static int decodeInt(byte[] data, int i) {
    return (data[i] & 0xff) << 24
      | (data[i + 1] & 0xff) << 16
      | (data[i + 2] & 0xff) << 8
      | (data[i + 3] & 0xff);
  }
Validate an opaque value from the header. This may be overridden from a
subclass where the opaque isn't expected to always be the same as the
request opaque.
src/main/java/net/spy/memcached/protocol/binary/OperationImpl.java