Digital-Research-Source-Code/CPM OPERATING SYSTEMS/CPM 68K/1.0X SOURCES/v102a/libe/ftoa.c

/*
 *	Ftoa routine with rounding
 */
#include <portab.h>
BYTE	*ftoa(x,str,prec)
FLOAT	 x;					/* Arg to convert	*/
BYTE	*str;					/* -> Output area	*/
WORD	 prec;					/* # digits right of dp */
{
REG	WORD	ie,i,k,ndig;			/* Temps		*/
	BYTE	*savstr;			/* Copy	of str to return*/
	DOUBLE	y;				/* Temp for rounding	*/
	
	savstr = str;				/* Preserve for later	*/
	ndig = (prec <= 0) ? 1 : ((prec > 22) ? 23 : prec+1);
	ie = 0;
	if(x < 0)				/* Fix for negative	*/
	{
	  *str++ = '-';
	   x = -x;				/* Negate		*/
	}
/*
 *	Normalize x to the range 0.0 <= x < 10.0
 */
	if(x > 0.0)
	{
	  while (x < 1.0)
	  {
	     x *= 10.0;
	     ie--;
	  }
	}
	while(x >= 10.0)
	{
	  x /= 10.0;
	  ie++;
	}
	ndig += ie;		/* Adjust digit count for size	*/
/*
 *	Now round.
 */
	for(y=i=1; i < ndig; i++)
		y = y / 10.0;		/* Compute round amount	*/
	x += (y / 2.0);			/* Round by 1/2 lsb	*/
	if(x >= 10.0) 			/* Did we push it over 10? */
	{
	  x = 1.0;
	  ie++;
	}
/*
 *	Now convert result
 */
	if(ie < 0)			/* Leading zeros are special */
	{
		*str++ = '0';
		*str++ = '.';
		if(ndig < 0) ie = ie -ndig;	/* For underflow */
		for(i = -1; i > ie; i--)	/* Out the zeros */
			*str++ = '0';
	}

	for(i=0; i<ndig; i++)
	{
		k = x;				/* Truncate	*/
		*str++ = k + '0';		/* ASCIIfy	*/
		if(i == ie)			/* Locate decimal point*/
			*str++ = '.';
		x -= (y=k);
		x *= 10.0;
	}
	*str++ = '\0';
	return(savstr);
}