sysdeps/ieee754/flt-32/mpn2flt.c

   1 /* Copyright (C) 1995-2015 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 Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the 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    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include "gmp.h"
  19 #include "gmp-impl.h"
  20 #include <ieee754.h>
  21 #include <float.h>
  22
  23 /* Convert a multi-precision integer of the needed number of bits (24 for
  24    float) and an integral power of two to a `float' in IEEE754 single-
  25    precision format.  */
  26
  27 float
  28 __mpn_construct_float (mp_srcptr frac_ptr, int expt, int sign)
  29 {
  30   union ieee754_float u;
  31
  32   u.ieee.negative = sign;
  33   u.ieee.exponent = expt + IEEE754_FLOAT_BIAS;
  34 #if BITS_PER_MP_LIMB > FLT_MANT_DIG
  35   u.ieee.mantissa = frac_ptr[0] & (((mp_limb_t) 1 << FLT_MANT_DIG) - 1);
  36 #else
  37   #error "mp_limb size " BITS_PER_MP_LIMB "not accounted for"
  38 #endif
  39
  40   return u.f;
  41 }