1  /* s_modfl.c -- long double version of s_modf.c.
       2   */
       3  
       4  /*
       5   * ====================================================
       6   * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
       7   *
       8   * Developed at SunPro, a Sun Microsystems, Inc. business.
       9   * Permission to use, copy, modify, and distribute this
      10   * software is freely granted, provided that this notice
      11   * is preserved.
      12   * ====================================================
      13   */
      14  
      15  #if defined(LIBM_SCCS) && !defined(lint)
      16  static char rcsid[] = "$NetBSD: $";
      17  #endif
      18  
      19  /*
      20   * modfl(long double x, long double *iptr)
      21   * return fraction part of x, and return x's integral part in *iptr.
      22   * Method:
      23   *	Bit twiddling.
      24   *
      25   * Exception:
      26   *	No exception.
      27   */
      28  
      29  #include <math.h>
      30  #include <math_private.h>
      31  #include <math_ldbl_opt.h>
      32  
      33  static const long double one = 1.0;
      34  
      35  long double __modfl(long double x, long double *iptr)
      36  {
      37  	int64_t i0,i1,j0;
      38  	uint64_t i;
      39  	double xhi, xlo;
      40  
      41  	ldbl_unpack (x, &xhi, &xlo);
      42  	EXTRACT_WORDS64 (i0, xhi);
      43  	EXTRACT_WORDS64 (i1, xlo);
      44  	i1 &= 0x000fffffffffffffLL;
      45  	j0 = ((i0>>52)&0x7ff)-0x3ff;	/* exponent of x */
      46  	if(j0<52) {			/* integer part in high x */
      47  	    if(j0<0) {			/* |x|<1 */
      48  		/* *iptr = +-0 */
      49  		INSERT_WORDS64 (xhi, i0&0x8000000000000000ULL);
      50  		*iptr = xhi;
      51  		return x;
      52  	    } else {
      53  		i = (0x000fffffffffffffLL)>>j0;
      54  		if(((i0&i)|(i1&0x7fffffffffffffffLL))==0) {		/* x is integral */
      55  		    *iptr = x;
      56  		    /* return +-0 */
      57  		    INSERT_WORDS64 (xhi, i0&0x8000000000000000ULL);
      58  		    x = xhi;
      59  		    return x;
      60  		} else {
      61  		    INSERT_WORDS64 (xhi, i0&(~i));
      62  		    *iptr = xhi;
      63  		    return x - *iptr;
      64  		}
      65  	    }
      66  	} else if (j0>103) {		/* no fraction part */
      67  	    *iptr = x*one;
      68  	    /* We must handle NaNs separately.  */
      69  	    if ((i0 & 0x7fffffffffffffffLL) > 0x7ff0000000000000LL)
      70  	      return x*one;
      71  	    /* return +-0 */
      72  	    INSERT_WORDS64 (xhi, i0&0x8000000000000000ULL);
      73  	    x = xhi;
      74  	    return x;
      75  	} else {			/* fraction part in low x */
      76  	    i = -1ULL>>(j0-52);
      77  	    if((i1&i)==0) { 		/* x is integral */
      78  		*iptr = x;
      79  		/* return +-0 */
      80  		INSERT_WORDS64 (xhi, i0&0x8000000000000000ULL);
      81  		x = xhi;
      82  		return x;
      83  	    } else {
      84  		INSERT_WORDS64 (xhi, i0);
      85  		INSERT_WORDS64 (xlo, i1&(~i));
      86  		*iptr = ldbl_pack (xhi, xlo);
      87  		return x - *iptr;
      88  	    }
      89  	}
      90  }
      91  #if IS_IN (libm)
      92  long_double_symbol (libm, __modfl, modfl);
      93  #else
      94  long_double_symbol (libc, __modfl, modfl);
      95  #endif