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 <sys/types.h>
19 #include <string.h>
20 #include <stdlib.h>
21
22 #include "bitmap.h"
23
24 #define BITMAP_WTYPE u_int
25 #define BITMAP_MAX (1<<24)
26 #define BITMAP_BYTES (sizeof(BITMAP_WTYPE))
27 #define BITMAP_BITS (sizeof(BITMAP_WTYPE) * 8)
28 #define BITMAP_WMASK ((BITMAP_WTYPE)BITMAP_BITS - 1)
29 struct bitmap {
30 BITMAP_WTYPE *d;
31 size_t len; /* number of words allocated */
32 size_t top; /* index of top word allocated */
33 };
34
35 struct bitmap *
bitmap_new(void)36 bitmap_new(void)
37 {
38 struct bitmap *ret;
39
40 if ((ret = calloc(1, sizeof(*ret))) == NULL)
41 return NULL;
42 if ((ret->d = calloc(1, BITMAP_BYTES)) == NULL) {
43 free(ret);
44 return NULL;
45 }
46 ret->len = 1;
47 ret->top = 0;
48 return ret;
49 }
50
51 void
bitmap_free(struct bitmap * b)52 bitmap_free(struct bitmap *b)
53 {
54 if (b != NULL && b->d != NULL) {
55 bitmap_zero(b);
56 free(b->d);
57 b->d = NULL;
58 }
59 free(b);
60 }
61
62 void
bitmap_zero(struct bitmap * b)63 bitmap_zero(struct bitmap *b)
64 {
65 memset(b->d, 0, b->len * BITMAP_BYTES);
66 b->top = 0;
67 }
68
69 int
bitmap_test_bit(struct bitmap * b,u_int n)70 bitmap_test_bit(struct bitmap *b, u_int n)
71 {
72 if (b->top >= b->len)
73 return 0; /* invalid */
74 if (b->len == 0 || (n / BITMAP_BITS) > b->top)
75 return 0;
76 return (b->d[n / BITMAP_BITS] >> (n & BITMAP_WMASK)) & 1;
77 }
78
79 static int
reserve(struct bitmap * b,u_int n)80 reserve(struct bitmap *b, u_int n)
81 {
82 BITMAP_WTYPE *tmp;
83 size_t nlen;
84
85 if (b->top >= b->len || n > BITMAP_MAX)
86 return -1; /* invalid */
87 nlen = (n / BITMAP_BITS) + 1;
88 if (b->len < nlen) {
89 if ((tmp = recallocarray(b->d, b->len,
90 nlen, BITMAP_BYTES)) == NULL)
91 return -1;
92 b->d = tmp;
93 b->len = nlen;
94 }
95 return 0;
96 }
97
98 int
bitmap_set_bit(struct bitmap * b,u_int n)99 bitmap_set_bit(struct bitmap *b, u_int n)
100 {
101 int r;
102 size_t offset;
103
104 if ((r = reserve(b, n)) != 0)
105 return r;
106 offset = n / BITMAP_BITS;
107 if (offset > b->top)
108 b->top = offset;
109 b->d[offset] |= (BITMAP_WTYPE)1 << (n & BITMAP_WMASK);
110 return 0;
111 }
112
113 /* Resets b->top to point to the most significant bit set in b->d */
114 static void
retop(struct bitmap * b)115 retop(struct bitmap *b)
116 {
117 if (b->top >= b->len)
118 return;
119 while (b->top > 0 && b->d[b->top] == 0)
120 b->top--;
121 }
122
123 void
bitmap_clear_bit(struct bitmap * b,u_int n)124 bitmap_clear_bit(struct bitmap *b, u_int n)
125 {
126 size_t offset;
127
128 if (b->top >= b->len || n > BITMAP_MAX)
129 return; /* invalid */
130 offset = n / BITMAP_BITS;
131 if (offset > b->top)
132 return;
133 b->d[offset] &= ~((BITMAP_WTYPE)1 << (n & BITMAP_WMASK));
134 /* The top may have changed as a result of the clear */
135 retop(b);
136 }
137
138 size_t
bitmap_nbits(struct bitmap * b)139 bitmap_nbits(struct bitmap *b)
140 {
141 size_t bits;
142 BITMAP_WTYPE w;
143
144 retop(b);
145 if (b->top >= b->len)
146 return 0; /* invalid */
147 if (b->len == 0 || (b->top == 0 && b->d[0] == 0))
148 return 0;
149 /* Find MSB set */
150 w = b->d[b->top];
151 bits = (b->top + 1) * BITMAP_BITS;
152 while (!(w & ((BITMAP_WTYPE)1 << (BITMAP_BITS - 1)))) {
153 w <<= 1;
154 bits--;
155 }
156 return bits;
157 }
158
159 size_t
bitmap_nbytes(struct bitmap * b)160 bitmap_nbytes(struct bitmap *b)
161 {
162 return (bitmap_nbits(b) + 7) / 8;
163 }
164
165 int
bitmap_to_string(struct bitmap * b,void * p,size_t l)166 bitmap_to_string(struct bitmap *b, void *p, size_t l)
167 {
168 u_char *s = (u_char *)p;
169 size_t i, j, k, need = bitmap_nbytes(b);
170
171 if (l < need || b->top >= b->len)
172 return -1;
173 if (l > need)
174 l = need;
175 /* Put the bytes from LSB backwards */
176 for (i = k = 0; i < b->top + 1; i++) {
177 for (j = 0; j < BITMAP_BYTES; j++) {
178 if (k >= l)
179 break;
180 s[need - 1 - k++] = (b->d[i] >> (j * 8)) & 0xff;
181 }
182 }
183 return 0;
184 }
185
186 int
bitmap_from_string(struct bitmap * b,const void * p,size_t l)187 bitmap_from_string(struct bitmap *b, const void *p, size_t l)
188 {
189 int r;
190 size_t i, offset, shift;
191 const u_char *s = (const u_char *)p;
192
193 if (l > BITMAP_MAX / 8)
194 return -1;
195 if ((r = reserve(b, l * 8)) != 0)
196 return r;
197 bitmap_zero(b);
198 if (l == 0)
199 return 0;
200 b->top = offset = ((l + (BITMAP_BYTES - 1)) / BITMAP_BYTES) - 1;
201 shift = ((l + (BITMAP_BYTES - 1)) % BITMAP_BYTES) * 8;
202 for (i = 0; i < l; i++) {
203 b->d[offset] |= (BITMAP_WTYPE)s[i] << shift;
204 if (shift == 0) {
205 offset--;
206 shift = BITMAP_BITS - 8;
207 } else
208 shift -= 8;
209 }
210 retop(b);
211 return 0;
212 }
213