SDL  2.0
s_scalbn.c
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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 const char rcsid[] =
15  "$NetBSD: s_scalbn.c,v 1.8 1995/05/10 20:48:08 jtc Exp $";
16 #endif
17 
18 /*
19  * scalbn (double x, int n)
20  * scalbn(x,n) returns x* 2**n computed by exponent
21  * manipulation rather than by actually performing an
22  * exponentiation or a multiplication.
23  */
24 
25 #include "math_libm.h"
26 #include "math_private.h"
27 
29 #ifdef __STDC__
30  static const double
31 #else
32  static double
33 #endif
34  two54 = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
35  twom54 = 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */
36  huge_val = 1.0e+300, tiny = 1.0e-300;
37 
39 #ifdef __STDC__
40  double scalbn(double x, int n)
41 #else
42  double scalbn(x, n)
43  double x;
44  int n;
45 #endif
46 {
47  int32_t k, hx, lx;
48  EXTRACT_WORDS(hx, lx, x);
49  k = (hx & 0x7ff00000) >> 20; /* extract exponent */
50  if (k == 0) { /* 0 or subnormal x */
51  if ((lx | (hx & 0x7fffffff)) == 0)
52  return x; /* +-0 */
53  x *= two54;
54  GET_HIGH_WORD(hx, x);
55  k = ((hx & 0x7ff00000) >> 20) - 54;
56  if (n < -50000)
57  return tiny * x; /* underflow */
58  }
59  if (k == 0x7ff)
60  return x + x; /* NaN or Inf */
61  k = k + n;
62  if (k > 0x7fe)
63  return huge_val * copysign(huge_val, x); /* overflow */
64  if (k > 0) { /* normal result */
65  SET_HIGH_WORD(x, (hx & 0x800fffff) | (k << 20));
66  return x;
67  }
68  if (k <= -54) {
69  if (n > 50000) /* in case integer overflow in n+k */
70  return huge_val * copysign(huge_val, x); /* overflow */
71  else
72  return tiny * copysign(tiny, x); /* underflow */
73  }
74  k += 54; /* subnormal result */
75  SET_HIGH_WORD(x, (hx & 0x800fffff) | (k << 20));
76  return x * twom54;
77 }
78 
#define GET_HIGH_WORD(i, d)
Definition: math_private.h:103
GLdouble n
signed int int32_t
GLint GLint GLint GLint GLint x
Definition: SDL_opengl.h:1567
tiny
Definition: e_pow.c:79
#define SET_HIGH_WORD(d, v)
Definition: math_private.h:131
#define scalbn
Definition: math_private.h:40
libm_hidden_proto(copysign)
Definition: s_scalbn.c:28
#define libm_hidden_def(x)
Definition: math_private.h:26
#define EXTRACT_WORDS(ix0, ix1, d)
Definition: math_private.h:93
return Display return Display Bool Bool int int int return Display XEvent Bool(*) XPointer return Display return Display Drawable _Xconst char unsigned int unsigned int return Display Pixmap Pixmap XColor XColor unsigned int unsigned int return Display _Xconst char char int char return Display Visual unsigned int int int char unsigned int unsigned int int int return Display Window Cursor return Display Window return Display Drawable GC int int unsigned int unsigned int return Display Drawable GC int int _Xconst char int return Display Drawable GC int int unsigned int unsigned int return Display return Display Cursor return Display GC return XModifierKeymap return char Display Window int return Display return Display Atom return Display Window XWindowAttributes return Display Window return Display XEvent Bool(*) XPointer return Display Window Bool unsigned int int int Window Cursor Time return Display Window int return KeySym return Display _Xconst char Bool return Display _Xconst char return XKeyEvent char int KeySym XComposeStatus return Display int int int XVisualInfo return Display Window int int return _Xconst char return Display XEvent return Display Drawable GC XImage int int int int unsigned int unsigned int return Display Window Window Window int int int int unsigned int return Display Window Window int int return Display Window unsigned int unsigned int return Display Window Bool long XEvent return Display GC unsigned long return Display Window int Time return Display Window Window return Display Window unsigned long return Display Window XSizeHints Display Colormap XColor int return char int XTextProperty return XFontStruct _Xconst char int int int int XCharStruct return Display Window return Display Time return Display Colormap return Display Window Window int int unsigned int unsigned int int int return Display Window int return XExtensionInfo Display char XExtensionHooks int XPointer return XExtensionInfo XExtensionInfo Display return Display return Display unsigned long Display GC Display char long Display xReply int Bool return Display Bool return Display int SDL_X11_XESetEventToWireRetType return Display Window Window Window Window unsigned int return Display XShmSegmentInfo return Display Drawable GC XImage int int int int unsigned int unsigned int Boo k)
Definition: SDL_x11sym.h:211
static double two54
Definition: e_log.c:79
huge_val
Definition: e_pow.c:79
#define copysign
Definition: math_private.h:34