You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
62 lines
1.5 KiB
62 lines
1.5 KiB
/* _FDscale function -- IEEE 754 version */
|
|
#include "wctype.h"
|
|
#include "xmath.h"
|
|
_STD_BEGIN
|
|
|
|
_CRTIMP2 short _FDscale(float *px, long lexp)
|
|
{ /* scale *px by 2^xexp with checking */
|
|
unsigned short *ps = (unsigned short *)px;
|
|
short xchar = (ps[_F0] & _FMASK) >> _FOFF;
|
|
|
|
if (xchar == _FMAX)
|
|
return ((ps[_F0] & _FFRAC) != 0 || ps[_F1] != 0
|
|
? NAN : INF);
|
|
else if (xchar == 0 && 0 < (xchar = _FDnorm(ps)))
|
|
return (0);
|
|
lexp += xchar;
|
|
if (_FMAX <= lexp)
|
|
{ /* overflow, return +/-INF */
|
|
*px = ps[_F0] & _FSIGN ? -_FInf._F : _FInf._F;
|
|
return (INF);
|
|
}
|
|
else if (0 < lexp)
|
|
{ /* finite result, repack */
|
|
ps[_F0] = ps[_F0] & ~_FMASK | (short)lexp << _FOFF;
|
|
return (FINITE);
|
|
}
|
|
else
|
|
{ /* denormalized, scale */
|
|
unsigned short sign = ps[_F0] & _FSIGN;
|
|
|
|
ps[_F0] = 1 << _FOFF | ps[_F0] & _FFRAC;
|
|
if (--lexp < -(16+_FOFF))
|
|
{ /* underflow, return +/-0 */
|
|
ps[_F0] = sign, ps[_F1] = 0;
|
|
return (0);
|
|
}
|
|
else
|
|
{ /* nonzero, align fraction */
|
|
short xexp = (short)lexp;
|
|
if (xexp <= -16)
|
|
ps[_F1] = ps[_F0], ps[_F0] = 0, xexp += 16;
|
|
if ((xexp = -xexp) != 0)
|
|
{ /* scale by bits */
|
|
ps[_F1] = ps[_F1] >> xexp
|
|
| ps[_F0] << (16 - xexp);
|
|
ps[_F0] >>= xexp;
|
|
}
|
|
ps[_F0] |= sign;
|
|
return (FINITE);
|
|
}
|
|
}
|
|
}
|
|
_STD_END
|
|
|
|
/*
|
|
* Copyright (c) 1994 by P.J. Plauger. ALL RIGHTS RESERVED.
|
|
* Consult your license regarding permissions and restrictions.
|
|
*/
|
|
|
|
/*
|
|
941029 pjp: added _STD machinery
|
|
*/
|