1 /* sf_scalbn.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 #include "fdlibm.h"
17 #include <limits.h>
18 #include <float.h>
19 
20 #if INT_MAX > 50000
21 #define OVERFLOW_INT 50000
22 #else
23 #define OVERFLOW_INT 30000
24 #endif
25 
26 #ifdef __STDC__
27 static const float
28 #else
29 static float
30 #endif
31 two25   =  3.355443200e+07,	/* 0x4c000000 */
32 twom25  =  2.9802322388e-08,	/* 0x33000000 */
33 huge   = 1.0e+30,
34 tiny   = 1.0e-30;
35 
36 #ifdef __STDC__
scalbnf(float x,int n)37 	float scalbnf (float x, int n)
38 #else
39 	float scalbnf (x,n)
40 	float x; int n;
41 #endif
42 {
43 	__int32_t  k,ix;
44 	__uint32_t hx;
45 
46 	GET_FLOAT_WORD(ix,x);
47 	hx = ix&0x7fffffff;
48         k = hx>>23;		/* extract exponent */
49 	if (FLT_UWORD_IS_ZERO(hx))
50 	    return x;
51         if (!FLT_UWORD_IS_FINITE(hx))
52 	    return x+x;		/* NaN or Inf */
53         if (FLT_UWORD_IS_SUBNORMAL(hx)) {
54 	    x *= two25;
55 	    GET_FLOAT_WORD(ix,x);
56 	    k = ((ix&0x7f800000)>>23) - 25;
57             if (n< -50000) return tiny*x; 	/*underflow*/
58         }
59         k = k+n;
60         if (k > FLT_LARGEST_EXP) return huge*copysignf(huge,x); /* overflow  */
61         if (k > 0) 				/* normal result */
62 	    {SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23)); return x;}
63         if (k < FLT_SMALLEST_EXP) {
64             if (n > OVERFLOW_INT) 	/* in case integer overflow in n+k */
65 		return huge*copysignf(huge,x);	/*overflow*/
66 	    else return tiny*copysignf(tiny,x);	/*underflow*/
67         }
68         k += 25;				/* subnormal result */
69 	SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23));
70         return x*twom25;
71 }
72 
73 #ifdef _DOUBLE_IS_32BITS
74 
75 #ifdef __STDC__
scalbn(double x,int n)76 	double scalbn(double x, int n)
77 #else
78 	double scalbn(x,n)
79 	double x;
80 	int n;
81 #endif
82 {
83 	return (double) scalbnf((float) x, n);
84 }
85 
86 #endif /* defined(_DOUBLE_IS_32BITS) */
87