131 lines
2.6 KiB
C
131 lines
2.6 KiB
C
|
/***
|
||
|
|
*util.c - utilities for fp transcendentals
|
||
|
|
*
|
||
|
|
* Copyright (c) 1991-1991, Microsoft Corporation. All rights reserved.
|
||
|
|
*
|
||
|
|
*Purpose:
|
||
|
|
* _set_exp and _add_exp are as those defined in Cody & Waite
|
||
|
|
*
|
||
|
|
*Revision History:
|
||
|
|
* 08-15-91 GDP written
|
||
|
|
* 10-20-91 GDP removed _rint, unsafe_intrnd
|
||
|
|
* 02-05-92 GDP added _fpclass
|
||
|
|
* 03-27-92 GDP added _d_min
|
||
|
|
* 06-23-92 GDP added _d_mzero
|
||
|
|
*
|
||
|
|
*******************************************************************************/
|
||
|
|
#include "trans.h"
|
||
|
|
|
||
|
|
/* define special values */
|
||
|
|
|
||
|
|
_dbl _d_inf = {SET_DBL (0x7ff00000, 0x0) }; //positive infinity
|
||
|
|
_dbl _d_ind = {SET_DBL (D_IND_HI, D_IND_LO)}; //real indefinite
|
||
|
|
_dbl _d_max = {SET_DBL (0x7fefffff, 0xffffffff)}; //max double
|
||
|
|
_dbl _d_min = {SET_DBL (0x00100000, 0x00000000)}; //min normalized double
|
||
|
|
_dbl _d_mzero = {SET_DBL (0x80000000, 0x00000000)}; //negative zero
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
double _set_exp(double x, int exp)
|
||
|
|
/* does not check validity of exp */
|
||
|
|
{
|
||
|
|
double retval;
|
||
|
|
int biased_exp;
|
||
|
|
retval = x;
|
||
|
|
biased_exp = exp + D_BIASM1;
|
||
|
|
*D_EXP(retval) = (unsigned short) (*D_EXP(x) & 0x800f | (biased_exp << 4));
|
||
|
|
return retval;
|
||
|
|
}
|
||
|
|
|
||
|
|
|
||
|
|
int _get_exp(double x)
|
||
|
|
{
|
||
|
|
signed short exp;
|
||
|
|
exp = (signed short)((*D_EXP(x) & 0x7ff0) >> 4);
|
||
|
|
exp -= D_BIASM1; //unbias
|
||
|
|
return (int) exp;
|
||
|
|
}
|
||
|
|
|
||
|
|
|
||
|
|
double _add_exp(double x, int exp)
|
||
|
|
{
|
||
|
|
return _set_exp(x, INTEXP(x)+exp);
|
||
|
|
}
|
||
|
|
|
||
|
|
|
||
|
|
double _set_bexp(double x, int bexp)
|
||
|
|
/* does not check validity of bexp */
|
||
|
|
{
|
||
|
|
double retval;
|
||
|
|
retval = x;
|
||
|
|
*D_EXP(retval) = (unsigned short) (*D_EXP(x) & 0x800f | (bexp << 4));
|
||
|
|
return retval;
|
||
|
|
}
|
||
|
|
|
||
|
|
|
||
|
|
int _sptype(double x)
|
||
|
|
{
|
||
|
|
if (IS_D_INF(x))
|
||
|
|
return T_PINF;
|
||
|
|
if (IS_D_MINF(x))
|
||
|
|
return T_NINF;
|
||
|
|
if (IS_D_QNAN(x))
|
||
|
|
return T_QNAN;
|
||
|
|
if (IS_D_SNAN(x))
|
||
|
|
return T_SNAN;
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
/***
|
||
|
|
*double _decomp(double x, double *expptr)
|
||
|
|
*
|
||
|
|
*Purpose:
|
||
|
|
* decompose a number to a normalized mantisa and exponent
|
||
|
|
*
|
||
|
|
*Entry:
|
||
|
|
*
|
||
|
|
*Exit:
|
||
|
|
*
|
||
|
|
*Exceptions:
|
||
|
|
*
|
||
|
|
*******************************************************************************/
|
||
|
|
|
||
|
|
double _decomp(double x, int *pexp)
|
||
|
|
{
|
||
|
|
int exp;
|
||
|
|
double man;
|
||
|
|
|
||
|
|
if (x == 0) {
|
||
|
|
man = 0;
|
||
|
|
exp = 0;
|
||
|
|
}
|
||
|
|
else if (IS_D_DENORM(x)) {
|
||
|
|
int neg;
|
||
|
|
|
||
|
|
exp = 1-D_BIASM1;
|
||
|
|
neg = x < 0.0;
|
||
|
|
while((*D_EXP(x) & 0x0010) == 0) {
|
||
|
|
/* shift mantissa to the left until bit 52 is 1 */
|
||
|
|
(*D_HI(x)) <<= 1;
|
||
|
|
if (*D_LO(x) & 0x80000000)
|
||
|
|
(*D_HI(x)) |= 0x1;
|
||
|
|
(*D_LO(x)) <<= 1;
|
||
|
|
exp--;
|
||
|
|
}
|
||
|
|
(*D_EXP(x)) &= 0xffef; /* clear bit 52 */
|
||
|
|
if (neg) {
|
||
|
|
(*D_EXP(x)) |= 0x8000; /* set sign bit */
|
||
|
|
}
|
||
|
|
man = _set_exp(x,0);
|
||
|
|
}
|
||
|
|
else {
|
||
|
|
man = _set_exp(x,0);
|
||
|
|
exp = INTEXP(x);
|
||
|
|
}
|
||
|
|
|
||
|
|
*pexp = exp;
|
||
|
|
return man;
|
||
|
|
}
|