| 1 | /* |
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| 2 | * ==================================================== |
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| 3 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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| 4 | * |
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| 5 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
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| 6 | * Permission to use, copy, modify, and distribute this |
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| 7 | * software is freely granted, provided that this notice |
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| 8 | * is preserved. |
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| 9 | * ==================================================== |
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| 10 | */ |
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| 11 | |
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| 12 | /* |
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| 13 | * modf(double x, double *iptr) |
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| 14 | * return fraction part of x, and return x's integral part in *iptr. |
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| 15 | * Method: |
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| 16 | * Bit twiddling. |
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| 17 | * |
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| 18 | * Exception: |
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| 19 | * No exception. |
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| 20 | */ |
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| 21 | |
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| 22 | #include <math.h> |
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| 23 | #include <math_private.h> |
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| 24 | #include <libm-alias-double.h> |
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| 25 | #include <stdint.h> |
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| 26 | |
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| 27 | static const double one = 1.0; |
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| 28 | |
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| 29 | double |
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| 30 | __modf(double x, double *iptr) |
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| 31 | { |
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| 32 | int64_t i0; |
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| 33 | int32_t j0; |
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| 34 | EXTRACT_WORDS64(i0,x); |
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| 35 | j0 = ((i0>>52)&0x7ff)-0x3ff; /* exponent of x */ |
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| 36 | if(j0<52) { /* integer part in x */ |
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| 37 | if(j0<0) { /* |x|<1 */ |
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| 38 | /* *iptr = +-0 */ |
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| 39 | INSERT_WORDS64(*iptr,i0&UINT64_C(0x8000000000000000)); |
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| 40 | return x; |
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| 41 | } else { |
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| 42 | uint64_t i = UINT64_C(0x000fffffffffffff)>>j0; |
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| 43 | if((i0&i)==0) { /* x is integral */ |
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| 44 | *iptr = x; |
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| 45 | /* return +-0 */ |
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| 46 | INSERT_WORDS64(x,i0&UINT64_C(0x8000000000000000)); |
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| 47 | return x; |
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| 48 | } else { |
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| 49 | INSERT_WORDS64(*iptr,i0&(~i)); |
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| 50 | return x - *iptr; |
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| 51 | } |
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| 52 | } |
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| 53 | } else { /* no fraction part */ |
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| 54 | *iptr = x*one; |
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| 55 | /* We must handle NaNs separately. */ |
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| 56 | if (j0 == 0x400 && (i0 & UINT64_C(0xfffffffffffff))) |
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| 57 | return x*one; |
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| 58 | INSERT_WORDS64(x,i0&UINT64_C(0x8000000000000000)); /* return +-0 */ |
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| 59 | return x; |
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| 60 | } |
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| 61 | } |
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| 62 | #ifndef __modf |
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| 63 | libm_alias_double (__modf, modf) |
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| 64 | #endif |
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| 65 | |
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