s_floorf.c

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/* 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,jj0;
    u_int32_t i;
    GET_FLOAT_WORD(i0,x);
    jj0 = ((i0>>23)&0xff)-0x7f;
    if(jj0<23) {
        if(jj0<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)>>jj0;
        if((i0&i)==0) return x; /* x is integral */
        if(huge+x>(float)0.0) { /* raise inexact flag */
            if(i0<0) i0 += (0x00800000)>>jj0;
            i0 &= (~i);
        }
        }
    } else {
        if(jj0==0x80) return x+x;   /* inf or NaN */
        else return x;      /* x is integral */
    }
    SET_FLOAT_WORD(x,i0);
    return x;
}