/// <summary>
/// The worker thread entry point for polling the MailSlot. Threads will queue until a Mutex becomes
/// available for a particular channel.
/// </summary>
/// <param name="state"></param>
private void MailSlotChecker(object state)
{
MailSlotThreadInfo info = (MailSlotThreadInfo)state;
bool isOwner = false;
string mutextKey = string.Concat(mutexNetworkDispatcher, ".", info.ChannelName);
using (Mutex mutex = new Mutex(true, mutextKey, out isOwner))
{
// if doesn't own mutex then wait
if (!isOwner)
{
try
{
mutex.WaitOne();
isOwner = true;
}
catch (ThreadInterruptedException) { } // shut down thread
catch (AbandonedMutexException)
{
// This thread is now the owner
isOwner = true;
}
}
if (isOwner)
{
// enter message read loop
ProcessMessages(info);
// if this thread owns mutex then release it
mutex.ReleaseMutex();
}
}
}
/// <summary>
/// Helper method starts up a new listener thread for a given channel.
/// </summary>
/// <param name="channelName">The channel name.</param>
/// <returns></returns>
private MailSlotThreadInfo StartNewThread(string channelName)
{
// create and start the thread at low priority
Thread thread = new Thread(new ParameterizedThreadStart(MailSlotChecker));
thread.Priority = ThreadPriority.Lowest;
thread.IsBackground = true;
MailSlotThreadInfo info = new MailSlotThreadInfo(channelName, thread);
thread.Start(info);
return(info);
}
/// <summary>
/// This helper method puts the thread into a read message
/// loop.
/// </summary>
/// <param name="info"></param>
private void ProcessMessages(MailSlotThreadInfo info)
{
int bytesToRead = 512, maxMessageSize = 0, messageCount = 0, readTimeout = 0;
// for as long as thread is alive and the channel is registered then act as the MailSlot reader
while (!disposed && activeThreads.ContainsKey(info.ChannelName))
{
// if the channel mailslot is not open try to open it
if (!info.HasValidFileHandle)
{
info.FileHandle = Native.CreateMailslot(string.Concat(mailSlotIdentifier, info.ChannelName), 0, Native.MAILSLOT_WAIT_FOREVER, IntPtr.Zero);
}
// if there is a valid read handle try to read messages
if (info.HasValidFileHandle)
{
byte[] buffer = new byte[bytesToRead];
uint bytesRead = 0;
// this blocks until a message is received, the message cannot be buffered with overlap structure
// so the bytes array must be larger than the current item in order to read the complete message
while (Native.ReadFile(info.FileHandle, buffer, (uint)bytesToRead, out bytesRead, IntPtr.Zero))
{
ProcessMessage(buffer, bytesRead);
// reset buffer size
bytesToRead = 512;
buffer = new byte[bytesToRead];
}
int code = Marshal.GetLastWin32Error();
switch (code)
{
case Native.ERROR_INSUFFICIENT_BUFFER:
// insufficent buffer size, we need to the increase buffer size to read the current item
Native.GetMailslotInfo(info.FileHandle, ref maxMessageSize, ref bytesToRead, ref messageCount, ref readTimeout);
break;
case Native.ERROR_INVALID_HANDLE:
// close handle if invalid
if (info.HasValidFileHandle)
{
Native.CloseHandle(info.FileHandle);
info.FileHandle = IntPtr.Zero;
}
break;
case Native.ERROR_HANDLE_EOF:
// read handle has been closed
info.FileHandle = IntPtr.Zero;
break;
}
}
}
}
/// <summary>
/// Unregisters the current instance from the given channel. No more messages will be
/// processed, and another process will be allowed to obtain the listener lock.
/// </summary>
/// <param name="channelName"></param>
public void UnRegisterChannel(string channelName)
{
MailSlotThreadInfo info = null;
if (activeThreads.TryGetValue(channelName, out info))
{
// only lock if changing
lock (lockObj)
{
// double check has not been modified before lock
if (activeThreads.TryGetValue(channelName, out info))
{
// removing form hash shuts down the thread loop
activeThreads.Remove(channelName);
}
}
if (info != null)
{
// close any read handles
if (info.HasValidFileHandle)
{
Native.CloseHandle(info.FileHandle);
}
if (info.Thread.IsAlive)
{
// interrupt incase of asleep thread
info.Thread.Interrupt();
}
if (info.Thread.IsAlive)
{
// attempt to join thread
if (!info.Thread.Join(500))
{
// if no response within timeout, force abort
//info.Thread.Abort(); //Do nothing
}
}
}
}
}
/// <summary>
/// Helper method starts up a new listener thread for a given channel.
/// </summary>
/// <param name="channelName">The channel name.</param>
/// <returns></returns>
private MailSlotThreadInfo StartNewThread(string channelName)
{
// create and start the thread at low priority
Thread thread = new Thread(new ParameterizedThreadStart(MailSlotChecker));
thread.Priority = ThreadPriority.Lowest;
thread.IsBackground = true;
MailSlotThreadInfo info = new MailSlotThreadInfo(channelName, thread);
thread.Start(info);
return info;
}
/// <summary>
/// This helper method puts the thread into a read message
/// loop.
/// </summary>
/// <param name="info"></param>
private void ProcessMessages(MailSlotThreadInfo info)
{
int bytesToRead = 512, maxMessageSize = 0, messageCount = 0, readTimeout = 0;
// for as long as thread is alive and the channel is registered then act as the MailSlot reader
while (!disposed && activeThreads.ContainsKey(info.ChannelName))
{
// if the channel mailslot is not open try to open it
if (!info.HasValidFileHandle)
{
info.FileHandle = Native.CreateMailslot(string.Concat(mailSlotIdentifier, info.ChannelName), 0, Native.MAILSLOT_WAIT_FOREVER, IntPtr.Zero);
}
// if there is a valid read handle try to read messages
if (info.HasValidFileHandle)
{
byte[] buffer = new byte[bytesToRead];
uint bytesRead = 0;
// this blocks until a message is received, the message cannot be buffered with overlap structure
// so the bytes array must be larger than the current item in order to read the complete message
while (Native.ReadFile(info.FileHandle, buffer, (uint)bytesToRead, out bytesRead, IntPtr.Zero))
{
ProcessMessage(buffer, bytesRead);
// reset buffer size
bytesToRead = 512;
buffer = new byte[bytesToRead];
}
int code = Marshal.GetLastWin32Error();
switch (code)
{
case Native.ERROR_INSUFFICIENT_BUFFER:
// insufficent buffer size, we need to the increase buffer size to read the current item
Native.GetMailslotInfo(info.FileHandle, ref maxMessageSize, ref bytesToRead, ref messageCount, ref readTimeout);
break;
case Native.ERROR_INVALID_HANDLE:
// close handle if invalid
if (info.HasValidFileHandle)
{
Native.CloseHandle(info.FileHandle);
info.FileHandle = IntPtr.Zero;
}
break;
case Native.ERROR_HANDLE_EOF:
// read handle has been closed
info.FileHandle = IntPtr.Zero;
break;
}
}
}
}