format.c

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      return cnt;
    default:
      PUTC((char)*fmt);
      cnt++;
    }
  }
  /* NOTREACHED */
}

static long double pten[] =
{
  1e1L, 1e2L, 1e4L, 1e8L, 1e16L, 1e32L, 1e64L, 1e128L, 1e256L,
  1e512L, 1e1024L, 1e2048L, 1e4096L
};

static long double ptenneg[] =
{
  1e-1L, 1e-2L, 1e-4L, 1e-8L, 1e-16L, 1e-32L, 1e-64L, 1e-128L, 1e-256L,
  1e-512L, 1e-1024L, 1e-2048L, 1e-4096L
};

#define MAXP 4096
#define NP   12
#define P    (4294967296.0L * 4294967296.0L * 2.0L)   /* 2^65 */
static long double INVPREC = P;
static long double PREC = 1.0L/P;
#undef P
/*
 * Defining FAST_LDOUBLE_CONVERSION results in a little bit faster
 * version, which might be less accurate (about 1 bit) for long
 * double. For 'normal' double it doesn't matter.
 */
/* #define FAST_LDOUBLE_CONVERSION */

static int
cvtl(long double number, int prec, int flags, char *signp, unsigned char fmtch,
     char *startp, char *endp)
{
  char *p, *t;
  long double fract;
  int dotrim, expcnt, gformat;
  long double integer, tmp;

  if ((expcnt = isspeciall(number, startp)))
    return(expcnt);

  dotrim = expcnt = gformat = 0;
  /* fract = modfl(number, &integer); */
  integer = number;

  /* get an extra slot for rounding. */
  t = ++startp;

  p = endp - 1;
  if (integer)
  {
    int i, lp=NP, pt=MAXP;
#ifndef FAST_LDOUBLE_CONVERSION
    long double oint = integer, dd=1.0L;
#endif
    if (integer > INVPREC)
    {
      integer *= PREC;
      while(lp >= 0) {
	if (integer >= pten[lp])
	{
	  expcnt += pt;
	  integer *= ptenneg[lp];
#ifndef FAST_LDOUBLE_CONVERSION
	  dd *= pten[lp];
#endif
	}
	pt >>= 1;
	lp--;
      }
#ifndef FAST_LDOUBLE_CONVERSION
      integer = oint/dd;
#else
      integer *= INVPREC;
#endif
    }
    /*
     * Do we really need this ?
     */
    for (i = 0; i < expcnt; i++)
      *p-- = '0';
  }
  number = integer;
  fract = modfl(number, &integer);
  /*
   * get integer portion of number; put into the end of the buffer; the
   * .01 is added for modf(356.0 / 10, &integer) returning .59999999...
   */
  for (; integer; ++expcnt)
  {
    tmp = modfl(integer * 0.1L , &integer);
    *p-- = tochar((int)((tmp + .01L) * 10));
  }
  switch(fmtch)
  {
  case 'f':
    /* reverse integer into beginning of buffer */
    if (expcnt)
      for (; ++p < endp; *t++ = *p);
    else
      *t++ = '0';
    /*
     * if precision required or alternate flag set, add in a
     * decimal point.
     */
    if (prec || flags&ALT)
      *t++ = decimal;
    /* if requires more precision and some fraction left */
    if (fract)
    {
      if (prec)
	do {
	  fract = modfl(fract * 10.0L, &tmp);
	  *t++ = tochar((int)tmp);
	} while (--prec && fract);
      if (fract)
	startp = roundl(fract, (int *)NULL, startp,
			t - 1, (char)0, signp);
    }
    for (; prec--; *t++ = '0');
    break;
  case 'e':
  case 'E':
  eformat:
    if (expcnt)
    {
      *t++ = *++p;
      if (prec || flags&ALT)
	*t++ = decimal;
      /* if requires more precision and some integer left */
      for (; prec && ++p < endp; --prec)
	*t++ = *p;
      /*
       * if done precision and more of the integer component,
       * round using it; adjust fract so we don't re-round
       * later.
       */
      if (!prec && ++p < endp)
      {
	fract = 0;
	startp = roundl((long double)0.0L, &expcnt,
			startp, t - 1, *p, signp);
      }
      /* adjust expcnt for digit in front of decimal */
      --expcnt;
    }
    /* until first fractional digit, decrement exponent */
    else if (fract)
    {
      int lp=NP, pt=MAXP;
#ifndef FAST_LDOUBLE_CONVERSION
      long double ofract = fract, dd=1.0L;
#endif
      expcnt = -1;
      if (fract < PREC)
      {
	fract *= INVPREC;
	while(lp >= 0)
	{
	  if (fract <= ptenneg[lp])
	  {
	    expcnt -= pt;
	    fract *= pten[lp];
#ifndef FAST_LDOUBLE_CONVERSION
	    dd *= pten[lp];
#endif
	  }
	  pt >>= 1;
	  lp--;
	}
#ifndef FAST_LDOUBLE_CONVERSION
	fract = ofract*dd;
#else
	fract *= PREC;
#endif
      }
      /* adjust expcnt for digit in front of decimal */
      for (			/* expcnt = -1 */ ;; --expcnt)
      {
	fract = modfl(fract * 10.0L, &tmp);
	if (tmp)
	  break;
      }
      *t++ = tochar((int)tmp);
      if (prec || flags&ALT)
	*t++ = decimal;
    }
    else
    {
      *t++ = '0';
      if (prec || flags&ALT)
	*t++ = decimal;
    }
    /* if requires more precision and some fraction left */
    if (fract)
    {
      if (prec)
	do {
	  fract = modfl(fract * 10.0L, &tmp);
	  *t++ = tochar((int)tmp);
	} while (--prec && fract);
      if (fract)
	startp = roundl(fract, &expcnt, startp,
			t - 1, (char)0, signp);
    }
    /* if requires more precision */
    for (; prec--; *t++ = '0');

    /* unless alternate flag, trim any g/G format trailing 0's */
    if (gformat && !(flags&ALT))
    {
      while (t > startp && *--t == '0');
      if (*t == decimal)
	--t;
      ++t;
    }
    t = exponentl(t, expcnt, fmtch);
    break;
  case 'g':
  case 'G':
    /* a precision of 0 is treated as a precision of 1. */
    if (!prec)
      ++prec;
    /*
     * ``The style used depends on the value converted; style e
     * will be used only if the exponent resulting from the
     * conversion is less than -4 or greater than the precision.''
     *	-- ANSI X3J11
     */
    if (expcnt > prec || (!expcnt && fract && fract < .0001))
    {
      /*
       * g/G format counts "significant digits, not digits of
       * precision; for the e/E format, this just causes an
       * off-by-one problem, i.e. g/G considers the digit
       * before the decimal point significant and e/E doesn't
       * count it as precision.
       */
      --prec;
      fmtch -= 2;		/* G->E, g->e */
      gformat = 1;
      goto eformat;
    }
    /*
     * reverse integer into beginning of buffer,
     * note, decrement precision
     */
    if (expcnt)
      for (; ++p < endp; *t++ = *p, --prec);
    else
      *t++ = '0';
    /*
     * if precision required or alternate flag set, add in a
     * decimal point.  If no digits yet, add in leading 0.
     */
    if (prec || flags&ALT)
    {
      dotrim = 1;
      *t++ = decimal;
    }
    else
      dotrim = 0;
    /* if requires more precision and some fraction left */
    while (prec && fract)
    {
      fract = modfl(fract * 10.0L, &tmp);
      *t++ = tochar((int)tmp);
      prec--;
    }
    if (fract)
      startp = roundl(fract, (int *)NULL, startp, t - 1,
		      (char)0, signp);
    /* alternate format, adds 0's for precision, else trim 0's */
    if (flags&ALT)
      for (; prec--; *t++ = '0');
    else if (dotrim)
    {
      while (t > startp && *--t == '0');
      if (*t != decimal)
	++t;
    }
  }
  return t - startp;
}

static char *
roundl(long double fract, int *expv, char *start, char *end, char ch,
       char *signp)
{
  long double tmp;

  if (fract)
  {
    if (fract == 0.5L)
    {
      char *e = end;
      if (*e == '.')
	e--;
      if (*e == '0' || *e == '2' || *e == '4'
	  || *e == '6' || *e == '8')
      {
	tmp = 3.0;
	goto start;
      }
    }
    (void)modfl(fract * 10.0L, &tmp);
  }
  else
    tmp = todigit(ch);
 start:
  if (tmp > 4)
    for (;; --end)
    {
      if (*end == decimal)
	--end;
      if (++*end <= '9')
	break;
      *end = '0';
      if (end == start)
      {
	if (expv)
	{		/* e/E; increment exponent */
	  *end = '1';
	  ++*expv;
	}
	else
	{			/* f; add extra digit */
	  *--end = '1';
	  --start;
	}
	break;
      }
    }
  /* ``"%.3f", (double)-0.0004'' gives you a negative 0. */
  else if (*signp == '-')
    for (;; --end)
    {
      if (*end == decimal)
	--end;
      if (*end != '0')
	break;
      if (end == start)
	*signp = 0;
    }
  return start;
}

static char *
exponentl(char *p, int expv, unsigned char fmtch)
{
  char *t;
  char expbuf[MAXEXPLD];

  *p++ = fmtch;
  if (expv < 0)
  {
    expv = -expv;
    *p++ = '-';
  }
  else
    *p++ = '+';
  t = expbuf + MAXEXPLD;
  if (expv > 9)
  {
    do {
      *--t = tochar(expv % 10);
    } while ((expv /= 10) > 9);
    *--t = tochar(expv);
    for (; t < expbuf + MAXEXPLD; *p++ = *t++);
  }
  else
  {
    *p++ = '0';
    *p++ = tochar(expv);
  }
  return p;
}

static int
isspeciall(long double d, char *bufp)
{
  struct IEEExp {
    unsigned manl:32;
    unsigned manh:32;
    unsigned exp:15;
    unsigned sign:1;
  } *ip = (struct IEEExp *)&d;

  nan = 0;  /* don't assume the static is 0 (emacs) */
  if (ip->exp != 0x7fff)
    return(0);
  if ((ip->manh & 0x7fffffff) || ip->manl)
  {
    strcpy(bufp, "NaN");
    nan = 1;			/* kludge: we don't need the sign,  it's not nice
				   but it should work */
  }
  else
    (void)strcpy(bufp, "Inf");
  return(3);
}