// C# binding for epoll event services in libsimpleio.so

// Copyright (C)2017-2023, Philip Munts dba Munts Technologies.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// * Redistributions of source code must retain the above copyright notice,
//   this list of conditions and the following disclaimer.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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 COPYRIGHT HOLDER OR CONTRIBUTORS 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.

using System.Runtime.InteropServices;

namespace IO.Bindings
{
    public static partial class libsimpleio
    {
        // epoll events, extracted from /usr/include/sys/epoll.h

        private const int EPOLLIN      = 0x00000001;
        private const int EPOLLPRI     = 0x00000002;
        private const int EPOLLOUT     = 0x00000004;
        private const int EPOLLRDNORM  = 0x00000040;
        private const int EPOLLRDBAND  = 0x00000080;
        private const int EPOLLWRNORM  = 0x00000100;
        private const int EPOLLWRBAND  = 0x00000200;
        private const int EPOLLMSG     = 0x00000400;
        private const int EPOLLERR     = 0x00000008;
        private const int EPOLLHUP     = 0x00000010;
        private const int EPOLLRDHUP   = 0x00002000;
        private const int EPOLLWAKEUP  = 0x20000000;
        private const int EPOLLONESHOT = 0x40000000;
        private const int EPOLLET      = -2147483648;

        /// <summary>
        /// Open an <c>epoll</c> event dispatcher.
        /// </summary>
        /// <param name="epfd">File descriptor.</param>
        /// <param name="error">Error code.  Zero upon success or an <c>errno</c>
        /// value upon failure.</param>
        [DllImport("simpleio")]
        public static extern void EVENT_open(out int epfd, out int error);

        /// <summary>
        /// Register a file descriptor with an <c>epoll</c> event dispatcher.
        /// </summary>
        /// <param name="epfd">File descriptor for the dispatcher.</param>
        /// <param name="fd">File descriptor to register for events.</param>
        /// <param name="events">Events to register for.  May be a sum of the
        /// individual event flags.</param>
        /// <param name="handle">Event handle.</param>
        /// <param name="error">Error code.  Zero upon success or an <c>errno</c>
        /// value upon failure.</param>
        [DllImport("simpleio")]
        public static extern void EVENT_register_fd(int epfd, int fd,
            int events, int handle, out int error);

        /// <summary>
        /// Modify a file registration.
        /// </summary>
        /// <param name="epfd">File descriptor for the dispatcher.</param>
        /// <param name="fd">File descriptor to register for events.</param>
        /// <param name="events">Events to register for.  May be a sum of the
        /// individual event flags.</param>
        /// <param name="handle">Event handle.</param>
        /// <param name="error">Error code.  Zero upon success or an <c>errno</c>
        /// value upon failure.</param>
        [DllImport("simpleio")]
        public static extern void EVENT_modify_fd(int epfd, int fd,
            int events, int handle, out int error);

        /// <summary>
        /// Unregister a file from an <c>epoll</c> dispatcher.
        /// </summary>
        /// <param name="epfd">File descriptor for the dispatcher.></param>
        /// <param name="fd">File descriptor.</param>
        /// <param name="error">Error code.  Zero upon success or an <c>errno</c>
        /// value upon failure.</param>
        [DllImport("simpleio")]
        public static extern void EVENT_unregister_fd(int epfd, int fd,
            out int error);

        /// <summary>
        /// Wait for events from an <c>epoll</c> dispatcher.
        /// </summary>
        /// <param name="epfd">File descriptor for the displatcher.</param>
        /// <param name="fd">File descriptor the event is applicable to.</param>
        /// <param name="events">Events that occurred.  May be a sum of the
        /// individual event flags.</param>
        /// <param name="handle">Event handle provided whent the file descriptor
        /// was registered.</param>
        /// <param name="timeoutms">Time in milliseconds to wait for an event.</param>
        /// <param name="error">Error code.  Zero upon success or an <c>errno</c>
        /// value upon failure.</param>
        [DllImport("simpleio")]
        public static extern void EVENT_wait(int epfd, out int fd,
            out int events, out int handle, int timeoutms, out int error);

        /// <summary>
        /// Close an <c>epoll</c> event dispatcher.
        /// </summary>
        /// <param name="epfd">File descriptor.</param>
        /// <param name="error">Error code.  Zero upon success or an <c>errno</c>
        /// value upon failure.</param>
        [DllImport("simpleio")]
        public static extern void EVENT_close(int epfd, out int error);
    }
}