sysdeps/ieee754/ldbl-128/s_modfl.c

   1 /* s_modfl.c -- long double version of s_modf.c.
   2  * Conversion to IEEE quad long double by Jakub Jelinek, jj@ultra.linux.cz.
   3  */
   4
   5 /*
   6  * ====================================================
   7  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   8  *
   9  * Developed at SunPro, a Sun Microsystems, Inc. business.
  10  * Permission to use, copy, modify, and distribute this
  11  * software is freely granted, provided that this notice
  12  * is preserved.
  13  * ====================================================
  14  */
  15
  16 #if defined(LIBM_SCCS) && !defined(lint)
  17 static char rcsid[] = "$NetBSD: $";
  18 #endif
  19
  20 /*
  21  * modfl(long double x, long double *iptr)
  22  * return fraction part of x, and return x's integral part in *iptr.
  23  * Method:
  24  *      Bit twiddling.
  25  *
  26  * Exception:
  27  *      No exception.
  28  */
  29
  30 #include <math.h>
  31 #include <math_private.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         u_int64_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 weak_alias (__modfl, modfl)