1/* $OpenBSD: bitmap.c,v 1.9 2017/10/20 01:56:39 djm Exp $ */
2/*
3 * Copyright (c) 2015 Damien Miller <djm@mindrot.org>
4 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17
18#include "includes.h"
19
20#include <sys/types.h>
21#include <string.h>
22#include <stdlib.h>
23
24#include "bitmap.h"
25
26#define BITMAP_WTYPE	u_int
27#define BITMAP_MAX	(1<<24)
28#define BITMAP_BYTES	(sizeof(BITMAP_WTYPE))
29#define BITMAP_BITS	(sizeof(BITMAP_WTYPE) * 8)
30#define BITMAP_WMASK	((BITMAP_WTYPE)BITMAP_BITS - 1)
31struct bitmap {
32	BITMAP_WTYPE *d;
33	size_t len; /* number of words allocated */
34	size_t top; /* index of top word allocated */
35};
36
37struct bitmap *
38bitmap_new(void)
39{
40	struct bitmap *ret;
41
42	if ((ret = calloc(1, sizeof(*ret))) == NULL)
43		return NULL;
44	if ((ret->d = calloc(1, BITMAP_BYTES)) == NULL) {
45		free(ret);
46		return NULL;
47	}
48	ret->len = 1;
49	ret->top = 0;
50	return ret;
51}
52
53void
54bitmap_free(struct bitmap *b)
55{
56	if (b != NULL && b->d != NULL) {
57		bitmap_zero(b);
58		free(b->d);
59		b->d = NULL;
60	}
61	free(b);
62}
63
64void
65bitmap_zero(struct bitmap *b)
66{
67	memset(b->d, 0, b->len * BITMAP_BYTES);
68	b->top = 0;
69}
70
71int
72bitmap_test_bit(struct bitmap *b, u_int n)
73{
74	if (b->top >= b->len)
75		return 0; /* invalid */
76	if (b->len == 0 || (n / BITMAP_BITS) > b->top)
77		return 0;
78	return (b->d[n / BITMAP_BITS] >> (n & BITMAP_WMASK)) & 1;
79}
80
81static int
82reserve(struct bitmap *b, u_int n)
83{
84	BITMAP_WTYPE *tmp;
85	size_t nlen;
86
87	if (b->top >= b->len || n > BITMAP_MAX)
88		return -1; /* invalid */
89	nlen = (n / BITMAP_BITS) + 1;
90	if (b->len < nlen) {
91		if ((tmp = recallocarray(b->d, b->len,
92		    nlen, BITMAP_BYTES)) == NULL)
93			return -1;
94		b->d = tmp;
95		b->len = nlen;
96	}
97	return 0;
98}
99
100int
101bitmap_set_bit(struct bitmap *b, u_int n)
102{
103	int r;
104	size_t offset;
105
106	if ((r = reserve(b, n)) != 0)
107		return r;
108	offset = n / BITMAP_BITS;
109	if (offset > b->top)
110		b->top = offset;
111	b->d[offset] |= (BITMAP_WTYPE)1 << (n & BITMAP_WMASK);
112	return 0;
113}
114
115/* Resets b->top to point to the most significant bit set in b->d */
116static void
117retop(struct bitmap *b)
118{
119	if (b->top >= b->len)
120		return;
121	while (b->top > 0 && b->d[b->top] == 0)
122		b->top--;
123}
124
125void
126bitmap_clear_bit(struct bitmap *b, u_int n)
127{
128	size_t offset;
129
130	if (b->top >= b->len || n > BITMAP_MAX)
131		return; /* invalid */
132	offset = n / BITMAP_BITS;
133	if (offset > b->top)
134		return;
135	b->d[offset] &= ~((BITMAP_WTYPE)1 << (n & BITMAP_WMASK));
136	/* The top may have changed as a result of the clear */
137	retop(b);
138}
139
140size_t
141bitmap_nbits(struct bitmap *b)
142{
143	size_t bits;
144	BITMAP_WTYPE w;
145
146	retop(b);
147	if (b->top >= b->len)
148		return 0; /* invalid */
149	if (b->len == 0 || (b->top == 0 && b->d[0] == 0))
150		return 0;
151	/* Find MSB set */
152	w = b->d[b->top];
153	bits = (b->top + 1) * BITMAP_BITS;
154	while (!(w & ((BITMAP_WTYPE)1 << (BITMAP_BITS - 1)))) {
155		w <<= 1;
156		bits--;
157	}
158	return bits;
159}
160
161size_t
162bitmap_nbytes(struct bitmap *b)
163{
164	return (bitmap_nbits(b) + 7) / 8;
165}
166
167int
168bitmap_to_string(struct bitmap *b, void *p, size_t l)
169{
170	u_char *s = (u_char *)p;
171	size_t i, j, k, need = bitmap_nbytes(b);
172
173	if (l < need || b->top >= b->len)
174		return -1;
175	if (l > need)
176		l = need;
177	/* Put the bytes from LSB backwards */
178	for (i = k = 0; i < b->top + 1; i++) {
179		for (j = 0; j < BITMAP_BYTES; j++) {
180			if (k >= l)
181				break;
182			s[need - 1 - k++] = (b->d[i] >> (j * 8)) & 0xff;
183		}
184	}
185	return 0;
186}
187
188int
189bitmap_from_string(struct bitmap *b, const void *p, size_t l)
190{
191	int r;
192	size_t i, offset, shift;
193	const u_char *s = (const u_char *)p;
194
195	if (l > BITMAP_MAX / 8)
196		return -1;
197	if ((r = reserve(b, l * 8)) != 0)
198		return r;
199	bitmap_zero(b);
200	if (l == 0)
201		return 0;
202	b->top = offset = ((l + (BITMAP_BYTES - 1)) / BITMAP_BYTES) - 1;
203	shift = ((l + (BITMAP_BYTES - 1)) % BITMAP_BYTES) * 8;
204	for (i = 0; i < l; i++) {
205		b->d[offset] |= (BITMAP_WTYPE)s[i] << shift;
206		if (shift == 0) {
207			offset--;
208			shift = BITMAP_BITS - 8;
209		} else
210			shift -= 8;
211	}
212	retop(b);
213	return 0;
214}
215