1 /* mpi-bit.c - MPI bit level fucntions
2 * Copyright (C) 1998, 1999 Free Software Foundation, Inc.
4 * This file is part of GnuPG.
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.
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.
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
21 #include "mpi-internal.h"
24 const unsigned char __clz_tab[] = {
25 0, 1, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5,
26 5, 5, 5, 5, 5, 5, 5, 5,
27 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
28 6, 6, 6, 6, 6, 6, 6, 6,
29 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
30 7, 7, 7, 7, 7, 7, 7, 7,
31 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
32 7, 7, 7, 7, 7, 7, 7, 7,
33 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
34 8, 8, 8, 8, 8, 8, 8, 8,
35 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
36 8, 8, 8, 8, 8, 8, 8, 8,
37 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
38 8, 8, 8, 8, 8, 8, 8, 8,
39 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
40 8, 8, 8, 8, 8, 8, 8, 8,
43 #define A_LIMB_1 ((mpi_limb_t) 1)
46 * Sometimes we have MSL (most significant limbs) which are 0;
47 * this is for some reasons not good, so this function removes them.
49 void mpi_normalize(MPI a)
51 for (; a->nlimbs && !a->d[a->nlimbs - 1]; a->nlimbs--)
56 * Return the number of bits in A.
58 unsigned mpi_get_nbits(MPI a)
65 mpi_limb_t alimb = a->d[a->nlimbs - 1];
67 count_leading_zeros(n, alimb);
69 n = BITS_PER_MPI_LIMB;
70 n = BITS_PER_MPI_LIMB - n + (a->nlimbs - 1) * BITS_PER_MPI_LIMB;
75 EXPORT_SYMBOL_GPL(mpi_get_nbits);
78 * Test whether bit N is set.
80 int mpi_test_bit(MPI a, unsigned n)
82 unsigned limbno, bitno;
85 limbno = n / BITS_PER_MPI_LIMB;
86 bitno = n % BITS_PER_MPI_LIMB;
88 if (limbno >= a->nlimbs)
89 return 0; /* too far left: this is a 0 */
91 return (limb & (A_LIMB_1 << bitno)) ? 1 : 0;
97 int mpi_set_bit(MPI a, unsigned n)
99 unsigned limbno, bitno;
101 limbno = n / BITS_PER_MPI_LIMB;
102 bitno = n % BITS_PER_MPI_LIMB;
104 if (limbno >= a->nlimbs) { /* resize */
105 if (a->alloced >= limbno)
106 if (mpi_resize(a, limbno + 1) < 0)
108 a->nlimbs = limbno + 1;
110 a->d[limbno] |= (A_LIMB_1 << bitno);
115 * Set bit N of A. and clear all bits above
117 int mpi_set_highbit(MPI a, unsigned n)
119 unsigned limbno, bitno;
121 limbno = n / BITS_PER_MPI_LIMB;
122 bitno = n % BITS_PER_MPI_LIMB;
124 if (limbno >= a->nlimbs) { /* resize */
125 if (a->alloced >= limbno)
126 if (mpi_resize(a, limbno + 1) < 0)
128 a->nlimbs = limbno + 1;
130 a->d[limbno] |= (A_LIMB_1 << bitno);
131 for (bitno++; bitno < BITS_PER_MPI_LIMB; bitno++)
132 a->d[limbno] &= ~(A_LIMB_1 << bitno);
133 a->nlimbs = limbno + 1;
138 * clear bit N of A and all bits above
140 void mpi_clear_highbit(MPI a, unsigned n)
142 unsigned limbno, bitno;
144 limbno = n / BITS_PER_MPI_LIMB;
145 bitno = n % BITS_PER_MPI_LIMB;
147 if (limbno >= a->nlimbs)
148 return; /* not allocated, so need to clear bits :-) */
150 for (; bitno < BITS_PER_MPI_LIMB; bitno++)
151 a->d[limbno] &= ~(A_LIMB_1 << bitno);
152 a->nlimbs = limbno + 1;
158 void mpi_clear_bit(MPI a, unsigned n)
160 unsigned limbno, bitno;
162 limbno = n / BITS_PER_MPI_LIMB;
163 bitno = n % BITS_PER_MPI_LIMB;
165 if (limbno >= a->nlimbs)
166 return; /* don't need to clear this bit, it's to far to left */
167 a->d[limbno] &= ~(A_LIMB_1 << bitno);
171 * Shift A by N bits to the right
172 * FIXME: should use alloc_limb if X and A are same.
174 int mpi_rshift(MPI x, MPI a, unsigned n)
181 if (RESIZE_IF_NEEDED(x, (size_t) xsize) < 0)
186 mpihelp_rshift(xp, a->d, xsize, n);
187 MPN_NORMALIZE(xp, xsize);
194 * Shift A by COUNT limbs to the left
195 * This is used only within the MPI library
197 int mpi_lshift_limbs(MPI a, unsigned int count)
206 if (RESIZE_IF_NEEDED(a, n + count) < 0)
209 for (i = n - 1; i >= 0; i--)
210 ap[i + count] = ap[i];
211 for (i = 0; i < count; i++)
218 * Shift A by COUNT limbs to the right
219 * This is used only within the MPI library
221 void mpi_rshift_limbs(MPI a, unsigned int count)
224 mpi_size_t n = a->nlimbs;
232 for (i = 0; i < n - count; i++)
233 ap[i] = ap[i + count];