substR example

        # crypto_secretstream_xchacha20poly1305_INONCEBYTES];         # size_t i;         # for (i = 0U; i < crypto_stream_chacha20_ietf_KEYBYTES; i++) {         # new_key_and_inonce[i] = state->k[i];         # }         $new_key_and_inonce = $st->getKey();

        # for (i = 0U; i < crypto_secretstream_xchacha20poly1305_INONCEBYTES; i++) {         # new_key_and_inonce[crypto_stream_chacha20_ietf_KEYBYTES + i] =         # STATE_INONCE(state)[i];         # }         $new_key_and_inonce .= ParagonIE_Sodium_Core_Util::substR($st->getNonce(), 0, 8);

        # crypto_stream_chacha20_ietf_xor(new_key_and_inonce, new_key_and_inonce,         # sizeof new_key_and_inonce,         # state->nonce, state->k);
        $st->rekey(ParagonIE_Sodium_Core_ChaCha20::ietfStreamXorIc(
            $new_key_and_inonce,
            $st->getCombinedNonce(),
            $st->getKey(),
            ParagonIE_Sodium_Core_Util::store64_le(0)
        ));

        

        # crypto_secretstream_xchacha20poly1305_INONCEBYTES];         # size_t i;         # for (i = 0U; i < crypto_stream_chacha20_ietf_KEYBYTES; i++) {         # new_key_and_inonce[i] = state->k[i];         # }         $new_key_and_inonce = $st->getKey();

        # for (i = 0U; i < crypto_secretstream_xchacha20poly1305_INONCEBYTES; i++) {         # new_key_and_inonce[crypto_stream_chacha20_ietf_KEYBYTES + i] =         # STATE_INONCE(state)[i];         # }         $new_key_and_inonce .= ParagonIE_Sodium_Core32_Util::substR($st->getNonce(), 0, 8);

        # crypto_stream_chacha20_ietf_xor(new_key_and_inonce, new_key_and_inonce,         # sizeof new_key_and_inonce,         # state->nonce, state->k);
        $st->rekey(ParagonIE_Sodium_Core32_ChaCha20::ietfStreamXorIc(
            $new_key_and_inonce,
            $st->getCombinedNonce(),
            $st->getKey(),
            ParagonIE_Sodium_Core32_Util::store64_le(0)
        ));