org.netxms.base.NXCPMessageReceiver Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of netxms-base Show documentation
NetXMS base classes and commonly used utility code
The newest version!
/**
 * NetXMS - open source network management system
 * Copyright (C) 2003-2020 Victor Kirhenshtein
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * 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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
package org.netxms.base;

import java.io.IOException;
import java.io.InputStream;
import java.util.Arrays;

/**
 * Message receiver for NXCP protocol
 */
public class NXCPMessageReceiver
{
   private int defaultBufferSize;
   private int maxBufferSize;
	private byte[] recvBuffer;
	private int bufferPos = 0;

   /**
    * @see java.lang.Object#toString()
    */
   @Override
   public String toString()
   {
      return "NXCPMessageReceiver [defaultBufferSize=" + defaultBufferSize
            + " maxBufferSize=" + maxBufferSize + " recvBuffer=" + recvBuffer
            + " bufferPos=" + bufferPos;
   }

   /**
    * Create new receiver.
    *
    * @param defaultBufferSize default receiving buffer size (in bytes)
    * @param maxBufferSize maximum receiving buffer size (in bytes)
    */
	public NXCPMessageReceiver(int defaultBufferSize, int maxBufferSize)
	{
	   this.defaultBufferSize = defaultBufferSize;
	   this.maxBufferSize = maxBufferSize;
		recvBuffer = new byte[defaultBufferSize];
	}
	
	/**
	 * Get message size from byte array
	 * 
	 * @param header byte array containing message header
	 * @return message size in bytes
	 */
   private long getMessageSize(final byte[] header)
	{
		return (((long)header[4] << 24) & 0xFF000000) | 
		       (((long)header[5] << 16) & 0x00FF0000) | 
		       (((long)header[6] << 8) & 0x0000FF00) |
		       ((long)header[7] & 0x000000FF);
	}
	
	/**
    * Get message from receiver's buffer
    * 
    * @return message object or null if there are not enough data in the buffer
    * @throws IOException if read from underlying data input stream fails
    * @throws NXCPException if message is too large
    */
   private NXCPMessage getMessageFromBuffer(EncryptionContext ectx) throws IOException, NXCPException
	{
		NXCPMessage msg = null;

		if (bufferPos >= NXCPMessage.HEADER_SIZE)
		{
			final long size = getMessageSize(recvBuffer);
			if (size <= bufferPos)
			{
				// Entire message in buffer, create new message object
				try
				{
					msg = new NXCPMessage(recvBuffer, ectx);
				}
				finally
				{
					System.arraycopy(recvBuffer, (int)size, recvBuffer, 0, bufferPos - (int)size);
					bufferPos -= size;

					// Shrink buffer if possible
					if ((recvBuffer.length > defaultBufferSize) && (bufferPos < defaultBufferSize))
					{
					   recvBuffer = Arrays.copyOf(recvBuffer, defaultBufferSize);
					}
				}
			}
			else if (size > recvBuffer.length)
			{
			   if (size <= maxBufferSize)
			   {
			      recvBuffer = Arrays.copyOf(recvBuffer, (int)size);
			   }
			   else
			   {
			      throw new NXCPException(NXCPException.MESSAGE_TOO_LARGE);
			   }
			}
		}
		return msg;
	}

	/**
    * Receive NXCP message from input stream
    * 
    * @param in input stream
    * @param ectx encryption context
    * @return message object
    * @throws IOException if read from input stream fails
    * @throws NXCPException if message is too large or if communication session is closed
    */
	public NXCPMessage receiveMessage(final InputStream in, EncryptionContext ectx) throws IOException, NXCPException
	{
		NXCPMessage msg = null;

		// Receive bytes from network if we don't have full message in buffer 
		while(true)
		{
			msg = getMessageFromBuffer(ectx);
			if (msg != null)
				break;
			final int bytes = in.read(recvBuffer, bufferPos, recvBuffer.length - bufferPos);
			if (bytes == -1)
				throw new NXCPException(NXCPException.SESSION_CLOSED);
			bufferPos += bytes;
		}

		return msg;
	}
}