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2aa62f2b 1/* @(#)s_scalbn.c 5.1 93/09/24 */\r
2/*\r
3 * ====================================================\r
4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.\r
5 *\r
6 * Developed at SunPro, a Sun Microsystems, Inc. business.\r
7 * Permission to use, copy, modify, and distribute this\r
8 * software is freely granted, provided that this notice\r
9 * is preserved.\r
10 * ====================================================\r
11 */\r
12#include <LibConfig.h>\r
13#include <sys/EfiCdefs.h>\r
14#if defined(LIBM_SCCS) && !defined(lint)\r
15__RCSID("$NetBSD: s_scalbn.c,v 1.12 2002/05/26 22:01:58 wiz Exp $");\r
16#endif\r
17\r
18/*\r
19 * scalbn (double x, int n)\r
20 * scalbn(x,n) returns x* 2**n computed by exponent\r
21 * manipulation rather than by actually performing an\r
22 * exponentiation or a multiplication.\r
23 */\r
24\r
25#include "math.h"\r
26#include "math_private.h"\r
27\r
28static const double\r
29two54 = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */\r
30twom54 = 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */\r
31huge = 1.0e+300,\r
32tiny = 1.0e-300;\r
33\r
34double\r
35scalbn(double x, int n)\r
36{\r
37 int32_t k,hx,lx;\r
38 EXTRACT_WORDS(hx,lx,x);\r
39 k = (hx&0x7ff00000)>>20; /* extract exponent */\r
40 if (k==0) { /* 0 or subnormal x */\r
41 if ((lx|(hx&0x7fffffff))==0) return x; /* +-0 */\r
42 x *= two54;\r
43 GET_HIGH_WORD(hx,x);\r
44 k = ((hx&0x7ff00000)>>20) - 54;\r
45 if (n< -50000) return tiny*x; /*underflow*/\r
46 }\r
47 if (k==0x7ff) return x+x; /* NaN or Inf */\r
48 k = k+n;\r
49 if (k > 0x7fe) return huge*copysign(huge,x); /* overflow */\r
50 if (k > 0) /* normal result */\r
51 {SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20)); return x;}\r
52 if (k <= -54) {\r
53 if (n > 50000) /* in case integer overflow in n+k */\r
54 return huge*copysign(huge,x); /*overflow*/\r
55 else return tiny*copysign(tiny,x); /*underflow*/\r
56 }\r
57 k += 54; /* subnormal result */\r
58 SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20));\r
59 return x*twom54;\r
60}\r