FLocal/ThirdParty/mysql-connector-net-6.2.3/MySql.Data/Provider/Source/common/MyNetworkStream.cs

// Copyright (c) 2009 Sun Microsystems, Inc.
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License version 2 as published by
// the Free Software Foundation
//
// There are special exceptions to the terms and conditions of the GPL 
// as it is applied to this software. View the full text of the 
// exception in file EXCEPTIONS in the directory of this software 
// distribution.
//
// 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA 

using System;
using System.Net.Sockets;

internal class MyNetworkStream : NetworkStream
{
    /// <summary>
    /// Wrapper around NetworkStream.
    /// 
    /// MyNetworkStream is equivalent to NetworkStream, except 
    /// 1. It throws TimeoutException if read or write timeout occurs, instead 
    /// of IOException, to match behavior of other streams (named pipe and 
    /// shared memory). This property comes handy in TimedStream.
    ///
    /// 2. It implements workarounds for WSAEWOULDBLOCK errors, that can start 
    /// occuring after stream has times out. For a discussion about the CLR bug,
    /// refer to  http://tinyurl.com/lhgpyf. This error should never occur, as
    /// we're not using asynchronous operations, but apparerntly it does occur
    /// directly after timeout has expired.
    /// The workaround is hinted in the URL above and implemented like this:
    /// For each IO operation, if it throws WSAEWOULDBLOCK, we explicitely set
    /// the socket to Blocking and retry the operation once again.
    /// </summary>
    const int MaxRetryCount = 2;
    Socket socket;

    public MyNetworkStream(Socket socket, bool ownsSocket)
        : base(socket, ownsSocket)
    {
        this.socket = socket;
    }

    bool IsTimeoutException(SocketException e)
    {
#if CF
       return (e.NativeErrorCode == 10060);
#else
        return (e.SocketErrorCode == SocketError.TimedOut);
#endif
    }

    bool IsWouldBlockException(SocketException e)
    {
#if CF
      return (e.NativeErrorCode == 10035);
#else
      return (e.SocketErrorCode == SocketError.WouldBlock);
#endif
    }


    void HandleOrRethrowException(Exception e)
    {
        Exception currentException = e;
        while (currentException != null)
        {
            if (currentException is SocketException)
            {
                SocketException socketException = (SocketException)currentException;
                if (IsWouldBlockException(socketException))
                {
                    // Workaround  for WSAEWOULDBLOCK
                    socket.Blocking= true;
                    // return to give the caller possibility to retry the call
                    return;
                }
                else if (IsTimeoutException(socketException))
                {
                    throw new TimeoutException(socketException.Message, e);
                }

            }
            currentException = currentException.InnerException;
        }
        throw (e);
    }


    public override int Read(byte[] buffer, int offset, int count)
    {
        int retry = 0;
        Exception exception = null;
        do
        {
            try
            {
                return base.Read(buffer, offset, count);
            }
            catch (Exception e)
            {
                exception = e;
                HandleOrRethrowException(e);
            }
        }
        while (++retry < MaxRetryCount);
        throw exception;
    }

    public override int ReadByte()
    {
        int retry = 0;
        Exception exception = null;
        do
        {
            try
            {
                return base.ReadByte();
            }
            catch (Exception e)
            {
                exception = e;
                HandleOrRethrowException(e);
            }
        }
        while (++retry < MaxRetryCount);
        throw exception;
    }

    public override void Write(byte[] buffer, int offset, int count)
    {
        int retry = 0;
        Exception exception = null;
        do
        {
            try
            {
                base.Write(buffer, offset, count);
                return;
            }
            catch (Exception e)
            {
                exception = e;
                HandleOrRethrowException(e);
            }
        }
        while (++retry < MaxRetryCount);
        throw exception;
    }

    public override void Flush()
    {
        int retry = 0;
        Exception exception = null;
        do
        {
            try
            {
                base.Flush();
                return;
            }
            catch (Exception e)
            {
                exception = e;
                HandleOrRethrowException(e);
            }
        }
        while (++retry < MaxRetryCount);
        throw exception;
    }

}