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/_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 (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);
}