source: branches/samba-3.2.x/source/lib/memcache.c@ 205

Last change on this file since 205 was 136, checked in by Paul Smedley, 17 years ago

Update trunk to 3.2.0rc1
File size: 8.7 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 "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 if (memcache_is_talloc((enum memcache_number)e->n)
67 && (e->valuelength == sizeof(void *))) {
68 DATA_BLOB key, value;
69 void *ptr;
70 memcache_element_parse(e, &key, &value);
71 memcpy(&ptr, value.data, sizeof(ptr));
72 TALLOC_FREE(ptr);
73 }
74 SAFE_FREE(e);
75 }
76 return 0;
77}
78
79struct memcache *memcache_init(TALLOC_CTX *mem_ctx, size_t max_size)
80{
81 struct memcache *result;
82
83 result = TALLOC_ZERO_P(mem_ctx, struct memcache);
84 if (result == NULL) {
85 return NULL;
86 }
87 result->max_size = max_size;
88 talloc_set_destructor(result, memcache_destructor);
89 return result;
90}
91
92void memcache_set_global(struct memcache *cache)
93{
94 TALLOC_FREE(global_cache);
95 global_cache = cache;
96}
97
98static struct memcache_element *memcache_node2elem(struct rb_node *node)
99{
100 return (struct memcache_element *)
101 ((char *)node - offsetof(struct memcache_element, rb_node));
102}
103
104static void memcache_element_parse(struct memcache_element *e,
105 DATA_BLOB *key, DATA_BLOB *value)
106{
107 key->data = ((uint8 *)e) + offsetof(struct memcache_element, data);
108 key->length = e->keylength;
109 value->data = key->data + e->keylength;
110 value->length = e->valuelength;
111}
112
113static size_t memcache_element_size(size_t key_length, size_t value_length)
114{
115 return sizeof(struct memcache_element) - 1 + key_length + value_length;
116}
117
118static int memcache_compare(struct memcache_element *e, enum memcache_number n,
119 DATA_BLOB key)
120{
121 DATA_BLOB this_key, this_value;
122
123 if ((int)e->n < (int)n) return 1;
124 if ((int)e->n > (int)n) return -1;
125
126 if (e->keylength < key.length) return 1;
127 if (e->keylength > key.length) return -1;
128
129 memcache_element_parse(e, &this_key, &this_value);
130 return memcmp(this_key.data, key.data, key.length);
131}
132
133static struct memcache_element *memcache_find(
134 struct memcache *cache, enum memcache_number n, DATA_BLOB key)
135{
136 struct rb_node *node;
137
138 node = cache->tree.rb_node;
139
140 while (node != NULL) {
141 struct memcache_element *elem = memcache_node2elem(node);
142 int cmp;
143
144 cmp = memcache_compare(elem, n, key);
145 if (cmp == 0) {
146 return elem;
147 }
148 node = (cmp < 0) ? node->rb_left : node->rb_right;
149 }
150
151 return NULL;
152}
153
154bool memcache_lookup(struct memcache *cache, enum memcache_number n,
155 DATA_BLOB key, DATA_BLOB *value)
156{
157 struct memcache_element *e;
158
159 if (cache == NULL) {
160 cache = global_cache;
161 }
162 if (cache == NULL) {
163 return false;
164 }
165
166 e = memcache_find(cache, n, key);
167 if (e == NULL) {
168 return false;
169 }
170
171 if (cache->size != 0) {
172 /*
173 * Do LRU promotion only when we will ever shrink
174 */
175 if (e == cache->lru) {
176 cache->lru = e->prev;
177 }
178 DLIST_PROMOTE(cache->mru, e);
179 if (cache->mru == NULL) {
180 cache->mru = e;
181 }
182 }
183
184 memcache_element_parse(e, &key, value);
185 return true;
186}
187
188void *memcache_lookup_talloc(struct memcache *cache, enum memcache_number n,
189 DATA_BLOB key)
190{
191 DATA_BLOB value;
192 void *result;
193
194 if (!memcache_lookup(cache, n, key, &value)) {
195 return NULL;
196 }
197
198 if (value.length != sizeof(result)) {
199 return NULL;
200 }
201
202 memcpy(&result, value.data, sizeof(result));
203
204 return result;
205}
206
207static void memcache_delete_element(struct memcache *cache,
208 struct memcache_element *e)
209{
210 rb_erase(&e->rb_node, &cache->tree);
211
212 if (e == cache->lru) {
213 cache->lru = e->prev;
214 }
215 DLIST_REMOVE(cache->mru, e);
216
217 cache->size -= memcache_element_size(e->keylength, e->valuelength);
218
219 SAFE_FREE(e);
220}
221
222static void memcache_trim(struct memcache *cache)
223{
224 if (cache->max_size == 0) {
225 return;
226 }
227
228 while ((cache->size > cache->max_size) && (cache->lru != NULL)) {
229 memcache_delete_element(cache, cache->lru);
230 }
231}
232
233void memcache_delete(struct memcache *cache, enum memcache_number n,
234 DATA_BLOB key)
235{
236 struct memcache_element *e;
237
238 if (cache == NULL) {
239 cache = global_cache;
240 }
241 if (cache == NULL) {
242 return;
243 }
244
245 e = memcache_find(cache, n, key);
246 if (e == NULL) {
247 return;
248 }
249
250 memcache_delete_element(cache, e);
251}
252
253void memcache_add(struct memcache *cache, enum memcache_number n,
254 DATA_BLOB key, DATA_BLOB value)
255{
256 struct memcache_element *e;
257 struct rb_node **p;
258 struct rb_node *parent;
259 DATA_BLOB cache_key, cache_value;
260 size_t element_size;
261
262 if (cache == NULL) {
263 cache = global_cache;
264 }
265 if (cache == NULL) {
266 return;
267 }
268
269 if (key.length == 0) {
270 return;
271 }
272
273 e = memcache_find(cache, n, key);
274
275 if (e != NULL) {
276 memcache_element_parse(e, &cache_key, &cache_value);
277
278 if (value.length <= cache_value.length) {
279 /*
280 * We can reuse the existing record
281 */
282 memcpy(cache_value.data, value.data, value.length);
283 e->valuelength = value.length;
284 return;
285 }
286
287 memcache_delete_element(cache, e);
288 }
289
290 element_size = memcache_element_size(key.length, value.length);
291
292
293 e = (struct memcache_element *)SMB_MALLOC(element_size);
294
295 if (e == NULL) {
296 DEBUG(0, ("malloc failed\n"));
297 return;
298 }
299
300 e->n = n;
301 e->keylength = key.length;
302 e->valuelength = value.length;
303
304 memcache_element_parse(e, &cache_key, &cache_value);
305 memcpy(cache_key.data, key.data, key.length);
306 memcpy(cache_value.data, value.data, value.length);
307
308 parent = NULL;
309 p = &cache->tree.rb_node;
310
311 while (*p) {
312 struct memcache_element *elem = memcache_node2elem(*p);
313 int cmp;
314
315 parent = (*p);
316
317 cmp = memcache_compare(elem, n, key);
318
319 p = (cmp < 0) ? &(*p)->rb_left : &(*p)->rb_right;
320 }
321
322 rb_link_node(&e->rb_node, parent, p);
323 rb_insert_color(&e->rb_node, &cache->tree);
324
325 DLIST_ADD(cache->mru, e);
326 if (cache->lru == NULL) {
327 cache->lru = e;
328 }
329
330 cache->size += element_size;
331 memcache_trim(cache);
332}
333
334void memcache_add_talloc(struct memcache *cache, enum memcache_number n,
335 DATA_BLOB key, void *ptr)
336{
337 memcache_add(cache, n, key, data_blob_const(&ptr, sizeof(ptr)));
338}
339
340void memcache_flush(struct memcache *cache, enum memcache_number n)
341{
342 struct rb_node *node;
343
344 if (cache == NULL) {
345 cache = global_cache;
346 }
347 if (cache == NULL) {
348 return;
349 }
350
351 /*
352 * Find the smallest element of number n
353 */
354
355 node = cache->tree.rb_node;
356 if (node == NULL) {
357 return;
358 }
359
360 /*
361 * First, find *any* element of number n
362 */
363
364 while (true) {
365 struct memcache_element *elem = memcache_node2elem(node);
366 struct rb_node *next;
367
368 if ((int)elem->n == (int)n) {
369 break;
370 }
371
372 if ((int)elem->n < (int)n) {
373 next = node->rb_right;
374 }
375 else {
376 next = node->rb_left;
377 }
378 if (next == NULL) {
379 break;
380 }
381 node = next;
382 }
383
384 if (node == NULL) {
385 return;
386 }
387
388 /*
389 * Then, find the leftmost element with number n
390 */
391
392 while (true) {
393 struct rb_node *prev = rb_prev(node);
394 struct memcache_element *elem;
395
396 if (prev == NULL) {
397 break;
398 }
399 elem = memcache_node2elem(prev);
400 if ((int)elem->n != (int)n) {
401 break;
402 }
403 node = prev;
404 }
405
406 while (node != NULL) {
407 struct memcache_element *e = memcache_node2elem(node);
408 struct rb_node *next = rb_next(node);
409
410 if (e->n != n) {
411 break;
412 }
413
414 memcache_delete_element(cache, e);
415 node = next;
416 }
417}
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