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Annotation of OpenXM_contrib/gmp/mpz/get_d_2exp.c, Revision 1.1

1.1     ! ohara       1: /* double mpz_get_d_2exp (signed long int *exp, mpz_t src).
        !             2:
        !             3: Copyright 2001 Free Software Foundation, Inc.
        !             4:
        !             5: This file is part of the GNU MP Library.
        !             6:
        !             7: The GNU MP Library is free software; you can redistribute it and/or modify
        !             8: it under the terms of the GNU Lesser General Public License as published by
        !             9: the Free Software Foundation; either version 2.1 of the License, or (at your
        !            10: option) any later version.
        !            11:
        !            12: The GNU MP Library is distributed in the hope that it will be useful, but
        !            13: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
        !            14: or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
        !            15: License for more details.
        !            16:
        !            17: You should have received a copy of the GNU Lesser General Public License
        !            18: along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
        !            19: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
        !            20: MA 02111-1307, USA. */
        !            21:
        !            22: #include "gmp.h"
        !            23: #include "gmp-impl.h"
        !            24: #include "longlong.h"
        !            25:
        !            26: double
        !            27: mpz_get_d_2exp (signed long int *exp2, mpz_srcptr src)
        !            28: {
        !            29:   double res;
        !            30:   mp_size_t size, i, n_limbs_to_use;
        !            31:   int negative;
        !            32:   mp_ptr qp;
        !            33:   int cnt;
        !            34:
        !            35:   size = SIZ(src);
        !            36:   if (size == 0)
        !            37:     {
        !            38:       *exp2 = 0;
        !            39:       return 0.0;
        !            40:     }
        !            41:
        !            42:   negative = size < 0;
        !            43:   size = ABS (size);
        !            44:   qp = PTR(src);
        !            45:
        !            46:   n_limbs_to_use = MIN (LIMBS_PER_DOUBLE, size);
        !            47:   qp += size - n_limbs_to_use;
        !            48:   res = qp[0] / MP_BASE_AS_DOUBLE;
        !            49:   for (i = 1; i < n_limbs_to_use; i++)
        !            50:     res = (res + qp[i]) / MP_BASE_AS_DOUBLE;
        !            51:   count_leading_zeros (cnt, qp[n_limbs_to_use - 1]);
        !            52:   *exp2 = size * BITS_PER_MP_LIMB - cnt;
        !            53:   res = res * ((mp_limb_t) 1 << cnt);
        !            54:
        !            55:   return negative ? -res : res;
        !            56: }