s_scalbnf.c revision 97409 
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: head/lib/msun/src/s_scalbnf.c 97409 2002-05-28 17:51:46Z alfred $";
18#endif
19
20#include "math.h"
21#include "math_private.h"
22
23static const float
24two25   =  3.355443200e+07,	/* 0x4c000000 */
25twom25  =  2.9802322388e-08,	/* 0x33000000 */
26huge   = 1.0e+30,
27tiny   = 1.0e-30;
28
29	float scalbnf (float x, int n)
30{
31	int32_t k,ix;
32	GET_FLOAT_WORD(ix,x);
33        k = (ix&0x7f800000)>>23;		/* extract exponent */
34        if (k==0) {				/* 0 or subnormal x */
35            if ((ix&0x7fffffff)==0) return x; /* +-0 */
36	    x *= two25;
37	    GET_FLOAT_WORD(ix,x);
38	    k = ((ix&0x7f800000)>>23) - 25;
39            if (n< -50000) return tiny*x; 	/*underflow*/
40	    }
41        if (k==0xff) return x+x;		/* NaN or Inf */
42        k = k+n;
43        if (k >  0xfe) return huge*copysignf(huge,x); /* overflow  */
44        if (k > 0) 				/* normal result */
45	    {SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23)); return x;}
46        if (k <= -25)
47            if (n > 50000) 	/* in case integer overflow in n+k */
48		return huge*copysignf(huge,x);	/*overflow*/
49	    else return tiny*copysignf(tiny,x);	/*underflow*/
50        k += 25;				/* subnormal result */
51	SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23));
52        return x*twom25;
53}
54