TweetableFIPS202.c

#define R(a, n) a << n ^ a >> 64-n
#define L(i, n) for(U i = 0; i < n; i++)

#define S(x) \
  L(i, r) \
    s[i/8] ^= (U) x[i] << i%8*8

#define H(i,r,p,d) \
  int crypto_hash_sha3##i(C *h, const C *m, U n) \
  { \
    k(r*8, m, n, p, h, d); \
    return 0; \
  }

#define H2(i,r,p) \
  int crypto_hash_shake##i(C *h, U d, const C *m, U n) \
  { \
    k(r*8, m, n, p, h, d); \
    return 0; \
  }

typedef unsigned long long U;
typedef unsigned char C;

void F(U *s)
{
  C R = 1, r, x, y;
  U t, B[5], Y;

  L(n, 24)
  {
    L(i, 5)
    {
      B[i] = 0;
      L(j, 5)
        B[i] ^= s[i+5*j];
    }

    L(i,5)
    {
      t = B[(i+4)%5] ^ R(B[(i+1)%5], 1);
      L(j, 5)
        s[i+5*j] ^= t;
    }

    t = s[1];
    y = r = 0;
    x = 1;
    L(j, 24)
    {
      r += j + 1;
      Y = 2 * x + 3 * y;
      x = y;
      y = Y % 5;
      Y = s[x+5*y];
      s[x+5*y] = R(t, r % 64);
      t = Y;
    }

    L(j, 5)
    {
      L(i, 5)
        B[i] = s[i+5*j];
      L(i, 5)
        s[i+5*j] = B[i] ^ (~B[(i+1)%5] & B[(i+2)%5]);
    }

    L(j, 7)
      if ((R = (R << 1) ^ (113 * (R >> 7))) & 2)
        *s ^= 1ULL << ((1 << j) - 1);
  }
}

void k(C r, const C *m, U n, C p, C *h, U d)
{
  U s[25] = {0};
  C t[200] = {0};

  while (n >= r)
  {
    S(m);
    F(s);
    n -= r;
    m += r;
  }
  
  L(i, n)
    t[i] = m[i];
  t[n] = p;
  t[r-1] |= 128;
  S(t);
  
  L(i,d)
  {
    if(0 == i % r)
      F(s);
    h[i] = s[i%r/8] >> 8*(i%8);
  }
}

H(224,18,6,28)
H(256,17,6,32)
H(384,13,6,48)
H(512,9,6,64)
H2(128,21,31)
H2(256,17,31)