#include "params.h"
#include "small.h"

/* XXX: these functions rely on p mod 4 = 1 */

/* all coefficients in -1, 0, 1 */
void small_encode(unsigned char *c,const small *f)
{
  small c0;
  int i;

  for (i = 0;i < p/4;++i) {
    c0 = *f++ + 1;
    c0 += (*f++ + 1) << 2;
    c0 += (*f++ + 1) << 4;
    c0 += (*f++ + 1) << 6;
    *c++ = c0;
  }
  c0 = *f++ + 1;
  *c++ = c0;
}

void small_decode(small *f,const unsigned char *c)
{
  unsigned char c0;
  int i;

  for (i = 0;i < p/4;++i) {
    c0 = *c++;
    *f++ = ((small) (c0 & 3)) - 1; c0 >>= 2;
    *f++ = ((small) (c0 & 3)) - 1; c0 >>= 2;
    *f++ = ((small) (c0 & 3)) - 1; c0 >>= 2;
    *f++ = ((small) (c0 & 3)) - 1;
  }
  c0 = *c++;
  *f++ = ((small) (c0 & 3)) - 1;
}