1 // SPDX-License-Identifier: GPL-2.0
2 #include <stdio.h>
3 #include <stdlib.h>
4 #include <string.h>
5
6 #include <helpers/bitmask.h>
7
8 /* How many bits in an unsigned long */
9 #define bitsperlong (8 * sizeof(unsigned long))
10
11 /* howmany(a,b) : how many elements of size b needed to hold all of a */
12 #define howmany(x, y) (((x)+((y)-1))/(y))
13
14 /* How many longs in mask of n bits */
15 #define longsperbits(n) howmany(n, bitsperlong)
16
17 #define max(a, b) ((a) > (b) ? (a) : (b))
18
19 /*
20 * Allocate and free `struct bitmask *`
21 */
22
23 /* Allocate a new `struct bitmask` with a size of n bits */
24 struct bitmask *bitmask_alloc(unsigned int n)
25 {
26 struct bitmask *bmp;
27
28 bmp = malloc(sizeof(*bmp));
29 if (!bmp)
30 return 0;
31 bmp->size = n;
32 bmp->maskp = calloc(longsperbits(n), sizeof(unsigned long));
33 if (!bmp->maskp) {
34 free(bmp);
35 return 0;
36 }
37 return bmp;
38 }
39
40 /* Free `struct bitmask` */
41 void bitmask_free(struct bitmask *bmp)
42 {
43 if (!bmp)
44 return;
45 free(bmp->maskp);
46 bmp->maskp = (unsigned long *)0xdeadcdef; /* double free tripwire */
47 free(bmp);
48 }
49
50 /*
51 * The routines _getbit() and _setbit() are the only
52 * routines that actually understand the layout of bmp->maskp[].
53 *
54 * On little endian architectures, this could simply be an array of
55 * bytes. But the kernel layout of bitmasks _is_ visible to userspace
56 * via the sched_(set/get)affinity calls in Linux 2.6, and on big
57 * endian architectures, it is painfully obvious that this is an
58 * array of unsigned longs.
59 */
60
61 /* Return the value (0 or 1) of bit n in bitmask bmp */
62 static unsigned int _getbit(const struct bitmask *bmp, unsigned int n)
63 {
64 if (n < bmp->size)
65 return (bmp->maskp[n/bitsperlong] >> (n % bitsperlong)) & 1;
66 else
67 return 0;
68 }
69
70 /* Set bit n in bitmask bmp to value v (0 or 1) */
71 static void _setbit(struct bitmask *bmp, unsigned int n, unsigned int v)
72 {
73 if (n < bmp->size) {
74 if (v)
75 bmp->maskp[n/bitsperlong] |= 1UL << (n % bitsperlong);
76 else
77 bmp->maskp[n/bitsperlong] &=
78 ~(1UL << (n % bitsperlong));
79 }
80 }
81
82 /*
83 * When parsing bitmask lists, only allow numbers, separated by one
84 * of the allowed next characters.
85 *
86 * The parameter 'sret' is the return from a sscanf "%u%c". It is
87 * -1 if the sscanf input string was empty. It is 0 if the first
88 * character in the sscanf input string was not a decimal number.
89 * It is 1 if the unsigned number matching the "%u" was the end of the
90 * input string. It is 2 if one or more additional characters followed
91 * the matched unsigned number. If it is 2, then 'nextc' is the first
92 * character following the number. The parameter 'ok_next_chars'
93 * is the nul-terminated list of allowed next characters.
94 *
95 * The mask term just scanned was ok if and only if either the numbers
96 * matching the %u were all of the input or if the next character in
97 * the input past the numbers was one of the allowed next characters.
98 */
99 static int scan_was_ok(int sret, char nextc, const char *ok_next_chars)
100 {
101 return sret == 1 ||
102 (sret == 2 && strchr(ok_next_chars, nextc) != NULL);
103 }
104
105 static const char *nexttoken(const char *q, int sep)
106 {
107 if (q)
108 q = strchr(q, sep);
109 if (q)
110 q++;
111 return q;
112 }
113
114 /* Set a single bit i in bitmask */
115 struct bitmask *bitmask_setbit(struct bitmask *bmp, unsigned int i)
116 {
117 _setbit(bmp, i, 1);
118 return bmp;
119 }
120
121 /* Set all bits in bitmask: bmp = ~0 */
122 struct bitmask *bitmask_setall(struct bitmask *bmp)
123 {
124 unsigned int i;
125 for (i = 0; i < bmp->size; i++)
126 _setbit(bmp, i, 1);
127 return bmp;
128 }
129
130 /* Clear all bits in bitmask: bmp = 0 */
131 struct bitmask *bitmask_clearall(struct bitmask *bmp)
132 {
133 unsigned int i;
134 for (i = 0; i < bmp->size; i++)
135 _setbit(bmp, i, 0);
136 return bmp;
137 }
138
139 /* True if all bits are clear */
140 int bitmask_isallclear(const struct bitmask *bmp)
141 {
142 unsigned int i;
143 for (i = 0; i < bmp->size; i++)
144 if (_getbit(bmp, i))
145 return 0;
146 return 1;
147 }
148
149 /* True if specified bit i is set */
150 int bitmask_isbitset(const struct bitmask *bmp, unsigned int i)
151 {
152 return _getbit(bmp, i);
153 }
154
155 /* Number of lowest set bit (min) */
156 unsigned int bitmask_first(const struct bitmask *bmp)
157 {
158 return bitmask_next(bmp, 0);
159 }
160
161 /* Number of highest set bit (max) */
162 unsigned int bitmask_last(const struct bitmask *bmp)
163 {
164 unsigned int i;
165 unsigned int m = bmp->size;
166 for (i = 0; i < bmp->size; i++)
167 if (_getbit(bmp, i))
168 m = i;
169 return m;
170 }
171
172 /* Number of next set bit at or above given bit i */
173 unsigned int bitmask_next(const struct bitmask *bmp, unsigned int i)
174 {
175 unsigned int n;
176 for (n = i; n < bmp->size; n++)
177 if (_getbit(bmp, n))
178 break;
179 return n;
180 }
181
182 /*
183 * Parses a comma-separated list of numbers and ranges of numbers,
184 * with optional ':%u' strides modifying ranges, into provided bitmask.
185 * Some examples of input lists and their equivalent simple list:
186 * Input Equivalent to
187 * 0-3 0,1,2,3
188 * 0-7:2 0,2,4,6
189 * 1,3,5-7 1,3,5,6,7
190 * 0-3:2,8-15:4 0,2,8,12
191 */
192 int bitmask_parselist(const char *buf, struct bitmask *bmp)
193 {
194 const char *p, *q;
195
196 bitmask_clearall(bmp);
197
198 q = buf;
199 while (p = q, q = nexttoken(q, ','), p) {
200 unsigned int a; /* begin of range */
201 unsigned int b; /* end of range */
202 unsigned int s; /* stride */
203 const char *c1, *c2; /* next tokens after '-' or ',' */
204 char nextc; /* char after sscanf %u match */
205 int sret; /* sscanf return (number of matches) */
206
207 sret = sscanf(p, "%u%c", &a, &nextc);
208 if (!scan_was_ok(sret, nextc, ",-"))
209 goto err;
210 b = a;
211 s = 1;
212 c1 = nexttoken(p, '-');
213 c2 = nexttoken(p, ',');
214 if (c1 != NULL && (c2 == NULL || c1 < c2)) {
215 sret = sscanf(c1, "%u%c", &b, &nextc);
216 if (!scan_was_ok(sret, nextc, ",:"))
217 goto err;
218 c1 = nexttoken(c1, ':');
219 if (c1 != NULL && (c2 == NULL || c1 < c2)) {
220 sret = sscanf(c1, "%u%c", &s, &nextc);
221 if (!scan_was_ok(sret, nextc, ","))
222 goto err;
223 }
224 }
225 if (!(a <= b))
226 goto err;
227 if (b >= bmp->size)
228 goto err;
229 while (a <= b) {
230 _setbit(bmp, a, 1);
231 a += s;
232 }
233 }
234 return 0;
235 err:
236 bitmask_clearall(bmp);
237 return -1;
238 }
239
240 /*
241 * emit(buf, buflen, rbot, rtop, len)
242 *
243 * Helper routine for bitmask_displaylist(). Write decimal number
244 * or range to buf+len, suppressing output past buf+buflen, with optional
245 * comma-prefix. Return len of what would be written to buf, if it
246 * all fit.
247 */
248
249 static inline int emit(char *buf, int buflen, int rbot, int rtop, int len)
250 {
251 if (len > 0)
252 len += snprintf(buf + len, max(buflen - len, 0), ",");
253 if (rbot == rtop)
254 len += snprintf(buf + len, max(buflen - len, 0), "%d", rbot);
255 else
256 len += snprintf(buf + len, max(buflen - len, 0), "%d-%d",
257 rbot, rtop);
258 return len;
259 }
260
261 /*
262 * Write decimal list representation of bmp to buf.
263 *
264 * Output format is a comma-separated list of decimal numbers and
265 * ranges. Consecutively set bits are shown as two hyphen-separated
266 * decimal numbers, the smallest and largest bit numbers set in
267 * the range. Output format is compatible with the format
268 * accepted as input by bitmap_parselist().
269 *
270 * The return value is the number of characters which would be
271 * generated for the given input, excluding the trailing '\0', as
272 * per ISO C99.
273 */
274
275 int bitmask_displaylist(char *buf, int buflen, const struct bitmask *bmp)
276 {
277 int len = 0;
278 /* current bit is 'cur', most recently seen range is [rbot, rtop] */
279 unsigned int cur, rbot, rtop;
280
281 if (buflen > 0)
282 *buf = 0;
283 rbot = cur = bitmask_first(bmp);
284 while (cur < bmp->size) {
285 rtop = cur;
286 cur = bitmask_next(bmp, cur+1);
287 if (cur >= bmp->size || cur > rtop + 1) {
288 len = emit(buf, buflen, rbot, rtop, len);
289 rbot = cur;
290 }
291 }
292 return len;
293 }
294
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