windows-server-2003/base/crts/fpw32/tran/modf.c

/***
*modf.c - modf()
*
*       Copyright (c) 1991-2001, Microsoft Corporation. All rights reserved.
*
*Purpose:
*
*Revision History:
*        8-24-91  GDP   written
*        1-13-92  GDP   support IEEE exceptions
*        6-23-92  GDP   modified special return values for NCEG conformance
*       02-06-95  JWM   Mac merge
*       01-26-01  PML   Pentium4 merge
*       02-28-01  PML   Make sure 0.0 fraction return has correct sign
*
*******************************************************************************/

#include <math.h>
#include <trans.h>
#include <float.h>

extern double _frnd(double);
extern double _copysign (double x, double y);

/***
*double modf(double x, double *intptr)
*
*Purpose:
*   Split x into fractional and integer part
*   The signed fractional portion is returned
*   The integer portion is stored as a floating point value at intptr
*
*Entry:
*
*Exit:
*
*Exceptions:
*    I
*******************************************************************************/
static  uintptr_t newcw = (ICW & ~IMCW_RC) | (IRC_CHOP & IMCW_RC);

#if !defined(_M_IX86)
double modf(double x, double *intptr)
#else
double _modf_default(double x, double *intptr)
#endif
{
    uintptr_t savedcw;
    double result,intpart;

    /* save user fp control word */
    savedcw = _ctrlfp(0, 0);     /* get old control word */
    _ctrlfp(newcw,IMCW);        /* round towards 0 */

    /* check for infinity or NAN */
    if (IS_D_SPECIAL(x)){
        *intptr = QNAN_MODF;
        switch (_sptype(x)) {
        case T_PINF:
        case T_NINF:
            *intptr = x;
            result = _copysign(0, x);
            RETURN(savedcw,result);
        case T_QNAN:
            *intptr = x;
            return _handle_qnan1(OP_MODF, x, savedcw);
        default: //T_SNAN
            result = _s2qnan(x);
            *intptr = result;
            return _except1(FP_I, OP_MODF, x, result, savedcw);
        }
    }

    intpart = _frnd(x); //fix needed: this may set the P exception flag
                        //and pollute the fp status word

    *intptr = intpart;
    result = x - intpart;

    if (result == 0.0) {
	/* Make sure fractional part of 0.0 has the correct sign */
	*D_EXP(result) |= (*D_EXP(x) & 0x8000);
    }

    RETURN(savedcw,result);
}