newlib/libm/common/sf_trunc.c

   1 /*
   2  * ====================================================
   3  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   4  *
   5  * Developed at SunPro, a Sun Microsystems, Inc. business.
   6  * Permission to use, copy, modify, and distribute this
   7  * software is freely granted, provided that this notice
   8  * is preserved.
   9  * ====================================================
  10  */
  11
  12 #include "fdlibm.h"
  13
  14 #ifdef __STDC__
  15         float truncf(float x)
  16 #else
  17         float truncf(x)
  18         float x;
  19 #endif
  20 {
  21   __int32_t signbit, w, exponent_less_127;
  22
  23   GET_FLOAT_WORD(w,x);
  24
  25   /* Extract sign bit. */
  26   signbit = w & 0x80000000;
  27
  28   /* Extract exponent field. */
  29   exponent_less_127 = ((w & 0x7f800000) >> 23) - 127;
  30
  31   if (exponent_less_127 < 23)
  32     {
  33       if (exponent_less_127 < 0)
  34         {
  35           /* -1 < x < 1, so result is +0 or -0. */
  36           SET_FLOAT_WORD(x, signbit);
  37         }
  38       else
  39         {
  40           SET_FLOAT_WORD(x, signbit | (w & ~(0x007fffff >> exponent_less_127)));
  41         }
  42     }
  43   else
  44     {
  45       if (exponent_less_127 == 128)
  46         /* x is NaN or infinite. */
  47         return x + x;
  48
  49       /* All bits in the fraction field are relevant. */
  50     }
  51   return x;
  52 }
  53
  54 #ifdef _DOUBLE_IS_32BITS
  55
  56 #ifdef __STDC__
  57         double trunc(double x)
  58 #else
  59         double trunc(x)
  60         double x;
  61 #endif
  62 {
  63         return (double) truncf((float) x);
  64 }
  65
  66 #endif /* defined(_DOUBLE_IS_32BITS) */