sysdeps/ieee754/mpn2flt.c

   1 /* Copyright (C) 1995, 1997 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
  24 /* Convert a multi-precision integer of the needed number of bits (24 for
  25    float) and an integral power of two to a `float' in IEEE754 single-
  26    precision format.  */
  27
  28 float
  29 __mpn_construct_float (mp_srcptr frac_ptr, int expt, int sign)
  30 {
  31   union ieee754_float u;
  32
  33   u.ieee.negative = sign;
  34   u.ieee.exponent = expt + IEEE754_FLOAT_BIAS;
  35 #if BITS_PER_MP_LIMB > FLT_MANT_DIG
  36   u.ieee.mantissa = frac_ptr[0] & ((1 << FLT_MANT_DIG) - 1);
  37 #else
  38   #error "mp_limb size " BITS_PER_MP_LIMB "not accounted for"
  39 #endif
  40
  41   return u.f;
  42 }