POK
/home/jaouen/pok_official/pok/trunk/libpok/libm/scalbnf.c
00001 /*
00002  *                               POK header
00003  * 
00004  * The following file is a part of the POK project. Any modification should
00005  * made according to the POK licence. You CANNOT use this file or a part of
00006  * this file is this part of a file for your own project
00007  *
00008  * For more information on the POK licence, please see our LICENCE FILE
00009  *
00010  * Please follow the coding guidelines described in doc/CODING_GUIDELINES
00011  *
00012  *                                      Copyright (c) 2007-2009 POK team 
00013  *
00014  * Created by julien on Fri Jan 30 14:41:34 2009 
00015  */
00016 
00017 /* s_scalbnf.c -- float version of s_scalbn.c.
00018  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
00019  */
00020 
00021 /*
00022  * ====================================================
00023  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
00024  *
00025  * Developed at SunPro, a Sun Microsystems, Inc. business.
00026  * Permission to use, copy, modify, and distribute this
00027  * software is freely granted, provided that this notice
00028  * is preserved.
00029  * ====================================================
00030  */
00031 
00032 #ifdef POK_NEEDS_LIBMATH
00033 
00034 #include <libm.h>
00035 #include "math_private.h"
00036 
00037 static const float
00038 two25   =  3.355443200e+07,     /* 0x4c000000 */
00039 twom25  =  2.9802322388e-08,    /* 0x33000000 */
00040 huge   = 1.0e+30,
00041 tiny   = 1.0e-30;
00042 
00043 float
00044 scalbnf(float x, int n)
00045 {
00046         int32_t k,ix;
00047         GET_FLOAT_WORD(ix,x);
00048         k = (ix&0x7f800000)>>23;                /* extract exponent */
00049         if (k==0) {                             /* 0 or subnormal x */
00050             if ((ix&0x7fffffff)==0) return x; /* +-0 */
00051             x *= two25;
00052             GET_FLOAT_WORD(ix,x);
00053             k = ((ix&0x7f800000)>>23) - 25;
00054             if (n< -50000) return tiny*x;       /*underflow*/
00055             }
00056         if (k==0xff) return x+x;                /* NaN or Inf */
00057         k = k+n;
00058         if (k >  0xfe) return huge*copysignf(huge,x); /* overflow  */
00059         if (k > 0)                              /* normal result */
00060             {SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23)); return x;}
00061         if (k <= -25) {
00062             if (n > 50000)      /* in case integer overflow in n+k */
00063                 return huge*copysignf(huge,x);  /*overflow*/
00064             else return tiny*copysignf(tiny,x); /*underflow*/
00065         }
00066         k += 25;                                /* subnormal result */
00067         SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23));
00068         return x*twom25;
00069 }
00070 
00071 #endif