static int readFully(Reader reader, char[] dest, int offset, int len) throws IOException {
    int read = 0;
    while (read < len) {
      final int r = reader.read(dest, offset + read, len - read);
      if (r == -1) {
        break;
      }
      read += r;
    }
    return read;
  }
Return the index within <code>buf[start:start+count]</code> which is by <code>offset</code>
 code points from <code>index</code>.
linguistics/src/main/java/com/yahoo/language/simple/kstem/CharacterUtils.java