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| Rev | Author | Line No. | Line |
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| 2 | pj | 1 | /* @(#)s_ilogb.c 5.1 93/09/24 */ |
| 2 | /* |
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| 3 | * ==================================================== |
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| 4 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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| 5 | * |
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| 6 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
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| 7 | * Permission to use, copy, modify, and distribute this |
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| 8 | * software is freely granted, provided that this notice |
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| 9 | * is preserved. |
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| 10 | * ==================================================== |
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| 11 | */ |
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| 12 | |||
| 13 | #ifndef lint |
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| 14 | static char rcsid[] = "$\Id: s_ilogb.c,v 1.2.6.1 1997/02/23 11:03:19 joerg Exp $"; |
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| 15 | #endif |
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| 16 | |||
| 17 | /* ilogb(double x) |
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| 18 | * return the binary exponent of non-zero x |
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| 19 | * ilogb(0) = 0x80000001 |
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| 20 | * ilogb(inf/NaN) = 0x7fffffff (no signal is raised) |
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| 21 | */ |
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| 22 | |||
| 23 | #include "math.h" |
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| 24 | #include "math_private.h" |
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| 25 | |||
| 26 | #ifdef __STDC__ |
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| 27 | int __generic_ilogb(double x) |
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| 28 | #else |
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| 29 | int __generic_ilogb(x) |
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| 30 | double x; |
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| 31 | #endif |
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| 32 | { |
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| 33 | int32_t hx,lx,ix; |
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| 34 | |||
| 35 | EXTRACT_WORDS(hx,lx,x); |
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| 36 | hx &= 0x7fffffff; |
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| 37 | if(hx<0x00100000) { |
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| 38 | if((hx|lx)==0) |
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| 39 | return 0x80000001; /* ilogb(0) = 0x80000001 */ |
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| 40 | else /* subnormal x */ |
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| 41 | if(hx==0) { |
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| 42 | for (ix = -1043; lx>0; lx<<=1) ix -=1; |
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| 43 | } else { |
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| 44 | for (ix = -1022,hx<<=11; hx>0; hx<<=1) ix -=1; |
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| 45 | } |
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| 46 | return ix; |
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| 47 | } |
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| 48 | else if (hx<0x7ff00000) return (hx>>20)-1023; |
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| 49 | else return 0x7fffffff; |
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| 50 | } |