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/*

 * event notifier support

 *

 * Copyright Red Hat, Inc. 2010

 *

 * Authors:

 *  Michael S. Tsirkin <mst@redhat.com>

 *

 * This work is licensed under the terms of the GNU GPL, version 2.  See

 * the COPYING file in the top-level directory.

 */

#include "event_notifier.h"

#ifdef CONFIG_EVENTFD

#include <sys/eventfd.h>

#endif

int event_notifier_init(EventNotifier *e, int active)

{

#ifdef CONFIG_EVENTFD

    int fd = eventfd(!!active, EFD_NONBLOCK | EFD_CLOEXEC);

    if (fd < 0)

        return -errno;

    e->fd = fd;

    return 0;

#else

    return -ENOSYS;

#endif

}

void event_notifier_cleanup(EventNotifier *e)

{

    close(e->fd);

}

int event_notifier_get_fd(EventNotifier *e)

{

    return e->fd;

}

int event_notifier_test_and_clear(EventNotifier *e)

{

    uint64_t value;

    int r = read(e->fd, &value, sizeof(value));

    return r == sizeof(value);

}

int event_notifier_test(EventNotifier *e)

{

    uint64_t value;

    int r = read(e->fd, &value, sizeof(value));

    if (r == sizeof(value)) {

        /* restore previous value. */

        int s = write(e->fd, &value, sizeof(value));

        /* never blocks because we use EFD_SEMAPHORE.

         * If we didn't we'd get EAGAIN on overflow

         * and we'd have to write code to ignore it. */

        assert(s == sizeof(value));

    }

    return r == sizeof(value);

}