newlib/libm/common/sf_ilogb.c

   1 /* sf_ilogb.c -- float version of s_ilogb.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 <limits.h>
  17 #include "fdlibm.h"
  18
  19 #ifdef __STDC__
  20         int ilogbf(float x)
  21 #else
  22         int ilogbf(x)
  23         float x;
  24 #endif
  25 {
  26         __int32_t hx,ix;
  27
  28         GET_FLOAT_WORD(hx,x);
  29         hx &= 0x7fffffff;
  30         if(FLT_UWORD_IS_ZERO(hx))
  31             return FP_ILOGB0;   /* ilogb(0) = special case error */
  32         if(FLT_UWORD_IS_SUBNORMAL(hx)) {
  33             for (ix = -126,hx<<=8; hx>0; hx<<=1) ix -=1;
  34             return ix;
  35         }
  36         #if FP_ILOGBNAN != INT_MAX
  37         else if (FLT_UWORD_IS_NAN(hx)) return FP_ILOGBNAN;      /* NAN */
  38         #endif
  39         else if (!FLT_UWORD_IS_FINITE(hx)) return INT_MAX;
  40         else return (hx>>23)-127;
  41 }
  42
  43 #ifdef _DOUBLE_IS_32BITS
  44
  45 #ifdef __STDC__
  46         int ilogb(double x)
  47 #else
  48         int ilogb(x)
  49         double x;
  50 #endif
  51 {
  52         return ilogbf((float) x);
  53 }
  54
  55 #endif /* defined(_DOUBLE_IS_32BITS) */