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  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) */
  56.