sysdeps/ieee754/ldbl-96/s_modfl.c

   1 /* s_modfl.c -- long double version of s_modf.c.
   2  * Conversion to long double by Ulrich Drepper,
   3  * Cygnus Support, drepper@cygnus.com.
   4  */
   5
   6 /*
   7  * ====================================================
   8  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   9  *
  10  * Developed at SunPro, a Sun Microsystems, Inc. business.
  11  * Permission to use, copy, modify, and distribute this
  12  * software is freely granted, provided that this notice
  13  * is preserved.
  14  * ====================================================
  15  */
  16
  17 #if defined(LIBM_SCCS) && !defined(lint)
  18 static char rcsid[] = "$NetBSD: $";
  19 #endif
  20
  21 /*
  22  * modfl(long double x, long double *iptr)
  23  * return fraction part of x, and return x's integral part in *iptr.
  24  * Method:
  25  *      Bit twiddling.
  26  *
  27  * Exception:
  28  *      No exception.
  29  */
  30
  31 #include "math.h"
  32 #include "math_private.h"
  33
  34 #ifdef __STDC__
  35 static const long double one = 1.0;
  36 #else
  37 static long double one = 1.0;
  38 #endif
  39
  40 #ifdef __STDC__
  41         long double __modfl(long double x, long double *iptr)
  42 #else
  43         long double __modfl(x, iptr)
  44         long double x,*iptr;
  45 #endif
  46 {
  47         int32_t i0,i1,j0;
  48         u_int32_t i,se;
  49         GET_LDOUBLE_WORDS(se,i0,i1,x);
  50         j0 = (se&0x7fff)-0x3fff;        /* exponent of x */
  51         if(j0<32) {                     /* integer part in high x */
  52             if(j0<0) {                  /* |x|<1 */
  53                 SET_LDOUBLE_WORDS(*iptr,se&0x8000,0,0); /* *iptr = +-0 */
  54                 return x;
  55             } else {
  56                 i = (0x7fffffff)>>j0;
  57                 if(((i0&i)|i1)==0) {            /* x is integral */
  58                     *iptr = x;
  59                     SET_LDOUBLE_WORDS(x,se&0x8000,0,0); /* return +-0 */
  60                     return x;
  61                 } else {
  62                     SET_LDOUBLE_WORDS(*iptr,se,i0&(~i),0);
  63                     return x - *iptr;
  64                 }
  65             }
  66         } else if (j0>63) {             /* no fraction part */
  67             *iptr = x*one;
  68             /* We must handle NaNs separately.  */
  69             if (j0 == 0x4000 && ((i0 & 0x7fffffff) | i1))
  70               return x*one;
  71             SET_LDOUBLE_WORDS(x,se&0x8000,0,0); /* return +-0 */
  72             return x;
  73         } else {                        /* fraction part in low x */
  74             i = ((u_int32_t)(0x7fffffff))>>(j0-32);
  75             if((i1&i)==0) {             /* x is integral */
  76                 *iptr = x;
  77                 SET_LDOUBLE_WORDS(x,se&0x8000,0,0);     /* return +-0 */
  78                 return x;
  79             } else {
  80                 SET_LDOUBLE_WORDS(*iptr,se,i0,i1&(~i));
  81                 return x - *iptr;
  82             }
  83         }
  84 }
  85 weak_alias (__modfl, modfl)