#include <stdlib.h>
#include <math.h>
#include <ieee754.h>

#define	IEEE	1

/*
 *	ecvt converts to decimal
 *	the number of digits is specified by ndigit
 *	decpt is set to the position of the decimal point
 *	sign is set to 0 for positive, 1 for negative
 */

#ifdef IEEE

static inline int
__isspecial(double f, char *bp)
{
	union ieee754_double *ip = (union ieee754_double *) &f;

	if ((ip->ieee.exponent & 0x7ff) != 0x7ff)
		return(0);
	if (ip->ieee.mantissa0 || ip->ieee.mantissa1)
		strcpy(bp, "NaN");
	else if (ip->ieee.negative)
		strcpy(bp, "-Infinity");
	else
		strcpy(bp, "Infinity");
	return(1);
}

#define	NDIG	512
#else
#define	NDIG	80
#endif

static char*
cvt(double arg, size_t ndigits, int *decpt, int *sign, int eflag)
{
	register int r2;
	double fi, fj;
	register char *p, *p1;
	static char buf[NDIG];

#ifdef IEEE
	/* XXX */
	if (__isspecial(arg, buf))
		return(buf);
#endif
	if (ndigits>=NDIG-1)
		ndigits = NDIG-2;
	r2 = 0;
	*sign = 0;
	p = &buf[0];
	if (arg<0) {
		*sign = 1;
		arg = -arg;
	}
	arg = modf(arg, &fi);
	p1 = &buf[NDIG];
	/*
	 * Do integer part
	 */
	if (fi != 0) {
		p1 = &buf[NDIG];
		while (fi != 0) {
			fj = modf(fi/10, &fi);
			*--p1 = (int)((fj+.03)*10) + '0';
			r2++;
		}
		while (p1 < &buf[NDIG])
			*p++ = *p1++;
	} else if (arg > 0) {
		while ((fj = arg*10) < 1) {
			arg = fj;
			r2--;
		}
	}
	p1 = &buf[ndigits];
	if (eflag==0)
		p1 += r2;
	*decpt = r2;
	if (p1 < &buf[0]) {
		buf[0] = '\0';
		return(buf);
	}
	while (p<=p1 && p<&buf[NDIG]) {
		arg *= 10;
		arg = modf(arg, &fj);
		*p++ = (int)fj + '0';
	}
	if (p1 >= &buf[NDIG]) {
		buf[NDIG-1] = '\0';
		return(buf);
	}
	p = p1;
	*p1 += 5;
	while (*p1 > '9') {
		*p1 = '0';
		if (p1>buf)
			++*--p1;
		else {
			*p1 = '1';
			(*decpt)++;
			if (eflag==0) {
				if (p>buf)
					*p = '0';
				p++;
			}
		}
	}
	*p = '\0';
	return(buf);
}

char*
ecvt(double arg, size_t ndigits, int *decpt, int *sign)
{
	return(cvt(arg, ndigits, decpt, sign, 1));
}

char*
fcvt(double arg, size_t ndigits, int *decpt, int *sign)
{
	return(cvt(arg, ndigits, decpt, sign, 0));
}

