windows-nt-4.0/private/fp32/tran/frexp.c

/***
*frexp.c - get mantissa and exponent of a floating point number
*
*	Copyright (c) 1991-1991, Microsoft Corporation.	All rights reserved.
*
*Purpose:
*
*Revision History:
*   8-24-91	GDP	written
*   1-13-92	GDP	support IEEE exceptions
*
*******************************************************************************/
#include <math.h>
#include <trans.h>

/***
*double frexp(double x, double *expptr)
*
*Purpose:
*   The nomalized fraction f is returned: .5<=f<1
*   The exponent is stored in the object pointed by expptr
*
*Entry:
*
*Exit:
*
*Exceptions:
*    NAN: domain error
*
*******************************************************************************/
double frexp(double x, int *expptr)
{
    unsigned int savedcw;
    double man;

    /* save user fp control word */
    savedcw = _maskfp();

    /* check for infinity or NAN */
    if (IS_D_SPECIAL(x)){
	*expptr = INT_NAN;
	switch (_sptype(x)) {
	case T_PINF:
	    return _except1(FP_I, OP_FREXP, x, D_INF, savedcw);
	case T_NINF:
	    return _except1(FP_I, OP_FREXP, x, -D_INF, savedcw);
	case T_QNAN:
	    return _handle_qnan1(OP_FREXP, x, savedcw);
	default: //T_SNAN
	    return _except1(FP_I, OP_FREXP, x, _s2qnan(x), savedcw);
	}
    }

    man = _decomp(x, expptr);
    RETURN(savedcw,man);
}