SynchronizingStream.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / Shared / MS / Internal / IO / SynchronizingStream.cs / 1305600 / SynchronizingStream.cs
                        
                        
                            //------------------------------------------------------------------------------ 
//  Microsoft Avalon
//  Copyright (c) Microsoft Corporation, 2001
//
//  File:           SynchronizingStream.cs 
//
//  Description:    Stream that locks on given syncRoot before entering any public API's. 
// 
//  History:        01/20/06 - brucemac - created
//----------------------------------------------------------------------------- 

using System;
using System.Diagnostics;
using System.IO; 
using System.Windows;
 
namespace MS.Internal.IO.Packaging 
{
    ///  
    /// Wrap returned stream to protect non-thread-safe API's from race conditions
    /// 
    internal class SynchronizingStream : Stream
    { 
        //-----------------------------------------------------
        // 
        //  Constructors 
        //
        //----------------------------------------------------- 
        /// 
        /// Serializes access by locking on the given object
        /// 
        /// stream to read from (baseStream) 
        /// object to lock on
        internal SynchronizingStream(Stream stream, Object syncRoot) 
        { 
            if (stream == null)
                throw new ArgumentNullException("stream"); 

            if (syncRoot == null)
                throw new ArgumentNullException("syncRoot");
 
            _baseStream = stream;
            _syncRoot = syncRoot; 
        } 

        //------------------------------------------------------ 
        //
        //  Public Methods
        //
        //----------------------------------------------------- 

        ///  
        /// Return the bytes requested 
        /// 
        /// destination buffer 
        /// offset to write into that buffer
        /// how many bytes requested
        /// how many bytes were written into buffer
        public override int Read(byte[] buffer, int offset, int count) 
        {
            lock (_syncRoot) 
            { 
                CheckDisposed();
                return (_baseStream.Read(buffer, offset, count)); 
            }
        }

        ///  
        /// Read a single byte
        ///  
        /// The unsigned byte cast to an Int32, or -1 if at the end of the stream. 
        public override int ReadByte()
        { 
            lock (_syncRoot)
            {
                CheckDisposed();
                return (_baseStream.ReadByte()); 
            }
        } 
 
        /// 
        /// Write a single byte 
        /// 
        /// byte to write
        public override void WriteByte(byte b)
        { 
            lock (_syncRoot)
            { 
                CheckDisposed(); 
                _baseStream.WriteByte(b);
            } 
        }

        /// 
        /// Seek 
        /// 
        /// only zero is supported 
        /// only SeekOrigin.Begin is supported 
        /// zero
        public override long Seek(long offset, SeekOrigin origin) 
        {
            lock (_syncRoot)
            {
                CheckDisposed(); 
                return _baseStream.Seek(offset, origin);
            } 
        } 
        /// 
        /// SetLength 
        /// 
        /// not supported
        public override void SetLength(long newLength)
        { 
            lock (_syncRoot)
            { 
                CheckDisposed(); 
                _baseStream.SetLength(newLength);
            } 
        }

        /// 
        /// Write 
        /// 
        /// not supported 
        public override void Write(byte[] buf, int offset, int count) 
        {
            lock (_syncRoot) 
            {
                CheckDisposed();
                _baseStream.Write(buf, offset, count);
            } 
        }
 
        ///  
        /// Flush
        ///  
        /// not supported
        public override void Flush()
        {
            lock (_syncRoot) 
            {
                CheckDisposed(); 
                _baseStream.Flush(); 
            }
        } 

        //------------------------------------------------------
        //
        //  Public Properties 
        //
        //------------------------------------------------------ 
 
        /// 
        /// Is stream readable? 
        /// 
        public override bool CanRead
        {
            get 
            {
                lock (_syncRoot) 
                { 
                    return ((_baseStream != null) && _baseStream.CanRead);
                } 
            }
        }
        /// 
        /// Is stream seekable? 
        /// 
        /// We MUST support seek as this is used to implement ILockBytes.ReadAt() 
        public override bool CanSeek 
        {
            get 
            {
                lock (_syncRoot)
                {
                    return ((_baseStream != null) && _baseStream.CanSeek); 
                }
            } 
        } 
        /// 
        /// Is stream writeable? 
        /// 
        public override bool CanWrite
        {
            get 
            {
                lock (_syncRoot) 
                { 
                    return ((_baseStream != null) && _baseStream.CanWrite);
                } 
            }
        }

        ///  
        /// Logical byte position in this stream
        ///  
        public override long Position 
        {
            get 
            {
                lock (_syncRoot)
                {
                    CheckDisposed(); 
                    return _baseStream.Position;
                } 
            } 
            set
            { 
                lock (_syncRoot)
                {
                    CheckDisposed();
                    _baseStream.Position = value; 
                }
            } 
        } 

        ///  
        /// Length
        /// 
        public override long Length
        { 
            get
            { 
                lock (_syncRoot) 
                {
                    CheckDisposed(); 
                    return _baseStream.Length;
                }
            }
        } 

        //----------------------------------------------------- 
        // 
        //  Protected Methods
        // 
        //------------------------------------------------------
        protected override void Dispose(bool disposing)
        {
            lock (_syncRoot) 
            {
                try 
                { 
                    if (disposing && (_baseStream != null))
                    { 
                        // close the underlying Stream
                        _baseStream.Close();

                        // NOTE: We cannot set _syncRoot to null because it is used 
                        // on entry to every public method and property.
                    } 
                } 
                finally
                { 
                    base.Dispose(disposing);
                    _baseStream = null;
                }
            } 
        }
 
        //----------------------------------------------------- 
        //
        //  Private Methods 
        //
        //-----------------------------------------------------
        /// 
        /// CheckDisposed 
        /// 
        /// Pre-condition that lock has been acquired. 
        private void CheckDisposed() 
        {
            if (_baseStream == null) 
                throw new ObjectDisposedException("Stream");
        }

        //----------------------------------------------------- 
        //
        //  Private Fields 
        // 
        //------------------------------------------------------
        private Stream      _baseStream;    // stream we are wrapping 
        private Object      _syncRoot;      // object to lock on
    }
}
 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
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