code: private int find(UTF8String str, int start) {
      assert (str.numBytes > 0);
      while (start <= numBytes - str.numBytes) {
        if (ByteArrayMethods.arrayEquals(base, offset + start, str.base, str.offset, str.numBytes)) {
          return start;
        }
        start += 1;
      }
      return -1;
    }
docs: Find the `str` from left to right.