path: root/src/math/s_floorf.c

/* s_floorf.c -- float version of s_floor.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.
 * ====================================================
 */

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

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

static const float huge = 1.0e30;

float
floorf(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>(float)0.0) {/* return 0*sign(x) if |x|<1 */
                    if(i0>=0) {i0=0;}
                    else if((i0&0x7fffffff)!=0)
                        { i0=0xbf800000;}
                }
            } else {
                i = (0x007fffff)>>j0;
                if((i0&i)==0) return x; /* x is integral */
                if(huge+x>(float)0.0) { /* raise inexact flag */
                    if(i0<0) i0 += (0x00800000)>>j0;
                    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;
}