Diffstat (limited to 'pwmanager/libcrypt/mpi/generic/mpih-rshift.c') (more/less context) (ignore whitespace changes)
-rw-r--r-- | pwmanager/libcrypt/mpi/generic/mpih-rshift.c | 67 |
1 files changed, 67 insertions, 0 deletions
diff --git a/pwmanager/libcrypt/mpi/generic/mpih-rshift.c b/pwmanager/libcrypt/mpi/generic/mpih-rshift.c new file mode 100644 index 0000000..e40794f --- a/dev/null +++ b/pwmanager/libcrypt/mpi/generic/mpih-rshift.c | |||
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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 | |||
43 | mpi_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 | |||