code: public void setLength(int length) {
  		if (length < 0 || body.length == length) {
  			return;
  		}
  
  		int oldPos = pos;
  		pos = Math.min(pos, length);
  
  		byte[] newBody = new byte[length];
  		System.arraycopy(body, 0, newBody, 0, pos);
  		body = newBody;
  		
  		if (oldPos > pos) {
  			cachedString = null;
  		}
  	}
docs: Sets the current length of the body. If the current content is longer, the excessive data will be truncated.
  
  @param length the new length to set.