source: grub-pc/trunk/fuentes/grub-core/lib/libgcrypt-grub/mpi/mpih-rshift.c @ 22

Last change on this file since 22 was 22, checked in by mabarracus, 5 years ago

updated version and apply net.ifnames=0 into debian/rules

File size: 2.1 KB
Line 
1/* mpih-rshift.c  -  MPI helper functions
2 * Copyright (C) 1994, 1996, 1998, 1999,
3 *               2000, 2001, 2002 Free Software Foundation, Inc.
4 *
5 * This file is part of Libgcrypt.
6 *
7 * Libgcrypt is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU Lesser General Public License as
9 * published by the Free Software Foundation; either version 2.1 of
10 * the License, or (at your option) any later version.
11 *
12 * Libgcrypt is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15 * GNU Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with this program; if not, write to the Free Software
19 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
20 *
21 * Note: This code is heavily based on the GNU MP Library.
22 *       Actually it's the same code with only minor changes in the
23 *       way the data is stored; this is to support the abstraction
24 *       of an optional secure memory allocation which may be used
25 *       to avoid revealing of sensitive data due to paging etc.
26 */
27
28#include <config.h>
29#include <stdio.h>
30#include <stdlib.h>
31#include "mpi-internal.h"
32
33
34/* Shift U (pointed to by UP and USIZE limbs long) CNT bits to the right
35 * and store the USIZE least significant limbs of the result at WP.
36 * The bits shifted out to the right are returned.
37 *
38 * Argument constraints:
39 * 1. 0 < CNT < BITS_PER_MP_LIMB
40 * 2. If the result is to be written over the input, WP must be <= UP.
41 */
42
43mpi_limb_t
44_gcry_mpih_rshift( mpi_ptr_t wp, mpi_ptr_t up, mpi_size_t usize, unsigned cnt)
45{
46  mpi_limb_t high_limb, low_limb;
47  unsigned sh_1, sh_2;
48  mpi_size_t i;
49  mpi_limb_t retval;
50
51  sh_1 = cnt;
52  wp -= 1;
53  sh_2 = BITS_PER_MPI_LIMB - sh_1;
54  high_limb = up[0];
55  retval = high_limb << sh_2;
56  low_limb = high_limb;
57  for (i=1; i < usize; i++)
58    {
59      high_limb = up[i];
60      wp[i] = (low_limb >> sh_1) | (high_limb << sh_2);
61      low_limb = high_limb;
62    }
63  wp[i] = low_limb >> sh_1;
64
65  return retval;
66}
67
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