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SOURCES.ARC
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FP_PRT.C
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C/C++ Source or Header
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1987-04-22
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5KB
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335 lines
/* Modified: */
/* DWB Apr 89 Handle unnormalized numbers */
/* Fix exponent if .9... overflows */
#define MAXEC 40
static char *f_buf;
static int f_upper;
static char ec_buf[MAXEC+10];
static int ec_sign, ec_exp;
fp_print(x, fmtc, prec, ptmp)
float x;
char *ptmp;
{ register long lx, m;
register int e;
/* These routines have trouble with unnormalized numbers. */
lx = *(long*)&x;
if ((m = lx & 0xffffff00L) == 0 || (e = lx & 0x7f) == 0)
x = 0.0;
else if (m > 0L)
{ do
{ if (--e == 0)
{ x = 0.0;
goto uflo;
}
m <<= 1;
} while (m > 0L);
*(long*)&x = m | e | (lx & 0x80L);
uflo:
}
f_buf = ptmp;
f_upper = 0;
switch (fmtc) {
case 'E':
f_upper = 1;
case 'e':
e_print(x, prec);
break;
case 'F':
case 'f':
f_print(x, prec);
break;
case 'G':
f_upper = 1;
case 'g':
g_print(x, prec);
break;
}
}
static
e_print(x, prec)
float x;
{
int nsig;
register char *p;
if (prec < 0)
nsig = 7;
else
nsig = prec+1;
ec_pr(x, nsig, 0);
p = f_buf;
if (ec_sign)
*p++ = '-';
*p++ = ec_buf[0];
*p++ = '.';
if (nsig > 1)
strcpy(p, &ec_buf[1]);
p += strlen(p);
*p++ = f_upper ? 'E' : 'e';
ec_exp--;
if (ec_exp < 0) {
*p++ = '-';
ec_exp = -ec_exp;
}
if (ec_exp < 10)
*p++ = '0';
sprintf(p, "%d", ec_exp);
}
static
f_print(x, prec)
float x;
{
int nsig, nz, i;
register char *p;
if (prec < 0)
nsig = 6;
else
nsig = prec;
ec_pr(x, -nsig, 0);
p = f_buf;
if (ec_sign)
*p++ = '-';
if (ec_exp < 1) {
*p++ = '0';
} else {
strncpy(p, ec_buf, ec_exp);
p += ec_exp;
}
if (prec != 0 || nsig)
*p++ = '.';
if (nsig == 0) {
*p = 0;
return;
}
if (ec_exp < 0) {
nz = -ec_exp;
if (nz > nsig)
nz = nsig;
for (i=0; i<nz; i++)
*p++ = '0';
nsig -= nz;
if (nsig > 0) {
strncpy(p, ec_buf, nsig);
p += nsig;
}
*p = 0;
} else {
strcpy(p, &ec_buf[ec_exp]);
}
}
static
g_print(x, nsig)
float x;
{
int prec;
if (nsig < 0)
nsig = 6;
if (nsig < 1)
nsig = 1;
ec_pr(x, 1, 1);
if (ec_exp < -3 || ec_exp > nsig)
e_print(x, nsig-1);
else {
prec = nsig - ec_exp;
f_print(x, prec);
}
}
/*
* given x, ndig
* if ndig is > 0, indicates number of significant digits
* else -ndig is number of digits we want to the right of dec. pt.
* return the following:
* appropriate number of digits of significance in ec_buf
* ec_sign true if x was negative
* ec_exp indicates the decimal point relative to leftmost digit
*/
static
ec_pr(x, ndig, trunc)
float x;
{
int isneg;
int nhave;
long part;
int exp, newexp;
int ndigcpy = ndig;
float rem;
char tbuf[20];
/* ndig must be >= 1 and <= MAXEC */
if (x < 0.0) {
isneg = 1;
x = -x;
} else
isneg = 0;
/* get some digits */
somedig(x, &part, &rem, &exp);
sprintf(ec_buf, "%ld", part);
nhave = strlen(ec_buf);
exp = nhave + exp;
if (ndig <= 0) {
ndig = -ndig;
ndig += exp;
}
if (ndig < 1)
ndig = 1;
else if (ndig > MAXEC)
ndig = MAXEC;
/* get some more digits */
while (nhave < ndig+1 && nhave < MAXEC) {
if (rem == 0.0) {
while (nhave < ndig+1)
ec_buf[nhave++] = '0';
ec_buf[nhave] = 0;
break;
}
x = rem;
somedig(x, &part, &rem, &newexp);
sprintf(tbuf, "%ld", part);
newexp = strlen(tbuf) + newexp;
while (newexp++)
ec_buf[nhave++] = '0';
strcpy(&ec_buf[nhave], tbuf);
nhave = strlen(ec_buf);
}
if (fround(ndig, trunc))
{ if (ndigcpy <= 0)
strcpy(ec_buf+ndig, "0");
exp++;
}
ec_sign = isneg;
ec_exp = exp;
}
static
fround(n, trunc)
{
char *p;
int oflo = 0;
p = &ec_buf[n];
if (*p >= '5' && !trunc) {
p--;
while (p >= ec_buf) {
*p += 1;
if (*p < '9')
goto done;
*p = '0';
p--;
}
ec_buf[0] = '1';
oflo = 1;
}
done:
ec_buf[n] = 0;
return oflo;
}
static
somedig(x, lp, remp, expp)
float x;
long *lp;
float *remp;
int *expp;
{
int bexp, dexp;
long ipart;
float rem;
bexp = fgetexp(x);
dexp = 0;
while (bexp > 31) {
x *= 1E-3;
dexp += 3;
bexp = fgetexp(x);
}
while (bexp < 10) {
x *= 1E3;
dexp -= 3;
if (dexp < -24) {
ipart = 0;
dexp = 0;
rem = 0.0;
goto iszero;
}
bexp = fgetexp(x);
}
fsplit(x, &ipart, &rem);
iszero:
*lp = ipart;
*remp = rem;
*expp = dexp;
}
static
fgetexp(x)
float x;
{
char *p;
int i;
p = (char *)&x;
i = p[3] & 0x7f;
i -= 0x40;
return i;
}
static
fsplit(x, vp, rp)
float x, *rp;
long *vp;
{
long ival;
float rem;
int bexp, neg;
ival = *(long *)&x;
neg = ival & 0x80;
ival &= ~0xff;
bexp = fgetexp(x);
if (bexp < 1) {
ival = 0;
rem = x;
} else {
ival = (unsigned long)ival >> (32-bexp);
if (neg)
ival = -ival;
rem = x - (float)ival;
}
*vp = ival;
*rp = rem;
}