//
// System.Threading.Semaphore.cs
//
// Author:
//	Sebastien Pouliot  <sebastien@ximian.com>
//
// Copyright (C) 2005 Novell, Inc (http://www.novell.com)
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
// 
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//

using System.Runtime.ConstrainedExecution;
using System.Runtime.InteropServices;
using System.Security.AccessControl;
using System.Security.Permissions;
using System.Runtime.CompilerServices;
using System.IO;

namespace System.Threading {

	[ComVisible (false)]
	public sealed class Semaphore : WaitHandle {

		[MethodImplAttribute(MethodImplOptions.InternalCall)]
		private static extern IntPtr CreateSemaphore_internal (
			int initialCount, int maximumCount, string name,
			out bool createdNew);

		[MethodImplAttribute(MethodImplOptions.InternalCall)]
		private static extern int ReleaseSemaphore_internal (
			IntPtr handle, int releaseCount, out bool fail);

		[MethodImplAttribute (MethodImplOptions.InternalCall)]
		private static extern IntPtr OpenSemaphore_internal (string name, SemaphoreRights rights, out MonoIOError error);
		
		private Semaphore (IntPtr handle)
		{
			Handle = handle;
		}
		
		public Semaphore (int initialCount, int maximumCount)
			: this (initialCount, maximumCount, null)
		{
		}

		public Semaphore (int initialCount, int maximumCount, string name)
		{
			if (initialCount < 0)
				throw new ArgumentOutOfRangeException ("initialCount", "< 0");
			if (maximumCount < 1)
				throw new ArgumentOutOfRangeException ("maximumCount", "< 1");
			if (initialCount > maximumCount)
				throw new ArgumentException ("initialCount > maximumCount");

			bool created;
			
			Handle = CreateSemaphore_internal (initialCount,
							   maximumCount, name,
							   out created);
		}

		public Semaphore (int initialCount, int maximumCount, string name, out bool createdNew)
			: this (initialCount, maximumCount, name, out createdNew, null)
		{
		}

		[MonoTODO ("CreateSemaphore_internal does not support access control, semaphoreSecurity is ignored")]
		public Semaphore (int initialCount, int maximumCount, string name, out bool createdNew, 
			SemaphoreSecurity semaphoreSecurity)
		{
			if (initialCount < 0)
				throw new ArgumentOutOfRangeException ("initialCount", "< 0");
			if (maximumCount < 1)
				throw new ArgumentOutOfRangeException ("maximumCount", "< 1");
			if (initialCount > maximumCount)
				throw new ArgumentException ("initialCount > maximumCount");

			Handle = CreateSemaphore_internal (initialCount,
							   maximumCount, name,
							   out createdNew);
		}

		public SemaphoreSecurity GetAccessControl ()
		{
			return new SemaphoreSecurity (SafeWaitHandle,
						      AccessControlSections.Owner |
						      AccessControlSections.Group |
						      AccessControlSections.Access);
		}

		[PrePrepareMethod]
		[ReliabilityContract (Consistency.WillNotCorruptState, Cer.Success)]
		public int Release ()
		{
			return (Release (1));
		}

		[ReliabilityContract (Consistency.WillNotCorruptState, Cer.Success)]
		public int Release (int releaseCount)
		{
			if (releaseCount < 1)
				throw new ArgumentOutOfRangeException ("releaseCount");

			int ret;
			bool fail;
			
			ret = ReleaseSemaphore_internal (Handle, releaseCount,
							 out fail);

			if (fail) {
				throw new SemaphoreFullException ();
			}

			return (ret);
		}

		public void SetAccessControl (SemaphoreSecurity semaphoreSecurity)
		{
			if (semaphoreSecurity == null)
				throw new ArgumentNullException ("semaphoreSecurity");
				
			semaphoreSecurity.PersistModifications (SafeWaitHandle);
		}

		// static methods

#if !MOBILE
		public static Semaphore OpenExisting (string name)
		{
			return OpenExisting (name, SemaphoreRights.Synchronize | SemaphoreRights.Modify);
		}

		public static Semaphore OpenExisting (string name, SemaphoreRights rights)
		{
			if (name == null)
				throw new ArgumentNullException ("name");
			if ((name.Length ==0) || (name.Length > 260))
				throw new ArgumentException ("name", Locale.GetText ("Invalid length [1-260]."));

			MonoIOError error;
			IntPtr handle = OpenSemaphore_internal (name, rights,
								out error);
			if (handle == (IntPtr)null) {
				if (error == MonoIOError.ERROR_FILE_NOT_FOUND) {
					throw new WaitHandleCannotBeOpenedException (Locale.GetText ("Named Semaphore handle does not exist: ") + name);
				} else if (error == MonoIOError.ERROR_ACCESS_DENIED) {
					throw new UnauthorizedAccessException ();
				} else {
					throw new IOException (Locale.GetText ("Win32 IO error: ") + error.ToString ());
				}
			}
			
			return(new Semaphore (handle));
		}

		[SecurityPermissionAttribute (SecurityAction.LinkDemand, Flags = SecurityPermissionFlag.UnmanagedCode)]
		public static bool TryOpenExisting (string name, out Semaphore result)
		{
			return TryOpenExisting (name, SemaphoreRights.Synchronize | SemaphoreRights.Modify, out result);
		}

		[SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags = SecurityPermissionFlag.UnmanagedCode)]
		public static bool TryOpenExisting (string name, SemaphoreRights rights, out Semaphore result)
		{
			if (name == null)
				throw new ArgumentNullException ("name");
			if ((name.Length == 0) || (name.Length > 260))
				throw new ArgumentException ("name", Locale.GetText ("Invalid length [1-260]."));
			
			MonoIOError error;
			IntPtr handle = OpenSemaphore_internal (name, rights, out error);

			if (handle == (IntPtr)null) {
				result = null;
				return false;
			}

			result = new Semaphore (handle);
			return true;
		}
#else
		public static Semaphore OpenExisting (string name)
		{
			throw new NotSupportedException ();
		}

		public static Semaphore OpenExisting (string name, SemaphoreRights rights)
		{
			throw new NotSupportedException ();
		}

		public static bool TryOpenExisting (string name, out Semaphore result)
		{
			throw new NotSupportedException ();
		}

		public static bool TryOpenExisting (string name, SemaphoreRights rights, out Semaphore result)
		{
			throw new NotSupportedException ();
		}
#endif
	}
}