/* Copyright (C) 2014 Stony Brook University
   This file is part of Graphene Library OS.

   Graphene Library OS is free software: you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public License
   as published by the Free Software Foundation, either version 3 of the
   License, or (at your option) any later version.

   Graphene Library OS is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

/*
 * db_event.c
 *
 * This file contains implementation of Drawbridge event synchronization APIs.
 */

#include <atomic.h>
#include <errno.h>
#include <sys/time.h>

#include "api.h"
#include "pal.h"
#include "pal_defs.h"
#include "pal_error.h"
#include "pal_freebsd.h"
#include "pal_freebsd_defs.h"
#include "pal_internal.h"

int _DkEventCreate(PAL_HANDLE* event, bool initialState, bool isnotification) {
    PAL_HANDLE ev = malloc(HANDLE_SIZE(event));
    SET_HANDLE_TYPE(ev, event);
    ev->event.isnotification = isnotification;
    atomic_set(&ev->event.signaled, initialState ? 1 : 0);
    atomic_set(&ev->event.nwaiters, 0);
    *event = ev;
    return 0;
}

void _DkEventDestroy(PAL_HANDLE handle) {
    free(handle);
}

int _DkEventSet(PAL_HANDLE event, int wakeup) {
    int ret = 0;
    if (event->event.isnotification) {
        /* Leave it signaled, wake all */
        if (atomic_cmpxchg(&event->event.signaled, 0, 1) == 0) {
            int nwaiters = atomic_read(&event->event.nwaiters);
            if (nwaiters) {
                if (wakeup != -1 && nwaiters > wakeup)
                    nwaiters = wakeup;

                ret = INLINE_SYSCALL(_umtx_op, 5, &event->event.signaled, UMTX_OP_WAKE, nwaiters,
                                     NULL, NULL);
                if (IS_ERR(ret))
                    atomic_set(&event->event.signaled, 0);
            }
        }
    } else {
        /* Only one thread wakes up, leave unsignaled */
        ret = INLINE_SYSCALL(_umtx_op, 5, &event->event.signaled, UMTX_OP_WAKE, 1, NULL, NULL);
    }

    return IS_ERR(ret) ? PAL_ERROR_TRYAGAIN : ret;
}

int _DkEventWaitTimeout(PAL_HANDLE event, uint64_t timeout) {
    int ret = 0;
    if (!event->event.isnotification || !atomic_read(&event->event.signaled)) {
        struct timespec waittime;
        unsigned long sec      = timeout / 1000000UL;
        unsigned long microsec = timeout - (sec * 1000000UL);
        waittime.tv_sec        = sec;
        waittime.tv_nsec       = microsec * 1000;

        atomic_inc(&event->event.nwaiters);

        do {
            ret = INLINE_SYSCALL(_umtx_op, 5, &event->event.signaled, UMTX_OP_WAIT_UINT, 0, NULL,
                                 &waittime);
            if (IS_ERR(ret)) {
                if (ERRNO(ret) == EWOULDBLOCK) {
                    ret = 0;
                } else {
                    ret = unix_to_pal_error(ERRNO(ret));
                    break;
                }
            }
        } while (event->event.isnotification && !atomic_read(&event->event.signaled));

        atomic_dec(&event->event.nwaiters);
    }

    return ret;
}

int _DkEventWait(PAL_HANDLE event) {
    int ret = 0;

    if (!event->event.isnotification || !atomic_read(&event->event.signaled)) {
        atomic_inc(&event->event.nwaiters);

        do {
            ret = INLINE_SYSCALL(_umtx_op, 5, &event->event.signaled, UMTX_OP_WAIT, 0, NULL, NULL);
            if (IS_ERR(ret)) {
                if (ERRNO(ret) == EWOULDBLOCK) {
                    ret = 0;
                } else {
                    ret = unix_to_pal_error(ERRNO(ret));
                    break;
                }
            }
        } while (event->event.isnotification && !atomic_read(&event->event.signaled));

        atomic_dec(&event->event.nwaiters);
    }

    return ret;
}

int _DkEventClear(PAL_HANDLE event) {
    atomic_set(&event->event.signaled, 0);
    return 0;
}

static int event_close(PAL_HANDLE handle) {
    _DkEventSet(handle, -1);
    return 0;
}

static int event_wait(PAL_HANDLE handle, uint64_t timeout) {
    return timeout == NO_TIMEOUT ? _DkEventWait(handle) : _DkEventWaitTimeout(handle, timeout);
}

struct handle_ops event_ops = {
    .close = &event_close,
    .wait  = &event_wait,
};