source3/lib/memcache.c

   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
  23 static struct memcache *global_cache;
  24
  25 struct 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
  33 struct memcache {
  34         struct memcache_element *mru;
  35         struct rb_root tree;
  36         size_t size;
  37         size_t max_size;
  38 };
  39
  40 static void memcache_element_parse(struct memcache_element *e,
  41                                    DATA_BLOB *key, DATA_BLOB *value);
  42
  43 static 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
  61 static 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
  71 struct 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
  84 void memcache_set_global(struct memcache *cache)
  85 {
  86         TALLOC_FREE(global_cache);
  87         global_cache = cache;
  88 }
  89
  90 static 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
  96 static 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
 105 static 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
 110 static 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
 125 static 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
 146 bool 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                 DLIST_PROMOTE(cache->mru, e);
 165         }
 166
 167         memcache_element_parse(e, &key, value);
 168         return true;
 169 }
 170
 171 void *memcache_lookup_talloc(struct memcache *cache, enum memcache_number n,
 172                              DATA_BLOB key)
 173 {
 174         DATA_BLOB value;
 175         void *result;
 176
 177         if (!memcache_lookup(cache, n, key, &value)) {
 178                 return NULL;
 179         }
 180
 181         if (value.length != sizeof(result)) {
 182                 return NULL;
 183         }
 184
 185         memcpy(&result, value.data, sizeof(result));
 186
 187         return result;
 188 }
 189
 190 static void memcache_delete_element(struct memcache *cache,
 191                                     struct memcache_element *e)
 192 {
 193         rb_erase(&e->rb_node, &cache->tree);
 194
 195         DLIST_REMOVE(cache->mru, e);
 196
 197         if (memcache_is_talloc(e->n)) {
 198                 DATA_BLOB cache_key, cache_value;
 199                 void *ptr;
 200
 201                 memcache_element_parse(e, &cache_key, &cache_value);
 202                 SMB_ASSERT(cache_value.length == sizeof(ptr));
 203                 memcpy(&ptr, cache_value.data, sizeof(ptr));
 204                 TALLOC_FREE(ptr);
 205         }
 206
 207         cache->size -= memcache_element_size(e->keylength, e->valuelength);
 208
 209         SAFE_FREE(e);
 210 }
 211
 212 static void memcache_trim(struct memcache *cache)
 213 {
 214         if (cache->max_size == 0) {
 215                 return;
 216         }
 217
 218         while ((cache->size > cache->max_size) && DLIST_TAIL(cache->mru)) {
 219                 memcache_delete_element(cache, DLIST_TAIL(cache->mru));
 220         }
 221 }
 222
 223 void memcache_delete(struct memcache *cache, enum memcache_number n,
 224                      DATA_BLOB key)
 225 {
 226         struct memcache_element *e;
 227
 228         if (cache == NULL) {
 229                 cache = global_cache;
 230         }
 231         if (cache == NULL) {
 232                 return;
 233         }
 234
 235         e = memcache_find(cache, n, key);
 236         if (e == NULL) {
 237                 return;
 238         }
 239
 240         memcache_delete_element(cache, e);
 241 }
 242
 243 void memcache_add(struct memcache *cache, enum memcache_number n,
 244                   DATA_BLOB key, DATA_BLOB value)
 245 {
 246         struct memcache_element *e;
 247         struct rb_node **p;
 248         struct rb_node *parent;
 249         DATA_BLOB cache_key, cache_value;
 250         size_t element_size;
 251
 252         if (cache == NULL) {
 253                 cache = global_cache;
 254         }
 255         if (cache == NULL) {
 256                 return;
 257         }
 258
 259         if (key.length == 0) {
 260                 return;
 261         }
 262
 263         e = memcache_find(cache, n, key);
 264
 265         if (e != NULL) {
 266                 memcache_element_parse(e, &cache_key, &cache_value);
 267
 268                 if (value.length <= cache_value.length) {
 269                         if (memcache_is_talloc(e->n)) {
 270                                 void *ptr;
 271                                 SMB_ASSERT(cache_value.length == sizeof(ptr));
 272                                 memcpy(&ptr, cache_value.data, sizeof(ptr));
 273                                 TALLOC_FREE(ptr);
 274                         }
 275                         /*
 276                          * We can reuse the existing record
 277                          */
 278                         memcpy(cache_value.data, value.data, value.length);
 279                         e->valuelength = value.length;
 280                         return;
 281                 }
 282
 283                 memcache_delete_element(cache, e);
 284         }
 285
 286         element_size = memcache_element_size(key.length, value.length);
 287
 288
 289         e = (struct memcache_element *)SMB_MALLOC(element_size);
 290
 291         if (e == NULL) {
 292                 DEBUG(0, ("malloc failed\n"));
 293                 return;
 294         }
 295
 296         e->n = n;
 297         e->keylength = key.length;
 298         e->valuelength = value.length;
 299
 300         memcache_element_parse(e, &cache_key, &cache_value);
 301         memcpy(cache_key.data, key.data, key.length);
 302         memcpy(cache_value.data, value.data, value.length);
 303
 304         parent = NULL;
 305         p = &cache->tree.rb_node;
 306
 307         while (*p) {
 308                 struct memcache_element *elem = memcache_node2elem(*p);
 309                 int cmp;
 310
 311                 parent = (*p);
 312
 313                 cmp = memcache_compare(elem, n, key);
 314
 315                 p = (cmp < 0) ? &(*p)->rb_left : &(*p)->rb_right;
 316         }
 317
 318         rb_link_node(&e->rb_node, parent, p);
 319         rb_insert_color(&e->rb_node, &cache->tree);
 320
 321         DLIST_ADD(cache->mru, e);
 322
 323         cache->size += element_size;
 324         memcache_trim(cache);
 325 }
 326
 327 void memcache_add_talloc(struct memcache *cache, enum memcache_number n,
 328                          DATA_BLOB key, void *pptr)
 329 {
 330         void **ptr = (void **)pptr;
 331         void *p;
 332
 333         if (cache == NULL) {
 334                 cache = global_cache;
 335         }
 336         if (cache == NULL) {
 337                 return;
 338         }
 339
 340         p = talloc_move(cache, ptr);
 341         memcache_add(cache, n, key, data_blob_const(&p, sizeof(p)));
 342 }
 343
 344 void memcache_flush(struct memcache *cache, enum memcache_number n)
 345 {
 346         struct rb_node *node;
 347
 348         if (cache == NULL) {
 349                 cache = global_cache;
 350         }
 351         if (cache == NULL) {
 352                 return;
 353         }
 354
 355         /*
 356          * Find the smallest element of number n
 357          */
 358
 359         node = cache->tree.rb_node;
 360         if (node == NULL) {
 361                 return;
 362         }
 363
 364         /*
 365          * First, find *any* element of number n
 366          */
 367
 368         while (true) {
 369                 struct memcache_element *elem = memcache_node2elem(node);
 370                 struct rb_node *next;
 371
 372                 if ((int)elem->n == (int)n) {
 373                         break;
 374                 }
 375
 376                 if ((int)elem->n < (int)n) {
 377                         next = node->rb_right;
 378                 }
 379                 else {
 380                         next = node->rb_left;
 381                 }
 382                 if (next == NULL) {
 383                         break;
 384                 }
 385                 node = next;
 386         }
 387
 388         if (node == NULL) {
 389                 return;
 390         }
 391
 392         /*
 393          * Then, find the leftmost element with number n
 394          */
 395
 396         while (true) {
 397                 struct rb_node *prev = rb_prev(node);
 398                 struct memcache_element *elem;
 399
 400                 if (prev == NULL) {
 401                         break;
 402                 }
 403                 elem = memcache_node2elem(prev);
 404                 if ((int)elem->n != (int)n) {
 405                         break;
 406                 }
 407                 node = prev;
 408         }
 409
 410         while (node != NULL) {
 411                 struct memcache_element *e = memcache_node2elem(node);
 412                 struct rb_node *next = rb_next(node);
 413
 414                 if (e->n != n) {
 415                         break;
 416                 }
 417
 418                 memcache_delete_element(cache, e);
 419                 node = next;
 420         }
 421 }