| 1 | /* @(#)s_frexp.c 5.1 93/09/24 */
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| 2 | /*
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| 3 | * ====================================================
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| 4 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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| 5 | *
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| 6 | * Developed at SunPro, a Sun Microsystems, Inc. business.
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| 7 | * Permission to use, copy, modify, and distribute this
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| 8 | * software is freely granted, provided that this notice
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| 9 | * is preserved.
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| 10 | * ====================================================
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| 11 | */
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| 12 |
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| 13 | #ifndef lint
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| 14 | static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_frexp.c,v 1.10 2005/03/07 21:27:37 das Exp $";
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| 15 | #endif
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| 16 |
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| 17 | /*
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| 18 | * for non-zero x
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| 19 | * x = frexp(arg,&exp);
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| 20 | * return a double fp quantity x such that 0.5 <= |x| <1.0
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| 21 | * and the corresponding binary exponent "exp". That is
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| 22 | * arg = x*2^exp.
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| 23 | * If arg is inf, 0.0, or NaN, then frexp(arg,&exp) returns arg
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| 24 | * with *exp=0.
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| 25 | */
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| 26 |
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| 27 | #include <sys/cdefs.h>
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| 28 | #include <float.h>
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| 29 |
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| 30 | #include "math.h"
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| 31 | #include "math_private.h"
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| 32 |
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| 33 | static const double
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| 34 | two54 = 1.80143985094819840000e+16; /* 0x43500000, 0x00000000 */
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| 35 |
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| 36 | double
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| 37 | frexp(double x, int *eptr)
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| 38 | {
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| 39 | int32_t hx, ix, lx;
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| 40 | EXTRACT_WORDS(hx,lx,x);
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| 41 | ix = 0x7fffffff&hx;
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| 42 | *eptr = 0;
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| 43 | if(ix>=0x7ff00000||((ix|lx)==0)) return x; /* 0,inf,nan */
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| 44 | if (ix<0x00100000) { /* subnormal */
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| 45 | x *= two54;
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| 46 | GET_HIGH_WORD(hx,x);
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| 47 | ix = hx&0x7fffffff;
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| 48 | *eptr = -54;
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| 49 | }
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| 50 | *eptr += (ix>>20)-1022;
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| 51 | hx = (hx&0x800fffff)|0x3fe00000;
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| 52 | SET_HIGH_WORD(x,hx);
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| 53 | return x;
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| 54 | }
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| 55 |
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| 56 | #if (LDBL_MANT_DIG == 53)
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| 57 | __weak_reference(frexp, frexpl);
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| 58 | #endif
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