sysdeps/ieee754/mpn2ldbl.c

   1 /* Copyright (C) 1995, 1996, 1997, 1998 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Library General Public License as
   6    published by the Free Software Foundation; either version 2 of the
   7    License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Library General Public License for more details.
  13
  14    You should have received a copy of the GNU Library General Public
  15    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  16    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17    Boston, MA 02111-1307, USA.  */
  18
  19 #include "gmp.h"
  20 #include "gmp-impl.h"
  21 #include <ieee754.h>
  22 #include <float.h>
  23 #include <math.h>
  24
  25 #ifndef __NO_LONG_DOUBLE_MATH
  26
  27 /* Convert a multi-precision integer of the needed number of bits (64 for
  28    long double) and an integral power of two to a `long double' in IEEE854
  29    extended-precision format.  */
  30
  31 long double
  32 __mpn_construct_long_double (mp_srcptr frac_ptr, int expt, int sign)
  33 {
  34   union ieee854_long_double u;
  35
  36   u.ieee.negative = sign;
  37   u.ieee.exponent = expt + IEEE854_LONG_DOUBLE_BIAS;
  38 #if BITS_PER_MP_LIMB == 32
  39   u.ieee.mantissa1 = frac_ptr[0];
  40   u.ieee.mantissa0 = frac_ptr[1];
  41 #elif BITS_PER_MP_LIMB == 64
  42   u.ieee.mantissa1 = frac_ptr[0] & ((1L << 32) - 1);
  43   u.ieee.mantissa0 = frac_ptr[0] >> 32;
  44 #else
  45   #error "mp_limb size " BITS_PER_MP_LIMB "not accounted for"
  46 #endif
  47
  48   return u.d;
  49 }
  50
  51 #endif /* __NO_LONG_DOUBLE_MATH */