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 <libm-alias-ldouble.h>
      32  
      33  static const _Float128 one = 1.0;
      34  
      35  _Float128 __modfl(_Float128 x, _Float128 *iptr)
      36  {
      37  	int64_t i0,i1,j0;
      38  	uint64_t i;
      39  	GET_LDOUBLE_WORDS64(i0,i1,x);
      40  	j0 = ((i0>>48)&0x7fff)-0x3fff;	/* exponent of x */
      41  	if(j0<48) {			/* integer part in high x */
      42  	    if(j0<0) {			/* |x|<1 */
      43  		/* *iptr = +-0 */
      44  	        SET_LDOUBLE_WORDS64(*iptr,i0&0x8000000000000000ULL,0);
      45  		return x;
      46  	    } else {
      47  		i = (0x0000ffffffffffffLL)>>j0;
      48  		if(((i0&i)|i1)==0) {		/* x is integral */
      49  		    *iptr = x;
      50  		    /* return +-0 */
      51  		    SET_LDOUBLE_WORDS64(x,i0&0x8000000000000000ULL,0);
      52  		    return x;
      53  		} else {
      54  		    SET_LDOUBLE_WORDS64(*iptr,i0&(~i),0);
      55  		    return x - *iptr;
      56  		}
      57  	    }
      58  	} else if (j0>111) {		/* no fraction part */
      59  	    *iptr = x*one;
      60  	    /* We must handle NaNs separately.  */
      61  	    if (j0 == 0x4000 && ((i0 & 0x0000ffffffffffffLL) | i1))
      62  	      return x*one;
      63  	    /* return +-0 */
      64  	    SET_LDOUBLE_WORDS64(x,i0&0x8000000000000000ULL,0);
      65  	    return x;
      66  	} else {			/* fraction part in low x */
      67  	    i = -1ULL>>(j0-48);
      68  	    if((i1&i)==0) { 		/* x is integral */
      69  		*iptr = x;
      70  		/* return +-0 */
      71  		SET_LDOUBLE_WORDS64(x,i0&0x8000000000000000ULL,0);
      72  		return x;
      73  	    } else {
      74  		SET_LDOUBLE_WORDS64(*iptr,i0,i1&(~i));
      75  		return x - *iptr;
      76  	    }
      77  	}
      78  }
      79  libm_alias_ldouble (__modf, modf)