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  /*
      13   * modf(double x, double *iptr)
      14   * return fraction part of x, and return x's integral part in *iptr.
      15   * Method:
      16   *	Bit twiddling.
      17   *
      18   * Exception:
      19   *	No exception.
      20   */
      21  
      22  #include <math.h>
      23  #include <math_private.h>
      24  #include <libm-alias-double.h>
      25  #include <stdint.h>
      26  
      27  static const double one = 1.0;
      28  
      29  double
      30  __modf(double x, double *iptr)
      31  {
      32  	int64_t i0;
      33  	int32_t j0;
      34  	EXTRACT_WORDS64(i0,x);
      35  	j0 = ((i0>>52)&0x7ff)-0x3ff;	/* exponent of x */
      36  	if(j0<52) {			/* integer part in x */
      37  	    if(j0<0) {			/* |x|<1 */
      38  		/* *iptr = +-0 */
      39  		INSERT_WORDS64(*iptr,i0&UINT64_C(0x8000000000000000));
      40  		return x;
      41  	    } else {
      42  		uint64_t i = UINT64_C(0x000fffffffffffff)>>j0;
      43  		if((i0&i)==0) {		/* x is integral */
      44  		    *iptr = x;
      45  		    /* return +-0 */
      46  		    INSERT_WORDS64(x,i0&UINT64_C(0x8000000000000000));
      47  		    return x;
      48  		} else {
      49  		    INSERT_WORDS64(*iptr,i0&(~i));
      50  		    return x - *iptr;
      51  		}
      52  	    }
      53  	} else { /* no fraction part */
      54  	    *iptr = x*one;
      55  	    /* We must handle NaNs separately.  */
      56  	    if (j0 == 0x400 && (i0 & UINT64_C(0xfffffffffffff)))
      57  	      return x*one;
      58  	    INSERT_WORDS64(x,i0&UINT64_C(0x8000000000000000));	/* return +-0 */
      59  	    return x;
      60  	}
      61  }
      62  #ifndef __modf
      63  libm_alias_double (__modf, modf)
      64  #endif