POK
ilogb.c
1 /*
2  * POK header
3  *
4  * The following file is a part of the POK project. Any modification should
5  * made according to the POK licence. You CANNOT use this file or a part of
6  * this file is this part of a file for your own project
7  *
8  * For more information on the POK licence, please see our LICENCE FILE
9  *
10  * Please follow the coding guidelines described in doc/CODING_GUIDELINES
11  *
12  * Copyright (c) 2007-2009 POK team
13  *
14  * Created by julien on Fri Jan 30 14:41:34 2009
15  */
16 
17 /* @(#)s_ilogb.c 5.1 93/09/24 */
18 /*
19  * ====================================================
20  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
21  *
22  * Developed at SunPro, a Sun Microsystems, Inc. business.
23  * Permission to use, copy, modify, and distribute this
24  * software is freely granted, provided that this notice
25  * is preserved.
26  * ====================================================
27  */
28 
29 /* ilogb(double x)
30  * return the binary exponent of non-zero x
31  * ilogb(0) = 0x80000001
32  * ilogb(inf/NaN) = 0x7fffffff (no signal is raised)
33  */
34 
35 #ifdef POK_NEEDS_LIBMATH
36 
37 #include <libm.h>
38 #include "math_private.h"
39 
40 int
41 ilogb(double x)
42 {
43  int32_t hx,lx,ix;
44 
45  GET_HIGH_WORD(hx,x);
46  hx &= 0x7fffffff;
47  if(hx<0x00100000) {
48  GET_LOW_WORD(lx,x);
49  if((hx|lx)==0)
50  return 0x80000001; /* ilogb(0) = 0x80000001 */
51  else /* subnormal x */
52  if(hx==0) {
53  for (ix = -1043; lx>0; lx<<=1) ix -=1;
54  } else {
55  for (ix = -1022,hx<<=11; hx>0; hx<<=1) ix -=1;
56  }
57  return ix;
58  }
59  else if (hx<0x7ff00000) return (hx>>20)-1023;
60  else return 0x7fffffff;
61 }
62 
63 #endif