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Annotation of OpenXM_contrib/gmp/mpn/generic/rshift.c, Revision 1.1.1.3

1.1.1.3 ! ohara       1: /* mpn_rshift -- Shift right low level.
1.1       maekawa     2:
1.1.1.3 ! ohara       3: Copyright 1991, 1993, 1994, 1996, 2000, 2001, 2002 Free Software Foundation,
        !             4: Inc.
1.1       maekawa     5:
                      6: This file is part of the GNU MP Library.
                      7:
                      8: The GNU MP Library is free software; you can redistribute it and/or modify
1.1.1.2   maekawa     9: it under the terms of the GNU Lesser General Public License as published by
                     10: the Free Software Foundation; either version 2.1 of the License, or (at your
1.1       maekawa    11: option) any later version.
                     12:
                     13: The GNU MP Library is distributed in the hope that it will be useful, but
                     14: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
1.1.1.2   maekawa    15: or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
1.1       maekawa    16: License for more details.
                     17:
1.1.1.2   maekawa    18: You should have received a copy of the GNU Lesser General Public License
1.1       maekawa    19: along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
                     20: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
                     21: MA 02111-1307, USA. */
                     22:
                     23: #include "gmp.h"
                     24: #include "gmp-impl.h"
                     25:
1.1.1.3 ! ohara      26: /* Shift U (pointed to by up and N limbs long) cnt bits to the right
        !            27:    and store the n least significant limbs of the result at rp.
1.1       maekawa    28:    The bits shifted out to the right are returned.
                     29:
                     30:    Argument constraints:
1.1.1.3 ! ohara      31:    1. 0 < cnt < GMP_NUMB_BITS.
        !            32:    2. If the result is to be written over the input, rp must be <= up.
1.1       maekawa    33: */
                     34:
                     35: mp_limb_t
1.1.1.3 ! ohara      36: mpn_rshift (mp_ptr rp, mp_srcptr up, mp_size_t n, unsigned int cnt)
1.1       maekawa    37: {
1.1.1.3 ! ohara      38:   mp_limb_t high_limb, low_limb;
        !            39:   unsigned int tnc;
        !            40:   mp_size_t i;
1.1       maekawa    41:   mp_limb_t retval;
                     42:
1.1.1.3 ! ohara      43:   ASSERT (n >= 1);
        !            44:   ASSERT (cnt >= 1);
        !            45:   ASSERT (cnt < GMP_NUMB_BITS);
        !            46:   ASSERT (MPN_SAME_OR_INCR_P (rp, up, n));
        !            47:
        !            48:   tnc = GMP_NUMB_BITS - cnt;
        !            49:   high_limb = *up++;
        !            50:   retval = (high_limb << tnc) & GMP_NUMB_MASK;
        !            51:   low_limb = high_limb >> cnt;
1.1       maekawa    52:
1.1.1.3 ! ohara      53:   for (i = n - 1; i != 0; i--)
1.1       maekawa    54:     {
1.1.1.3 ! ohara      55:       high_limb = *up++;
        !            56:       *rp++ = low_limb | ((high_limb << tnc) & GMP_NUMB_MASK);
        !            57:       low_limb = high_limb >> cnt;
1.1       maekawa    58:     }
1.1.1.3 ! ohara      59:   *rp = low_limb;
1.1       maekawa    60:
                     61:   return retval;
                     62: }