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80 lines
1.9 KiB
C
80 lines
1.9 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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#ifndef lint
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static char rcsid[] = "$FreeBSD$";
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#endif
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/*
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* modf(double x, 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 double one = 1.0;
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double
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modf(double x, double *iptr)
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{
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int32_t i0,i1,j0;
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u_int32_t i;
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EXTRACT_WORDS(i0,i1,x);
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j0 = ((i0>>20)&0x7ff)-0x3ff; /* exponent of x */
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if(j0<20) { /* integer part in high x */
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if(j0<0) { /* |x|<1 */
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INSERT_WORDS(*iptr,i0&0x80000000,0); /* *iptr = +-0 */
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return x;
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} else {
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i = (0x000fffff)>>j0;
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if(((i0&i)|i1)==0) { /* x is integral */
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u_int32_t high;
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*iptr = x;
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GET_HIGH_WORD(high,x);
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INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */
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return x;
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} else {
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INSERT_WORDS(*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 (j0>51) { /* no fraction part */
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u_int32_t high;
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if (j0 == 0x400) { /* inf/NaN */
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*iptr = x;
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return 0.0 / x;
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}
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*iptr = x*one;
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GET_HIGH_WORD(high,x);
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INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */
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return x;
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} else { /* fraction part in low x */
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i = ((u_int32_t)(0xffffffff))>>(j0-20);
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if((i1&i)==0) { /* x is integral */
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u_int32_t high;
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*iptr = x;
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GET_HIGH_WORD(high,x);
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INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */
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return x;
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} else {
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INSERT_WORDS(*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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