ShareX/ShareX.HelpersLib/SingleInstanceApplication/ApplicationInstanceManager.cs

#region License Information (GPL v3)

/*
    ShareX - A program that allows you to take screenshots and share any file type
    Copyright (c) 2007-2016 ShareX Team

    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License
    as published by the Free Software Foundation; either version 2
    of the License, or (at your option) any later version.

    This program 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 General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.

    Optionally you can also view the license at <http://www.gnu.org/licenses/>.
*/

#endregion License Information (GPL v3)

using System;
using System.Diagnostics;
using System.Runtime.Remoting;
using System.Runtime.Remoting.Channels;
using System.Runtime.Remoting.Channels.Ipc;
using System.Threading;

namespace SingleInstanceApplication
{
    public static class ApplicationInstanceManager
    {
        [DebuggerStepThrough]
        public static bool CreateSingleInstance(string name, EventHandler<InstanceCallbackEventArgs> callback, string[] args)
        {
            string eventName = string.Format("{0}-{1}", Environment.MachineName, name);

            InstanceProxy.IsFirstInstance = false;
            InstanceProxy.CommandLineArgs = args;

            try
            {
                using (EventWaitHandle eventWaitHandle = EventWaitHandle.OpenExisting(eventName))
                {
                    UpdateRemoteObject(name);

                    if (eventWaitHandle != null) eventWaitHandle.Set();
                }

                Environment.Exit(0);
            }
            catch
            {
                InstanceProxy.IsFirstInstance = true;

                using (EventWaitHandle eventWaitHandle = new EventWaitHandle(false, EventResetMode.AutoReset, eventName))
                {
                    ThreadPool.RegisterWaitForSingleObject(eventWaitHandle, WaitOrTimerCallback, callback, Timeout.Infinite, false);
                }

                RegisterRemoteType(name);
            }

            return InstanceProxy.IsFirstInstance;
        }

        public static bool CreateSingleInstance(EventHandler<InstanceCallbackEventArgs> callback, string[] args)
        {
            try
            {
                return CreateSingleInstance("ShareX", callback, args);
            }
            catch
            {
            }

            return true;
        }

        private static void UpdateRemoteObject(string uri)
        {
            IpcClientChannel clientChannel = new IpcClientChannel();
            ChannelServices.RegisterChannel(clientChannel, true);

            InstanceProxy proxy = Activator.GetObject(typeof(InstanceProxy), string.Format("ipc://{0}{1}/{1}", Environment.MachineName, uri)) as InstanceProxy;

            if (proxy != null)
            {
                proxy.SetCommandLineArgs(InstanceProxy.IsFirstInstance, InstanceProxy.CommandLineArgs);
            }

            ChannelServices.UnregisterChannel(clientChannel);
        }

        private static void RegisterRemoteType(string uri)
        {
            IpcServerChannel serverChannel = new IpcServerChannel(Environment.MachineName + uri);
            ChannelServices.RegisterChannel(serverChannel, true);

            RemotingConfiguration.RegisterWellKnownServiceType(typeof(InstanceProxy), uri, WellKnownObjectMode.Singleton);

            Process process = Process.GetCurrentProcess();
            process.Exited += delegate
            {
                ChannelServices.UnregisterChannel(serverChannel);
            };
        }

        private static void WaitOrTimerCallback(object state, bool timedOut)
        {
            EventHandler<InstanceCallbackEventArgs> callback = state as EventHandler<InstanceCallbackEventArgs>;
            if (callback == null) return;

            callback(state, new InstanceCallbackEventArgs(InstanceProxy.IsFirstInstance, InstanceProxy.CommandLineArgs));
        }
    }
}