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#define DIGMAX 30 /* max # of digits in string */
#define DIGPREC 17 /* max # of significant digits */
#define ECVT 0
#define FCVT 1
static char digstr[DIGMAX + 1 + 1]; /* +1 for end of string */
/* +1 in case rounding adds */
/* another digit */
static double negtab[] =
{ 1e-256, 1e-128, 1e-64, 1e-32, 1e-16, 1e-8, 1e-4, 1e-2, 1e-1, 1.0 };
static double postab[] =
{ 1e+256, 1e+128, 1e+64, 1e+32, 1e+16, 1e+8, 1e+4, 1e+2, 1e+1 };
static char *_cvt();
/*************************
* Convert double val to a string of
* decimal digits.
* ndig = # of digits in resulting string
* Returns:
* *pdecpt = position of decimal point from left of first digit
* *psign = nonzero if value was negative
*/
char *
ecvt(val, ndig, pdecpt, psign)
double val;
int ndig, *pdecpt, *psign;
{
return _cvt(ECVT, val, ndig, pdecpt, psign);
}
char *
fcvt(val, nfrac, pdecpt, psign)
double val;
int nfrac, *pdecpt, *psign;
{
return _cvt(FCVT, val, nfrac, pdecpt, psign);
}
static char *
_cvt(cnvflag, val, ndig, pdecpt, psign)
double val;
int ndig, *pdecpt, *psign;
{
int decpt, pow, i;
char *p;
*psign = (val < 0) ? ((val = -val), 1) : 0;
ndig = (ndig < 0) ? 0 : (ndig < DIGMAX) ? ndig : DIGMAX;
if (val == 0) {
for (p = &digstr[0]; p < &digstr[ndig]; p++)
*p = '0';
decpt = 0;
} else {
/* Adjust things so that 1 <= val < 10 */
/* in these loops if val == MAXDOUBLE) */
decpt = 1;
pow = 256;
i = 0;
while (val < 1) {
while (val < negtab[i + 1]) {
val /= negtab[i];
decpt -= pow;
}
pow >>= 1;
i++;
}
pow = 256;
i = 0;
while (val >= 10) {
while (val >= postab[i]) {
val /= postab[i];
decpt += pow;
}
pow >>= 1;
i++;
}
if (cnvflag == FCVT) {
ndig += decpt;
ndig = (ndig < 0) ? 0 : (ndig < DIGMAX) ? ndig : DIGMAX;
}
/* Pick off digits 1 by 1 and stuff into digstr[] */
/* Do 1 extra digit for rounding purposes */
for (p = &digstr[0]; p <= &digstr[ndig]; p++) {
int n;
/* 'twould be silly to have zillions of digits */
/* when only DIGPREC are significant */
if (p >= &digstr[DIGPREC])
*p = '0';
else {
n = val;
*p = n + '0';
val = (val - n) * 10; /* get next digit */
}
}
if (*--p >= '5') { /* if we need to round */
while (1) {
if (p == &digstr[0]) { /* if at start */
ndig += cnvflag;
decpt++; /* shift dec pnt */
digstr[0] = '1'; /* "100000..." */
break;
}
*p = '0';
--p;
if (*p != '9') {
(*p)++;
break;
}
} /* while */
} /* if */
} /* else */
*pdecpt = decpt;
digstr[ndig] = 0; /* terminate string */
return &digstr[0];
}
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