dtoa.c

gcc的组建

      k0 = k;
      ilim0 = ilim;
      ieps = 2;			/* conservative */
      if (k > 0)
	{
	  ds = tens[k & 0xf];
	  j = k >> 4;
	  if (j & Bletch)
	    {
	      /* prevent overflows */
	      j &= Bletch - 1;
	      d.d /= bigtens[n_bigtens - 1];
	      ieps++;
	    }
	  for (; j; j >>= 1, i++)
	    if (j & 1)
	      {
		ieps++;
		ds *= bigtens[i];
	      }
	  d.d /= ds;
	}
      else if ((j1 = -k))
	{
	  d.d *= tens[j1 & 0xf];
	  for (j = j1 >> 4; j; j >>= 1, i++)
	    if (j & 1)
	      {
		ieps++;
		d.d *= bigtens[i];
	      }
	}
      if (k_check && d.d < 1. && ilim > 0)
	{
	  if (ilim1 <= 0)
	    goto fast_failed;
	  ilim = ilim1;
	  k--;
	  d.d *= 10.;
	  ieps++;
	}
      eps.d = ieps * d.d + 7.;
      word0 (eps) -= (P - 1) * Exp_msk1;
      if (ilim == 0)
	{
	  S = mhi = 0;
	  d.d -= 5.;
	  if (d.d > eps.d)
	    goto one_digit;
	  if (d.d < -eps.d)
	    goto no_digits;
	  goto fast_failed;
	}
#ifndef No_leftright
      if (leftright)
	{
	  /* Use Steele & White method of only
	   * generating digits needed.
	   */
	  eps.d = 0.5 / tens[ilim - 1] - eps.d;
	  for (i = 0;;)
	    {
	      L = d.d;
	      d.d -= L;
	      *s++ = '0' + (int) L;
	      if (d.d < eps.d)
		goto ret1;
	      if (1. - d.d < eps.d)
		goto bump_up;
	      if (++i >= ilim)
		break;
	      eps.d *= 10.;
	      d.d *= 10.;
	    }
	}
      else
	{
#endif
	  /* Generate ilim digits, then fix them up. */
	  eps.d *= tens[ilim - 1];
	  for (i = 1;; i++, d.d *= 10.)
	    {
	      L = d.d;
	      d.d -= L;
	      *s++ = '0' + (int) L;
	      if (i == ilim)
		{
		  if (d.d > 0.5 + eps.d)
		    goto bump_up;
		  else if (d.d < 0.5 - eps.d)
		    {
		      while (*--s == '0');
		      s++;
		      goto ret1;
		    }
		  break;
		}
	    }
#ifndef No_leftright
	}
#endif
    fast_failed:
      s = s0;
      d.d = d2.d;
      k = k0;
      ilim = ilim0;
    }

  /* Do we have a "small" integer? */

  if (be >= 0 && k <= Int_max)
    {
      /* Yes. */
      ds = tens[k];
      if (ndigits < 0 && ilim <= 0)
	{
	  S = mhi = 0;
	  if (ilim < 0 || d.d <= 5 * ds)
	    goto no_digits;
	  goto one_digit;
	}
      for (i = 1;; i++)
	{
	  L = d.d / ds;
	  d.d -= L * ds;
#ifdef Check_FLT_ROUNDS
	  /* If FLT_ROUNDS == 2, L will usually be high by 1 */
	  if (d.d < 0)
	    {
	      L--;
	      d.d += ds;
	    }
#endif
	  *s++ = '0' + (int) L;
	  if (i == ilim)
	    {
	      d.d += d.d;
	      if (d.d > ds || (d.d == ds && L & 1))
		{
		bump_up:
		  while (*--s == '9')
		    if (s == s0)
		      {
			k++;
			*s = '0';
			break;
		      }
		  ++*s++;
		}
	      break;
	    }
	  if (!(d.d *= 10.))
	    break;
	}
      goto ret1;
    }

  m2 = b2;
  m5 = b5;
  mhi = mlo = 0;
  if (leftright)
    {
      if (mode < 2)
	{
	  i =
#ifndef Sudden_Underflow
	    denorm ? be + (Bias + (P - 1) - 1 + 1) :
#endif
#ifdef IBM
	    1 + 4 * P - 3 - bbits + ((bbits + be - 1) & 3);
#else
	    1 + P - bbits;
#endif
	}
      else
	{
	  j = ilim - 1;
	  if (m5 >= j)
	    m5 -= j;
	  else
	    {
	      s5 += j -= m5;
	      b5 += j;
	      m5 = 0;
	    }
	  if ((i = ilim) < 0)
	    {
	      m2 -= i;
	      i = 0;
	    }
	}
      b2 += i;
      s2 += i;
      mhi = i2b (ptr, 1);
    }
  if (m2 > 0 && s2 > 0)
    {
      i = m2 < s2 ? m2 : s2;
      b2 -= i;
      m2 -= i;
      s2 -= i;
    }
  if (b5 > 0)
    {
      if (leftright)
	{
	  if (m5 > 0)
	    {
	      mhi = pow5mult (ptr, mhi, m5);
	      b1 = mult (ptr, mhi, b);
	      Bfree (ptr, b);
	      b = b1;
	    }
	  if ((j = b5 - m5))
	    b = pow5mult (ptr, b, j);
	}
      else
	b = pow5mult (ptr, b, b5);
    }
  S = i2b (ptr, 1);
  if (s5 > 0)
    S = pow5mult (ptr, S, s5);

  /* Check for special case that d is a normalized power of 2. */

  if (mode < 2)
    {
      if (!word1 (d) && !(word0 (d) & Bndry_mask)
#ifndef Sudden_Underflow
	  && word0(d) & Exp_mask
#endif
	)
	{
	  /* The special case */
	  b2 += Log2P;
	  s2 += Log2P;
	  spec_case = 1;
	}
      else
	spec_case = 0;
    }

  /* Arrange for convenient computation of quotients:
   * shift left if necessary so divisor has 4 leading 0 bits.
   *
   * Perhaps we should just compute leading 28 bits of S once
   * and for all and pass them and a shift to quorem, so it
   * can do shifts and ors to compute the numerator for q.
   */

#ifdef Pack_32
  if ((i = ((s5 ? 32 - hi0bits (S->_x[S->_wds - 1]) : 1) + s2) & 0x1f))
    i = 32 - i;
#else
  if ((i = ((s5 ? 32 - hi0bits (S->_x[S->_wds - 1]) : 1) + s2) & 0xf))
    i = 16 - i;
#endif
  if (i > 4)
    {
      i -= 4;
      b2 += i;
      m2 += i;
      s2 += i;
    }
  else if (i < 4)
    {
      i += 28;
      b2 += i;
      m2 += i;
      s2 += i;
    }
  if (b2 > 0)
    b = lshift (ptr, b, b2);
  if (s2 > 0)
    S = lshift (ptr, S, s2);
  if (k_check)
    {
      if (cmp (b, S) < 0)
	{
	  k--;
	  b = multadd (ptr, b, 10, 0);	/* we botched the k estimate */
	  if (leftright)
	    mhi = multadd (ptr, mhi, 10, 0);
	  ilim = ilim1;
	}
    }
  if (ilim <= 0 && mode > 2)
    {
      if (ilim < 0 || cmp (b, S = multadd (ptr, S, 5, 0)) <= 0)
	{
	  /* no digits, fcvt style */
	no_digits:
	  k = -1 - ndigits;
	  goto ret;
	}
    one_digit:
      *s++ = '1';
      k++;
      goto ret;
    }
  if (leftright)
    {
      if (m2 > 0)
	mhi = lshift (ptr, mhi, m2);

      /* Single precision case, */
      if (float_type)
	mhi = lshift (ptr, mhi, 29);

      /* Compute mlo -- check for special case
       * that d is a normalized power of 2.
       */

      mlo = mhi;
      if (spec_case)
	{
	  mhi = Balloc (ptr, mhi->_k);
	  Bcopy (mhi, mlo);
	  mhi = lshift (ptr, mhi, Log2P);
	}

      for (i = 1;; i++)
	{
	  dig = quorem (b, S) + '0';
	  /* Do we yet have the shortest decimal string
	   * that will round to d?
	   */
	  j = cmp (b, mlo);
	  delta = diff (ptr, S, mhi);
	  j1 = delta->_sign ? 1 : cmp (b, delta);
	  Bfree (ptr, delta);
#ifndef ROUND_BIASED
	  if (j1 == 0 && !mode && !(word1 (d) & 1))
	    {
	      if (dig == '9')
		goto round_9_up;
	      if (j > 0)
		dig++;
	      *s++ = dig;
	      goto ret;
	    }
#endif
	  if (j < 0 || (j == 0 && !mode
#ifndef ROUND_BIASED
	      && !(word1 (d) & 1)
#endif
	    ))
	    {
	      if (j1 > 0)
		{
		  b = lshift (ptr, b, 1);
		  j1 = cmp (b, S);
		  if ((j1 > 0 || (j1 == 0 && dig & 1))
		      && dig++ == '9')
		    goto round_9_up;
		}
	      *s++ = dig;
	      goto ret;
	    }
	  if (j1 > 0)
	    {
	      if (dig == '9')
		{		/* possible if i == 1 */
		round_9_up:
		  *s++ = '9';
		  goto roundoff;
		}
	      *s++ = dig + 1;
	      goto ret;
	    }
	  *s++ = dig;
	  if (i == ilim)
	    break;
	  b = multadd (ptr, b, 10, 0);
	  if (mlo == mhi)
	    mlo = mhi = multadd (ptr, mhi, 10, 0);
	  else
	    {
	      mlo = multadd (ptr, mlo, 10, 0);
	      mhi = multadd (ptr, mhi, 10, 0);
	    }
	}
    }
  else
    for (i = 1;; i++)
      {
	*s++ = dig = quorem (b, S) + '0';
	if (i >= ilim)
	  break;
	b = multadd (ptr, b, 10, 0);
      }

  /* Round off last digit */

  b = lshift (ptr, b, 1);
  j = cmp (b, S);
  if (j > 0 || (j == 0 && dig & 1))
    {
    roundoff:
      while (*--s == '9')
	if (s == s0)
	  {
	    k++;
	    *s++ = '1';
	    goto ret;
	  }
      ++*s++;
    }
  else
    {
      while (*--s == '0');
      s++;
    }
ret:
  Bfree (ptr, S);
  if (mhi)
    {
      if (mlo && mlo != mhi)
	Bfree (ptr, mlo);
      Bfree (ptr, mhi);
    }
ret1:
  Bfree (ptr, b);
  *s = 0;
  *decpt = k + 1;
  if (rve)
    *rve = s;
  return s0;
}


_VOID
_DEFUN (_dtoa,
	(_d, mode, ndigits, decpt, sign, rve, buf, float_type),
	double _d _AND
	int mode _AND
	int ndigits _AND
	int *decpt _AND
	int *sign _AND
	char **rve _AND
	char *buf _AND
	int float_type)
{
  struct _Jv_reent reent;
  char *p;
  memset (&reent, 0, sizeof reent);

  p = _dtoa_r (&reent, _d, mode, ndigits, decpt, sign, rve, float_type);
  strcpy (buf, p);

  return;
}