sysdeps/ieee754/mpn2ldbl.c

   1 /* Copyright (C) 1995, 1996 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
  16 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  17 Cambridge, MA 02139, USA.  */
  18
  19 #include "gmp.h"
  20 #include "gmp-impl.h"
  21 #include "ieee754.h"
  22 #include <float.h>
  23
  24 /* Convert a multi-precision integer of the needed number of bits (64 for
  25    long double) and an integral power of two to a `long double' in IEEE854
  26    extended-precision format.  */
  27
  28 long double
  29 __mpn_construct_long_double (mp_srcptr frac_ptr, int expt, int sign)
  30 {
  31   union ieee854_long_double u;
  32
  33   u.ieee.negative = sign;
  34   u.ieee.exponent = expt + IEEE854_LONG_DOUBLE_BIAS;
  35 #if BITS_PER_MP_LIMB == 32
  36   u.ieee.mantissa1 = frac_ptr[0];
  37   u.ieee.mantissa0 = frac_ptr[1];
  38 #elif BITS_PER_MP_LIMB == 64
  39   u.ieee.mantissa1 = frac_ptr[0] & ((1L << 32) - 1);
  40   u.ieee.mantissa0 = frac_ptr[0] >> 32;
  41 #else
  42   #error "mp_limb size " BITS_PER_MP_LIMB "not accounted for"
  43 #endif
  44
  45   return u.d;
  46 }