s_scalbnf.c

Go to the documentation of this file.

/* s_scalbnf.c -- float version of s_scalbn.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.
 * ====================================================
 */

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

static const float
two25   =  3.355443200e+07, /* 0x4c000000 */
twom25  =  2.9802322388e-08,    /* 0x33000000 */
huge   = 1.0e+30,
tiny   = 1.0e-30;

float
scalbnf(float x, int n)
{
    int32_t k,ix;
    GET_FLOAT_WORD(ix,x);
        k = (ix&0x7f800000)>>23;        /* extract exponent */
        if (k==0) {             /* 0 or subnormal x */
            if ((ix&0x7fffffff)==0) return x; /* +-0 */
        x *= two25;
        GET_FLOAT_WORD(ix,x);
        k = ((ix&0x7f800000)>>23) - 25; 
            if (n< -50000) return tiny*x;   /*underflow*/
        }
        if (k==0xff) return x+x;        /* NaN or Inf */
        k = k+n; 
        if (k >  0xfe) return huge*copysignf(huge,x); /* overflow  */
        if (k > 0)              /* normal result */
        {SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23)); return x;}
        if (k <= -25)
            if (n > 50000)  /* in case integer overflow in n+k */
        return huge*copysignf(huge,x);  /*overflow*/
        else return tiny*copysignf(tiny,x); /*underflow*/
        k += 25;                /* subnormal result */
    SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23));
        return x*twom25;
}

float
ldexpf(float x, int n)
{
    return scalbnf(x, n);
}