code: public void append(final ByteArrayBuffer b, final int off, final int len) {
          if (b == null) {
              return;
          }
          append(b.array(), off, len);
      }
docs: Appends {@code len} bytes to this buffer from the given source
  array starting at index {@code off}. The capacity of the buffer
  is increased, if necessary, to accommodate all {@code len} bytes.
  <p>
  The bytes are converted to chars using simple cast.
  
  @param   b        the bytes to be appended.
  @param   off      the index of the first byte to append.
  @param   len      the number of bytes to append.
  @throws IndexOutOfBoundsException if {@code off} is out of
  range, {@code len} is negative, or
  {@code off} + {@code len} is out of range.