sf_trunc.c

来自「KPIT GNU Tools is a set of GNU developme」· C语言 代码 · 共 67 行

/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice 
 * is preserved.
 * ====================================================
 */

#include "fdlibm.h"

#ifdef __STDC__
	float truncf(float x)
#else
	float truncf(x)
	float x;
#endif
{
  __int32_t signbit, w, exponent_less_127;

  GET_FLOAT_WORD(w,x);

  /* Extract sign bit. */
  signbit = w & 0x80000000;

  /* Extract exponent field. */
  exponent_less_127 = ((w & 0x7f800000) >> 23) - 127;

  if (exponent_less_127 < 23)
    {
      if (exponent_less_127 < 0)
        {
          /* -1 < x < 1, so result is +0 or -0. */
          SET_FLOAT_WORD(x, signbit);
        }
      else
        {
          SET_FLOAT_WORD(x, signbit | (w & ~(0x007fffff >> exponent_less_127)));
        }
    }
  else
    {
      if (exponent_less_127 == 255)
        /* x is NaN or infinite. */
        return x + x;

      /* All bits in the fraction field are relevant. */
    }
  return x;
}

#ifdef _DOUBLE_IS_32BITS

#ifdef __STDC__
	double trunc(double x)
#else
	double trunc(x)
	double x;
#endif
{
	return (double) truncf((float) x);
}

#endif /* defined(_DOUBLE_IS_32BITS) */