ParagonIE_Sodium_File::generichash

    public static function generichash($filePath, $key = '', $outputLength = 32)
    {
        /* Type checks: */
        if (!is_string($filePath)) {
            throw new TypeError('Argument 1 must be a string, ' . gettype($filePath) . ' given.');
        }
        if (!is_string($key)) {
            if (is_null($key)) {
                $key = '';
            } else {
                throw new TypeError('Argument 2 must be a string, ' . gettype($key) . ' given.');
            }
        }
        if (!is_int($outputLength)) {
            if (!is_numeric($outputLength)) {
                throw new TypeError('Argument 3 must be an integer, ' . gettype($outputLength) . ' given.');
            }
            $outputLength = (int) $outputLength;
        }

        /* Input validation: */
        if (!empty($key)) {
            if (self::strlen($key) < ParagonIE_Sodium_Compat::CRYPTO_GENERICHASH_KEYBYTES_MIN) {
                throw new TypeError('Argument 2 must be at least CRYPTO_GENERICHASH_KEYBYTES_MIN bytes');
            }
            if (self::strlen($key) > ParagonIE_Sodium_Compat::CRYPTO_GENERICHASH_KEYBYTES_MAX) {
                throw new TypeError('Argument 2 must be at most CRYPTO_GENERICHASH_KEYBYTES_MAX bytes');
            }
        }
        if ($outputLength < ParagonIE_Sodium_Compat::CRYPTO_GENERICHASH_BYTES_MIN) {
            throw new SodiumException('Argument 3 must be at least CRYPTO_GENERICHASH_BYTES_MIN');
        }
        if ($outputLength > ParagonIE_Sodium_Compat::CRYPTO_GENERICHASH_BYTES_MAX) {
            throw new SodiumException('Argument 3 must be at least CRYPTO_GENERICHASH_BYTES_MAX');
        }

        /** @var int $size */
        $size = filesize($filePath);
        if (!is_int($size)) {
            throw new SodiumException('Could not obtain the file size');
        }

        /** @var resource $fp */
        $fp = fopen($filePath, 'rb');
        if (!is_resource($fp)) {
            throw new SodiumException('Could not open input file for reading');
        }
        $ctx = ParagonIE_Sodium_Compat::crypto_generichash_init($key, $outputLength);
        while ($size > 0) {
            $blockSize = $size > 64
                ? 64
                : $size;
            $read = fread($fp, $blockSize);
            if (!is_string($read)) {
                throw new SodiumException('Could not read input file');
            }
            ParagonIE_Sodium_Compat::crypto_generichash_update($ctx, $read);
            $size -= $blockSize;
        }

        fclose($fp);
        return ParagonIE_Sodium_Compat::crypto_generichash_final($ctx, $outputLength);
    }