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       ---
       e_log10f.c (1630B)
       ---
            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 #ifndef lint
           17 static char rcsid[] = "$FreeBSD: src/lib/msun/src/e_log10f.c,v 1.8 2002/05/28 18:15:04 alfred Exp $";
           18 #endif
           19 
           20 #include "math.h"
           21 #include "math_private.h"
           22 
           23 static const float
           24 two25      =  3.3554432000e+07, /* 0x4c000000 */
           25 ivln10     =  4.3429449201e-01, /* 0x3ede5bd9 */
           26 log10_2hi  =  3.0102920532e-01, /* 0x3e9a2080 */
           27 log10_2lo  =  7.9034151668e-07; /* 0x355427db */
           28 
           29 static const float zero   =  0.0;
           30 
           31 float
           32 __ieee754_log10f(float x)
           33 {
           34         float y,z;
           35         int32_t i,k,hx;
           36 
           37         GET_FLOAT_WORD(hx,x);
           38 
           39         k=0;
           40         if (hx < 0x00800000) {                  /* x < 2**-126  */
           41             if ((hx&0x7fffffff)==0)
           42                 return -two25/zero;             /* log(+-0)=-inf */
           43             if (hx<0) return (x-x)/zero;        /* log(-#) = NaN */
           44             k -= 25; x *= two25; /* subnormal number, scale up x */
           45             GET_FLOAT_WORD(hx,x);
           46         }
           47         if (hx >= 0x7f800000) return x+x;
           48         k += (hx>>23)-127;
           49         i  = ((u_int32_t)k&0x80000000)>>31;
           50         hx = (hx&0x007fffff)|((0x7f-i)<<23);
           51         y  = (float)(k+i);
           52         SET_FLOAT_WORD(x,hx);
           53         z  = y*log10_2lo + ivln10*__ieee754_logf(x);
           54         return  z+y*log10_2hi;
           55 }