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5980be9b3c
This work is based in part on code from NetBSD libm, libc and kernel. The library is partly public domain and partly BSD-style licensed.
52 lines
1.3 KiB
C
52 lines
1.3 KiB
C
/* @(#)s_frexp.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 defined(LIBM_SCCS) && !defined(lint)
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__RCSID("$NetBSD: s_frexp.c,v 1.13 2008/09/28 18:54:55 christos Exp $");
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#endif
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/*
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* for non-zero x
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* x = frexp(arg,&exp);
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* return a double fp quantity x such that 0.5 <= |x| <1.0
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* and the corresponding binary exponent "exp". That is
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* arg = x*2^exp.
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* If arg is inf, 0.0, or NaN, then frexp(arg,&exp) returns arg
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* with *exp=0.
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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
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two54 = 1.80143985094819840000e+16; /* 0x43500000, 0x00000000 */
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double
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frexp(double x, int *eptr)
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{
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int32_t hx, ix, lx;
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EXTRACT_WORDS(hx,lx,x);
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ix = 0x7fffffff&hx;
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*eptr = 0;
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if(ix>=0x7ff00000||((ix|lx)==0)) return x; /* 0,inf,nan */
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if (ix<0x00100000) { /* subnormal */
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x *= two54;
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GET_HIGH_WORD(hx,x);
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ix = hx&0x7fffffff;
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*eptr = -54;
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}
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*eptr += ((uint32_t)ix>>20)-1022;
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hx = (hx&0x800fffff)|0x3fe00000;
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SET_HIGH_WORD(x,hx);
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return x;
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}
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