Function d2b

strings/dtoa.c:1234–1281

static Bigint *d2b(U *d, int *e, int *bits, Stack_alloc *alloc)
{
  Bigint *b;
  int de, k;
  ULong *x, y, z;
  int i;
#define d0 word0(d)
#define d1 word1(d)

  b= Balloc(1, alloc);
  x= b->p.x;

  z= d0 & Frac_mask;
  d0 &= 0x7fffffff;       /* clear sign bit, which we ignore */
  if ((de= (int)(d0 >> Exp_shift)))
    z|= Exp_msk1;
  if ((y= d1))
  {
    if ((k= lo0bits(&y)))
    {
      x[0]= y | z << (32 - k);
      z>>= k;
    }
    else
      x[0]= y;
    i= b->wds= (x[1]= z) ? 2 : 1;
  }
  else
  {
    k= lo0bits(&z);
    x[0]= z;
    i= b->wds= 1;
    k+= 32;
  }
  if (de)
  {
    *e= de - Bias - (P-1) + k;
    *bits= P - k;
  }
  else
  {
    *e= de - Bias - (P-1) + 1 + k;
    *bits= 32*i - hi0bits(x[i-1]);
  }
  return b;
#undef d0
#undef d1
}


static double ratio(Bigint *a, Bigint *b)