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| 4349 | Serge | 1 | |
| 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 | |||
| 14 | FUNCTION |
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| 15 | < |
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| 16 | INDEX |
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| 17 | ilogb |
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| 18 | INDEX |
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| 19 | ilogbf |
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| 20 | |||
| 21 | |||
| 22 | #include |
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| 23 | int ilogb(double <[val]>); |
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| 24 | int ilogbf(float <[val]>); |
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| 25 | |||
| 26 | |||
| 27 | #include |
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| 28 | int ilogb(<[val]>) |
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| 29 | double <[val]>; |
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| 30 | |||
| 31 | |||
| 32 | float <[val]>; |
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| 33 | |||
| 34 | |||
| 35 | |||
| 36 | |||
| 37 | |||
| 38 | 2**<[p]>. < |
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| 39 | <[val]>, and return <[p]>. The functions < |
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| 40 | < |
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| 41 | return <[m]>. |
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| 42 | |||
| 43 | |||
| 44 | |||
| 45 | |||
| 46 | floating-point argument. |
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| 47 | If <[val]> is <<0>>, they return < |
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| 48 | If <[val]> is infinite, they return < |
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| 49 | If <[val]> is NaN, they return < |
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| 50 | (< |
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| 51 | defined as INT_MIN or INT_MAX from limits.h. The value of FP_ILOGB0 may be |
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| 52 | either INT_MIN or -INT_MAX. The value of FP_ILOGBNAN may be either INT_MAX or |
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| 53 | INT_MIN.) |
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| 54 | |||
| 55 | |||
| 56 | @comment behavior of much of the Newlib math library. |
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| 57 | @comment BUGS |
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| 58 | @comment On errors, errno is not set per C99 and POSIX requirements even if |
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| 59 | @comment (math_errhandling & MATH_ERRNO) is non-zero. |
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| 60 | |||
| 61 | |||
| 62 | C99, POSIX |
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| 63 | */ |
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| 64 | |||
| 65 | |||
| 66 | * return the binary exponent of non-zero x |
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| 67 | * ilogb(0) = 0x80000001 |
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| 68 | * ilogb(inf/NaN) = 0x7fffffff (no signal is raised) |
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| 69 | */ |
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| 70 | |||
| 71 | |||
| 72 | #include "fdlibm.h" |
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| 73 | |||
| 74 | |||
| 75 | |||
| 76 | |||
| 77 | int ilogb(double x) |
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| 78 | #else |
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| 79 | int ilogb(x) |
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| 80 | double x; |
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| 81 | #endif |
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| 82 | { |
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| 83 | __int32_t hx,lx,ix; |
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| 84 | |||
| 85 | |||
| 86 | hx &= 0x7fffffff; |
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| 87 | if(hx<0x00100000) { |
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| 88 | if((hx|lx)==0) |
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| 89 | return FP_ILOGB0; /* ilogb(0) = special case error */ |
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| 90 | else /* subnormal x */ |
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| 91 | if(hx==0) { |
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| 92 | for (ix = -1043; lx>0; lx<<=1) ix -=1; |
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| 93 | } else { |
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| 94 | for (ix = -1022,hx<<=11; hx>0; hx<<=1) ix -=1; |
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| 95 | } |
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| 96 | return ix; |
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| 97 | } |
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| 98 | else if (hx<0x7ff00000) return (hx>>20)-1023; |
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| 99 | #if FP_ILOGBNAN != INT_MAX |
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| 100 | else if (hx>0x7ff00000) return FP_ILOGBNAN; /* NAN */ |
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| 101 | #endif |
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| 102 | else return INT_MAX; /* infinite (or, possibly, NAN) */ |
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| 103 | } |
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| 104 | |||
| 105 | |||
| 106 |