poll.c

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

/*
 * Copyright 2000-2003 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/_libevent_time.h>
#endif
#include <sys/queue.h>
#include <poll.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"

struct pollop {
    int event_count;        /* Highest number alloc */
    int nfds;                       /* Size of event_* */
    int fd_count;                   /* Size of idxplus1_by_fd */
    struct pollfd* event_set;
    struct event** event_r_back;
    struct event** event_w_back;
    int* idxplus1_by_fd; /* Index into event_set by fd; we add 1 so
                  * that 0 (which is easy to memset) can mean
                  * "no entry." */
};

static void* poll_init  (struct event_base*);
static int poll_add     (void*, struct event*);
static int poll_del     (void*, struct event*);
static int poll_dispatch    (struct event_base*, void*, struct timeval*);
static void poll_dealloc    (struct event_base*, void*);

const struct eventop pollops = {
    "poll",
    poll_init,
    poll_add,
    poll_del,
    poll_dispatch,
    poll_dealloc,
    0
};

static void*
poll_init(struct event_base* base)
{
    struct pollop* pollop;

    /* Disable poll when this environment variable is set */
    if (evutil_getenv("EVENT_NOPOLL"))
        return (NULL);

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

    evsignal_init(base);

    return (pollop);
}

#ifdef CHECK_INVARIANTS
static void
poll_check_ok(struct pollop* pop)
{
    int i, idx;
    struct event* ev;

    for (i = 0; i < pop->fd_count; ++i) {
        idx = pop->idxplus1_by_fd[i] - 1;
        if (idx < 0)
            continue;
        assert(pop->event_set[idx].fd == i);
        if (pop->event_set[idx].events & POLLIN) {
            ev = pop->event_r_back[idx];
            assert(ev);
            assert(ev->ev_events & EV_READ);
            assert(ev->ev_fd == i);
        }
        if (pop->event_set[idx].events & POLLOUT) {
            ev = pop->event_w_back[idx];
            assert(ev);
            assert(ev->ev_events & EV_WRITE);
            assert(ev->ev_fd == i);
        }
    }
    for (i = 0; i < pop->nfds; ++i) {
        struct pollfd* pfd = &pop->event_set[i];
        assert(pop->idxplus1_by_fd[pfd->fd] == i + 1);
    }
}
#else
#define poll_check_ok(pop)
#endif

static int
poll_dispatch(struct event_base* base, void* arg, struct timeval* tv)
{
    int res, i, j, msec = -1, nfds;
    struct pollop* pop = arg;

    poll_check_ok(pop);

    if (tv != NULL)
        msec = tv->tv_sec * 1000 + (tv->tv_usec + 999) / 1000;

    nfds = pop->nfds;
    res = poll(pop->event_set, nfds, msec);

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

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

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

    if (res == 0 || nfds == 0)
        return (0);

    i = random() % nfds;
    for (j = 0; j < nfds; j++) {
        struct event* r_ev = NULL, *w_ev = NULL;
        int what;
        if (++i == nfds)
            i = 0;
        what = pop->event_set[i].revents;

        if (!what)
            continue;

        res = 0;

        /* If the file gets closed notify */
        if (what & (POLLHUP | POLLERR))
            what |= POLLIN | POLLOUT;
        if (what & POLLIN) {
            res |= EV_READ;
            r_ev = pop->event_r_back[i];
        }
        if (what & POLLOUT) {
            res |= EV_WRITE;
            w_ev = pop->event_w_back[i];
        }
        if (res == 0)
            continue;

        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);
        }
    }

    return (0);
}

static int
poll_add(void* arg, struct event* ev)
{
    struct pollop* pop = arg;
    struct pollfd* pfd = NULL;
    int i;

    if (ev->ev_events & EV_SIGNAL)
        return (evsignal_add(ev));
    if (!(ev->ev_events & (EV_READ | EV_WRITE)))
        return (0);

    poll_check_ok(pop);
    if (pop->nfds + 1 >= pop->event_count) {
        struct pollfd* tmp_event_set;
        struct event** tmp_event_r_back;
        struct event** tmp_event_w_back;
        int tmp_event_count;

        if (pop->event_count < 32)
            tmp_event_count = 32;
        else
            tmp_event_count = pop->event_count * 2;

        /* We need more file descriptors */
        tmp_event_set = realloc(pop->event_set,
                                tmp_event_count * sizeof(struct pollfd));
        if (tmp_event_set == NULL) {
            event_warn("realloc");
            return (-1);
        }
        pop->event_set = tmp_event_set;

        tmp_event_r_back = realloc(pop->event_r_back,
                                   tmp_event_count * sizeof(struct event*));
        if (tmp_event_r_back == NULL) {
            /* event_set overallocated; that's okay. */
            event_warn("realloc");
            return (-1);
        }
        pop->event_r_back = tmp_event_r_back;

        tmp_event_w_back = realloc(pop->event_w_back,
                                   tmp_event_count * sizeof(struct event*));
        if (tmp_event_w_back == NULL) {
            /* event_set and event_r_back overallocated; that's
             * okay. */
            event_warn("realloc");
            return (-1);
        }
        pop->event_w_back = tmp_event_w_back;

        pop->event_count = tmp_event_count;
    }
    if (ev->ev_fd >= pop->fd_count) {
        int* tmp_idxplus1_by_fd;
        int new_count;
        if (pop->fd_count < 32)
            new_count = 32;
        else
            new_count = pop->fd_count * 2;
        while (new_count <= ev->ev_fd)
            new_count *= 2;
        tmp_idxplus1_by_fd =
            realloc(pop->idxplus1_by_fd, new_count * sizeof(int));
        if (tmp_idxplus1_by_fd == NULL) {
            event_warn("realloc");
            return (-1);
        }
        pop->idxplus1_by_fd = tmp_idxplus1_by_fd;
        memset(pop->idxplus1_by_fd + pop->fd_count,
               0, sizeof(int) * (new_count - pop->fd_count));
        pop->fd_count = new_count;
    }

    i = pop->idxplus1_by_fd[ev->ev_fd] - 1;
    if (i >= 0) {
        pfd = &pop->event_set[i];
    } else {
        i = pop->nfds++;
        pfd = &pop->event_set[i];
        pfd->events = 0;
        pfd->fd = ev->ev_fd;
        pop->event_w_back[i] = pop->event_r_back[i] = NULL;
        pop->idxplus1_by_fd[ev->ev_fd] = i + 1;
    }

    pfd->revents = 0;
    if (ev->ev_events & EV_WRITE) {
        pfd->events |= POLLOUT;
        pop->event_w_back[i] = ev;
    }
    if (ev->ev_events & EV_READ) {
        pfd->events |= POLLIN;
        pop->event_r_back[i] = ev;
    }
    poll_check_ok(pop);

    return (0);
}

/*
 * Nothing to be done here.
 */

static int
poll_del(void* arg, struct event* ev)
{
    struct pollop* pop = arg;
    struct pollfd* pfd = NULL;
    int i;

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

    if (!(ev->ev_events & (EV_READ | EV_WRITE)))
        return (0);

    poll_check_ok(pop);
    i = pop->idxplus1_by_fd[ev->ev_fd] - 1;
    if (i < 0)
        return (-1);

    /* Do we still want to read or write? */
    pfd = &pop->event_set[i];
    if (ev->ev_events & EV_READ) {
        pfd->events &= ~POLLIN;
        pop->event_r_back[i] = NULL;
    }
    if (ev->ev_events & EV_WRITE) {
        pfd->events &= ~POLLOUT;
        pop->event_w_back[i] = NULL;
    }
    poll_check_ok(pop);
    if (pfd->events)
        /* Another event cares about that fd. */
        return (0);

    /* Okay, so we aren't interested in that fd anymore. */
    pop->idxplus1_by_fd[ev->ev_fd] = 0;

    --pop->nfds;
    if (i != pop->nfds) {
        /*
         * Shift the last pollfd down into the now-unoccupied
         * position.
         */
        memcpy(&pop->event_set[i], &pop->event_set[pop->nfds],
               sizeof(struct pollfd));
        pop->event_r_back[i] = pop->event_r_back[pop->nfds];
        pop->event_w_back[i] = pop->event_w_back[pop->nfds];
        pop->idxplus1_by_fd[pop->event_set[i].fd] = i + 1;
    }

    poll_check_ok(pop);
    return (0);
}

static void
poll_dealloc(struct event_base* base, void* arg)
{
    struct pollop* pop = arg;

    evsignal_dealloc(base);
    if (pop->event_set)
        free(pop->event_set);
    if (pop->event_r_back)
        free(pop->event_r_back);
    if (pop->event_w_back)
        free(pop->event_w_back);
    if (pop->idxplus1_by_fd)
        free(pop->idxplus1_by_fd);

    memset(pop, 0, sizeof(struct pollop));
    free(pop);
}