ParagonIE_Sodium_Core32_SipHash::sipHash24

    public static function sipHash24($in, $key)
    {
        $inlen = self::strlen($in);

        # /* "somepseudorandomlygeneratedbytes" */
        # u64 v0 = 0x736f6d6570736575ULL;
        # u64 v1 = 0x646f72616e646f6dULL;
        # u64 v2 = 0x6c7967656e657261ULL;
        # u64 v3 = 0x7465646279746573ULL;
        $v = array(
            new ParagonIE_Sodium_Core32_Int64(
                array(0x736f, 0x6d65, 0x7073, 0x6575)
            ),
            new ParagonIE_Sodium_Core32_Int64(
                array(0x646f, 0x7261, 0x6e64, 0x6f6d)
            ),
            new ParagonIE_Sodium_Core32_Int64(
                array(0x6c79, 0x6765, 0x6e65, 0x7261)
            ),
            new ParagonIE_Sodium_Core32_Int64(
                array(0x7465, 0x6462, 0x7974, 0x6573)
            )
        );

        # u64 k0 = LOAD64_LE( k );
        # u64 k1 = LOAD64_LE( k + 8 );
        $k = array(
            ParagonIE_Sodium_Core32_Int64::fromReverseString(
                self::substr($key, 0, 8)
            ),
            ParagonIE_Sodium_Core32_Int64::fromReverseString(
                self::substr($key, 8, 8)
            )
        );

        # b = ( ( u64 )inlen ) << 56;
        $b = new ParagonIE_Sodium_Core32_Int64(
            array(($inlen << 8) & 0xffff, 0, 0, 0)
        );

        # v3 ^= k1;
        $v[3] = $v[3]->xorInt64($k[1]);
        # v2 ^= k0;
        $v[2] = $v[2]->xorInt64($k[0]);
        # v1 ^= k1;
        $v[1] = $v[1]->xorInt64($k[1]);
        # v0 ^= k0;
        $v[0] = $v[0]->xorInt64($k[0]);

        $left = $inlen;
        # for ( ; in != end; in += 8 )
        while ($left >= 8) {
            # m = LOAD64_LE( in );
            $m = ParagonIE_Sodium_Core32_Int64::fromReverseString(
                self::substr($in, 0, 8)
            );

            # v3 ^= m;
            $v[3] = $v[3]->xorInt64($m);

            # SIPROUND;
            # SIPROUND;
            $v = self::sipRound($v);
            $v = self::sipRound($v);

            # v0 ^= m;
            $v[0] = $v[0]->xorInt64($m);

            $in = self::substr($in, 8);
            $left -= 8;
        }

        # switch( left )
        #  {
        #     case 7: b |= ( ( u64 )in[ 6] )  << 48;
        #     case 6: b |= ( ( u64 )in[ 5] )  << 40;
        #     case 5: b |= ( ( u64 )in[ 4] )  << 32;
        #     case 4: b |= ( ( u64 )in[ 3] )  << 24;
        #     case 3: b |= ( ( u64 )in[ 2] )  << 16;
        #     case 2: b |= ( ( u64 )in[ 1] )  <<  8;
        #     case 1: b |= ( ( u64 )in[ 0] ); break;
        #     case 0: break;
        # }
        switch ($left) {
            case 7:
                $b = $b->orInt64(
                    ParagonIE_Sodium_Core32_Int64::fromInts(
                        0, self::chrToInt($in[6]) << 16
                    )
                );
            case 6:
                $b = $b->orInt64(
                    ParagonIE_Sodium_Core32_Int64::fromInts(
                        0, self::chrToInt($in[5]) << 8
                    )
                );
            case 5:
                $b = $b->orInt64(
                    ParagonIE_Sodium_Core32_Int64::fromInts(
                        0, self::chrToInt($in[4])
                    )
                );
            case 4:
                $b = $b->orInt64(
                    ParagonIE_Sodium_Core32_Int64::fromInts(
                        self::chrToInt($in[3]) << 24, 0
                    )
                );
            case 3:
                $b = $b->orInt64(
                    ParagonIE_Sodium_Core32_Int64::fromInts(
                        self::chrToInt($in[2]) << 16, 0
                    )
                );
            case 2:
                $b = $b->orInt64(
                    ParagonIE_Sodium_Core32_Int64::fromInts(
                        self::chrToInt($in[1]) << 8, 0
                    )
                );
            case 1:
                $b = $b->orInt64(
                    ParagonIE_Sodium_Core32_Int64::fromInts(
                        self::chrToInt($in[0]), 0
                    )
                );
            case 0:
                break;
        }

        # v3 ^= b;
        $v[3] = $v[3]->xorInt64($b);

        # SIPROUND;
        # SIPROUND;
        $v = self::sipRound($v);
        $v = self::sipRound($v);

        # v0 ^= b;
        $v[0] = $v[0]->xorInt64($b);

        // Flip the lower 8 bits of v2 which is ($v[4], $v[5]) in our implementation
        # v2 ^= 0xff;
        $v[2]->limbs[3] ^= 0xff;

        # SIPROUND;
        # SIPROUND;
        # SIPROUND;
        # SIPROUND;
        $v = self::sipRound($v);
        $v = self::sipRound($v);
        $v = self::sipRound($v);
        $v = self::sipRound($v);

        # b = v0 ^ v1 ^ v2 ^ v3;
        # STORE64_LE( out, b );
        return $v[0]
            ->xorInt64($v[1])
            ->xorInt64($v[2])
            ->xorInt64($v[3])
            ->toReverseString();
    }