ParagonIE_Sodium_File::onetimeauth_verify

    protected static function onetimeauth_verify(
        ParagonIE_Sodium_Core_Poly1305_State $state,
        $ifp,
        $tag = '',
        $mlen = 0
    ) {
        /** @var int $pos */
        $pos = self::ftell($ifp);

        /** @var int $iter */
        $iter = 1;

        /** @var int $incr */
        $incr = self::BUFFER_SIZE >> 6;

        while ($mlen > 0) {
            $blockSize = $mlen > self::BUFFER_SIZE
                ? self::BUFFER_SIZE
                : $mlen;
            $ciphertext = fread($ifp, $blockSize);
            if (!is_string($ciphertext)) {
                throw new SodiumException('Could not read input file');
            }
            $state->update($ciphertext);
            $mlen -= $blockSize;
            $iter += $incr;
        }
        $res = ParagonIE_Sodium_Core_Util::verify_16($tag, $state->finish());

        fseek($ifp, $pos, SEEK_SET);
        return $res;
    }