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81 lines
1.8 KiB
C
81 lines
1.8 KiB
C
/* @(#)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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#if defined(LIBM_SCCS) && !defined(lint)
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static char rcsid[] = "$NetBSD: s_floor.c,v 1.8 1995/05/10 20:47:20 jtc Exp $";
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#endif
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/*
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* floor(x)
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* Return x rounded toward -inf 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 floor(x).
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*/
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#include "math.h"
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#include "math_private.h"
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#ifdef __STDC__
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static const double huge = 1.0e300;
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#else
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static double huge = 1.0e300;
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#endif
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#ifdef __STDC__
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double floor(double x)
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#else
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double floor(x)
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double x;
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#endif
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{
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int32_t i0,i1,j0;
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u_int32_t i,j;
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EXTRACT_WORDS(i0,i1,x);
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j0 = ((i0>>20)&0x7ff)-0x3ff;
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if(j0<20) {
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if(j0<0) { /* raise inexact if x != 0 */
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if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */
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if(i0>=0) {i0=i1=0;}
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else if(((i0&0x7fffffff)|i1)!=0)
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{ i0=0xbff00000;i1=0;}
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}
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} else {
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i = (0x000fffff)>>j0;
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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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if(i0<0) i0 += (0x00100000)>>j0;
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i0 &= (~i); i1=0;
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}
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}
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} else if (j0>51) {
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if(j0==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))>>(j0-20);
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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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if(i0<0) {
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if(j0==20) i0+=1;
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else {
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j = i1+(1<<(52-j0));
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if(j<i1) i0 +=1 ; /* got a carry */
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i1=j;
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}
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}
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i1 &= (~i);
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}
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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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