src/math/s_truncf.c

/* @(#)s_floor.c 5.1 93/09/24 */
/*
 * ====================================================
 * 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.
 * ====================================================
 */

/*
 * truncf(x)
 * Return x rounded toward 0 to integral value
 * Method:
 *      Bit twiddling.
 * Exception:
 *      Inexact flag raised if x not equal to truncf(x).
 */

#include <math.h>
#include "math_private.h"

static const float huge = 1.0e30F;

float
truncf(float x)
{
        int32_t i0,j0;
        uint32_t i;
        GET_FLOAT_WORD(i0,x);
        j0 = ((i0>>23)&0xff)-0x7f;
        if(j0<23) {
            if(j0<0) {  /* raise inexact if x != 0 */
                if(huge+x>0.0F)         /* |x|<1, so return 0*sign(x) */
                    i0 &= 0x80000000;
            } else {
                i = (0x007fffff)>>j0;
                if((i0&i)==0) return x; /* x is integral */
                if(huge+x>0.0F)         /* raise inexact flag */
                    i0 &= (~i);
            }
        } else {
            if(j0==0x80) return x+x;    /* inf or NaN */
            else return x;              /* x is integral */
        }
        SET_FLOAT_WORD(x,i0);
        return x;
}