ReaderWriterLock.cs source code in C# .NET

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                         / DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / clr / src / BCL / System / Threading / ReaderWriterLock.cs / 1 / ReaderWriterLock.cs
                        

                        
                            // ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--== 
/*============================================================
** 
** Class:    RWLock 
**
** 
** Purpose: Defines the lock that implements
**          single-writer/multiple-reader semantics
**
** 
===========================================================*/
 
namespace System.Threading { 
 	using System.Threading;
    using System.Security.Permissions; 
	using System.Runtime.Remoting;
	using System;
	using System.Runtime.CompilerServices;
    using System.Runtime.InteropServices; 
    using System.Runtime.ConstrainedExecution;
 
    [HostProtection(Synchronization=true, ExternalThreading=true)] 
    [ComVisible(true)]
    public sealed class ReaderWriterLock: CriticalFinalizerObject 
    {
        /*
         * Constructor
         */ 
        public ReaderWriterLock()
        { 
            PrivateInitialize(); 
        }
 
        /*
         * Destructor
         */
        ~ReaderWriterLock() 
        {
            PrivateDestruct(); 
        } 

        /* 
         * Property that returns TRUE if the reader lock is held
         * by the current thread
         */
        public bool IsReaderLockHeld { 
            [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
            get { 
                return(PrivateGetIsReaderLockHeld()); 
                }
        } 

        /*
         * Property that returns TRUE if the writer lock is held
         * by the current thread 
         */
        public bool IsWriterLockHeld { 
            [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)] 
            get {
                return(PrivateGetIsWriterLockHeld()); 
                }
        }

        /* 
         * Property that returns the current writer sequence number.
         * The caller should be a reader or writer for getting 
         * meaningful results 
         */
        public int WriterSeqNum { 
            get {
                return(PrivateGetWriterSeqNum());
                }
        } 

        /* 
         * Acquires reader lock. The thread will block if a different 
         * thread has writer lock.
         */ 
        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        private extern void AcquireReaderLockInternal(int millisecondsTimeout);

        public void AcquireReaderLock(int millisecondsTimeout) 
        {
            AcquireReaderLockInternal(millisecondsTimeout); 
        } 

 
 		public void AcquireReaderLock(TimeSpan timeout)
		{
 			long tm = (long)timeout.TotalMilliseconds;
 			if (tm < -1 || tm > (long) Int32.MaxValue) 
				throw new ArgumentOutOfRangeException("timeout", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegOrNegative1"));
 			AcquireReaderLockInternal((int)tm); 
		} 

        /* 
         * Acquires writer lock. The thread will block if a different
         * thread has reader lock. It will dead lock if this thread
         * has reader lock. Use UpgardeToWriterLock when you are not
         * sure if the thread has reader lock 
         */
        [MethodImplAttribute(MethodImplOptions.InternalCall)] 
        private extern void AcquireWriterLockInternal(int millisecondsTimeout); 

        public void AcquireWriterLock(int millisecondsTimeout) 
        {
            AcquireWriterLockInternal(millisecondsTimeout);
        }
 
		public void AcquireWriterLock(TimeSpan timeout)
		{ 
 			long tm = (long)timeout.TotalMilliseconds; 
			if (tm < -1 || tm > (long) Int32.MaxValue)
 				throw new ArgumentOutOfRangeException("timeout", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegOrNegative1")); 
 			AcquireWriterLockInternal((int)tm);
		}

 
        /*
         * Releases reader lock. 
         */ 
        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)] 
        private extern void ReleaseReaderLockInternal();

        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
        public void ReleaseReaderLock() 
        {
            ReleaseReaderLockInternal(); 
        } 

        /* 
         * Releases writer lock.
         */
        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)] 
        private extern void ReleaseWriterLockInternal();
 
        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)] 
        public void ReleaseWriterLock()
        { 
            ReleaseWriterLockInternal();
        }

        /* 
         * Upgardes the thread to a writer. If the thread has is a
         * reader, it is possible that the reader lock was 
         * released before writer lock was acquired. 
         */
        public LockCookie UpgradeToWriterLock(int millisecondsTimeout) 
        {
            LockCookie result = new LockCookie ();
            FCallUpgradeToWriterLock (ref result, millisecondsTimeout);
            return result; 
        }
 
        [MethodImplAttribute(MethodImplOptions.InternalCall)] 
        private extern void FCallUpgradeToWriterLock(ref LockCookie result, int millisecondsTimeout);
 
 		public LockCookie UpgradeToWriterLock(TimeSpan timeout)
		{
			long tm = (long)timeout.TotalMilliseconds;
			if (tm < -1 || tm > (long) Int32.MaxValue) 
 				throw new ArgumentOutOfRangeException("timeout", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegOrNegative1"));
			return UpgradeToWriterLock((int)tm); 
 		} 

        /* 
         * Restores the lock status of the thread to the one it was
         * in when it called UpgradeToWriterLock.
         */
        [MethodImplAttribute(MethodImplOptions.InternalCall)] 
        private extern void DowngradeFromWriterLockInternal(ref LockCookie lockCookie);
 
        public void DowngradeFromWriterLock(ref LockCookie lockCookie) 
        {
            DowngradeFromWriterLockInternal(ref lockCookie); 
        }

        /*
         * Releases the lock irrespective of the number of times the thread 
         * acquired the lock
         */ 
        public LockCookie ReleaseLock() 
        {
            LockCookie result = new LockCookie (); 
            FCallReleaseLock (ref result);
            return result;
        }
 
        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        private extern void FCallReleaseLock(ref LockCookie result); 
 
        /*
         * Restores the lock status of the thread to the one it was 
         * in when it called ReleaseLock.
         */
        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        private extern void RestoreLockInternal(ref LockCookie lockCookie); 

        public void RestoreLock(ref LockCookie lockCookie) 
        { 
            RestoreLockInternal(ref lockCookie);
        } 

        /*
         * Internal helper that returns TRUE if the reader lock is held
         * by the current thread 
         */
        [MethodImplAttribute(MethodImplOptions.InternalCall)] 
        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)] 
        private extern bool PrivateGetIsReaderLockHeld();
 
        /*
         * Internal helper that returns TRUE if the writer lock is held
         * by the current thread
         */ 
        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)] 
        private extern bool PrivateGetIsWriterLockHeld(); 

        /* 
         * Internal helper that returns the current writer sequence
         * number. The caller should be a reader or writer for getting
         * meaningful results
         */ 
        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        private extern int PrivateGetWriterSeqNum(); 
 
        /*
         * Returns true if there were intermediate writes since the 
         * sequence number was obtained. The caller should be
         * a reader or writer for getting meaningful results
         */
        [MethodImplAttribute(MethodImplOptions.InternalCall)] 
        public extern bool AnyWritersSince(int seqNum);
 
        // Initialize state kept inside the lock 
        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        private extern void PrivateInitialize(); 

        // Destruct resource associated with the lock
        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        private extern void PrivateDestruct(); 

        // State 
#pragma warning disable 169 
#pragma warning disable 414  // These fields are not used from managed.
        private IntPtr _hWriterEvent; 
        private IntPtr _hReaderEvent;
        private IntPtr _hObjectHandle;
        private int _dwState = 0;
        private int _dwULockID = 0; 
        private int _dwLLockID = 0;
        private int _dwWriterID = 0; 
        private int _dwWriterSeqNum = 0; 
        private short _wWriterLevel;
#if RWLOCK_STATISTICS 
        // WARNING: You must explicitly #define RWLOCK_STATISTICS when you
        // build in both the VM and BCL directories if you want this.
        private int _dwReaderEntryCount = 0;
        private int _dwReaderContentionCount = 0; 
        private int _dwWriterEntryCount = 0;
        private int _dwWriterContentionCount = 0; 
        private int _dwEventsReleasedCount = 0; 
#endif // RWLOCK_STATISTICS
#pragma warning restore 414 
#pragma warning restore 169
    }
}

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