1  /* e_fmodl.c -- long double version of e_fmod.c.
       2   */
       3  /*
       4   * ====================================================
       5   * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
       6   *
       7   * Developed at SunPro, a Sun Microsystems, Inc. business.
       8   * Permission to use, copy, modify, and distribute this
       9   * software is freely granted, provided that this notice
      10   * is preserved.
      11   * ====================================================
      12   */
      13  
      14  /* __ieee754_remainderl(x,p)
      15   * Return :
      16   *	returns  x REM p  =  x - [x/p]*p as if in infinite
      17   *	precise arithmetic, where [x/p] is the (infinite bit)
      18   *	integer nearest x/p (in half way case choose the even one).
      19   * Method :
      20   *	Based on fmodl() return x-[x/p]chopped*p exactlp.
      21   */
      22  
      23  #include <math.h>
      24  #include <math_private.h>
      25  #include <libm-alias-finite.h>
      26  
      27  static const long double zero = 0.0L;
      28  
      29  
      30  long double
      31  __ieee754_remainderl(long double x, long double p)
      32  {
      33  	int64_t hx,hp;
      34  	uint64_t sx,lx,lp;
      35  	long double p_half;
      36  	double xhi, xlo, phi, plo;
      37  
      38  	ldbl_unpack (x, &xhi, &xlo);
      39  	EXTRACT_WORDS64 (hx, xhi);
      40  	EXTRACT_WORDS64 (lx, xlo);
      41  	ldbl_unpack (p, &phi, &plo);
      42  	EXTRACT_WORDS64 (hp, phi);
      43  	EXTRACT_WORDS64 (lp, plo);
      44  	sx = hx&0x8000000000000000ULL;
      45  	lp ^= hp & 0x8000000000000000ULL;
      46  	hp &= 0x7fffffffffffffffLL;
      47  	lx ^= sx;
      48  	hx &= 0x7fffffffffffffffLL;
      49  	if (lp == 0x8000000000000000ULL)
      50  	  lp = 0;
      51  	if (lx == 0x8000000000000000ULL)
      52  	  lx = 0;
      53  
      54      /* purge off exception values */
      55  	if(hp==0) return (x*p)/(x*p);	/* p = 0 */
      56  	if((hx>=0x7ff0000000000000LL)||			/* x not finite */
      57  	   (hp>0x7ff0000000000000LL))			/* p is NaN */
      58  	    return (x*p)/(x*p);
      59  
      60  
      61  	if (hp<=0x7fdfffffffffffffLL) x = __ieee754_fmodl(x,p+p);	/* now x < 2p */
      62  	if (((hx-hp)|(lx-lp))==0) return zero*x;
      63  	x  = fabsl(x);
      64  	p  = fabsl(p);
      65  	if (hp<0x0020000000000000LL) {
      66  	    if(x+x>p) {
      67  		x-=p;
      68  		if(x+x>=p) x -= p;
      69  	    }
      70  	} else {
      71  	    p_half = 0.5L*p;
      72  	    if(x>p_half) {
      73  		x-=p;
      74  		if(x>=p_half) x -= p;
      75  	    }
      76  	}
      77  	if (sx)
      78  	  x = -x;
      79  	return x;
      80  }
      81  libm_alias_finite (__ieee754_remainderl, __remainderl)