1/* e_log10f.c -- float version of e_log10.c.
2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
3 */
4
5/*
6 * ====================================================
7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
8 *
9 * Developed at SunPro, a Sun Microsystems, Inc. business.
10 * Permission to use, copy, modify, and distribute this
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11 * software is freely granted, provided that this notice
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| 11 * software is freely granted, provided that this notice |
12 * is preserved.
13 * ====================================================
14 */
15
16#ifndef lint
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17static char rcsid[] = "$Id: e_log10f.c,v 1.1.1.1 1994/08/19 09:39:56 jkh Exp $";
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| 17static char rcsid[] = "$Id: e_log10f.c,v 1.2 1995/04/07 23:23:23 bde Exp $"; |
18#endif
19
20#include "math.h"
21#include "math_private.h"
22
23#ifdef __STDC__
24static const float
25#else
26static float
27#endif
28two25 = 3.3554432000e+07, /* 0x4c000000 */
29ivln10 = 4.3429449201e-01, /* 0x3ede5bd9 */
30log10_2hi = 3.0102920532e-01, /* 0x3e9a2080 */
31log10_2lo = 7.9034151668e-07; /* 0x355427db */
32
33#ifdef __STDC__
34static const float zero = 0.0;
35#else
36static float zero = 0.0;
37#endif
38
39#ifdef __STDC__
40 float __ieee754_log10f(float x)
41#else
42 float __ieee754_log10f(x)
43 float x;
44#endif
45{
46 float y,z;
47 int32_t i,k,hx;
48
49 GET_FLOAT_WORD(hx,x);
50
51 k=0;
52 if (hx < 0x00800000) { /* x < 2**-126 */
53 if ((hx&0x7fffffff)==0)
54 return -two25/zero; /* log(+-0)=-inf */
55 if (hx<0) return (x-x)/zero; /* log(-#) = NaN */
56 k -= 25; x *= two25; /* subnormal number, scale up x */
57 GET_FLOAT_WORD(hx,x);
58 }
59 if (hx >= 0x7f800000) return x+x;
60 k += (hx>>23)-127;
61 i = ((u_int32_t)k&0x80000000)>>31;
62 hx = (hx&0x007fffff)|((0x7f-i)<<23);
63 y = (float)(k+i);
64 SET_FLOAT_WORD(x,hx);
65 z = y*log10_2lo + ivln10*__ieee754_logf(x);
66 return z+y*log10_2hi;
67}
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