73 lines
1.8 KiB
C
73 lines
1.8 KiB
C
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/* @(#)s_nextafter.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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__FBSDID("$FreeBSD$");
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/*
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* We assume that a long double has a 15-bit exponent. On systems
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* where long double is the same as double, nexttoward() is an alias
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* for nextafter(), so we don't use this routine.
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*/
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#include <float.h>
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#include "fpmath.h"
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#include "math.h"
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#include "math_private.h"
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#if LDBL_MAX_EXP != 0x4000
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#error "Unsupported long double format"
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#endif
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double
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nexttoward(double x, long double y)
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{
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union IEEEl2bits uy;
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volatile double t;
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int32_t hx,ix;
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u_int32_t lx;
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EXTRACT_WORDS(hx,lx,x);
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ix = hx&0x7fffffff; /* |x| */
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uy.e = y;
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if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) ||
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(uy.bits.exp == 0x7fff &&
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((uy.bits.manh&~LDBL_NBIT)|uy.bits.manl) != 0))
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return x+y; /* x or y is nan */
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if(x==y) return (double)y; /* x=y, return y */
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if(x==0.0) {
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INSERT_WORDS(x,uy.bits.sign<<31,1); /* return +-minsubnormal */
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t = x*x;
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if(t==x) return t; else return x; /* raise underflow flag */
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}
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if(hx>0.0 ^ x < y) { /* x -= ulp */
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if(lx==0) hx -= 1;
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lx -= 1;
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} else { /* x += ulp */
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lx += 1;
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if(lx==0) hx += 1;
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}
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ix = hx&0x7ff00000;
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if(ix>=0x7ff00000) return x+x; /* overflow */
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if(ix<0x00100000) { /* underflow */
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t = x*x;
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if(t!=x) { /* raise underflow flag */
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INSERT_WORDS(x,hx,lx);
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return x;
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}
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}
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INSERT_WORDS(x,hx,lx);
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return x;
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}
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