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| 2 | /* @(#)s_modf.c 5.1 93/09/24 */ |
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| 3 | /* |
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| 4 | * ==================================================== |
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| 5 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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| 6 | * |
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| 7 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
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| 8 | * Permission to use, copy, modify, and distribute this |
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| 9 | * software is freely granted, provided that this notice |
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| 10 | * is preserved. |
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| 11 | * ==================================================== |
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| 12 | */ |
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| 13 | |
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| 14 | /* |
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| 15 | * modf(double x, double *iptr) |
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| 16 | * return fraction part of x, and return x's integral part in *iptr. |
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| 17 | * Method: |
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| 18 | * Bit twiddling. |
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| 19 | * |
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| 20 | * Exception: |
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| 21 | * No exception. |
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| 22 | */ |
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| 23 | |
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| 24 | #include <libm/fdlibm.h> |
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| 25 | |
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| 26 | #ifdef __STDC__ |
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| 27 | static const double one = 1.0; |
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| 28 | #else |
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| 29 | static double one = 1.0; |
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| 30 | #endif |
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| 31 | |
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| 32 | #ifdef __STDC__ |
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| 33 | double modf(double x, double *iptr) |
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| 34 | #else |
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| 35 | double modf(x, iptr) |
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| 36 | double x,*iptr; |
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| 37 | #endif |
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| 38 | { |
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| 39 | int i0,i1,n0,n1,j0; |
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| 40 | unsigned i; |
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| 41 | n0 = (*((int *)&one)>>29)^1; /* high word index */ |
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| 42 | n1 = 1-n0; |
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| 43 | i0 = *(n0+(int*)&x); /* high x */ |
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| 44 | i1 = *(n1+(int*)&x); /* low x */ |
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| 45 | j0 = ((i0>>20)&0x7ff)-0x3ff; /* exponent of x */ |
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| 46 | if(j0<20) { /* integer part in high x */ |
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| 47 | if(j0<0) { /* |x|<1 */ |
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| 48 | *(n0+(int*)iptr) = i0&0x80000000; |
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| 49 | *(n1+(int*)iptr) = 0; /* *iptr = +-0 */ |
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| 50 | return x; |
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| 51 | } else { |
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| 52 | i = (0x000fffff)>>j0; |
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| 53 | if(((i0&i)|i1)==0) { /* x is integral */ |
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| 54 | *iptr = x; |
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| 55 | *(n0+(int*)&x) &= 0x80000000; |
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| 56 | *(n1+(int*)&x) = 0; /* return +-0 */ |
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| 57 | return x; |
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| 58 | } else { |
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| 59 | *(n0+(int*)iptr) = i0&(~i); |
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| 60 | *(n1+(int*)iptr) = 0; |
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| 61 | return x - *iptr; |
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| 62 | } |
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| 63 | } |
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| 64 | } else if (j0>51) { /* no fraction part */ |
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| 65 | *iptr = x*one; |
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| 66 | *(n0+(int*)&x) &= 0x80000000; |
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| 67 | *(n1+(int*)&x) = 0; /* return +-0 */ |
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| 68 | return x; |
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| 69 | } else { /* fraction part in low x */ |
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| 70 | i = ((unsigned)(0xffffffff))>>(j0-20); |
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| 71 | if((i1&i)==0) { /* x is integral */ |
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| 72 | *iptr = x; |
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| 73 | *(n0+(int*)&x) &= 0x80000000; |
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| 74 | *(n1+(int*)&x) = 0; /* return +-0 */ |
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| 75 | return x; |
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| 76 | } else { |
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| 77 | *(n0+(int*)iptr) = i0; |
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| 78 | *(n1+(int*)iptr) = i1&(~i); |
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| 79 | return x - *iptr; |
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| 80 | } |
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| 81 | } |
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| 82 | } |
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