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/*
 * Copyright (C) 2006-2010 Alfresco Software Limited.
 *
 * This file is part of Alfresco
 *
 * Alfresco is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Alfresco 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with Alfresco. If not, see .
 */

package org.filesys.smb.server;

import org.filesys.netbios.NetBIOSSession;
import org.filesys.netbios.RFCNetBIOSProtocol;
import org.filesys.smb.PacketTypeV1;
import org.filesys.smb.SMBStatus;
import org.filesys.util.DataPacker;

/**
 * SMB packet type class
 * 
 * @author gkspencer
 */
public class SMBPacket {

	// SMB packet offsets, assuming an RFC NetBIOS transport
	public static final int SIGNATURE 		= RFCNetBIOSProtocol.HEADER_LEN;
	public static final int COMMAND 		= 4 + RFCNetBIOSProtocol.HEADER_LEN;
	public static final int ERRORCODE 		= 5 + RFCNetBIOSProtocol.HEADER_LEN;
	public static final int ERRORCLASS 		= 5 + RFCNetBIOSProtocol.HEADER_LEN;
	public static final int ERROR 			= 7 + RFCNetBIOSProtocol.HEADER_LEN;
	public static final int FLAGS 			= 9 + RFCNetBIOSProtocol.HEADER_LEN;
	public static final int FLAGS2 			= 10 + RFCNetBIOSProtocol.HEADER_LEN;
	public static final int PIDHIGH 		= 12 + RFCNetBIOSProtocol.HEADER_LEN;
	public static final int SID 			= 18 + RFCNetBIOSProtocol.HEADER_LEN;
	public static final int SEQNO 			= 20 + RFCNetBIOSProtocol.HEADER_LEN;
	public static final int TID 			= 24 + RFCNetBIOSProtocol.HEADER_LEN;
	public static final int PID 			= 26 + RFCNetBIOSProtocol.HEADER_LEN;
	public static final int UID 			= 28 + RFCNetBIOSProtocol.HEADER_LEN;
	public static final int MID 			= 30 + RFCNetBIOSProtocol.HEADER_LEN;
	public static final int WORDCNT 		= 32 + RFCNetBIOSProtocol.HEADER_LEN;
	public static final int ANDXCOMMAND 	= 33 + RFCNetBIOSProtocol.HEADER_LEN;
	public static final int ANDXRESERVED 	= 34 + RFCNetBIOSProtocol.HEADER_LEN;
	public static final int PARAMWORDS 		= 33 + RFCNetBIOSProtocol.HEADER_LEN;

	// SMB packet header length for a transaction type request
	public static final int TRANS_HEADERLEN = 66 + RFCNetBIOSProtocol.HEADER_LEN;

	// Minimum receive length for a valid SMB packet
	public static final int MIN_RXLEN = 32;

	// Default buffer size to allocate for SMB packets
	public static final int DEFAULT_BUFSIZE = 4096;

	// Flag bits
	public static final int FLG_SUBDIALECT 	= 0x01;
	public static final int FLG_CASELESS 	= 0x08;
	public static final int FLG_CANONICAL 	= 0x10;
	public static final int FLG_OPLOCK 		= 0x20;
	public static final int FLG_NOTIFY 		= 0x40;
	public static final int FLG_RESPONSE 	= 0x80;

	// Flag2 bits
	public static final int FLG2_LONGFILENAMES 		= 0x0001;
	public static final int FLG2_EXTENDEDATTRIB 	= 0x0002;
	public static final int FLG2_SECURITYSIGS 		= 0x0004;
	public static final int FLG2_LONGNAMESUSED 		= 0x0040;
	public static final int FLG2_EXTENDNEGOTIATE 	= 0x0800;
	public static final int FLG2_DFSRESOLVE 		= 0x1000;
	public static final int FLG2_READIFEXE 			= 0x2000;
	public static final int FLG2_LONGERRORCODE 		= 0x4000;
	public static final int FLG2_UNICODE 			= 0x8000;

	// Security mode bits
	public static final int SEC_USER = 0x0001;
	public static final int SEC_ENCRYPT = 0x0002;

	// Raw mode bits
	public static final int RAW_READ = 0x0001;
	public static final int RAW_WRITE = 0x0002;

	// SMB packet buffer
	private byte[] m_smbbuf;

	// Packet type
	private int m_pkttype;

	// Current byte area pack/unpack position
	protected int m_pos;
	protected int m_endpos;

	/**
	 * Default constructor
	 */
	public SMBPacket() {
		m_smbbuf = new byte[DEFAULT_BUFSIZE];
		InitializeBuffer();
	}

	/**
	 * Construct an SMB packet using the specified packet buffer.
	 *
	 * @param buf SMB packet buffer.
	 */
	public SMBPacket(byte[] buf) {
		m_smbbuf = buf;
	}

	/**
	 * Construct an SMB packet of the specified size.
	 *
	 * @param siz Size of SMB packet buffer to allocate.
	 */
	public SMBPacket(int siz) {
		m_smbbuf = new byte[siz];
		InitializeBuffer();
	}

	/**
	 * Copy constructor
	 *
	 * @param pkt SMBPacket
	 */
	public SMBPacket(SMBPacket pkt) {

		// Allocate a new buffer
		m_smbbuf = new byte[pkt.getBuffer().length];

		// Copy the valid data to the new packet
		System.arraycopy(pkt.getBuffer(), 0, m_smbbuf, 0, pkt.getLength());
	}

	/**
	 * Clear the data byte count
	 */
	public final void clearBytes() {
		int offset = getByteOffset() - 2;
		DataPacker.putIntelShort(0, m_smbbuf, offset);
	}

	/**
	 * Dump the SMB packet to the debug stream
	 */
	public final void DumpPacket() {
	}

	/**
	 * Check if the error class/code match the specified error/class
	 *
	 * @param errClass int
	 * @param errCode  int
	 * @return boolean
	 */
	public final boolean equalsError(int errClass, int errCode) {
		if (getErrorClass() == errClass && getErrorCode() == errCode)
			return true;
		return false;
	}

	/**
	 * Get the secondary command code
	 *
	 * @return Secondary command code
	 */
	public final int getAndXCommand() {
		return (int) (m_smbbuf[ANDXCOMMAND] & 0xFF);
	}

	/**
	 * Return the byte array used for the SMB packet
	 *
	 * @return Byte array used for the SMB packet.
	 */
	public final byte[] getBuffer() {
		return m_smbbuf;
	}

	/**
	 * Return the total buffer size available to the SMB request
	 *
	 * @return Total SMB buffer length available.
	 */
	public final int getBufferLength() {
		return m_smbbuf.length - RFCNetBIOSProtocol.HEADER_LEN;
	}

	/**
	 * Get the data byte count for the SMB packet
	 *
	 * @return Data byte count
	 */
	public final int getByteCount() {

		// Calculate the offset of the byte count
		int pos = PARAMWORDS + (2 * getParameterCount());
		return (int) DataPacker.getIntelShort(m_smbbuf, pos);
	}

	/**
	 * Get the data byte area offset within the SMB packet
	 *
	 * @return Data byte offset within the SMB packet.
	 */
	public final int getByteOffset() {

		// Calculate the offset of the byte buffer
		int pCnt = getParameterCount();
		int pos = WORDCNT + (2 * pCnt) + 3;
		return pos;
	}

	/**
	 * Get the SMB command
	 *
	 * @return SMB command code.
	 */
	public final int getCommand() {
		return (int) (m_smbbuf[COMMAND] & 0xFF);
	}

	/**
	 * Determine if normal or long error codes have been returned
	 *
	 * @return boolean
	 */
	public final boolean hasLongErrorCode() {
		if ((getFlags2() & FLG2_LONGERRORCODE) == 0)
			return false;
		return true;
	}

	/**
	 * Check if the packet contains ASCII or V1Unicode strings
	 *
	 * @return boolean
	 */
	public final boolean isUnicode() {
		return (getFlags2() & FLG2_UNICODE) != 0 ? true : false;
	}

	/**
	 * Check if the packet is using caseless filenames
	 *
	 * @return boolean
	 */
	public final boolean isCaseless() {
		return (getFlags() & FLG_CASELESS) != 0 ? true : false;
	}

	/**
	 * Check if long file names are being used
	 *
	 * @return boolean
	 */
	public final boolean isLongFileNames() {
		return (getFlags2() & FLG2_LONGFILENAMES) != 0 ? true : false;
	}

	/**
	 * Check if long error codes are being used
	 *
	 * @return boolean
	 */
	public final boolean isLongErrorCode() {
		return (getFlags2() & FLG2_LONGERRORCODE) != 0 ? true : false;
	}

	/**
	 * Get the SMB error class
	 *
	 * @return SMB error class.
	 */
	public final int getErrorClass() {
		return (int) m_smbbuf[ERRORCLASS] & 0xFF;
	}

	/**
	 * Get the SMB error code
	 *
	 * @return SMB error code.
	 */
	public final int getErrorCode() {
		return (int) m_smbbuf[ERROR] & 0xFF;
	}

	/**
	 * Get the SMB flags value.
	 *
	 * @return SMB flags value.
	 */
	public final int getFlags() {
		return (int) m_smbbuf[FLAGS] & 0xFF;
	}

	/**
	 * Get the SMB flags2 value.
	 *
	 * @return SMB flags2 value.
	 */
	public final int getFlags2() {
		return (int) DataPacker.getIntelShort(m_smbbuf, FLAGS2);
	}

	/**
	 * Calculate the total used packet length.
	 *
	 * @return Total used packet length.
	 */
	public final int getLength() {
		return (getByteOffset() + getByteCount()) - SIGNATURE;
	}

	/**
	 * Get the long SMB error code
	 *
	 * @return Long SMB error code.
	 */
	public final int getLongErrorCode() {
		return DataPacker.getIntelInt(m_smbbuf, ERRORCODE);
	}

	/**
	 * Get the multiplex identifier.
	 *
	 * @return Multiplex identifier.
	 */
	public final int getMultiplexId() {
		return DataPacker.getIntelShort(m_smbbuf, MID);
	}

	/**
	 * Get a parameter word from the SMB packet.
	 *
	 * @param idx Parameter index (zero based).
	 * @return Parameter word value.
	 * @throws java.lang.IndexOutOfBoundsException If the parameter index is out of range.
	 */
	public final int getParameter(int idx)
			throws java.lang.IndexOutOfBoundsException {

		// Range check the parameter index
		if (idx > getParameterCount())
			throw new java.lang.IndexOutOfBoundsException();

		// Calculate the parameter word offset
		int pos = WORDCNT + (2 * idx) + 1;
		return (int) (DataPacker.getIntelShort(m_smbbuf, pos) & 0xFFFF);
	}

	/**
	 * Get the specified parameter words, as an int value.
	 *
	 * @param idx Parameter index (zero based).
	 * @return int
	 */
	public final int getParameterLong(int idx) {
		int pos = WORDCNT + (2 * idx) + 1;
		return DataPacker.getIntelInt(m_smbbuf, pos);
	}

	/**
	 * Get the parameter count
	 *
	 * @return Parameter word count.
	 */
	public final int getParameterCount() {
		return (int) m_smbbuf[WORDCNT];
	}

	/**
	 * Get the process indentifier (PID)
	 *
	 * @return Process identifier value.
	 */
	public final int getProcessId() {
		return DataPacker.getIntelShort(m_smbbuf, PID);
	}

	/**
	 * Get the tree identifier (TID)
	 *
	 * @return Tree identifier (TID)
	 */
	public final int getTreeId() {
		return DataPacker.getIntelShort(m_smbbuf, TID);
	}

	/**
	 * Get the user identifier (UID)
	 *
	 * @return User identifier (UID)
	 */
	public final int getUserId() {
		return DataPacker.getIntelShort(m_smbbuf, UID);
	}

	/**
	 * Initialize the SMB packet buffer.
	 */
	private final void InitializeBuffer() {

		// Set the packet signature
		m_smbbuf[SIGNATURE] = (byte) 0xFF;
		m_smbbuf[SIGNATURE + 1] = (byte) 'S';
		m_smbbuf[SIGNATURE + 2] = (byte) 'M';
		m_smbbuf[SIGNATURE + 3] = (byte) 'B';
	}

	/**
	 * Determine if this packet is an SMB response, or command packet
	 *
	 * @return true if this SMB packet is a response, else false
	 */
	public final boolean isResponse() {
		int resp = getFlags();
		if ((resp & FLG_RESPONSE) != 0)
			return true;
		return false;
	}

	/**
	 * Check if the response packet is valid, ie. type and flags
	 *
	 * @return true if the SMB packet is a response packet and the response is valid, else false.
	 */
	public final boolean isValidResponse() {

		// Check if this is a response packet, and the correct type of packet
		if (isResponse() && getCommand() == m_pkttype) {

			// Check if standard error codes or NT 32-bit error codes are being used
			if ((getFlags2() & FLG2_LONGERRORCODE) == 0) {
				if (getErrorClass() == SMBStatus.Success)
					return true;
			}
			else if (getLongErrorCode() == SMBStatus.NTSuccess)
				return true;
		}
		return false;
	}

	/**
	 * Pack a byte (8 bit) value into the byte area
	 *
	 * @param val byte
	 */
	public final void packByte(byte val) {
		m_smbbuf[m_pos++] = val;
	}

	/**
	 * Pack a byte (8 bit) value into the byte area
	 *
	 * @param val int
	 */
	public final void packByte(int val) {
		m_smbbuf[m_pos++] = (byte) val;
	}

	/**
	 * Pack the specified bytes into the byte area
	 *
	 * @param byts byte[]
	 * @param len  int
	 */
	public final void packBytes(byte[] byts, int len) {
		for (int i = 0; i < len; i++)
			m_smbbuf[m_pos++] = byts[i];
	}

	/**
	 * Pack a string using either ASCII or V1Unicode into the byte area
	 *
	 * @param str String
	 * @param uni boolean
	 */
	public final void packString(String str, boolean uni) {

		// Check for V1Unicode or ASCII
		if (uni) {

			// Word align the buffer position, pack the V1Unicode string
			m_pos = DataPacker.wordAlign(m_pos);
			DataPacker.putUnicodeString(str, m_smbbuf, m_pos, true);
			m_pos += (str.length() * 2) + 2;
		}
		else {

			// Pack the ASCII string
			DataPacker.putString(str, m_smbbuf, m_pos, true);
			m_pos += str.length() + 1;
		}
	}

	/**
	 * Pack a word (16 bit) value into the byte area
	 *
	 * @param val int
	 */
	public final void packWord(int val) {
		DataPacker.putIntelShort(val, m_smbbuf, m_pos);
		m_pos += 2;
	}

	/**
	 * Pack a 32 bit integer value into the byte area
	 *
	 * @param val int
	 */
	public final void packInt(int val) {
		DataPacker.putIntelInt(val, m_smbbuf, m_pos);
		m_pos += 4;
	}

	/**
	 * Pack a long integer (64 bit) value into the byte area
	 *
	 * @param val long
	 */
	public final void packLong(long val) {
		DataPacker.putIntelLong(val, m_smbbuf, m_pos);
		m_pos += 8;
	}

	/**
	 * Return the current byte area buffer position
	 *
	 * @return int
	 */
	public final int getPosition() {
		return m_pos;
	}

	/**
	 * Unpack a byte value from the byte area
	 *
	 * @return int
	 */
	public final int unpackByte() {
		return (int) m_smbbuf[m_pos++];
	}

	/**
	 * Unpack a block of bytes from the byte area
	 *
	 * @param len int
	 * @return byte[]
	 */
	public final byte[] unpackBytes(int len) {
		if (len <= 0)
			return null;

		byte[] buf = new byte[len];
		System.arraycopy(m_smbbuf, m_pos, buf, 0, len);
		m_pos += len;
		return buf;
	}

	/**
	 * Unpack a word (16 bit) value from the byte area
	 *
	 * @return int
	 */
	public final int unpackWord() {
		int val = DataPacker.getIntelShort(m_smbbuf, m_pos);
		m_pos += 2;
		return val;
	}

	/**
	 * Unpack an integer (32 bit) value from the byte/parameter area
	 *
	 * @return int
	 */
	public final int unpackInt() {
		int val = DataPacker.getIntelInt(m_smbbuf, m_pos);
		m_pos += 4;
		return val;
	}

	/**
	 * Unpack a long integer (64 bit) value from the byte area
	 *
	 * @return long
	 */
	public final long unpackLong() {
		long val = DataPacker.getIntelLong(m_smbbuf, m_pos);
		m_pos += 8;
		return val;
	}

	/**
	 * Unpack a string from the byte area
	 *
	 * @param uni boolean
	 * @return String
	 */
	public final String unpackString(boolean uni) {

		// Check for V1Unicode or ASCII
		String ret = null;

		if (uni) {

			// Word align the current buffer position
			m_pos = DataPacker.wordAlign(m_pos);
			ret = DataPacker.getUnicodeString(m_smbbuf, m_pos, 255);
			if (ret != null)
				m_pos += (ret.length() * 2) + 2;
		}
		else {

			// Unpack the ASCII string
			ret = DataPacker.getString(m_smbbuf, m_pos, 255);
			if (ret != null)
				m_pos += ret.length() + 1;
		}

		// Return the string
		return ret;
	}

	/**
	 * Unpack a string from the byte area
	 *
	 * @param len int
	 * @param uni boolean
	 * @return String
	 */
	public final String unpackString(int len, boolean uni) {

		// Check for V1Unicode or ASCII
		String ret = null;

		if (uni) {

			// Word align the current buffer position
			m_pos = DataPacker.wordAlign(m_pos);
			ret = DataPacker.getUnicodeString(m_smbbuf, m_pos, len);
			if (ret != null)
				m_pos += (ret.length() * 2);
		}
		else {

			// Unpack the ASCII string
			ret = DataPacker.getString(m_smbbuf, m_pos, len);
			if (ret != null)
				m_pos += ret.length();
		}

		// Return the string
		return ret;
	}

	/**
	 * Check if there is more data in the byte area
	 *
	 * @return boolean
	 */
	public final boolean hasMoreData() {
		if (m_pos < m_endpos)
			return true;
		return false;
	}

	/**
	 * Receive an SMB response packet.
	 *
	 * @param sess NetBIOS session to receive the SMB packet on.
	 * @throws java.io.IOException If an I/O error occurs.
	 */
	private final void ReceiveSMB(NetBIOSSession sess)
			throws java.io.IOException {

		if (sess.Receive(m_smbbuf) >= MIN_RXLEN)
			return;

		// Not enough data received for an SMB header
		throw new java.io.IOException("Short NetBIOS receive");
	}

	/**
	 * Set the secondary SMB command
	 *
	 * @param cmd Secondary SMB command code.
	 */
	public final void setAndXCommand(int cmd) {

		// Set the chained command packet type
		m_smbbuf[ANDXCOMMAND] = (byte) cmd;
		m_smbbuf[ANDXRESERVED] = (byte) 0;

		// If the AndX command is disabled clear the offset to the chained packet
		if (cmd == PacketTypeV1.NoChainedCommand)
			setParameter(1, 0);
	}

	/**
	 * Set the data byte count for this SMB packet
	 *
	 * @param cnt Data byte count.
	 */
	public final void setByteCount(int cnt) {
		int offset = getByteOffset() - 2;
		DataPacker.putIntelShort(cnt, m_smbbuf, offset);
	}

	/**
	 * Set the data byte count for this SMB packet
	 */

	public final void setByteCount() {
		int offset = getByteOffset() - 2;
		int len = m_pos - getByteOffset();
		DataPacker.putIntelShort(len, m_smbbuf, offset);
	}

	/**
	 * Set the data byte area in the SMB packet
	 *
	 * @param byts Byte array containing the data to be copied to the SMB packet.
	 */
	public final void setBytes(byte[] byts) {
		int offset = getByteOffset() - 2;
		DataPacker.putIntelShort(byts.length, m_smbbuf, offset);

		offset += 2;

		for (int idx = 0; idx < byts.length; m_smbbuf[offset + idx] = byts[idx++])
			;
	}

	/**
	 * Set the SMB command
	 *
	 * @param cmd SMB command code
	 */
	public final void setCommand(int cmd) {
		m_pkttype = cmd;
		m_smbbuf[COMMAND] = (byte) cmd;
	}

	/**
	 * Set the SMB error class.
	 *
	 * @param cl SMB error class.
	 */
	public final void setErrorClass(int cl) {
		m_smbbuf[ERRORCLASS] = (byte) (cl & 0xFF);
	}

	/**
	 * Set the SMB error code
	 *
	 * @param sts SMB error code.
	 */
	public final void setErrorCode(int sts) {
		m_smbbuf[ERROR] = (byte) (sts & 0xFF);
	}

	/**
	 * Set the SMB flags value.
	 *
	 * @param flg SMB flags value.
	 */
	public final void setFlags(int flg) {
		m_smbbuf[FLAGS] = (byte) flg;
	}

	/**
	 * Set the SMB flags2 value.
	 *
	 * @param flg SMB flags2 value.
	 */
	public final void setFlags2(int flg) {
		DataPacker.putIntelShort(flg, m_smbbuf, FLAGS2);
	}

	/**
	 * Set the multiplex identifier.
	 *
	 * @param mid Multiplex identifier
	 */
	public final void setMultiplexId(int mid) {
		DataPacker.putIntelShort(mid, m_smbbuf, MID);
	}

	/**
	 * Set the specified parameter word.
	 *
	 * @param idx Parameter index (zero based).
	 * @param val Parameter value.
	 */
	public final void setParameter(int idx, int val) {
		int pos = WORDCNT + (2 * idx) + 1;
		DataPacker.putIntelShort(val, m_smbbuf, pos);
	}

	/**
	 * Set the specified parameter words.
	 *
	 * @param idx Parameter index (zero based).
	 * @param val Parameter value.
	 */

	public final void setParameterLong(int idx, int val) {
		int pos = WORDCNT + (2 * idx) + 1;
		DataPacker.putIntelInt(val, m_smbbuf, pos);
	}

	/**
	 * Set the parameter count
	 *
	 * @param cnt Parameter word count.
	 */
	public final void setParameterCount(int cnt) {
		m_smbbuf[WORDCNT] = (byte) cnt;
	}

	/**
	 * Set the process identifier value (PID).
	 *
	 * @param pid Process identifier value.
	 */
	public final void setProcessId(int pid) {
		DataPacker.putIntelShort(pid, m_smbbuf, PID);
	}

	/**
	 * Set the packet sequence number, for connectionless commands.
	 *
	 * @param seq Sequence number.
	 */
	public final void setSeqNo(int seq) {
		DataPacker.putIntelShort(seq, m_smbbuf, SEQNO);
	}

	/**
	 * Set the session id.
	 *
	 * @param sid Session id.
	 */
	public final void setSID(int sid) {
		DataPacker.putIntelShort(sid, m_smbbuf, SID);
	}

	/**
	 * Set the tree identifier (TID)
	 *
	 * @param tid Tree identifier value.
	 */
	public final void setTreeId(int tid) {
		DataPacker.putIntelShort(tid, m_smbbuf, TID);
	}

	/**
	 * Set the user identifier (UID)
	 *
	 * @param uid User identifier value.
	 */
	public final void setUserId(int uid) {
		DataPacker.putIntelShort(uid, m_smbbuf, UID);
	}

	/**
	 * Align the byte area pointer on an int (32bit) boundary
	 */
	public final void alignBytePointer() {
		m_pos = DataPacker.longwordAlign(m_pos);
	}

	/**
	 * Reset the byte/parameter pointer area for packing/unpacking data items from the packet
	 */
	public final void resetBytePointer() {
		m_pos = getByteOffset();
		m_endpos = m_pos + getByteCount();
	}

	/**
	 * Reset the byte/parameter pointer area for packing/unpacking data items from the packet, and
	 * align the buffer on an int (32bit) boundary
	 */
	public final void resetBytePointerAlign() {
		m_pos = DataPacker.longwordAlign(getByteOffset());
		m_endpos = m_pos + getByteCount();
	}

	/**
	 * Reset the byte/parameter pointer area for packing/unpacking paramaters from the packet
	 */
	public final void resetParameterPointer() {
		m_pos = PARAMWORDS;
	}

	/**
	 * Set the unpack pointer to the specified offset, for AndX processing
	 *
	 * @param off int
	 * @param len int
	 */
	public final void setBytePointer(int off, int len) {
		m_pos = off;
		m_endpos = m_pos + len;
	}

	/**
	 * Skip a number of bytes in the parameter/byte area
	 *
	 * @param cnt int
	 */
	public final void skipBytes(int cnt) {
		m_pos += cnt;
	}
}