source: vendor/FreeBSD-msun/current/src/s_modff.c

/* s_modff.c -- float version of s_modf.c.
 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
 */

/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

#ifndef lint
static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_modff.c,v 1.7 2002/05/28 18:15:04 alfred Exp $";
#endif

#include "math.h"
#include "math_private.h"

static const float one = 1.0;

float
modff(float x, float *iptr)
{
        int32_t i0,j0;
        u_int32_t i;
        GET_FLOAT_WORD(i0,x);
        j0 = ((i0>>23)&0xff)-0x7f;      /* exponent of x */
        if(j0<23) {                     /* integer part in x */
            if(j0<0) {                  /* |x|<1 */
                SET_FLOAT_WORD(*iptr,i0&0x80000000);    /* *iptr = +-0 */
                return x;
            } else {
                i = (0x007fffff)>>j0;
                if((i0&i)==0) {                 /* x is integral */
                    u_int32_t ix;
                    *iptr = x;
                    GET_FLOAT_WORD(ix,x);
                    SET_FLOAT_WORD(x,ix&0x80000000);    /* return +-0 */
                    return x;
                } else {
                    SET_FLOAT_WORD(*iptr,i0&(~i));
                    return x - *iptr;
                }
            }
        } else {                        /* no fraction part */
            u_int32_t ix;
            *iptr = x*one;
            GET_FLOAT_WORD(ix,x);
            SET_FLOAT_WORD(x,ix&0x80000000);    /* return +-0 */
            return x;
        }
}