1 /* Copyright (C) 1995,1996,1997,2002,2003 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, write to the Free 16 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 17 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 (53 for 25 double) and an integral power of two to a `double' in IEEE754 double- 26 precision format. */ 27 28 double 29 __mpn_construct_double (mp_srcptr frac_ptr, int expt, int negative) 30 { 31 union ieee754_double u; 32 33 u.ieee.negative = negative; 34 u.ieee.exponent = expt + IEEE754_DOUBLE_BIAS; 35 #if BITS_PER_MP_LIMB == 32 36 u.ieee.mantissa1 = frac_ptr[0]; 37 u.ieee.mantissa0 = frac_ptr[1] & (((mp_limb_t) 1 38 << (DBL_MANT_DIG - 32)) - 1); 39 #elif BITS_PER_MP_LIMB == 64 40 u.ieee.mantissa1 = frac_ptr[0] & (((mp_limb_t) 1 << 32) - 1); 41 u.ieee.mantissa0 = (frac_ptr[0] >> 32) & (((mp_limb_t) 1 42 << (DBL_MANT_DIG - 32)) - 1); 43 #else 44 #error "mp_limb size " BITS_PER_MP_LIMB "not accounted for" 45 #endif 46 47 return u.d; 48 } 49