// Implements Serpent encoder 
// (see section 2 of ../docs for algorithm details)
// (rodric rabbah, <rabbah@mit.edu>)

void->void pipeline Serpent
{
    int testvector = 2;

    add PlainTextSource(testvector);
    add SerpentEncoder(testvector);
    add HexPrinter(CIPHERTEXT, NBITS);
}

bit->bit pipeline SerpentEncoder(int vector)
{
    // perform initial permutation
    add Permute(NBITS, IP);
    
    for (int i = 0; i < MAXROUNDS; i++) {
        // perform round i
        add R(vector, i);  
    }

    // perform final permutation
    add Permute(NBITS, FP);
}


// substitution boxes
bit->bit filter Sbox(int round) 
{
    work push 4 pop 4 {
        int val = pop();
        val = (pop() << 1) | val;
        val = (pop() << 2) | val;
        val = (pop() << 3) | val;

        int out = SBOXES[round][val];
        push((bit)((out & 0x1) >> 0));
        push((bit)((out & 0x2) >> 1));
        push((bit)((out & 0x4) >> 2));
        push((bit)((out & 0x8) >> 3));
    }
}

// round functions
bit->bit pipeline R(int vector, int round)
{
    add bit->bit splitjoin {
        split roundrobin(NBITS, 0);
        add Identity<bit>;
        add KeySchedule(vector, round);
        join roundrobin(1);
    }

    add Xor(2);

    add Sbox(round % 8);

    if (round < MAXROUNDS - 1) {
        add rawL();
    } else {
        add bit->bit splitjoin {
            split roundrobin(NBITS, 0);
            add Identity<bit>;
            add KeySchedule(vector, MAXROUNDS);
            join roundrobin(1);
        }
        add Xor(2);
    }
}