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Annotation of OpenXM_contrib/gmp/mpz/get_d_2exp.c, Revision 1.1.1.1

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: }