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/* ef_log10.c -- float version of e_log10.c.

 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.

 */

/*

 * ====================================================

 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.

 *

 * Developed at SunPro, a Sun Microsystems, Inc. business.

 * Permission to use, copy, modify, and distribute this

 * software is freely granted, provided that this notice

 * is preserved.

 * ====================================================

 */

#include "fdlibm.h"

#ifdef __STDC__

static const float

#else

static float

#endif

two25      =  3.3554432000e+07, /* 0x4c000000 */

ivln10     =  4.3429449201e-01, /* 0x3ede5bd9 */

log10_2hi  =  3.0102920532e-01, /* 0x3e9a2080 */

log10_2lo  =  7.9034151668e-07; /* 0x355427db */

#ifdef __STDC__

static const float zero   =  0.0;

#else

static float zero   =  0.0;

#endif

#ifdef __STDC__

        float __ieee754_log10f(float x)

#else

        float __ieee754_log10f(x)

        float x;

#endif

{

        float y,z;

        __int32_t i,k,hx;

        GET_FLOAT_WORD(hx,x);

        k=0;

        if (FLT_UWORD_IS_ZERO(hx&0x7fffffff))

            return -two25/zero;             /* log(+-0)=-inf */

        if (hx<0) return (x-x)/zero;        /* log(-#) = NaN */

        if (!FLT_UWORD_IS_FINITE(hx)) return x+x;

        if (FLT_UWORD_IS_SUBNORMAL(hx)) {

            k -= 25; x *= two25; /* subnormal number, scale up x */

            GET_FLOAT_WORD(hx,x);

        }

        k += (hx>>23)-127;

        i  = ((__uint32_t)k&0x80000000)>>31;

        hx = (hx&0x007fffff)|((0x7f-i)<<23);

        y  = (float)(k+i);

        SET_FLOAT_WORD(x,hx);

        z  = y*log10_2lo + ivln10*__ieee754_logf(x);

        return  z+y*log10_2hi;

}