darling-libkqueue/kevent.c

/*
 * Copyright (c) 2009 Mark Heily <mark@heily.com>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/* To get asprintf(3) */
#define _GNU_SOURCE

#include <errno.h>
#include <fcntl.h>
#include <poll.h>
#include <signal.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/queue.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <string.h>
#include <unistd.h>

#include "sys/event.h"
#include "private.h"

const char *
kevent_dump(struct kevent *kev)
{
    char buf[512];
    snprintf(&buf[0], sizeof(buf), "[filter=%d,flags=%d,ident=%u,udata=%p]", 
            kev->filter,
            kev->flags,
            (u_int) kev->ident,
            kev->udata);
    return (strdup(buf));
}

static void
kevent_error(struct kevent *dst, const struct kevent *src, int data)
{
    memcpy(dst, src, sizeof(*src));
    dst->data = data;
}

static int
kevent_copyin(struct kqueue *kq, const struct kevent *src, int nchanges,
        struct kevent *eventlist, int nevents)
{
    struct knote  *dst;
    struct filter *filt;
    int kn_alloc,status;

    for (; nchanges > 0; src++, nchanges--) {

        if ((filt = filter_lookup(kq, src->filter)) == NULL) {
            status = -EINVAL;
            goto err_out;
        }

        /*
         * Retrieve an existing knote object, or create a new one.
         */
        kn_alloc = 0;
        dst = knote_lookup(filt, src->ident);
        if (dst == NULL) {
           if (src->flags & EV_ADD) {
               if ((dst = knote_new(filt)) == NULL) {
                   status = -ENOMEM;
                   goto err_out;
               }
               dbg_puts(kevent_dump(&dst->kev));
               kn_alloc = 1;
           } else if (src->flags & EV_ENABLE 
                   || src->flags & EV_DISABLE
                   || src->flags & EV_DELETE) {
               status = -ENOENT;
               goto err_out;
           } else {
               /* flags == 0 or no action */
               status = -EINVAL;
               goto err_out;
           }
        }

        if (filt->kf_copyin(filt, dst, src) < 0) {
            status = -EBADMSG;
            goto err_out;
        }

        /*
         * Update the knote flags based on src->flags.
         */
        if (src->flags & EV_ENABLE)
            KNOTE_ENABLE(dst);
        if (src->flags & EV_DISABLE) 
            KNOTE_DISABLE(dst);
        if (src->flags & EV_DELETE) 
            knote_free(dst);
        if (src->flags & EV_RECEIPT) {
            status = 0;
            goto err_out;
        }

        continue;

err_out:
        if (status != 0 && kn_alloc)
            knote_free(dst);
        if (nevents > 0) {
            kevent_error(eventlist++, src, status);
            nevents--;
        } else {
            return (-1);
        }
    }

    return (0);
}

int
kevent(int kqfd, const struct kevent *changelist, int nchanges,
        struct kevent *eventlist, int nevents,
        const struct timespec *timeout)
{
    struct kqueue *kq;
    struct filter *filt;
    fd_set fds;
    int i, rv, n, nret;

    errno = 0;

    kq = kqueue_lookup(kqfd);
    if (kq == NULL) {
        dbg_printf("fd lookup failed; fd=%d", kqfd);
        errno = EINVAL;
        return (-1);
    }

    /*
     * Process each kevent on the changelist.
     */
    if (nchanges) {
        kqueue_lock(kq);
        rv = kevent_copyin(kq, changelist, nchanges, eventlist, nevents);
        kqueue_unlock(kq);
        if (rv < 0)
            return (-1); 
    }

    /* Determine if we need to wait for events. */
    if (nevents == 0)
        return (0);
    if (nevents > MAX_KEVENT)
        nevents = MAX_KEVENT;

    /*
     * Wait for one or more filters to have events.
     */
wait_for_events:
    fds = kq->kq_fds;
    n = pselect(kq->kq_nfds, &fds, NULL , NULL, timeout, NULL);
    if (n < 0) {
        if (errno == EINTR) {
            dbg_puts("signal caught");
            return (-1);
        }
        dbg_perror("pselect(2)");
        return (-1);
    }
    dbg_printf("pselect(2): %d bits set", n);
    if (n == 0)
        return (0);

    /* 
     * Process each event and place it on the eventlist
     */ 
    nret = 0;
    kqueue_lock(kq);
    for (i = 0; (i < EVFILT_SYSCOUNT && n > 0 && nevents > 0); i++) {
        dbg_printf("eventlist: n = %d nevents = %d", n, nevents);
        filt = &kq->kq_filt[i]; 
        dbg_printf("pfd[%d] = %d", i, filt->kf_pfd);
        if (FD_ISSET(filt->kf_pfd, &fds)) {
            dbg_printf("event(s) for filter #%d", i);
            rv = filt->kf_copyout(filt, eventlist, nevents);
            if (rv < 0) {
                kqueue_unlock(kq);
                dbg_puts("kevent_copyout failed");
                return (-1);
            }
            nret += rv;
            eventlist += rv;
            nevents -= rv;
            n--;
        }
    }
    kqueue_unlock(kq);

    /* Handle spurious wakeups where no events are generated. */
    if (nret == 0)
        goto wait_for_events;

    return (nret);
}