summaryrefslogtreecommitdiff
path: root/src/basic/bitmap.c
blob: e7e19b3b6696dfcd82d86d0738e5caf2cbfcf550 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/

/***
  This file is part of systemd.

  Copyright 2015 Tom Gundersen

  systemd is free software; you can redistribute it and/or modify it
  under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation; either version 2.1 of the License, or
  (at your option) any later version.

  systemd is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/

#include "util.h"

#include "bitmap.h"

struct Bitmap {
        uint64_t *bitmaps;
        size_t n_bitmaps;
        size_t bitmaps_allocated;
};

/* Bitmaps are only meant to store relatively small numbers
 * (corresponding to, say, an enum), so it is ok to limit
 * the max entry. 64k should be plenty. */
#define BITMAPS_MAX_ENTRY 0xffff

/* This indicates that we reached the end of the bitmap */
#define BITMAP_END ((unsigned) -1)

#define BITMAP_NUM_TO_OFFSET(n)           ((n) / (sizeof(uint64_t) * 8))
#define BITMAP_NUM_TO_REM(n)              ((n) % (sizeof(uint64_t) * 8))
#define BITMAP_OFFSET_TO_NUM(offset, rem) ((offset) * sizeof(uint64_t) * 8 + (rem))

Bitmap *bitmap_new(void) {
        return new0(Bitmap, 1);
}

void bitmap_free(Bitmap *b) {
        if (!b)
                return;

        free(b->bitmaps);
        free(b);
}

int bitmap_ensure_allocated(Bitmap **b) {
        Bitmap *a;

        assert(b);

        if (*b)
                return 0;

        a = bitmap_new();
        if (!a)
                return -ENOMEM;

        *b = a;

        return 0;
}

int bitmap_set(Bitmap *b, unsigned n) {
        uint64_t bitmask;
        unsigned offset;

        assert(b);

        /* we refuse to allocate huge bitmaps */
        if (n > BITMAPS_MAX_ENTRY)
                return -ERANGE;

        offset = BITMAP_NUM_TO_OFFSET(n);

        if (offset >= b->n_bitmaps) {
                if (!GREEDY_REALLOC0(b->bitmaps, b->bitmaps_allocated, offset + 1))
                        return -ENOMEM;

                b->n_bitmaps = offset + 1;
        }

        bitmask = UINT64_C(1) << BITMAP_NUM_TO_REM(n);

        b->bitmaps[offset] |= bitmask;

        return 0;
}

void bitmap_unset(Bitmap *b, unsigned n) {
        uint64_t bitmask;
        unsigned offset;

        if (!b)
                return;

        offset = BITMAP_NUM_TO_OFFSET(n);

        if (offset >= b->n_bitmaps)
                return;

        bitmask = UINT64_C(1) << BITMAP_NUM_TO_REM(n);

        b->bitmaps[offset] &= ~bitmask;
}

bool bitmap_isset(Bitmap *b, unsigned n) {
        uint64_t bitmask;
        unsigned offset;

        if (!b)
                return false;

        offset = BITMAP_NUM_TO_OFFSET(n);

        if (offset >= b->n_bitmaps)
                return false;

        bitmask = UINT64_C(1) << BITMAP_NUM_TO_REM(n);

        return !!(b->bitmaps[offset] & bitmask);
}

bool bitmap_isclear(Bitmap *b) {
        unsigned i;

        assert(b);

        for (i = 0; i < b->n_bitmaps; i++)
                if (b->bitmaps[i] != 0)
                        return false;

        return true;
}

void bitmap_clear(Bitmap *b) {
        assert(b);

        b->n_bitmaps = 0;
}

bool bitmap_iterate(Bitmap *b, Iterator *i, unsigned *n) {
        uint64_t bitmask;
        unsigned offset, rem;

        assert(i);
        assert(n);

        if (!b || i->idx == BITMAP_END)
                return false;

        offset = BITMAP_NUM_TO_OFFSET(i->idx);
        rem = BITMAP_NUM_TO_REM(i->idx);
        bitmask = UINT64_C(1) << rem;

        for (; offset < b->n_bitmaps; offset ++) {
                if (b->bitmaps[offset]) {
                        for (; bitmask; bitmask <<= 1, rem ++) {
                                if (b->bitmaps[offset] & bitmask) {
                                        *n = BITMAP_OFFSET_TO_NUM(offset, rem);
                                        i->idx = *n + 1;

                                        return true;
                                }
                        }
                }

                rem = 0;
                bitmask = 1;
        }

        i->idx = BITMAP_END;

        return false;
}

bool bitmap_equal(Bitmap *a, Bitmap *b) {
        size_t common_n_bitmaps;
        Bitmap *c;
        unsigned i;

        if (!a ^ !b)
                return false;

        if (!a)
                return true;

        common_n_bitmaps = MIN(a->n_bitmaps, b->n_bitmaps);
        if (memcmp(a->bitmaps, b->bitmaps, sizeof(uint64_t) * common_n_bitmaps) != 0)
                return false;

        c = a->n_bitmaps > b->n_bitmaps ? a : b;
        for (i = common_n_bitmaps; i < c->n_bitmaps; i++)
                if (c->bitmaps[i] != 0)
                        return false;

        return true;
}