Merge pull request #3 from heuripedes/master
[picodrive.git] / platform / gp2x / code940 / uClibc / s_scalbn.c
1 /* @(#)s_scalbn.c 5.1 93/09/24 */
2 /*
3  * ====================================================
4  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
5  *
6  * Developed at SunPro, a Sun Microsystems, Inc. business.
7  * Permission to use, copy, modify, and distribute this
8  * software is freely granted, provided that this notice
9  * is preserved.
10  * ====================================================
11  */
12
13 #if defined(LIBM_SCCS) && !defined(lint)
14 static char rcsid[] = "$NetBSD: s_scalbn.c,v 1.8 1995/05/10 20:48:08 jtc Exp $";
15 #endif
16
17 /*
18  * scalbn (double x, int n)
19  * scalbn(x,n) returns x* 2**n  computed by  exponent
20  * manipulation rather than by actually performing an
21  * exponentiation or a multiplication.
22  */
23
24 #include "math.h"
25 #include "math_private.h"
26
27 #ifdef __STDC__
28 static const double
29 #else
30 static double
31 #endif
32 two54   =  1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
33 twom54  =  5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */
34 huge   = 1.0e+300,
35 tiny   = 1.0e-300;
36
37 #ifdef __STDC__
38         double scalbn (double x, int n)
39 #else
40         double scalbn (x,n)
41         double x; int n;
42 #endif
43 {
44         int32_t k,hx,lx;
45         EXTRACT_WORDS(hx,lx,x);
46         k = (hx&0x7ff00000)>>20;                /* extract exponent */
47         if (k==0) {                             /* 0 or subnormal x */
48             if ((lx|(hx&0x7fffffff))==0) return x; /* +-0 */
49             x *= two54;
50             GET_HIGH_WORD(hx,x);
51             k = ((hx&0x7ff00000)>>20) - 54;
52             if (n< -50000) return tiny*x;       /*underflow*/
53             }
54         if (k==0x7ff) return x+x;               /* NaN or Inf */
55         k = k+n;
56         if (k >  0x7fe) return huge*copysign(huge,x); /* overflow  */
57         if (k > 0)                              /* normal result */
58             {SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20)); return x;}
59         if (k <= -54) {
60             if (n > 50000)      /* in case integer overflow in n+k */
61                 return huge*copysign(huge,x);   /*overflow*/
62             else return tiny*copysign(tiny,x);  /*underflow*/
63         }
64         k += 54;                                /* subnormal result */
65         SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20));
66         return x*twom54;
67 }