disallow updates after squeezes

        if self.state == Finalized {

            self.init()?;

        }

        if self.state == Squeeze {

            // [`EVP_DigestUpdate`], depending on the implementation, may allow Updates after Squeezes.

            // But, [FIPS 202], as shown in Figure 7, has a distinguished absorbing phase followed by a squeezing phase.

            // Indeed, the [`sha3.c`] implmentation disallows Updates after Squeezes.

            // For consistency, we always return an error when Update is called after Squeeze.

            //

            // [`EVP_DigestUpdate`]: https://github.com/openssl/openssl/blob/b3bb214720f20f3b126ae4b9c330e9a48b835415/crypto/evp/digest.c#L385-L393

            // [FIPS 202]: https://dx.doi.org/10.6028/NIST.FIPS.202

            // [`sha3.c`]: https://github.com/openssl/openssl/blob/b3bb214720f20f3b126ae4b9c330e9a48b835415/crypto/sha/sha3.c#L52-L63

            let errors = ErrorStack::get();

            return Err(errors);

        }

        unsafe {

            cvt(ffi::EVP_DigestUpdate(

                self.ctx,