// **********************************************************************
//
// Copyright (c) 2003-2006 ZeroC, Inc. All rights reserved.
//
// This copy of Ice is licensed to you under the terms described in the
// ICE_LICENSE file included in this distribution.
//
// **********************************************************************

package IceInternal;

public final class ThreadPool
{
    private final static boolean TRACE_REGISTRATION = false;
    private final static boolean TRACE_INTERRUPT = false;
    private final static boolean TRACE_SHUTDOWN = false;
    private final static boolean TRACE_SELECT = false;
    private final static boolean TRACE_EXCEPTION = false;
    private final static boolean TRACE_THREAD = false;
    private final static boolean TRACE_STACK_TRACE = false;

    public
    ThreadPool(Instance instance, String prefix, int timeout)
    {
        _instance = instance;
        _destroyed = false;
        _prefix = prefix;
        _timeout = timeout;
	_threadIndex = 0;
	_running = 0;
	_inUse = 0;
	_load = 1.0;
	_promote = true;
	_warnUdp = _instance.initializationData().properties.getPropertyAsInt("Ice.Warn.Datagrams") > 0;

	//
	// If we are in thread per connection mode, no thread pool should
	// ever be created.
	//
	assert(!_instance.threadPerConnection());

	String programName = _instance.initializationData().properties.getProperty("Ice.ProgramName");
        if(programName.length() > 0)
        {
            _programNamePrefix = programName + "-";
        }
	else
	{
	    _programNamePrefix = "";
	}

	Network.SocketPair pair = Network.createPipe();
        _fdIntrRead = (java.nio.channels.ReadableByteChannel)pair.source;
        _fdIntrWrite = pair.sink;

        try
        {
            _selector = java.nio.channels.Selector.open();
            pair.source.configureBlocking(false);
            _fdIntrReadKey = pair.source.register(_selector, java.nio.channels.SelectionKey.OP_READ);
        }
        catch(java.io.IOException ex)
        {
            Ice.SyscallException sys = new Ice.SyscallException();
            sys.initCause(ex);
            throw sys;
        }

        //
        // The Selector holds a Set representing the selected keys. The
        // Set reference doesn't change, so we obtain it once here.
        //
        _keys = _selector.selectedKeys();

	//
	// We use just one thread as the default. This is the fastest
	// psossible setting, still allows one level of nesting, and
	// doesn't require to make the servants thread safe.
	//
	int size = _instance.initializationData().properties.getPropertyAsIntWithDefault(_prefix + ".Size", 1);
	if(size < 1)
	{
	    String s = _prefix + ".Size < 1; Size adjusted to 1";
	    _instance.initializationData().logger.warning(s);
	    size = 1;
	}		

	int sizeMax = 
	    _instance.initializationData().properties.getPropertyAsIntWithDefault(_prefix + ".SizeMax", size);
	if(sizeMax < size)
	{
	    String s = _prefix + ".SizeMax < " + _prefix + ".Size; SizeMax adjusted to Size (" + size + ")";
	    _instance.initializationData().logger.warning(s);
	    sizeMax = size;
	}
		
	int sizeWarn = _instance.initializationData().properties.getPropertyAsIntWithDefault(
								_prefix + ".SizeWarn", sizeMax * 80 / 100);
	if(sizeWarn > sizeMax)
	{
	    String s = _prefix + ".SizeWarn > " + _prefix + ".SizeMax; adjusted SizeWarn to SizeMax (" + sizeMax + ")";
	    _instance.initializationData().logger.warning(s);
	    sizeWarn = sizeMax;
	}

	_size = size;
	_sizeMax = sizeMax;
	_sizeWarn = sizeWarn;
	
	try
        {
            _threads = new java.util.ArrayList();
            for(int i = 0; i < _size; i++)
            {
		EventHandlerThread thread = new EventHandlerThread(_programNamePrefix + _prefix + "-" +
								   _threadIndex++);
                _threads.add(thread);
		thread.start();
		++_running;
            }
        }
        catch(RuntimeException ex)
        {
	    java.io.StringWriter sw = new java.io.StringWriter();
	    java.io.PrintWriter pw = new java.io.PrintWriter(sw);
	    ex.printStackTrace(pw);
	    pw.flush();
	    String s = "cannot create thread for `" + _prefix + "':\n" + sw.toString();
	    _instance.initializationData().logger.error(s);

            destroy();
	    joinWithAllThreads();
            throw ex;
        }
    }

    protected synchronized void
    finalize()
        throws Throwable
    {
        IceUtil.Assert.FinalizerAssert(_destroyed);
    }

    public synchronized void
    destroy()
    {
        if(TRACE_SHUTDOWN)
        {
            trace("destroy");
        }

        assert(!_destroyed);
	assert(_handlerMap.isEmpty());
	assert(_changes.isEmpty());
        _destroyed = true;
        setInterrupt();
    }

    public synchronized void
    _register(java.nio.channels.SelectableChannel fd, EventHandler handler)
    {
        if(TRACE_REGISTRATION)
        {
            trace("adding handler of type " + handler.getClass().getName() + " for channel " + fd);
        }
	assert(!_destroyed);
        _changes.add(new FdHandlerPair(fd, handler));
        setInterrupt();
    }

    public synchronized void
    unregister(java.nio.channels.SelectableChannel fd)
    {
        if(TRACE_REGISTRATION)
        {
            if(TRACE_STACK_TRACE)
            {
                java.io.StringWriter sw = new java.io.StringWriter();
                try
                {
                    throw new RuntimeException();
                }
                catch(RuntimeException ex)
                {
                    java.io.PrintWriter pw = new java.io.PrintWriter(sw);
                    ex.printStackTrace(pw);
                    pw.flush();
                }
                trace("removing handler for channel " + fd + "\n" + sw.toString());
            }
            else
            {
                trace("removing handler for channel " + fd);
            }
        }

	assert(!_destroyed);
        _changes.add(new FdHandlerPair(fd, null));
        setInterrupt();
    }

    public void
    promoteFollower()
    {
        if(_sizeMax > 1)
        {
	    synchronized(this)
	    {
		assert(!_promote);
		_promote = true;
		notify();
		    
		if(!_destroyed)
		{
		    assert(_inUse >= 0);
		    ++_inUse;
		    
		    if(_inUse == _sizeWarn)
		    {
			String s = "thread pool `" + _prefix + "' is running low on threads\n"
			    + "Size=" + _size + ", " + "SizeMax=" + _sizeMax + ", " + "SizeWarn=" + _sizeWarn;
			_instance.initializationData().logger.warning(s);
		    }
		    
		    assert(_inUse <= _running);
		    if(_inUse < _sizeMax && _inUse == _running)
		    {
			try
			{
			    EventHandlerThread thread = new EventHandlerThread(_programNamePrefix + _prefix + "-" +
									       _threadIndex++);
			    _threads.add(thread);
			    thread.start();
			    ++_running;
			}
			catch(RuntimeException ex)
			{
			    java.io.StringWriter sw = new java.io.StringWriter();
			    java.io.PrintWriter pw = new java.io.PrintWriter(sw);
			    ex.printStackTrace(pw);
			    pw.flush();
			    String s = "cannot create thread for `" + _prefix + "':\n" + sw.toString();
			    _instance.initializationData().logger.error(s);
			}
		    }
		}
	    }
        }
    }

    public void
    joinWithAllThreads()
    {
	//
	// _threads is immutable after destroy() has been called,
	// therefore no synchronization is needed. (Synchronization
	// wouldn't be possible here anyway, because otherwise the
	// other threads would never terminate.)
	//
	java.util.Iterator i = _threads.iterator();
	while(i.hasNext())
	{
	    EventHandlerThread thread = (EventHandlerThread)i.next();
	    
            while(true)
            {
                try
                {
                    thread.join();
                    break;
                }
                catch(InterruptedException ex)
                {
                }
            }
        }

	//
	// Cleanup the selector, and the socket pair.
	//
	try
	{
	    if(_selector != null)
	    {
		try
		{
		    _selector.close();
		}
		catch(java.io.IOException ex)
		{
		    //
		    // BUGFIX:
		    //
		    // Ignore this exception. This shouldn't happen
		    // but for some reasons the close() call raises
		    // "java.io.IOException: Bad file descriptor" on
		    // Mac OS X 10.3.x (it works fine on OS X 10.4.x)
		    //
		}
		_selector = null;
	    }

	    if(_fdIntrWrite != null)
	    {
		try
		{
		    _fdIntrWrite.close();
		}
		catch(java.io.IOException ex)
		{
		    //
		    // BUGFIX:
		    //
		    // Ignore this exception. This shouldn't happen
		    // but for some reasons the close() call raises
		    // "java.io.IOException: No such file or
		    // directory" under Linux with JDK 1.4.2.
		    //
		}
		_fdIntrWrite = null;
	    }

	    if(_fdIntrRead != null)
	    {
		_fdIntrRead.close();
		_fdIntrRead = null;
	    }
	}
	catch(java.io.IOException ex)
	{
	    java.io.StringWriter sw = new java.io.StringWriter();
	    java.io.PrintWriter pw = new java.io.PrintWriter(sw);
	    ex.printStackTrace(pw);
	    pw.flush();
	    String s = "exception in `" + _prefix + "' while calling close():\n" + sw.toString();
	    _instance.initializationData().logger.error(s);
	}
    }

    public String
    prefix()
    {
	return _prefix;
    }
    
    private void
    clearInterrupt()
    {
        if(TRACE_INTERRUPT)
        {
            trace("clearInterrupt");
            if(TRACE_STACK_TRACE)
            {
                try
                {
                    throw new RuntimeException();
                }
                catch(RuntimeException ex)
                {
                    ex.printStackTrace();
                }
            }
        }

        byte b = 0;

        java.nio.ByteBuffer buf = java.nio.ByteBuffer.allocate(1);
        try
        {
            while(true)
            {
                buf.rewind();
                if(_fdIntrRead.read(buf) != 1)
                {
                    break;
                }

                if(TRACE_INTERRUPT)
                {
                    trace("clearInterrupt got byte " + (int)buf.get(0));
                }

                b = buf.get(0);
                break;
            }
        }
        catch(java.io.IOException ex)
        {
            Ice.SocketException se = new Ice.SocketException();
            se.initCause(ex);
            throw se;
        }
    }

    private void
    setInterrupt()
    {
        if(TRACE_INTERRUPT)
        {
            trace("setInterrupt()");
            if(TRACE_STACK_TRACE)
            {
                try
                {
                    throw new RuntimeException();
                }
                catch(RuntimeException ex)
                {
                    ex.printStackTrace();
                }
            }
        }

        java.nio.ByteBuffer buf = java.nio.ByteBuffer.allocate(1);
        buf.put(0, (byte)0);
        while(buf.hasRemaining())
        {
            try
            {
                _fdIntrWrite.write(buf);
            }
            catch(java.io.IOException ex)
            {
                Ice.SocketException se = new Ice.SocketException();
                se.initCause(ex);
                throw se;
            }
        }
    }

    //
    // Each thread supplies a BasicStream, to avoid creating excessive
    // garbage (Java only).
    //
    private boolean
    run(BasicStream stream)
    {
	if(_sizeMax > 1)
	{
	    synchronized(this)
	    {
		while(!_promote)
		{
		    try
		    {
			wait();
		    }
		    catch(InterruptedException ex)
		    {
		    }
		}
		
		_promote = false;
	    }
	    
	    if(TRACE_THREAD)
	    {
		trace("thread " + Thread.currentThread() + " has the lock");
	    }
	}

	while(true)
        {
	    if(TRACE_REGISTRATION)
	    {
		java.util.Set keys = _selector.keys();
		trace("selecting on " + keys.size() + " channels:");
		java.util.Iterator i = keys.iterator();
		while(i.hasNext())
		{
		    java.nio.channels.SelectionKey key = (java.nio.channels.SelectionKey)i.next();
		    trace("  " + key.channel());
		}
	    }

	    EventHandler handler = null;

	    //
	    // Only call select() if there are no pending handlers with additional data
	    // for us to read.
	    //
	    if(!_pendingHandlers.isEmpty())
	    {
		handler = (EventHandler)_pendingHandlers.removeFirst();
	    }
	    else
	    {
		select();
	    }

	    boolean finished = false;
	    boolean shutdown = false;

	    if(handler == null)
	    {
		synchronized(this)
		{
		    if(_keys.size() == 0) // We initiate a shutdown if there is a thread pool timeout.
		    {
			if(TRACE_SELECT)
			{
			    trace("timeout");
			}
			
			assert(_timeout > 0);
			_timeout = 0;
			shutdown = true;
		    }
		    else
		    {
			if(_keys.contains(_fdIntrReadKey) && _fdIntrReadKey.isReadable())
			{
			    if(TRACE_SELECT || TRACE_INTERRUPT)
			    {
				trace("detected interrupt");
			    }
			    
			    //
			    // There are two possiblities for an interrupt:
			    //
			    // 1. The thread pool has been destroyed.
			    //
			    // 2. An event handler was registered or unregistered.
			    //
			    
			    //
			    // Thread pool destroyed?
			    //
			    if(_destroyed)
			    {
				if(TRACE_SHUTDOWN)
				{
				    trace("destroyed, thread id = " + Thread.currentThread());
				}
				
				//
				// Don't clear the interrupt fd if
				// destroyed, so that the other threads
				// exit as well.
				//
				return true;
			    }
			    
			    //
			    // Remove the interrupt channel from the
			    // selected key set.
			    //
			    _keys.remove(_fdIntrReadKey);
			    
			    clearInterrupt();
			    
			    //
			    // An event handler must have been registered
			    // or unregistered.
			    //
			    assert(!_changes.isEmpty());
			    FdHandlerPair change = (FdHandlerPair)_changes.removeFirst();
			    
			    if(change.handler != null) // Addition if handler is set.
			    {
				int op;
				if((change.fd.validOps() & java.nio.channels.SelectionKey.OP_READ) > 0)
				{
				    op = java.nio.channels.SelectionKey.OP_READ;
				}
				else
				{
				    op = java.nio.channels.SelectionKey.OP_ACCEPT;
				}
				    
				java.nio.channels.SelectionKey key = null;
				try
				{
				    key = change.fd.register(_selector, op, change.handler);
				}
				catch(java.nio.channels.ClosedChannelException ex)
				{
				    assert(false);
				}
				_handlerMap.put(change.fd, new HandlerKeyPair(change.handler, key));
				    
				if(TRACE_REGISTRATION)
				{
				    trace("added handler (" + change.handler.getClass().getName() + ") for fd " +
					  change.fd);
				}
				    
				continue;
			    }
			    else // Removal if handler is not set.
			    {
				HandlerKeyPair pair = (HandlerKeyPair)_handlerMap.remove(change.fd);
				assert(pair != null);
				handler = pair.handler;
				finished = true;
				pair.key.cancel();
				    
				if(TRACE_REGISTRATION)
				{
				    trace("removed handler (" + handler.getClass().getName() + ") for fd " +
					  change.fd);
				}
				    
				// Don't continue; we have to call
				// finished() on the event handler below,
				// outside the thread synchronization.
			    }
			}
			else
			{
			    java.nio.channels.SelectionKey key = null;
			    java.util.Iterator iter = _keys.iterator();
			    while(iter.hasNext())
			    {
				//
				// Ignore selection keys that have been cancelled
				//
				java.nio.channels.SelectionKey k = (java.nio.channels.SelectionKey)iter.next();
				iter.remove();
				if(k.isValid() && key != _fdIntrReadKey)
				{
				    if(TRACE_SELECT)
				    {
					trace("found a key: " + keyToString(k));
				    }
				    
				    key = k;
				    break;
				}
			    }
			    
			    if(key == null)
			    {
				if(TRACE_SELECT)
				{
				    trace("didn't find a valid key");
				}
				
				continue;
			    }
			    
			    handler = (EventHandler)key.attachment();
			}
		    }
		}
	    }

	    //
	    // Now we are outside the thread synchronization.
	    //
	    
	    if(shutdown)
	    {
		if(TRACE_SHUTDOWN)
		{
		    trace("shutdown detected");
		}
		
		//
		// Initiate server shutdown.
		//
		ObjectAdapterFactory factory;
		try
		{
		    factory = _instance.objectAdapterFactory();
		}
		catch(Ice.CommunicatorDestroyedException e)
		{
		    continue;
		}

		promoteFollower();
		factory.shutdown();

		//
		// No "continue", because we want shutdown to be done in
		// its own thread from this pool. Therefore we called
		// promoteFollower().
		//
	    }
	    else
	    {
		assert(handler != null);

		if(finished)
		{
		    //
		    // Notify a handler about its removal from
		    // the thread pool.
		    //
		    try
		    {
			handler.finished(this);
		    }
		    catch(Ice.LocalException ex)
		    {
			java.io.StringWriter sw = new java.io.StringWriter();
			java.io.PrintWriter pw = new java.io.PrintWriter(sw);
			ex.printStackTrace(pw);
			pw.flush();
			String s = "exception in `" + _prefix + "' while calling finished():\n" +
			    sw.toString() + "\n" + handler.toString();
			_instance.initializationData().logger.error(s);
		    }

		    //
		    // No "continue", because we want finished() to be
		    // called in its own thread from this pool. Note
		    // that this means that finished() must call
		    // promoteFollower().
		    //
		}
		else
		{
		    //
		    // If the handler is "readable", try to read a
		    // message.
		    //
		    try
		    {
			if(handler.readable())
			{
			    try
			    {
				//
				// If read returns true, the handler has more data for the thread pool
				// to process.
				//
				if(read(handler))
				{
				    _pendingHandlers.add(handler);
				}
			    }
			    catch(Ice.TimeoutException ex) // Expected.
			    {
				continue;
			    }
			    catch(Ice.DatagramLimitException ex) // Expected.
			    {
				continue;
			    }
			    catch(Ice.SocketException ex)
			    {
				if(TRACE_EXCEPTION)
				{
				    trace("informing handler (" + handler.getClass().getName() +
					  ") about exception " + ex);
				    ex.printStackTrace();
				}
				    
				handler.exception(ex);
				continue;
			    }
			    catch(Ice.LocalException ex)
			    {
				if(handler.datagram())
				{
				    if(_instance.initializationData().properties.getPropertyAsInt(
										"Ice.Warn.Connections") > 0)
				    {
					_instance.initializationData().logger.warning(
					    "datagram connection exception:\n" + ex + "\n" + handler.toString());
				    }
				}
				else
				{
				    if(TRACE_EXCEPTION)
				    {
					trace("informing handler (" + handler.getClass().getName() +
					      ") about exception " + ex);
					ex.printStackTrace();
				    }
				    
				    handler.exception(ex);
				}
				continue;
			    }
				
			    stream.swap(handler._stream);
			    assert(stream.pos() == stream.size());
			}
			    
			//
			// Provide a new message to the handler.
			//
			try
			{
			    handler.message(stream, this);
			}
			catch(Ice.LocalException ex)
			{
			    java.io.StringWriter sw = new java.io.StringWriter();
			    java.io.PrintWriter pw = new java.io.PrintWriter(sw);
			    ex.printStackTrace(pw);
			    pw.flush();
			    String s = "exception in `" + _prefix + "' while calling message():\n" +
				sw.toString() + "\n" + handler.toString();
			    _instance.initializationData().logger.error(s);
			}

			//
			// No "continue", because we want message() to
			// be called in its own thread from this
			// pool. Note that this means that message()
			// must call promoteFollower().
			//
		    }
		    finally
		    {
			stream.reset();
		    }
		}
	    }

	    if(_sizeMax > 1)
	    {
		synchronized(this)
		{
		    if(!_destroyed)
		    {
			//
			// First we reap threads that have been
			// destroyed before.
			//
			int sz = _threads.size();
			assert(_running <= sz);
			if(_running < sz)
			{
			    java.util.Iterator i = _threads.iterator();
			    while(i.hasNext())
			    {
				EventHandlerThread thread = (EventHandlerThread)i.next();

				if(!thread.isAlive())
				{
				    try
				    {
					thread.join();
					i.remove();
				    }
				    catch(InterruptedException ex)
				    {
				    }
				}
			    }
			}
			
			//
			// Now we check if this thread can be destroyed, based
			// on a load factor.
			//

			//
			// The load factor jumps immediately to the number of
			// threads that are currently in use, but decays
			// exponentially if the number of threads in use is
			// smaller than the load factor. This reflects that we
			// create threads immediately when they are needed,
			// but want the number of threads to slowly decline to
			// the configured minimum.
			//
			double inUse = (double)_inUse;
			if(_load < inUse)
			{
			    _load = inUse;
			}
			else
			{
			    final double loadFactor = 0.05; // TODO: Configurable?
			    final double oneMinusLoadFactor = 1 - loadFactor;
			    _load = _load * oneMinusLoadFactor + _inUse * loadFactor;
			}

			if(_running > _size)
			{
			    int load = (int)(_load + 0.5);

			    //
			    // We add one to the load factor because one
			    // additional thread is needed for select().
			    //
			    if(load + 1 < _running)
			    {
				assert(_inUse > 0);
				--_inUse;
				
				assert(_running > 0);
				--_running;
				
				return false;
			    }
			}
			
			assert(_inUse > 0);
			--_inUse;
		    }

		    while(!_promote)
		    {
			try
			{
			    wait();
			}
			catch(InterruptedException ex)
			{
			}
		    }
		    
		    _promote = false;
		}
		
		if(TRACE_THREAD)
		{
		    trace("thread " + Thread.currentThread() + " has the lock");
		}
	    }
        }
    }

    private boolean
    read(EventHandler handler)
    {
	boolean moreData = false;

        BasicStream stream = handler._stream;

        if(stream.size() == 0)
        {
            stream.resize(Protocol.headerSize, true);
            stream.pos(0);
        }

        if(stream.pos() != stream.size())
        {
            moreData = handler.read(stream);
            assert(stream.pos() == stream.size());
        }

        int pos = stream.pos();
	if(pos < Protocol.headerSize)
	{
	    //
	    // This situation is possible for small UDP packets.
	    //
	    throw new Ice.IllegalMessageSizeException();
	}
        stream.pos(0);
	byte[] m = new byte[4];
	m[0] = stream.readByte();
	m[1] = stream.readByte();
	m[2] = stream.readByte();
	m[3] = stream.readByte();
	if(m[0] != Protocol.magic[0] || m[1] != Protocol.magic[1]
	   || m[2] != Protocol.magic[2] || m[3] != Protocol.magic[3])
	{
	    Ice.BadMagicException ex = new Ice.BadMagicException();
	    ex.badMagic = m;
	    throw ex;
	}

	byte pMajor = stream.readByte();
	byte pMinor = stream.readByte();
	if(pMajor != Protocol.protocolMajor || pMinor > Protocol.protocolMinor)
	{
	    Ice.UnsupportedProtocolException e = new Ice.UnsupportedProtocolException();
	    e.badMajor = pMajor < 0 ? pMajor + 255 : pMajor;
	    e.badMinor = pMinor < 0 ? pMinor + 255 : pMinor;
	    e.major = Protocol.protocolMajor;
	    e.minor = Protocol.protocolMinor;
	    throw e;
	}

	byte eMajor = stream.readByte();
	byte eMinor = stream.readByte();
	if(eMajor != Protocol.encodingMajor || eMinor > Protocol.encodingMinor)
	{
	    Ice.UnsupportedEncodingException e = new Ice.UnsupportedEncodingException();
	    e.badMajor = eMajor < 0 ? eMajor + 255 : eMajor;
	    e.badMinor = eMinor < 0 ? eMinor + 255 : eMinor;
	    e.major = Protocol.encodingMajor;
	    e.minor = Protocol.encodingMinor;
	    throw e;
	}

        byte messageType = stream.readByte();
        byte compress = stream.readByte();
        int size = stream.readInt();
        if(size < Protocol.headerSize)
        {
            throw new Ice.IllegalMessageSizeException();
        }
        if(size > _instance.messageSizeMax())
        {
            throw new Ice.MemoryLimitException();
        }
        if(size > stream.size())
        {
            stream.resize(size, true);
        }
        stream.pos(pos);

        if(stream.pos() != stream.size())
	{
	    if(handler.datagram())
	    {
		if(_warnUdp)
		{
		    _instance.initializationData().logger.warning("DatagramLimitException: maximum size of "
		                               			  + stream.pos() + " exceeded");
		}
		stream.pos(0);
		stream.resize(0, true);
		throw new Ice.DatagramLimitException();
	    }
	    else
	    {
		moreData = handler.read(stream);
		assert(stream.pos() == stream.size());
	    }
        }

	return moreData;
    }

/*
 *  Commented out because it is unused.
 *
    private void
    selectNonBlocking()
    {
        while(true)
        {
            try
            {
                if(TRACE_SELECT)
                {
                    trace("non-blocking select on " + _selector.keys().size() + " keys, thread id = " +
                          Thread.currentThread());
                }

                _selector.selectNow();

                if(TRACE_SELECT)
                {
                    if(_keys.size() > 0)
                    {
                        trace("after selectNow, there are " + _keys.size() + " selected keys:");
                        java.util.Iterator i = _keys.iterator();
                        while(i.hasNext())
                        {
                            java.nio.channels.SelectionKey key = (java.nio.channels.SelectionKey)i.next();
                            trace("  " + keyToString(key));
                        }
                    }
                }

                break;
            }
            catch(java.io.InterruptedIOException ex)
            {
                continue;
            }
            catch(java.io.IOException ex)
            {
                //
                // Pressing Ctrl-C causes select() to raise an
                // IOException, which seems like a JDK bug. We trap
                // for that special case here and ignore it.
                // Hopefully we're not masking something important!
                //
                if(ex.getMessage().indexOf("Interrupted system call") != -1)
                {
                    continue;
                }

                Ice.SocketException se = new Ice.SocketException();
                se.initCause(ex);
                //throw se;
		java.io.StringWriter sw = new java.io.StringWriter();
		java.io.PrintWriter pw = new java.io.PrintWriter(sw);
		se.printStackTrace(pw);
		pw.flush();
		String s = "exception in `" + _prefix + "':\n" + sw.toString();
		_instance.initializationData().logger.error(s);
		continue;
            }
        }
    }
*/

    private void
    select()
    {
        int ret = 0;

        while(true)
        {
            try
            {
                if(TRACE_SELECT)
                {
                    trace("select on " + _selector.keys().size() + " keys, thread id = " + Thread.currentThread());
                }

		if(_timeout > 0)
		{
		    ret = _selector.select(_timeout * 1000);
		}
		else
		{
		    ret = _selector.select();
		}
            }
            catch(java.io.IOException ex)
            {
                //
                // Pressing Ctrl-C causes select() to raise an
                // IOException, which seems like a JDK bug. We trap
                // for that special case here and ignore it.
                // Hopefully we're not masking something important!
                //
                if(Network.interrupted(ex))
                {
                    continue;
                }

                Ice.SocketException se = new Ice.SocketException();
                se.initCause(ex);
                //throw se;
		java.io.StringWriter sw = new java.io.StringWriter();
		java.io.PrintWriter pw = new java.io.PrintWriter(sw);
		se.printStackTrace(pw);
		pw.flush();
		String s = "exception in `" + _prefix + "':\n" + sw.toString();
		_instance.initializationData().logger.error(s);
		continue;
            }

            if(TRACE_SELECT)
            {
                trace("select() returned " + ret + ", _keys.size() = " + _keys.size());
            }

            break;
        }
    }

    private void
    trace(String msg)
    {
        System.err.println(_prefix + ": " + msg);
    }

    private String
    keyToString(java.nio.channels.SelectionKey key)
    {
        String ops = "[";
        if(key.isAcceptable())
        {
            ops += " OP_ACCEPT";
        }
        if(key.isReadable())
        {
            ops += " OP_READ";
        }
        if(key.isConnectable())
        {
            ops += " OP_CONNECT";
        }
        if(key.isWritable())
        {
            ops += " OP_WRITE";
        }
        ops += " ]";
        return key.channel() + " " + ops;
    }

    private static final class FdHandlerPair
    {
        java.nio.channels.SelectableChannel fd;
        EventHandler handler;

        FdHandlerPair(java.nio.channels.SelectableChannel fd, EventHandler handler)
        {
            this.fd = fd;
            this.handler = handler;
        }
    }

    private static final class HandlerKeyPair
    {
        EventHandler handler;
        java.nio.channels.SelectionKey key;

        HandlerKeyPair(EventHandler handler, java.nio.channels.SelectionKey key)
        {
            this.handler = handler;
            this.key = key;
        }
    }

    private Instance _instance;
    private boolean _destroyed;
    private final String _prefix;
    private final String _programNamePrefix;

    private java.nio.channels.ReadableByteChannel _fdIntrRead;
    private java.nio.channels.SelectionKey _fdIntrReadKey;
    private java.nio.channels.WritableByteChannel _fdIntrWrite;
    private java.nio.channels.Selector _selector;
    private java.util.Set _keys;

    private java.util.LinkedList _changes = new java.util.LinkedList();

    private java.util.HashMap _handlerMap = new java.util.HashMap();

    private int _timeout;

    //
    // Since the Java5 SSL transceiver can read more data from the socket than is
    // actually requested, we have to keep a separate list of handlers that need
    // the thread pool to read more data before it re-enters a blocking call to
    // select().
    //
    private java.util.LinkedList _pendingHandlers = new java.util.LinkedList();

    private final class EventHandlerThread extends Thread
    {
        EventHandlerThread(String name)
        {
            super(name);
        }

        public void
        run()
        {
	    if(_instance.initializationData().threadHook != null)
	    {
	        _instance.initializationData().threadHook.start();
	    }

            BasicStream stream = new BasicStream(_instance);

	    boolean promote;

            try
            {
		promote = ThreadPool.this.run(stream);
            }
            catch(Ice.LocalException ex)
            {
                java.io.StringWriter sw = new java.io.StringWriter();
                java.io.PrintWriter pw = new java.io.PrintWriter(sw);
                ex.printStackTrace(pw);
                pw.flush();
                String s = "exception in `" + _prefix + "' thread " + getName() + ":\n" + sw.toString();
                _instance.initializationData().logger.error(s);
		promote = true;
            }
            catch(java.lang.Exception ex)
            {
                java.io.StringWriter sw = new java.io.StringWriter();
                java.io.PrintWriter pw = new java.io.PrintWriter(sw);
                ex.printStackTrace(pw);
                pw.flush();
                String s = "unknown exception in `" + _prefix + "' thread " + getName() + ":\n" + sw.toString();
                _instance.initializationData().logger.error(s);
		promote = true;
            }

	    if(promote && _sizeMax > 1)
	    {
		//
		// Promote a follower, but w/o modifying _inUse or
		// creating new threads.
		//
		synchronized(ThreadPool.this)
		{
		    assert(!_promote);
		    _promote = true;
		    ThreadPool.this.notify();
		}
	    }

            if(TRACE_THREAD)
            {
                trace("run() terminated");
            }

	    if(_instance.initializationData().threadHook != null)
	    {
	        _instance.initializationData().threadHook.stop();
	    }
        }
    }

    private final int _size; // Number of threads that are pre-created.
    private final int _sizeMax; // Maximum number of threads.
    private final int _sizeWarn; // If _inUse reaches _sizeWarn, a "low on threads" warning will be printed.

    private java.util.ArrayList _threads; // All threads, running or not.
    private int _threadIndex; // For assigning thread names.
    private int _running; // Number of running threads.
    private int _inUse; // Number of threads that are currently in use.
    private double _load; // Current load in number of threads.

    private boolean _promote;

    private final boolean _warnUdp;
}