/*      $OpenBSD: kqueue.c,v 1.43 2024/03/23 22:51:49 yasuoka 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.
 */

#include <sys/types.h>
#include <sys/time.h>
#include <sys/queue.h>
#include <sys/event.h>

#include <assert.h>
#include <errno.h>
#include <inttypes.h>
#include <limits.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

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

#define EVLIST_X_KQINKERNEL     0x1000

#define NEVENT          64

struct kqop {
        struct kevent *changes;
        int nchanges;
        struct kevent *events;
        struct event_list evsigevents[NSIG];
        int nevents;
        int kq;
        pid_t pid;
};

static void *kq_init    (struct event_base *);
static int kq_add       (void *, struct event *);
static int kq_del       (void *, struct event *);
static int kq_dispatch  (struct event_base *, void *, struct timeval *);
static int kq_insert    (struct kqop *, struct kevent *);
static void kq_dealloc (struct event_base *, void *);

const struct eventop kqops = {
        "kqueue",
        kq_init,
        kq_add,
        kq_del,
        kq_dispatch,
        kq_dealloc,
        1 /* need reinit */
};

static void *
kq_init(struct event_base *base)
{
        int i, kq;
        struct kqop *kqueueop;

        /* Disable kqueue when this environment variable is set */
        if (!issetugid() && getenv("EVENT_NOKQUEUE"))
                return (NULL);

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

        /* Initialize the kernel queue */

        if ((kq = kqueue()) == -1) {
                event_warn("kqueue");
                free (kqueueop);
                return (NULL);
        }

        kqueueop->kq = kq;

        kqueueop->pid = getpid();

        /* Initialize fields */
        kqueueop->changes = calloc(NEVENT, sizeof(struct kevent));
        if (kqueueop->changes == NULL) {
                free (kqueueop);
                return (NULL);
        }
        kqueueop->events = calloc(NEVENT, sizeof(struct kevent));
        if (kqueueop->events == NULL) {
                free (kqueueop->changes);
                free (kqueueop);
                return (NULL);
        }
        kqueueop->nevents = NEVENT;

        /* we need to keep track of multiple events per signal */
        for (i = 0; i < NSIG; ++i) {
                TAILQ_INIT(&kqueueop->evsigevents[i]);
        }

        return (kqueueop);
}

static int
kq_insert(struct kqop *kqop, struct kevent *kev)
{
        int nevents = kqop->nevents;

        if (kqop->nchanges == nevents) {
                struct kevent *newchange;
                struct kevent *newresult;

                if (nevents > INT_MAX / 2) {
                        event_warnx("%s: integer overflow", __func__);
                        return (-1);
                }
                nevents *= 2;

                newchange = recallocarray(kqop->changes,
                    kqop->nevents, nevents, sizeof(struct kevent));
                if (newchange == NULL) {
                        event_warn("%s: recallocarray", __func__);
                        return (-1);
                }
                kqop->changes = newchange;

                newresult = recallocarray(kqop->events,
                    kqop->nevents, nevents, sizeof(struct kevent));

                /*
                 * If we fail, we don't have to worry about freeing,
                 * the next realloc will pick it up.
                 */
                if (newresult == NULL) {
                        event_warn("%s: recallocarray", __func__);
                        return (-1);
                }
                kqop->events = newresult;

                kqop->nevents = nevents;
        }

        memcpy(&kqop->changes[kqop->nchanges++], kev, sizeof(struct kevent));

        event_debug(("%s: fd %d %s%s",
                __func__, (int)kev->ident,
                kev->filter == EVFILT_READ ? "EVFILT_READ" : "EVFILT_WRITE",
                kev->flags == EV_DELETE ? " (del)" : ""));

        return (0);
}

static void
kq_sighandler(int sig)
{
        /* Do nothing here */
}

static int
kq_dispatch(struct event_base *base, void *arg, struct timeval *tv)
{
        struct kqop *kqop = arg;
        struct kevent *changes = kqop->changes;
        struct kevent *events = kqop->events;
        struct event *ev;
        struct timespec ts, *ts_p = NULL;
        int i, res;

        if (tv != NULL) {
                TIMEVAL_TO_TIMESPEC(tv, &ts);
                ts_p = &ts;
        }

        res = kevent(kqop->kq, kqop->nchanges ? changes : NULL, kqop->nchanges,
            events, kqop->nevents, ts_p);
        kqop->nchanges = 0;
        if (res == -1) {
                if (errno != EINTR) {
                        event_warn("kevent");
                        return (-1);
                }

                return (0);
        }

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

        for (i = 0; i < res; i++) {
                int which = 0;

                if (events[i].flags & EV_ERROR) {
                        switch (events[i].data) {

                        /* Can occur on delete if we are not currently
                         * watching any events on this fd.  That can
                         * happen when the fd was closed and another
                         * file was opened with that fd. */
                        case ENOENT:
                        /* Can occur for reasons not fully understood
                         * on FreeBSD. */
                        case EINVAL:
                                continue;
                        /* Can occur on a delete if the fd is closed.  Can
                         * occur on an add if the fd was one side of a pipe,
                         * and the other side was closed. */
                        case EBADF:
                                continue;
                        /* These two can occur on an add if the fd was one side
                         * of a pipe, and the other side was closed. */
                        case EPERM:
                        case EPIPE:
                                /* Report read events, if we're listening for
                                 * them, so that the user can learn about any
                                 * add errors.  (If the operation was a
                                 * delete, then udata should be cleared.) */
                                if (events[i].udata) {
                                        /* The operation was an add:
                                         * report the error as a read. */
                                        which |= EV_READ;
                                        break;
                                } else {
                                        /* The operation was a del:
                                         * report nothing. */
                                        continue;
                                }

                        /* Other errors shouldn't occur. */
                        default:
                                errno = events[i].data;
                                return (-1);
                        }
                } else if (events[i].filter == EVFILT_READ) {
                        which |= EV_READ;
                } else if (events[i].filter == EVFILT_WRITE) {
                        which |= EV_WRITE;
                } else if (events[i].filter == EVFILT_SIGNAL) {
                        which |= EV_SIGNAL;
                }

                if (!which)
                        continue;

                if (events[i].filter == EVFILT_SIGNAL) {
                        struct event_list *head =
                            (struct event_list *)events[i].udata;
                        TAILQ_FOREACH(ev, head, ev_signal_next) {
                                event_active(ev, which, events[i].data);
                        }
                } else {
                        ev = (struct event *)events[i].udata;

                        if (!(ev->ev_events & EV_PERSIST))
                                ev->ev_flags &= ~EVLIST_X_KQINKERNEL;

                        event_active(ev, which, 1);
                }
        }

        return (0);
}


static int
kq_add(void *arg, struct event *ev)
{
        struct kqop *kqop = arg;
        struct kevent kev;

        if (ev->ev_events & EV_SIGNAL) {
                int nsignal = EVENT_SIGNAL(ev);

                assert(nsignal >= 0 && nsignal < NSIG);
                if (TAILQ_EMPTY(&kqop->evsigevents[nsignal])) {
                        struct timespec timeout = { 0, 0 };

                        memset(&kev, 0, sizeof(kev));
                        kev.ident = nsignal;
                        kev.filter = EVFILT_SIGNAL;
                        kev.flags = EV_ADD;
                        kev.udata = &kqop->evsigevents[nsignal];

                        /* Be ready for the signal if it is sent any
                         * time between now and the next call to
                         * kq_dispatch. */
                        if (kevent(kqop->kq, &kev, 1, NULL, 0, &timeout) == -1)
                                return (-1);

                        if (_evsignal_set_handler(ev->ev_base, nsignal,
                                kq_sighandler) == -1)
                                return (-1);
                }

                TAILQ_INSERT_TAIL(&kqop->evsigevents[nsignal], ev,
                    ev_signal_next);
                ev->ev_flags |= EVLIST_X_KQINKERNEL;
                return (0);
        }

        if (ev->ev_events & EV_READ) {
                memset(&kev, 0, sizeof(kev));
                kev.ident = ev->ev_fd;
                kev.filter = EVFILT_READ;
                /* Make it behave like select() and poll() */
                kev.fflags = NOTE_EOF;
                kev.flags = EV_ADD;
                if (!(ev->ev_events & EV_PERSIST))
                        kev.flags |= EV_ONESHOT;
                kev.udata = ev;

                if (kq_insert(kqop, &kev) == -1)
                        return (-1);

                ev->ev_flags |= EVLIST_X_KQINKERNEL;
        }

        if (ev->ev_events & EV_WRITE) {
                memset(&kev, 0, sizeof(kev));
                kev.ident = ev->ev_fd;
                kev.filter = EVFILT_WRITE;
                kev.flags = EV_ADD;
                if (!(ev->ev_events & EV_PERSIST))
                        kev.flags |= EV_ONESHOT;
                kev.udata = ev;

                if (kq_insert(kqop, &kev) == -1)
                        return (-1);

                ev->ev_flags |= EVLIST_X_KQINKERNEL;
        }

        return (0);
}

static int
kq_del(void *arg, struct event *ev)
{
        int i, j;
        struct kqop *kqop = arg;
        struct kevent kev;

        if (!(ev->ev_flags & EVLIST_X_KQINKERNEL))
                return (0);

        if (ev->ev_events & EV_SIGNAL) {
                int nsignal = EVENT_SIGNAL(ev);
                struct timespec timeout = { 0, 0 };

                assert(nsignal >= 0 && nsignal < NSIG);
                TAILQ_REMOVE(&kqop->evsigevents[nsignal], ev, ev_signal_next);
                if (TAILQ_EMPTY(&kqop->evsigevents[nsignal])) {
                        memset(&kev, 0, sizeof(kev));
                        kev.ident = nsignal;
                        kev.filter = EVFILT_SIGNAL;
                        kev.flags = EV_DELETE;

                        /* Because we insert signal events
                         * immediately, we need to delete them
                         * immediately, too */
                        if (kevent(kqop->kq, &kev, 1, NULL, 0, &timeout) == -1)
                                return (-1);

                        if (_evsignal_restore_handler(ev->ev_base,
                                nsignal) == -1)
                                return (-1);
                }

                ev->ev_flags &= ~EVLIST_X_KQINKERNEL;
                return (0);
        }

        for (i = j = 0; i < kqop->nchanges; i++) {
                if (kqop->changes[i].udata == ev &&
                    (kqop->changes[i].flags & EV_ADD) != 0)
                        continue;       /* delete this */
                if (i != j)
                        memcpy(&kqop->changes[j], &kqop->changes[i],
                            sizeof(struct kevent));
                j++;
        }
        if (kqop->nchanges != j) {
                kqop->nchanges = j;
                ev->ev_flags &= ~EVLIST_X_KQINKERNEL;
                return (0);
        }

        if (ev->ev_events & EV_READ) {
                memset(&kev, 0, sizeof(kev));
                kev.ident = ev->ev_fd;
                kev.filter = EVFILT_READ;
                kev.flags = EV_DELETE;

                if (kq_insert(kqop, &kev) == -1)
                        return (-1);

                ev->ev_flags &= ~EVLIST_X_KQINKERNEL;
        }

        if (ev->ev_events & EV_WRITE) {
                memset(&kev, 0, sizeof(kev));
                kev.ident = ev->ev_fd;
                kev.filter = EVFILT_WRITE;
                kev.flags = EV_DELETE;

                if (kq_insert(kqop, &kev) == -1)
                        return (-1);

                ev->ev_flags &= ~EVLIST_X_KQINKERNEL;
        }

        return (0);
}

static void
kq_dealloc(struct event_base *base, void *arg)
{
        struct kqop *kqop = arg;

        evsignal_dealloc(base);

        free(kqop->changes);
        free(kqop->events);
        if (kqop->kq >= 0 && kqop->pid == getpid())
                close(kqop->kq);

        memset(kqop, 0, sizeof(struct kqop));
        free(kqop);
}