StdLib/LibC/Math/s_modf.c

/* @(#)s_modf.c 5.1 93/09/24 */
/*
 * ====================================================
 * 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  <LibConfig.h>
#include  <sys/EfiCdefs.h>
#if defined(LIBM_SCCS) && !defined(lint)
__RCSID("$NetBSD: s_modf.c,v 1.11 2002/05/26 22:01:57 wiz Exp $");
#endif

/*
 * modf(double x, double *iptr)
 * return fraction part of x, and return x's integral part in *iptr.
 * Method:
 *  Bit twiddling.
 *
 * Exception:
 *  No exception.
 */

#include "math.h"
#include "math_private.h"

static const double one = 1.0;

double
modf(double x, double *iptr)
{
  int32_t i0,i1,j0;
  u_int32_t i;
  EXTRACT_WORDS(i0,i1,x);
  j0 = ((i0>>20)&0x7ff)-0x3ff;  /* exponent of x */
  if(j0<20) {     /* integer part in high x */
      if(j0<0) {      /* |x|<1 */
          INSERT_WORDS(*iptr,i0&0x80000000,0);  /* *iptr = +-0 */
    return x;
      } else {
    i = (0x000fffff)>>j0;
    if(((i0&i)|i1)==0) {    /* x is integral */
        u_int32_t high;
        *iptr = x;
        GET_HIGH_WORD(high,x);
        INSERT_WORDS(x,high&0x80000000,0);  /* return +-0 */
        return x;
    } else {
        INSERT_WORDS(*iptr,i0&(~i),0);
        return x - *iptr;
    }
      }
  } else if (j0>51) {   /* no fraction part */
      u_int32_t high;
      *iptr = x*one;
      GET_HIGH_WORD(high,x);
      INSERT_WORDS(x,high&0x80000000,0);  /* return +-0 */
      return x;
  } else {      /* fraction part in low x */
      i = ((u_int32_t)(0xffffffff))>>(j0-20);
      if((i1&i)==0) {     /* x is integral */
          u_int32_t high;
    *iptr = x;
    GET_HIGH_WORD(high,x);
    INSERT_WORDS(x,high&0x80000000,0);  /* return +-0 */
    return x;
      } else {
          INSERT_WORDS(*iptr,i0,i1&(~i));
    return x - *iptr;
      }
  }
}