code: public void write(byte[] b, int off, int len) throws IOException {
  	if (b != null) {
  	    if (off + len > b.length) {
  		len = b.length - off;
  	    }
  	    if (len <= 0) {
  		return;
  	    }
  	    pos += blob.write(b, off, pos, len);
  	}
      }
docs: Write blob data.
  @param b byte array to be written.
  @param off offset within byte array
  @param len length of data to be written