winsup/cygwin/math/nextafterl.c

   1 /**
   2  * This file has no copyright assigned and is placed in the Public Domain.
   3  * This file is part of the mingw-w64 runtime package.
   4  * No warranty is given; refer to the file DISCLAIMER.PD within this package.
   5  */
   6 /*
   7    nextafterl.c
   8    Contributed by Danny Smith <dannysmith@users.sourceforge.net>
   9    No copyright claimed, absolutely no warranties.
  10
  11    2005-05-09
  12 */
  13
  14 #include <math.h>
  15
  16 long double
  17 nextafterl (long double x, long double y)
  18 {
  19   union {
  20       long double ld;
  21       struct {
  22         /* packed attribute is unnecessary on x86/x64 for these three variables */
  23         unsigned long long mantissa;
  24         unsigned short expn;
  25         unsigned short pad;
  26       } parts;
  27   } u;
  28
  29   /* The normal bit is explicit for long doubles, unlike
  30      float and double.  */
  31   static const unsigned long long normal_bit = 0x8000000000000000ull;
  32   u.ld = 0.0L;
  33   if (isnan (y) || isnan (x))
  34     return x + y;
  35
  36   if (x == y )
  37      /* nextafter (0.0, -O.0) should return -0.0.  */
  38      return y;
  39
  40   u.ld = x;
  41   if (x == 0.0L)
  42     {
  43       u.parts.mantissa = 1ull;
  44       return y > 0.0L ? u.ld : -u.ld;
  45     }
  46
  47   if (((x > 0.0L) ^ (y > x)) == 0)
  48     {
  49       u.parts.mantissa++;
  50       if ((u.parts.mantissa & ~normal_bit) == 0ull)
  51         u.parts.expn++;
  52     }
  53   else
  54     {
  55       if ((u.parts.mantissa & ~normal_bit) == 0ull)
  56         u.parts.expn--;
  57       u.parts.mantissa--;
  58     }
  59
  60   /* If we have updated the expn of a normal number,
  61      or moved from denormal to normal, [re]set the normal bit.  */
  62   if (u.parts.expn & 0x7fff)
  63     u.parts.mantissa |=  normal_bit;
  64
  65   return u.ld;
  66 }
  67
  68 /* nexttowardl is the same function with a different name.  */
  69 long double
  70 nexttowardl (long double, long double) __attribute__ ((alias("nextafterl")));
  71