skbuf.get(this.data, dstOffset, index, length);
System.arraycopy(src, srcOffset, this.data, dstOffset, length);
	public int add(SocketBuffer skbuf, int index, int length) {		if (length > getFreeSize()) {			throw new IllegalArgumentException("Not enough free space");		}		final int dstOffset = this.used;		skbuf.get(this.data, dstOffset, index, length);		this.used += length;		return dstOffset;	}