void sc25519_window3()

in sc25519.c [221:256]

• 34 lines of code
• 3 McCabe index (conditional complexity)

void sc25519_window3(signed char r[85], const sc25519 *s)
{
  char carry;
  int i;
  for(i=0;i<10;i++)
  {
    r[8*i+0]  =  s->v[3*i+0]       & 7;
    r[8*i+1]  = (s->v[3*i+0] >> 3) & 7;
    r[8*i+2]  = (s->v[3*i+0] >> 6) & 7;
    r[8*i+2] ^= (s->v[3*i+1] << 2) & 7;
    r[8*i+3]  = (s->v[3*i+1] >> 1) & 7;
    r[8*i+4]  = (s->v[3*i+1] >> 4) & 7;
    r[8*i+5]  = (s->v[3*i+1] >> 7) & 7;
    r[8*i+5] ^= (s->v[3*i+2] << 1) & 7;
    r[8*i+6]  = (s->v[3*i+2] >> 2) & 7;
    r[8*i+7]  = (s->v[3*i+2] >> 5) & 7;
  }
  r[8*i+0]  =  s->v[3*i+0]       & 7;
  r[8*i+1]  = (s->v[3*i+0] >> 3) & 7;
  r[8*i+2]  = (s->v[3*i+0] >> 6) & 7;
  r[8*i+2] ^= (s->v[3*i+1] << 2) & 7;
  r[8*i+3]  = (s->v[3*i+1] >> 1) & 7;
  r[8*i+4]  = (s->v[3*i+1] >> 4) & 7;

  /* Making it signed */
  carry = 0;
  for(i=0;i<84;i++)
  {
    r[i] += carry;
    r[i+1] += r[i] >> 3;
    r[i] &= 7;
    carry = r[i] >> 2;
    r[i] -= carry<<3;
  }
  r[84] += carry;
}