67 lines
1.6 KiB
C
67 lines
1.6 KiB
C
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/* @(#)s_floor.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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#include <sys/cdefs.h>
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#if 0
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__FBSDID("$FreeBSD: src/lib/msun/src/s_trunc.c,v 1.1 2004/06/20 09:25:43 das Exp $");
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#endif
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#if defined(LIBM_SCCS) && !defined(lint)
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__RCSID("$NetBSD: s_trunc.c,v 1.3 2008/04/25 22:21:53 christos Exp $");
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#endif
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/*
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* trunc(x)
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* Return x rounded toward 0 to integral value
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* Method:
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* Bit twiddling.
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* Exception:
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* Inexact flag raised if x not equal to trunc(x).
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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 huge = 1.0e300;
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double
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trunc(double x)
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{
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int32_t i0,i1,jj0;
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uint32_t i;
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EXTRACT_WORDS(i0,i1,x);
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jj0 = ((i0>>20)&0x7ff)-0x3ff;
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if(jj0<20) {
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if(jj0<0) { /* raise inexact if x != 0 */
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if(huge+x>0.0) {/* |x|<1, so return 0*sign(x) */
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i0 &= 0x80000000U;
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i1 = 0;
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}
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} else {
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i = (0x000fffff)>>jj0;
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if(((i0&i)|i1)==0) return x; /* x is integral */
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if(huge+x>0.0) { /* raise inexact flag */
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i0 &= (~i); i1=0;
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}
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}
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} else if (jj0>51) {
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if(jj0==0x400) return x+x; /* inf or NaN */
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else return x; /* x is integral */
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} else {
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i = ((u_int32_t)(0xffffffff))>>(jj0-20);
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if((i1&i)==0) return x; /* x is integral */
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if(huge+x>0.0) /* raise inexact flag */
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i1 &= (~i);
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}
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INSERT_WORDS(x,i0,i1);
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return x;
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}
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