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cdec9cb5 DK |
1 | /* mpi-bit.c - MPI bit level fucntions |
2 | * Copyright (C) 1998, 1999 Free Software Foundation, Inc. | |
3 | * | |
4 | * This file is part of GnuPG. | |
5 | * | |
6 | * GnuPG is free software; you can redistribute it and/or modify | |
7 | * it under the terms of the GNU General Public License as published by | |
8 | * the Free Software Foundation; either version 2 of the License, or | |
9 | * (at your option) any later version. | |
10 | * | |
11 | * GnuPG is distributed in the hope that it will be useful, | |
12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
14 | * GNU General Public License for more details. | |
15 | * | |
16 | * You should have received a copy of the GNU General Public License | |
17 | * along with this program; if not, write to the Free Software | |
18 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA | |
19 | */ | |
20 | ||
21 | #include "mpi-internal.h" | |
22 | #include "longlong.h" | |
23 | ||
cdec9cb5 DK |
24 | #define A_LIMB_1 ((mpi_limb_t) 1) |
25 | ||
26 | /**************** | |
27 | * Sometimes we have MSL (most significant limbs) which are 0; | |
28 | * this is for some reasons not good, so this function removes them. | |
29 | */ | |
30 | void mpi_normalize(MPI a) | |
31 | { | |
32 | for (; a->nlimbs && !a->d[a->nlimbs - 1]; a->nlimbs--) | |
33 | ; | |
34 | } | |
35 | ||
36 | /**************** | |
37 | * Return the number of bits in A. | |
38 | */ | |
39 | unsigned mpi_get_nbits(MPI a) | |
40 | { | |
41 | unsigned n; | |
42 | ||
43 | mpi_normalize(a); | |
44 | ||
45 | if (a->nlimbs) { | |
46 | mpi_limb_t alimb = a->d[a->nlimbs - 1]; | |
47 | if (alimb) | |
aacf29bf | 48 | n = count_leading_zeros(alimb); |
cdec9cb5 DK |
49 | else |
50 | n = BITS_PER_MPI_LIMB; | |
51 | n = BITS_PER_MPI_LIMB - n + (a->nlimbs - 1) * BITS_PER_MPI_LIMB; | |
52 | } else | |
53 | n = 0; | |
54 | return n; | |
55 | } | |
56 | EXPORT_SYMBOL_GPL(mpi_get_nbits); |