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 #ifdef __STDC__
  34 static const long double one = 1.0;
  35 #else
  36 static long double one = 1.0;
  37 #endif
  38
  39 #ifdef __STDC__
  40         long double __modfl(long double x, long double *iptr)
  41 #else
  42         long double __modfl(x, iptr)
  43         long double x,*iptr;
  44 #endif
  45 {
  46         int64_t i0,i1,j0;
  47         u_int64_t i;
  48         GET_LDOUBLE_WORDS64(i0,i1,x);
  49         j0 = ((i0>>48)&0x7fff)-0x3fff;  /* exponent of x */
  50         if(j0<48) {                     /* integer part in high x */
  51             if(j0<0) {                  /* |x|<1 */
  52                 /* *iptr = +-0 */
  53                 SET_LDOUBLE_WORDS64(*iptr,i0&0x8000000000000000ULL,0);
  54                 return x;
  55             } else {
  56                 i = (0x0000ffffffffffffLL)>>j0;
  57                 if(((i0&i)|i1)==0) {            /* x is integral */
  58                     *iptr = x;
  59                     /* return +-0 */
  60                     SET_LDOUBLE_WORDS64(x,i0&0x8000000000000000ULL,0);
  61                     return x;
  62                 } else {
  63                     SET_LDOUBLE_WORDS64(*iptr,i0&(~i),0);
  64                     return x - *iptr;
  65                 }
  66             }
  67         } else if (j0>111) {            /* no fraction part */
  68             *iptr = x*one;
  69             /* We must handle NaNs separately.  */
  70             if (j0 == 0x4000 && ((i0 & 0x0000ffffffffffffLL) | i1))
  71               return x*one;
  72             /* return +-0 */
  73             SET_LDOUBLE_WORDS64(x,i0&0x8000000000000000ULL,0);
  74             return x;
  75         } else {                        /* fraction part in low x */
  76             i = -1ULL>>(j0-48);
  77             if((i1&i)==0) {             /* x is integral */
  78                 *iptr = x;
  79                 /* return +-0 */
  80                 SET_LDOUBLE_WORDS64(x,i0&0x8000000000000000ULL,0);
  81                 return x;
  82             } else {
  83                 SET_LDOUBLE_WORDS64(*iptr,i0,i1&(~i));
  84                 return x - *iptr;
  85             }
  86         }
  87 }
  88 weak_alias (__modfl, modfl)