sysdeps/ieee754/dbl-64/wordsize-64/s_modf.c

   1 /* Rewritten for 64-bit machines by Ulrich Drepper <drepper@gmail.com>.  */
   2 /*
   3  * ====================================================
   4  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   5  *
   6  * Developed at SunPro, a Sun Microsystems, Inc. business.
   7  * Permission to use, copy, modify, and distribute this
   8  * software is freely granted, provided that this notice
   9  * is preserved.
  10  * ====================================================
  11  */
  12
  13 /*
  14  * modf(double x, double *iptr)
  15  * return fraction part of x, and return x's integral part in *iptr.
  16  * Method:
  17  *      Bit twiddling.
  18  *
  19  * Exception:
  20  *      No exception.
  21  */
  22
  23 #include <math.h>
  24 #include <math_private.h>
  25
  26 static const double one = 1.0;
  27
  28 double
  29 __modf(double x, double *iptr)
  30 {
  31         int64_t i0;
  32         int32_t j0;
  33         EXTRACT_WORDS64(i0,x);
  34         j0 = ((i0>>52)&0x7ff)-0x3ff;    /* exponent of x */
  35         if(j0<52) {                     /* integer part in x */
  36             if(j0<0) {                  /* |x|<1 */
  37                 /* *iptr = +-0 */
  38                 INSERT_WORDS64(*iptr,i0&UINT64_C(0x8000000000000000));
  39                 return x;
  40             } else {
  41                 uint64_t i = UINT64_C(0x000fffffffffffff)>>j0;
  42                 if((i0&i)==0) {         /* x is integral */
  43                     *iptr = x;
  44                     /* return +-0 */
  45                     INSERT_WORDS64(x,i0&UINT64_C(0x8000000000000000));
  46                     return x;
  47                 } else {
  48                     INSERT_WORDS64(*iptr,i0&(~i));
  49                     return x - *iptr;
  50                 }
  51             }
  52         } else { /* no fraction part */
  53             *iptr = x*one;
  54             /* We must handle NaNs separately.  */
  55             if (j0 == 0x400 && (i0 & UINT64_C(0xfffffffffffff)))
  56               return x*one;
  57             INSERT_WORDS64(x,i0&UINT64_C(0x8000000000000000));  /* return +-0 */
  58             return x;
  59         }
  60 }
  61 weak_alias (__modf, modf)
  62 #ifdef NO_LONG_DOUBLE
  63 strong_alias (__modf, __modfl)
  64 weak_alias (__modf, modfl)
  65 #endif