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
11 * software is freely granted, provided that this notice
12 * is preserved.
13 * ====================================================
14 */
15
16#if defined(LIBM_SCCS) && !defined(lint)
17static char rcsid[] = "$NetBSD: e_log10f.c,v 1.5 1995/05/10 20:45:53 jtc 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/(x-x);		/* log(+-0)=-inf */
55            if (hx<0) return (x-x)/(x-x);	/* 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}
68