return this;
    }

    @Override
    public HashCode hash() {
      return hashBytes(stream.byteArray(), 0, stream.length());
    }
  }

  // Just to access the byte[] without introducing an unnecessary copy
  private static final class ExposedByteArrayOutputStream extends ByteArrayOutputStream {
    ExposedByteArrayOutputStream(int expectedInputSize) {
      super(expectedInputSize);
    }

introduce a Go variable that points at the C variable (the linker can
be told to initialize this pointer).  For example, if the gmp library
provided

	mpz_t zero;

then cgo would rewrite a reference to C.zero by introducing

	var _C_zero *C.mpz_t

and then replacing all instances of C.zero with (*_C_zero).

Cgo's most interesting translation is for functions.  If xxx is a C