* @throws MemoryNotMappedException
	 *             If the file not mapped into memory
	 * @throws MemoryReadException
	 *             If some exception occurs when reading the memory.
	 */
	public int readInt(int pos) throws MemoryNotMappedException,
			MemoryReadException {
		if (mapBuf == null)
			throw new MemoryNotMappedException(
					"the file not mapped into memory.");
		if (pos < 0)
			throw new MemoryReadException("the memory map is underflow.");
		if (pos > this.capacity - 4)
			throw new MemoryReadException("the memory map is overflow.");
		readLock.lock();
		try {
			mapBuf.position(pos);
			return mapBuf.getInt();
		} finally {
			readLock.unlock();
		}
	}

	/**
	 * 在內存映象的指定位置讀取一個長整數
	 * 
	 * @param pos
	 *            The dest position of the memory map.
	 * @return The long nubmer if successed.
	 * @throws MemoryNotMappedException
	 *             If the file not mapped into memory
	 * @throws MemoryReadException
	 *             If some exception occurs when reading the memory.
	 */
	public long readLong(int pos) throws MemoryNotMappedException,
			MemoryReadException {
		if (mapBuf == null)
			throw new MemoryNotMappedException(
					"the file not mapped into memory.");
		if (pos < 0)
			throw new MemoryReadException("the memory map is underflow.");
		if (pos > this.capacity - 8)
			throw new MemoryReadException("the memory map is overflow.");
		readLock.lock();
		try {
			mapBuf.position(pos);
			return mapBuf.getLong();
		} finally {
			readLock.unlock();
		}
	}

	/**
	 * 在內存映象的指定位置讀取指定長度的字節數據
	 * 
	 * @param pos
	 *            The dest position of the memory map.
	 * @param len
	 *            The length of data.
	 * @return The long nubmer if successed.
	 * @throws MemoryNotMappedException
	 *             If the file not mapped into memory
	 * @throws MemoryReadException
	 *             If some exception occurs when reading the memory.
	 */
	public byte[] readBytes(int pos, int len) throws MemoryNotMappedException,
			MemoryReadException {
		if (mapBuf == null)
			throw new MemoryNotMappedException(
					"the file not mapped into memory.");
		if (pos < 0)
			throw new MemoryReadException("the memory map is underflow.");
		if (pos > this.capacity - len)
			throw new MemoryReadException("the memory map is overflow.");
		readLock.lock();
		try {
			mapBuf.position(pos);
			byte[] dst = new byte[len];
			mapBuf.get(dst);
			return dst;
		} finally {
			readLock.unlock();
		}
	}

	/**
	 * 在內存映象的指定位置重置一個字節
	 * 
	 * @param pos
	 *            The dest position of the memory map.
	 * @param value
	 *            The byte value of new data.
	 * @return The old value at the given position.
	 * @throws MemoryNotMappedException
	 *             If the file not mapped into memory
	 * @throws MemoryReadException
	 *             If some exception occurs when reading the memory.
	 */
	public byte readAndWrite(int pos, byte value) {
		if (mapBuf == null)
			throw new MemoryNotMappedException(
					"the file not mapped into memory.");
		if (pos < 0)
			throw new MemoryReadException("the memory map is underflow.");
		if (pos > this.capacity - 1)
			throw new MemoryReadException("the memory map is overflow.");
		writeLock.lock();
		try {
			mapBuf.position(pos);
			byte ret = mapBuf.get();
			mapBuf.position(pos);
			mapBuf.putInt(value);
			// mapBuf.force();
			return ret;
		} finally {
			writeLock.unlock();
		}
	}

	/**
	 * 在內存映象的指定位置重置一個整數
	 * 
	 * @param pos
	 *            The dest position of the memory map.
	 * @param value
	 *            The integer value of new data.
	 * @return The old value at the given position.
	 * @throws MemoryNotMappedException
	 *             If the file not mapped into memory
	 * @throws MemoryReadException
	 *             If some exception occurs when reading the memory.
	 */
	public int readAndWrite(int pos, int value) {
		if (mapBuf == null)
			throw new MemoryNotMappedException(
					"the file not mapped into memory.");
		if (pos < 0)
			throw new MemoryReadException("the memory map is underflow.");
		if (pos > this.capacity - 4)
			throw new MemoryReadException("the memory map is overflow.");
		writeLock.lock();
		try {
			mapBuf.position(pos);
			int ret = mapBuf.getInt();
			mapBuf.position(pos);
			mapBuf.putInt(value);
			// mapBuf.force();
			return ret;
		} finally {
			writeLock.unlock();
		}
	}

	/**
	 * 在內存映象的指定位置重置一塊的值
	 * 
	 * @param pos
	 *            The dest position of the memory map.
	 * @param value
	 *            The bytes array value of new data.
	 * @return The old bytes array at the given position.
	 * @throws MemoryNotMappedException
	 *             If the file not mapped into memory
	 * @throws MemoryReadException
	 *             If some exception occurs when reading the memory.
	 */
	public byte[] readAndWrite(int pos, byte[] value) {
		if (mapBuf == null)
			throw new MemoryNotMappedException(
					"the file not mapped into memory.");
		if (pos < 0)
			throw new MemoryReadException("the memory map is underflow.");
		if (pos > this.capacity - value.length)
			throw new MemoryReadException("the memory map is overflow.");
		writeLock.lock();
		try {
			mapBuf.position(pos);
			byte[] ret = new byte[value.length];
			mapBuf.get(ret);
			mapBuf.position(pos);
			mapBuf.put(value);
			// mapBuf.force();
			return ret;
		} finally {
			writeLock.unlock();
		}
	}

	/**
	 * 在內存映象的指定位置整數相加
	 * 
	 * @param pos
	 *            The dest position of the memory map.
	 * @param delta
	 *            The integer value of added data.
	 * @return The old integer value at the given position.
	 * @throws MemoryNotMappedException
	 *             If the file not mapped into memory
	 * @throws MemoryReadException
	 *             If some exception occurs when reading the memory.
	 */
	public int readAndAdd(int pos, int delta) {
		if (mapBuf == null)
			throw new MemoryNotMappedException(
					"the file not mapped into memory.");
		if (pos < 0)
			throw new MemoryReadException("the memory map is underflow.");
		if (pos > this.capacity - 4)
			throw new MemoryReadException("the memory map is overflow.");
		writeLock.lock();
		try {
			mapBuf.position(pos);
			int ret = mapBuf.getInt();
			mapBuf.position(pos);
			mapBuf.putInt(ret + delta);
			// mapBuf.force();
			return ret;
		} finally {
			writeLock.unlock();
		}
	}

	/**
	 * 在內存映象的指定位置整數相加
	 * 
	 * @param pos
	 *            The dest position of the memory map.
	 * @param delta
	 *            The integer value of added data.
	 * @return The new integer value at the given position.
	 * @throws MemoryNotMappedException
	 *             If the file not mapped into memory
	 * @throws MemoryReadException
	 *             If some exception occurs when reading the memory.
	 */
	public int addAndRead(int pos, int delta) {
		if (mapBuf == null)
			throw new MemoryNotMappedException(
					"the file not mapped into memory.");
		if (pos < 0)
			throw new MemoryReadException("the memory map is underflow.");
		if (pos > this.capacity - 4)
			throw new MemoryReadException("the memory map is overflow.");
		writeLock.lock();
		try {
			mapBuf.position(pos);
			int ret = mapBuf.getInt();
			mapBuf.position(pos);
			ret += delta;
			mapBuf.putInt(ret);
			// mapBuf.force();
			return ret;
		} finally {
			writeLock.unlock();
		}
	}

	/**
	 * 在內存映象的指定位置整數加一
	 * 
	 * @param pos
	 *            The dest position of the memory map.
	 * @return The old integer value at the given position.
	 * @throws MemoryNotMappedException
	 *             If the file not mapped into memory
	 * @throws MemoryReadException
	 *             If some exception occurs when reading the memory.
	 */
	public int readAndIncrement(int pos) {
		if (mapBuf == null)
			throw new MemoryNotMappedException(
					"the file not mapped into memory.");
		if (pos < 0)
			throw new MemoryReadException("the memory map is underflow.");
		if (pos > this.capacity - 4)
			throw new MemoryReadException("the memory map is overflow.");
		writeLock.lock();
		try {
			mapBuf.position(pos);
			int ret = mapBuf.getInt();
			mapBuf.position(pos);
			mapBuf.putInt(ret + 1);
			// mapBuf.force();
			return ret;
		} finally {
			writeLock.unlock();
		}
	}

	/**
	 * 在內存映象的指定位置整數加一
	 * 
	 * @param pos
	 *            The dest position of the memory map.
	 * @return The new integer value at the given position.
	 * @throws MemoryNotMappedException
	 *             If the file not mapped into memory
	 * @throws MemoryReadException
	 *             If some exception occurs when reading the memory.
	 */
	public int incrementAndRead(int pos) {
		if (mapBuf == null)
			throw new MemoryNotMappedException(
					"the file not mapped into memory.");
		if (pos < 0)
			throw new MemoryReadException("the memory map is underflow.");
		if (pos > this.capacity - 4)
			throw new MemoryReadException("the memory map is overflow.");
		writeLock.lock();
		try {
			mapBuf.position(pos);
			int ret = mapBuf.getInt();
			mapBuf.position(pos);
			mapBuf.putInt(++ret);
			// mapBuf.force();
			return ret;
		} finally {
			writeLock.unlock();
		}
	}

	/**
	 * 在內存映象的指定位置整數減一
	 * 
	 * @param pos
	 *            The dest position of the memory map.
	 * @return The old integer value at the given position.
	 * @throws MemoryNotMappedException
	 *             If the file not mapped into memory
	 * @throws MemoryReadException
	 *             If some exception occurs when reading the memory.
	 */
	public int readAndDecrement(int pos) {
		if (mapBuf == null)
			throw new MemoryNotMappedException(
					"the file not mapped into memory.");
		if (pos < 0)
			throw new MemoryReadException("the memory map is underflow.");
		if (pos > this.capacity - 4)
			throw new MemoryReadException("the memory map is overflow.");
		writeLock.lock();
		try {
			mapBuf.position(pos);
			int ret = mapBuf.getInt();
			mapBuf.position(pos);
			mapBuf.putInt(ret - 1);
			// mapBuf.force();
			return ret;
		} finally {
			writeLock.unlock();
		}
	}

	/**
	 * 在內存映象的指定位置整數減一
	 * 
	 * @param pos
	 *            The dest position of the memory map.
	 * @return The new integer value at the given position.
	 * @throws MemoryNotMappedException
	 *             If the file not mapped into memory
	 * @throws MemoryReadException
	 *             If some exception occurs when reading the memory.
	 */
	public int decrementAndRead(int pos) {
		if (mapBuf == null)
			throw new MemoryNotMappedException(
					"the file not mapped into memory.");
		if (pos < 0)
			throw new MemoryReadException("the memory map is underflow.");
		if (pos > this.capacity - 4)
			throw new MemoryReadException("the memory map is overflow.");
		writeLock.lock();
		try {
			mapBuf.position(pos);
			int ret = mapBuf.getInt();
			mapBuf.position(pos);
			mapBuf.putInt(--ret);
			// mapBuf.force();
			return ret;
		} finally {
			writeLock.unlock();
		}
	}

	public boolean isLoaded() {
		if (mapBuf == null) {
			return false;
		}
		return mapBuf.isLoaded();
	}

	public MappedByteBuffer force() {
		return this.force();
	}

}