source: branches/samba-3.5.x/source3/lib/memcache.c@ 736

Last change on this file since 736 was 414, checked in by Herwig Bauernfeind, 15 years ago

Samba 3.5.0: Initial import
File size: 8.6 KB
Line 
1/*
2 Unix SMB/CIFS implementation.
3 In-memory cache
4 Copyright (C) Volker Lendecke 2007
5
6 This program 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 3 of the License, or
9 (at your option) any later version.
10
11 This program 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, see <http://www.gnu.org/licenses/>.
18*/
19
20#include "memcache.h"
21#include "../lib/util/rbtree.h"
22
23static struct memcache *global_cache;
24
25struct memcache_element {
26 struct rb_node rb_node;
27 struct memcache_element *prev, *next;
28 size_t keylength, valuelength;
29 uint8 n; /* This is really an enum, but save memory */
30 char data[1]; /* placeholder for offsetof */
31};
32
33struct memcache {
34 struct memcache_element *mru, *lru;
35 struct rb_root tree;
36 size_t size;
37 size_t max_size;
38};
39
40static void memcache_element_parse(struct memcache_element *e,
41 DATA_BLOB *key, DATA_BLOB *value);
42
43static bool memcache_is_talloc(enum memcache_number n)
44{
45 bool result;
46
47 switch (n) {
48 case GETPWNAM_CACHE:
49 case PDB_GETPWSID_CACHE:
50 case SINGLETON_CACHE_TALLOC:
51 result = true;
52 break;
53 default:
54 result = false;
55 break;
56 }
57
58 return result;
59}
60
61static int memcache_destructor(struct memcache *cache) {
62 struct memcache_element *e, *next;
63
64 for (e = cache->mru; e != NULL; e = next) {
65 next = e->next;
66 SAFE_FREE(e);
67 }
68 return 0;
69}
70
71struct memcache *memcache_init(TALLOC_CTX *mem_ctx, size_t max_size)
72{
73 struct memcache *result;
74
75 result = TALLOC_ZERO_P(mem_ctx, struct memcache);
76 if (result == NULL) {
77 return NULL;
78 }
79 result->max_size = max_size;
80 talloc_set_destructor(result, memcache_destructor);
81 return result;
82}
83
84void memcache_set_global(struct memcache *cache)
85{
86 TALLOC_FREE(global_cache);
87 global_cache = cache;
88}
89
90static struct memcache_element *memcache_node2elem(struct rb_node *node)
91{
92 return (struct memcache_element *)
93 ((char *)node - offsetof(struct memcache_element, rb_node));
94}
95
96static void memcache_element_parse(struct memcache_element *e,
97 DATA_BLOB *key, DATA_BLOB *value)
98{
99 key->data = ((uint8 *)e) + offsetof(struct memcache_element, data);
100 key->length = e->keylength;
101 value->data = key->data + e->keylength;
102 value->length = e->valuelength;
103}
104
105static size_t memcache_element_size(size_t key_length, size_t value_length)
106{
107 return sizeof(struct memcache_element) - 1 + key_length + value_length;
108}
109
110static int memcache_compare(struct memcache_element *e, enum memcache_number n,
111 DATA_BLOB key)
112{
113 DATA_BLOB this_key, this_value;
114
115 if ((int)e->n < (int)n) return 1;
116 if ((int)e->n > (int)n) return -1;
117
118 if (e->keylength < key.length) return 1;
119 if (e->keylength > key.length) return -1;
120
121 memcache_element_parse(e, &this_key, &this_value);
122 return memcmp(this_key.data, key.data, key.length);
123}
124
125static struct memcache_element *memcache_find(
126 struct memcache *cache, enum memcache_number n, DATA_BLOB key)
127{
128 struct rb_node *node;
129
130 node = cache->tree.rb_node;
131
132 while (node != NULL) {
133 struct memcache_element *elem = memcache_node2elem(node);
134 int cmp;
135
136 cmp = memcache_compare(elem, n, key);
137 if (cmp == 0) {
138 return elem;
139 }
140 node = (cmp < 0) ? node->rb_left : node->rb_right;
141 }
142
143 return NULL;
144}
145
146bool memcache_lookup(struct memcache *cache, enum memcache_number n,
147 DATA_BLOB key, DATA_BLOB *value)
148{
149 struct memcache_element *e;
150
151 if (cache == NULL) {
152 cache = global_cache;
153 }
154 if (cache == NULL) {
155 return false;
156 }
157
158 e = memcache_find(cache, n, key);
159 if (e == NULL) {
160 return false;
161 }
162
163 if (cache->size != 0) {
164 /*
165 * Do LRU promotion only when we will ever shrink
166 */
167 if (e == cache->lru) {
168 cache->lru = e->prev;
169 }
170 DLIST_PROMOTE(cache->mru, e);
171 if (cache->mru == NULL) {
172 cache->mru = e;
173 }
174 }
175
176 memcache_element_parse(e, &key, value);
177 return true;
178}
179
180void *memcache_lookup_talloc(struct memcache *cache, enum memcache_number n,
181 DATA_BLOB key)
182{
183 DATA_BLOB value;
184 void *result;
185
186 if (!memcache_lookup(cache, n, key, &value)) {
187 return NULL;
188 }
189
190 if (value.length != sizeof(result)) {
191 return NULL;
192 }
193
194 memcpy(&result, value.data, sizeof(result));
195
196 return result;
197}
198
199static void memcache_delete_element(struct memcache *cache,
200 struct memcache_element *e)
201{
202 rb_erase(&e->rb_node, &cache->tree);
203
204 if (e == cache->lru) {
205 cache->lru = e->prev;
206 }
207 DLIST_REMOVE(cache->mru, e);
208
209 if (memcache_is_talloc(e->n)) {
210 DATA_BLOB cache_key, cache_value;
211 void *ptr;
212
213 memcache_element_parse(e, &cache_key, &cache_value);
214 SMB_ASSERT(cache_value.length == sizeof(ptr));
215 memcpy(&ptr, cache_value.data, sizeof(ptr));
216 TALLOC_FREE(ptr);
217 }
218
219 cache->size -= memcache_element_size(e->keylength, e->valuelength);
220
221 SAFE_FREE(e);
222}
223
224static void memcache_trim(struct memcache *cache)
225{
226 if (cache->max_size == 0) {
227 return;
228 }
229
230 while ((cache->size > cache->max_size) && (cache->lru != NULL)) {
231 memcache_delete_element(cache, cache->lru);
232 }
233}
234
235void memcache_delete(struct memcache *cache, enum memcache_number n,
236 DATA_BLOB key)
237{
238 struct memcache_element *e;
239
240 if (cache == NULL) {
241 cache = global_cache;
242 }
243 if (cache == NULL) {
244 return;
245 }
246
247 e = memcache_find(cache, n, key);
248 if (e == NULL) {
249 return;
250 }
251
252 memcache_delete_element(cache, e);
253}
254
255void memcache_add(struct memcache *cache, enum memcache_number n,
256 DATA_BLOB key, DATA_BLOB value)
257{
258 struct memcache_element *e;
259 struct rb_node **p;
260 struct rb_node *parent;
261 DATA_BLOB cache_key, cache_value;
262 size_t element_size;
263
264 if (cache == NULL) {
265 cache = global_cache;
266 }
267 if (cache == NULL) {
268 return;
269 }
270
271 if (key.length == 0) {
272 return;
273 }
274
275 e = memcache_find(cache, n, key);
276
277 if (e != NULL) {
278 memcache_element_parse(e, &cache_key, &cache_value);
279
280 if (value.length <= cache_value.length) {
281 if (memcache_is_talloc(e->n)) {
282 void *ptr;
283 SMB_ASSERT(cache_value.length == sizeof(ptr));
284 memcpy(&ptr, cache_value.data, sizeof(ptr));
285 TALLOC_FREE(ptr);
286 }
287 /*
288 * We can reuse the existing record
289 */
290 memcpy(cache_value.data, value.data, value.length);
291 e->valuelength = value.length;
292 return;
293 }
294
295 memcache_delete_element(cache, e);
296 }
297
298 element_size = memcache_element_size(key.length, value.length);
299
300
301 e = (struct memcache_element *)SMB_MALLOC(element_size);
302
303 if (e == NULL) {
304 DEBUG(0, ("malloc failed\n"));
305 return;
306 }
307
308 e->n = n;
309 e->keylength = key.length;
310 e->valuelength = value.length;
311
312 memcache_element_parse(e, &cache_key, &cache_value);
313 memcpy(cache_key.data, key.data, key.length);
314 memcpy(cache_value.data, value.data, value.length);
315
316 parent = NULL;
317 p = &cache->tree.rb_node;
318
319 while (*p) {
320 struct memcache_element *elem = memcache_node2elem(*p);
321 int cmp;
322
323 parent = (*p);
324
325 cmp = memcache_compare(elem, n, key);
326
327 p = (cmp < 0) ? &(*p)->rb_left : &(*p)->rb_right;
328 }
329
330 rb_link_node(&e->rb_node, parent, p);
331 rb_insert_color(&e->rb_node, &cache->tree);
332
333 DLIST_ADD(cache->mru, e);
334 if (cache->lru == NULL) {
335 cache->lru = e;
336 }
337
338 cache->size += element_size;
339 memcache_trim(cache);
340}
341
342void memcache_add_talloc(struct memcache *cache, enum memcache_number n,
343 DATA_BLOB key, void *pptr)
344{
345 void **ptr = (void **)pptr;
346 void *p;
347
348 if (cache == NULL) {
349 cache = global_cache;
350 }
351 if (cache == NULL) {
352 return;
353 }
354
355 p = talloc_move(cache, ptr);
356 memcache_add(cache, n, key, data_blob_const(&p, sizeof(p)));
357}
358
359void memcache_flush(struct memcache *cache, enum memcache_number n)
360{
361 struct rb_node *node;
362
363 if (cache == NULL) {
364 cache = global_cache;
365 }
366 if (cache == NULL) {
367 return;
368 }
369
370 /*
371 * Find the smallest element of number n
372 */
373
374 node = cache->tree.rb_node;
375 if (node == NULL) {
376 return;
377 }
378
379 /*
380 * First, find *any* element of number n
381 */
382
383 while (true) {
384 struct memcache_element *elem = memcache_node2elem(node);
385 struct rb_node *next;
386
387 if ((int)elem->n == (int)n) {
388 break;
389 }
390
391 if ((int)elem->n < (int)n) {
392 next = node->rb_right;
393 }
394 else {
395 next = node->rb_left;
396 }
397 if (next == NULL) {
398 break;
399 }
400 node = next;
401 }
402
403 if (node == NULL) {
404 return;
405 }
406
407 /*
408 * Then, find the leftmost element with number n
409 */
410
411 while (true) {
412 struct rb_node *prev = rb_prev(node);
413 struct memcache_element *elem;
414
415 if (prev == NULL) {
416 break;
417 }
418 elem = memcache_node2elem(prev);
419 if ((int)elem->n != (int)n) {
420 break;
421 }
422 node = prev;
423 }
424
425 while (node != NULL) {
426 struct memcache_element *e = memcache_node2elem(node);
427 struct rb_node *next = rb_next(node);
428
429 if (e->n != n) {
430 break;
431 }
432
433 memcache_delete_element(cache, e);
434 node = next;
435 }
436}
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