events & EV_SIGNAL)
                return (evsignal_del(ev));

        if (sop->event_fds < ev->ev_fd) {
                check_selectop(sop);
                return (0);
        }

        if (ev->ev_events & EV_READ) {
                FD_CLR(ev->ev_fd, sop->event_readset_in);
                sop->event_r_by_fd[ev->ev_fd] = NULL;
        }

        if (ev->ev_events & EV_WRITE) {
                FD_CLR(ev->ev_fd, sop->event_writeset_in);
                sop->event_w_by_fd[ev->ev_fd] = NULL;
        }

        check_selectop(sop);
        return (0);
}

static void
select_dealloc(struct event_base *base, void *arg)
{
        struct selectop *sop = arg;

        evsignal_dealloc(base);
        if (sop->event_readset_in)
                free(sop->event_readset_in);
        if (sop->event_writeset_in)
                free(sop->event_writeset_in);
        if (sop->event_readset_out)
                free(sop->event_readset_out);
        if (sop->event_writeset_out)
                free(sop->event_writeset_out);
        if (sop->event_r_by_fd)
                free(sop->event_r_by_fd);
        if (sop->event_w_by_fd)
                free(sop->event_w_by_fd);

        memset(sop, 0, sizeof(struct selectop));
        free(sop);
}