ParagonIE_Sodium_Core32_BLAKE2b::init

    public static function init(
        $key = null,
        $outlen = 64,
        $salt = null,
        $personal = null
    ) {
        self::pseudoConstructor();
        $klen = 0;

        if ($key !== null) {
            if (count($key) > 64) {
                throw new SodiumException('Invalid key size');
            }
            $klen = count($key);
        }

        if ($outlen > 64) {
            throw new SodiumException('Invalid output size');
        }

        $ctx = self::context();

        $p = new SplFixedArray(64);
        // Zero our param buffer...
        for ($i = 64; --$i;) {
            $p[$i] = 0;
        }

        $p[0] = $outlen; // digest_length
        $p[1] = $klen;   // key_length
        $p[2] = 1;       // fanout
        $p[3] = 1;       // depth

        if ($salt instanceof SplFixedArray) {
            // salt: [32] through [47]
            for ($i = 0; $i < 16; ++$i) {
                $p[32 + $i] = (int) $salt[$i];
            }
        }
        if ($personal instanceof SplFixedArray) {
            // personal: [48] through [63]
            for ($i = 0; $i < 16; ++$i) {
                $p[48 + $i] = (int) $personal[$i];
            }
        }

        $ctx[0][0] = self::xor64(
            $ctx[0][0],
            self::load64($p, 0)
        );

        if ($salt instanceof SplFixedArray || $personal instanceof SplFixedArray) {
            // We need to do what blake2b_init_param() does:
            for ($i = 1; $i < 8; ++$i) {
                $ctx[0][$i] = self::xor64(
                    $ctx[0][$i],
                    self::load64($p, $i << 3)
                );
            }
        }

        if ($klen > 0 && $key instanceof SplFixedArray) {
            $block = new SplFixedArray(128);
            for ($i = 128; $i--;) {
                $block[$i] = 0;
            }
            for ($i = $klen; $i--;) {
                $block[$i] = $key[$i];
            }
            self::update($ctx, $block, 128);
            $ctx[4] = 128;
        }

        return $ctx;
    }