@Override
    protected void engineUpdate(byte[] input, int offset, int len) {
        final NativeRef.EVP_MD_CTX ctxLocal = ctx;
        if (signing) {
            NativeCrypto.EVP_DigestSignUpdate(ctxLocal, input, offset, len);
        } else {
            NativeCrypto.EVP_DigestVerifyUpdate(ctxLocal, input, offset, len);
        }
    }
Configures the public key algorithm context ({@code EVP_PKEY_CTX}) associated with this
operation.

<p>The default implementation does nothing.

@param ctx reference to the context ({@code EVP_PKEY_CTX}).
common/src/main/java/org/conscrypt/OpenSSLSignature.java