gonzui

    1: /* s_scalbnf.c -- float version of s_scalbn.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 "math.h"
   17: #include "math_private.h"
   18: 
   19: static const float
   20: two25   =  3.355443200e+07,     /* 0x4c000000 */
   21: twom25  =  2.9802322388e-08,    /* 0x33000000 */
   22: huge   = 1.0e+30,
   23: tiny   = 1.0e-30;
   24: 
   25: float
   26: scalbnf(float x, int n)
   27: {
   28:         int32_t k,ix;
   29:         GET_FLOAT_WORD(ix,x);
   30:         k = (ix&0x7f800000)>>23;                /* extract exponent */
   31:         if (k==0) {                             /* 0 or subnormal x */
   32:             if ((ix&0x7fffffff)==0) return x; /* +-0 */
   33:             x *= two25;
   34:             GET_FLOAT_WORD(ix,x);
   35:             k = ((ix&0x7f800000)>>23) - 25; 
   36:             if (n< -50000) return tiny*x;       /*underflow*/
   37:             }
   38:         if (k==0xff) return x+x;                /* NaN or Inf */
   39:         k = k+n; 
   40:         if (k >  0xfe) return huge*copysignf(huge,x); /* overflow  */
   41:         if (k > 0)                              /* normal result */
   42:             {SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23)); return x;}
   43:         if (k <= -25)
   44:             if (n > 50000)      /* in case integer overflow in n+k */
   45:                 return huge*copysignf(huge,x);        /*overflow*/
   46:             else return tiny*copysignf(tiny,x);        /*underflow*/
   47:         k += 25;                                /* subnormal result */
   48:         SET_FLOAT_WORD(x,(ix&0x807fffff)|(k<<23));
   49:         return x*twom25;
   50: }
   51: 
   52: float
   53: ldexpf(float x, int n)
   54: {
   55:         return scalbnf(x, n);
   56: }