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73 lines
1.8 KiB
C
73 lines
1.8 KiB
C
/* @(#)s_modf.c 5.1 93/09/24 */
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/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunPro, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*/
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/*
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* modfl(long double x, long double *iptr)
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* return fraction part of x, and return x's integral part in *iptr.
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* Method:
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* Bit twiddling.
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*
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* Exception:
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* No exception.
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*/
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#include <math.h>
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#include "math_private.h"
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static const long double one = 1.0;
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long double
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modfl(long double x, long double *iptr)
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{
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int64_t i0,i1,jj0;
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u_int64_t i;
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GET_LDOUBLE_WORDS64(i0,i1,x);
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jj0 = ((i0>>48)&0x7fff)-0x3fff; /* exponent of x */
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if(jj0<48) { /* integer part in high x */
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if(jj0<0) { /* |x|<1 */
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/* *iptr = +-0 */
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SET_LDOUBLE_WORDS64(*iptr,i0&0x8000000000000000ULL,0);
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return x;
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} else {
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i = (0x0000ffffffffffffLL)>>jj0;
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if(((i0&i)|i1)==0) { /* x is integral */
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*iptr = x;
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/* return +-0 */
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SET_LDOUBLE_WORDS64(x,i0&0x8000000000000000ULL,0);
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return x;
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} else {
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SET_LDOUBLE_WORDS64(*iptr,i0&(~i),0);
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return x - *iptr;
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}
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}
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} else if (jj0>111) { /* no fraction part */
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*iptr = x*one;
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/* We must handle NaNs separately. */
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if (jj0 == 0x4000 && ((i0 & 0x0000ffffffffffffLL) | i1))
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return x*one;
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/* return +-0 */
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SET_LDOUBLE_WORDS64(x,i0&0x8000000000000000ULL,0);
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return x;
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} else { /* fraction part in low x */
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i = -1ULL>>(jj0-48);
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if((i1&i)==0) { /* x is integral */
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*iptr = x;
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/* return +-0 */
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SET_LDOUBLE_WORDS64(x,i0&0x8000000000000000ULL,0);
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return x;
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} else {
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SET_LDOUBLE_WORDS64(*iptr,i0,i1&(~i));
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return x - *iptr;
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}
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}
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}
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