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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 | ||
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, | |
41 | }; | |
42 | ||
43 | #define A_LIMB_1 ((mpi_limb_t) 1) | |
44 | ||
45 | /**************** | |
46 | * Sometimes we have MSL (most significant limbs) which are 0; | |
47 | * this is for some reasons not good, so this function removes them. | |
48 | */ | |
49 | void mpi_normalize(MPI a) | |
50 | { | |
51 | for (; a->nlimbs && !a->d[a->nlimbs - 1]; a->nlimbs--) | |
52 | ; | |
53 | } | |
54 | ||
55 | /**************** | |
56 | * Return the number of bits in A. | |
57 | */ | |
58 | unsigned mpi_get_nbits(MPI a) | |
59 | { | |
60 | unsigned n; | |
61 | ||
62 | mpi_normalize(a); | |
63 | ||
64 | if (a->nlimbs) { | |
65 | mpi_limb_t alimb = a->d[a->nlimbs - 1]; | |
66 | if (alimb) | |
67 | count_leading_zeros(n, alimb); | |
68 | else | |
69 | n = BITS_PER_MPI_LIMB; | |
70 | n = BITS_PER_MPI_LIMB - n + (a->nlimbs - 1) * BITS_PER_MPI_LIMB; | |
71 | } else | |
72 | n = 0; | |
73 | return n; | |
74 | } | |
75 | EXPORT_SYMBOL_GPL(mpi_get_nbits); | |
76 | ||
77 | /**************** | |
78 | * Test whether bit N is set. | |
79 | */ | |
80 | int mpi_test_bit(MPI a, unsigned n) | |
81 | { | |
82 | unsigned limbno, bitno; | |
83 | mpi_limb_t limb; | |
84 | ||
85 | limbno = n / BITS_PER_MPI_LIMB; | |
86 | bitno = n % BITS_PER_MPI_LIMB; | |
87 | ||
88 | if (limbno >= a->nlimbs) | |
89 | return 0; /* too far left: this is a 0 */ | |
90 | limb = a->d[limbno]; | |
91 | return (limb & (A_LIMB_1 << bitno)) ? 1 : 0; | |
92 | } | |
93 | ||
94 | /**************** | |
95 | * Set bit N of A. | |
96 | */ | |
97 | int mpi_set_bit(MPI a, unsigned n) | |
98 | { | |
99 | unsigned limbno, bitno; | |
100 | ||
101 | limbno = n / BITS_PER_MPI_LIMB; | |
102 | bitno = n % BITS_PER_MPI_LIMB; | |
103 | ||
104 | if (limbno >= a->nlimbs) { /* resize */ | |
105 | if (a->alloced >= limbno) | |
106 | if (mpi_resize(a, limbno + 1) < 0) | |
107 | return -ENOMEM; | |
108 | a->nlimbs = limbno + 1; | |
109 | } | |
110 | a->d[limbno] |= (A_LIMB_1 << bitno); | |
111 | return 0; | |
112 | } | |
113 | ||
114 | /**************** | |
115 | * Set bit N of A. and clear all bits above | |
116 | */ | |
117 | int mpi_set_highbit(MPI a, unsigned n) | |
118 | { | |
119 | unsigned limbno, bitno; | |
120 | ||
121 | limbno = n / BITS_PER_MPI_LIMB; | |
122 | bitno = n % BITS_PER_MPI_LIMB; | |
123 | ||
124 | if (limbno >= a->nlimbs) { /* resize */ | |
125 | if (a->alloced >= limbno) | |
126 | if (mpi_resize(a, limbno + 1) < 0) | |
127 | return -ENOMEM; | |
128 | a->nlimbs = limbno + 1; | |
129 | } | |
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; | |
134 | return 0; | |
135 | } | |
136 | ||
137 | /**************** | |
138 | * clear bit N of A and all bits above | |
139 | */ | |
140 | void mpi_clear_highbit(MPI a, unsigned n) | |
141 | { | |
142 | unsigned limbno, bitno; | |
143 | ||
144 | limbno = n / BITS_PER_MPI_LIMB; | |
145 | bitno = n % BITS_PER_MPI_LIMB; | |
146 | ||
147 | if (limbno >= a->nlimbs) | |
148 | return; /* not allocated, so need to clear bits :-) */ | |
149 | ||
150 | for (; bitno < BITS_PER_MPI_LIMB; bitno++) | |
151 | a->d[limbno] &= ~(A_LIMB_1 << bitno); | |
152 | a->nlimbs = limbno + 1; | |
153 | } | |
154 | ||
155 | /**************** | |
156 | * Clear bit N of A. | |
157 | */ | |
158 | void mpi_clear_bit(MPI a, unsigned n) | |
159 | { | |
160 | unsigned limbno, bitno; | |
161 | ||
162 | limbno = n / BITS_PER_MPI_LIMB; | |
163 | bitno = n % BITS_PER_MPI_LIMB; | |
164 | ||
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); | |
168 | } | |
169 | ||
170 | /**************** | |
171 | * Shift A by N bits to the right | |
172 | * FIXME: should use alloc_limb if X and A are same. | |
173 | */ | |
174 | int mpi_rshift(MPI x, MPI a, unsigned n) | |
175 | { | |
176 | mpi_ptr_t xp; | |
177 | mpi_size_t xsize; | |
178 | ||
179 | xsize = a->nlimbs; | |
180 | x->sign = a->sign; | |
181 | if (RESIZE_IF_NEEDED(x, (size_t) xsize) < 0) | |
182 | return -ENOMEM; | |
183 | xp = x->d; | |
184 | ||
185 | if (xsize) { | |
186 | mpihelp_rshift(xp, a->d, xsize, n); | |
187 | MPN_NORMALIZE(xp, xsize); | |
188 | } | |
189 | x->nlimbs = xsize; | |
190 | return 0; | |
191 | } | |
192 | ||
193 | /**************** | |
194 | * Shift A by COUNT limbs to the left | |
195 | * This is used only within the MPI library | |
196 | */ | |
197 | int mpi_lshift_limbs(MPI a, unsigned int count) | |
198 | { | |
199 | mpi_ptr_t ap = a->d; | |
200 | int n = a->nlimbs; | |
201 | int i; | |
202 | ||
203 | if (!count || !n) | |
204 | return 0; | |
205 | ||
206 | if (RESIZE_IF_NEEDED(a, n + count) < 0) | |
207 | return -ENOMEM; | |
208 | ||
209 | for (i = n - 1; i >= 0; i--) | |
210 | ap[i + count] = ap[i]; | |
211 | for (i = 0; i < count; i++) | |
212 | ap[i] = 0; | |
213 | a->nlimbs += count; | |
214 | return 0; | |
215 | } | |
216 | ||
217 | /**************** | |
218 | * Shift A by COUNT limbs to the right | |
219 | * This is used only within the MPI library | |
220 | */ | |
221 | void mpi_rshift_limbs(MPI a, unsigned int count) | |
222 | { | |
223 | mpi_ptr_t ap = a->d; | |
224 | mpi_size_t n = a->nlimbs; | |
225 | unsigned int i; | |
226 | ||
227 | if (count >= n) { | |
228 | a->nlimbs = 0; | |
229 | return; | |
230 | } | |
231 | ||
232 | for (i = 0; i < n - count; i++) | |
233 | ap[i] = ap[i + count]; | |
234 | ap[i] = 0; | |
235 | a->nlimbs -= count; | |
236 | } |