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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 | FUNCTION |
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| 16 | <<modf>>, <<modff>>---split fractional and integer parts |
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| 17 | |
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| 18 | INDEX |
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| 19 | modf |
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| 20 | INDEX |
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| 21 | modff |
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| 22 | |
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| 23 | SYNOPSIS |
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| 24 | #include <math.h> |
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| 25 | double modf(double <[val]>, double *<[ipart]>); |
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| 26 | float modff(float <[val]>, float *<[ipart]>); |
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| 27 | |
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| 28 | DESCRIPTION |
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| 29 | <<modf>> splits the double <[val]> apart into an integer part |
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| 30 | and a fractional part, returning the fractional part and |
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| 31 | storing the integer part in <<*<[ipart]>>>. No rounding |
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| 32 | whatsoever is done; the sum of the integer and fractional |
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| 33 | parts is guaranteed to be exactly equal to <[val]>. That |
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| 34 | is, if <[realpart]> = modf(<[val]>, &<[intpart]>); then |
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| 35 | `<<<[realpart]>+<[intpart]>>>' is the same as <[val]>. |
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| 36 | <<modff>> is identical, save that it takes and returns |
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| 37 | <<float>> rather than <<double>> values. |
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| 38 | |
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| 39 | RETURNS |
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| 40 | The fractional part is returned. Each result has the same |
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| 41 | sign as the supplied argument <[val]>. |
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| 42 | |
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| 43 | PORTABILITY |
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| 44 | <<modf>> is ANSI C. <<modff>> is an extension. |
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| 45 | |
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| 46 | QUICKREF |
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| 47 | modf ansi pure |
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| 48 | modff - pure |
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| 49 | |
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| 50 | */ |
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| 51 | |
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| 52 | /* |
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| 53 | * modf(double x, double *iptr) |
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| 54 | * return fraction part of x, and return x's integral part in *iptr. |
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| 55 | * Method: |
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| 56 | * Bit twiddling. |
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| 57 | * |
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| 58 | * Exception: |
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| 59 | * No exception. |
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| 60 | */ |
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| 61 | |
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| 62 | #include "fdlibm.h" |
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| 63 | |
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| 64 | #ifndef _DOUBLE_IS_32BITS |
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| 65 | |
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| 66 | #ifdef __STDC__ |
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| 67 | static const double one = 1.0; |
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| 68 | #else |
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| 69 | static double one = 1.0; |
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| 70 | #endif |
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| 71 | |
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| 72 | #ifdef __STDC__ |
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| 73 | double modf(double x, double *iptr) |
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| 74 | #else |
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| 75 | double modf(x, iptr) |
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| 76 | double x,*iptr; |
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| 77 | #endif |
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| 78 | { |
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| 79 | __int32_t i0,i1,j0; |
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| 80 | __uint32_t i; |
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| 81 | EXTRACT_WORDS(i0,i1,x); |
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| 82 | j0 = ((i0>>20)&0x7ff)-0x3ff; /* exponent of x */ |
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| 83 | if(j0<20) { /* integer part in high x */ |
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| 84 | if(j0<0) { /* |x|<1 */ |
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| 85 | INSERT_WORDS(*iptr,i0&0x80000000,0); /* *iptr = +-0 */ |
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| 86 | return x; |
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| 87 | } else { |
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| 88 | i = (0x000fffff)>>j0; |
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| 89 | if(((i0&i)|i1)==0) { /* x is integral */ |
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| 90 | __uint32_t high; |
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| 91 | *iptr = x; |
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| 92 | GET_HIGH_WORD(high,x); |
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| 93 | INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */ |
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| 94 | return x; |
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| 95 | } else { |
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| 96 | INSERT_WORDS(*iptr,i0&(~i),0); |
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| 97 | return x - *iptr; |
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| 98 | } |
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| 99 | } |
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| 100 | } else if (j0>51) { /* no fraction part */ |
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| 101 | __uint32_t high; |
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| 102 | *iptr = x*one; |
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| 103 | GET_HIGH_WORD(high,x); |
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| 104 | INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */ |
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| 105 | return x; |
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| 106 | } else { /* fraction part in low x */ |
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| 107 | i = ((__uint32_t)(0xffffffff))>>(j0-20); |
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| 108 | if((i1&i)==0) { /* x is integral */ |
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| 109 | __uint32_t high; |
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| 110 | *iptr = x; |
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| 111 | GET_HIGH_WORD(high,x); |
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| 112 | INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */ |
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| 113 | return x; |
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| 114 | } else { |
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| 115 | INSERT_WORDS(*iptr,i0,i1&(~i)); |
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| 116 | return x - *iptr; |
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| 117 | } |
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| 118 | } |
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| 119 | } |
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| 120 | |
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| 121 | #endif /* _DOUBLE_IS_32BITS */ |
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