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#include <sys/cdefs.h>
17#if defined(LIBM_SCCS) && !defined(lint)
18__RCSID("$NetBSD: e_log10f.c,v 1.7 1999/07/02 15:37:40 simonb Exp $");
19#endif
20
21#include "math.h"
22#include "math_private.h"
23
24static const float
25two25      =  3.3554432000e+07, /* 0x4c000000 */
26ivln10     =  4.3429449201e-01, /* 0x3ede5bd9 */
27log10_2hi  =  3.0102920532e-01, /* 0x3e9a2080 */
28log10_2lo  =  7.9034151668e-07; /* 0x355427db */
29
30static const float zero   =  0.0;
31
32float
33__ieee754_log10f(float x)
34{
35	float y,z;
36	int32_t i,k,hx;
37
38	GET_FLOAT_WORD(hx,x);
39
40        k=0;
41        if (hx < 0x00800000) {                  /* x < 2**-126  */
42            if ((hx&0x7fffffff)==0)
43                return -two25/zero;             /* log(+-0)=-inf */
44            if (hx<0) return (x-x)/zero;        /* log(-#) = NaN */
45            k -= 25; x *= two25; /* subnormal number, scale up x */
46	    GET_FLOAT_WORD(hx,x);
47        }
48	if (hx >= 0x7f800000) return x+x;
49	k += (hx>>23)-127;
50	i  = ((u_int32_t)k&0x80000000)>>31;
51        hx = (hx&0x007fffff)|((0x7f-i)<<23);
52        y  = (float)(k+i);
53	SET_FLOAT_WORD(x,hx);
54	z  = y*log10_2lo + ivln10*__ieee754_logf(x);
55	return  z+y*log10_2hi;
56}
57