s_scalbnf.c revision 302408 
1/* s_scalbnf.c -- float version of s_scalbn.c.
2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
3 */
4
5/*
6 * ====================================================
7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
8 *
9 * Developed at SunPro, a Sun Microsystems, Inc. business.
10 * Permission to use, copy, modify, and distribute this
11 * software is freely granted, provided that this notice
12 * is preserved.
13 * ====================================================
14 */
15
16#ifndef lint
17static char rcsid[] = "$FreeBSD: stable/11/lib/msun/src/s_scalbnf.c 143205 2005-03-07 04:52:43Z das $";
18#endif
19
20#include <sys/cdefs.h>
21
22#include "math.h"
23#include "math_private.h"
24
25static const float
26two25   =  3.355443200e+07,	/* 0x4c000000 */
27twom25  =  2.9802322388e-08,	/* 0x33000000 */
28huge   = 1.0e+30,
29tiny   = 1.0e-30;
30
31float
32scalbnf (float x, int n)
33{
34	int32_t k,ix;
35	GET_FLOAT_WORD(ix,x);
36        k = (ix&0x7f800000)>>23;		/* extract exponent */
37        if (k==0) {				/* 0 or subnormal x */
38            if ((ix&0x7fffffff)==0) return x; /* +-0 */
39	    x *= two25;
40	    GET_FLOAT_WORD(ix,x);
41	    k = ((ix&0x7f800000)>>23) - 25;
42            if (n< -50000) return tiny*x; 	/*underflow*/
43	    }
44        if (k==0xff) return x+x;		/* NaN or Inf */
45        k = k+n;
46        if (k >  0xfe) return huge*copysignf(huge,x); /* overflow  */
47        if (k > 0) 				/* normal result */
48	    {SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23)); return x;}
49        if (k <= -25)
50            if (n > 50000) 	/* in case integer overflow in n+k */
51		return huge*copysignf(huge,x);	/*overflow*/
52	    else return tiny*copysignf(tiny,x);	/*underflow*/
53        k += 25;				/* subnormal result */
54	SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23));
55        return x*twom25;
56}
57
58__strong_reference(scalbnf, ldexpf);
59