DuplicateMessageDetector.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / cdf / src / NetFx40 / System.ServiceModel.Discovery / System / ServiceModel / Channels / DuplicateMessageDetector.cs / 1305376 / DuplicateMessageDetector.cs
                        

                        
                            //------------------------------------------------------------ 
// Copyright (c) Microsoft Corporation.  All rights reserved.
//-----------------------------------------------------------

namespace System.ServiceModel.Channels 
{
    using System; 
    using System.Runtime; 
    using System.Security.Cryptography;
    using System.ServiceModel.Discovery; 

    sealed class DuplicateMessageDetector : IDisposable
    {
        HashAlgorithm hashAlgorithm; 

        [Fx.Tag.Cache(typeof(string), Fx.Tag.CacheAttrition.PartialPurgeOnEachAccess, SizeLimit = "maxListLength parameter to constructor")] 
        DuplicateDetector duplicateDetector; 
        [Fx.Tag.SynchronizationObject()]
        object thisLock; 
        bool disposed;

        public DuplicateMessageDetector(int maxListLength)
        { 
            Fx.Assert(maxListLength > 0, "maxListLength must be > 0");
 
            this.disposed = false; 
            this.hashAlgorithm = HashAlgorithm.Create();
            this.thisLock = new object(); 

            this.duplicateDetector = new DuplicateDetector(maxListLength);
        }
 
        public bool IsDuplicate(ArraySegment msgBytes, out string hashString)
        { 
            Fx.Assert(msgBytes != null, "messageBytes can't be null"); 
            Fx.Assert(msgBytes.Count > 0, "messageBytes.Count must be > 0");
 
            byte[] hash;

            bool notDuplicate = true;
            lock (this.thisLock) 
            {
                if (disposed) 
                { 
                    throw FxTrace.Exception.AsError(new ObjectDisposedException(this.GetType().ToString()));
                } 

                hash = this.hashAlgorithm.ComputeHash(msgBytes.Array, msgBytes.Offset, msgBytes.Count);
            }
 
            hashString = Convert.ToBase64String(hash);
 
            Fx.Assert(string.IsNullOrEmpty(hashString) == false, "computed hashstring is null or empty"); 

            lock (this.thisLock) 
            {
                //the act of retreiving an existing item pushes it to the front of the MRU list, ensuring
                //that the oldest hashes are trimmed first when we hit the max length.
                notDuplicate = this.duplicateDetector.AddIfNotDuplicate(hashString); 
            }
 
            return !notDuplicate; 
        }
 
        public void RemoveEntry(string msgHash)
        {
            Fx.Assert(!string.IsNullOrEmpty(msgHash), "Message hash should never be null or empty");
 
            lock (this.thisLock)
            { 
                if (this.disposed) 
                {
                    throw FxTrace.Exception.AsError(new ObjectDisposedException(this.GetType().ToString())); 
                }

                this.duplicateDetector.Remove(msgHash);
            } 
        }
 
        public void Dispose() 
        {
            if (this.disposed) 
            {
                return;
            }
 
            lock (this.thisLock)
            { 
                if (!this.disposed) 
                {
                    this.disposed = true; 
                    if (this.duplicateDetector != null)
                    {
                        this.duplicateDetector.Clear();
                    } 

                    this.hashAlgorithm.Clear(); 
                    this.hashAlgorithm = null; 
                }
            } 
        }
    }
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.

Link Menu

Network programming in C#, Network Programming in VB.NET, Network Programming in .NET
This book is available now!
Buy at Amazon US or
Buy at Amazon UK