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
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)
48 n = count_leading_zeros(alimb);
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);