libquadmath/strtod/mpn2flt128.c

   1 /* Copyright (C) 1995,1996,1997,1998,1999,2002,2003
   2         Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <config.h>
  21 #include <float.h>
  22 #include <math.h>
  23 #include "../printf/gmp-impl.h"
  24
  25 /* Convert a multi-precision integer of the needed number of bits (113 for
  26    long double) and an integral power of two to a `long double' in IEEE854
  27    quad-precision format.  */
  28
  29 __float128
  30 mpn_construct_float128 (mp_srcptr frac_ptr, int expt, int sign)
  31 {
  32   ieee854_float128 u;
  33
  34   u.ieee.negative = sign;
  35   u.ieee.exponent = expt + IEEE854_FLOAT128_BIAS;
  36 #if BITS_PER_MP_LIMB == 32
  37   u.ieee.mant_low = (((uint64_t) frac_ptr[1]) << 32)
  38                     | (frac_ptr[0] & 0xffffffff);
  39   u.ieee.mant_high = (((uint64_t) frac_ptr[3]
  40                        & (((mp_limb_t) 1 << (FLT128_MANT_DIG - 96)) - 1))
  41                       << 32) | (frac_ptr[2] & 0xffffffff);
  42 #elif BITS_PER_MP_LIMB == 64
  43   u.ieee.mant_low = frac_ptr[0];
  44   u.ieee.mant_high = frac_ptr[1]
  45                      & (((mp_limb_t) 1 << (FLT128_MANT_DIG - 64)) - 1);
  46 #else
  47   #error "mp_limb size " BITS_PER_MP_LIMB "not accounted for"
  48 #endif
  49
  50   return u.value;
  51 }