lib/util/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 "replace.h"
  21 #include <talloc.h>
  22 #include "../lib/util/samba_util.h"
  23 #include "../lib/util/debug.h"
  24 #include "../lib/util/dlinklist.h"
  25 #include "../lib/util/rbtree.h"
  26 #include "memcache.h"
  27
  28 static struct memcache *global_cache;
  29
  30 struct memcache_element {
  31         struct rb_node rb_node;
  32         struct memcache_element *prev, *next;
  33         size_t keylength, valuelength;
  34         uint8_t n;              /* This is really an enum, but save memory */
  35         char data[1];           /* placeholder for offsetof */
  36 };
  37
  38 struct memcache {
  39         struct memcache_element *mru;
  40         struct rb_root tree;
  41         size_t size;
  42         size_t max_size;
  43 };
  44
  45 static void memcache_element_parse(struct memcache_element *e,
  46                                    DATA_BLOB *key, DATA_BLOB *value);
  47
  48 static bool memcache_is_talloc(enum memcache_number n)
  49 {
  50         bool result;
  51
  52         switch (n) {
  53         case GETPWNAM_CACHE:
  54         case PDB_GETPWSID_CACHE:
  55         case SINGLETON_CACHE_TALLOC:
  56                 result = true;
  57                 break;
  58         default:
  59                 result = false;
  60                 break;
  61         }
  62
  63         return result;
  64 }
  65
  66 static int memcache_destructor(struct memcache *cache) {
  67         struct memcache_element *e, *next;
  68
  69         for (e = cache->mru; e != NULL; e = next) {
  70                 next = e->next;
  71                 TALLOC_FREE(e);
  72         }
  73         return 0;
  74 }
  75
  76 struct memcache *memcache_init(TALLOC_CTX *mem_ctx, size_t max_size)
  77 {
  78         struct memcache *result;
  79
  80         result = talloc_zero(mem_ctx, struct memcache);
  81         if (result == NULL) {
  82                 return NULL;
  83         }
  84         result->max_size = max_size;
  85         talloc_set_destructor(result, memcache_destructor);
  86         return result;
  87 }
  88
  89 void memcache_set_global(struct memcache *cache)
  90 {
  91         TALLOC_FREE(global_cache);
  92         global_cache = cache;
  93 }
  94
  95 static struct memcache_element *memcache_node2elem(struct rb_node *node)
  96 {
  97         return (struct memcache_element *)
  98                 ((char *)node - offsetof(struct memcache_element, rb_node));
  99 }
 100
 101 static void memcache_element_parse(struct memcache_element *e,
 102                                    DATA_BLOB *key, DATA_BLOB *value)
 103 {
 104         key->data = ((uint8_t *)e) + offsetof(struct memcache_element, data);
 105         key->length = e->keylength;
 106         value->data = key->data + e->keylength;
 107         value->length = e->valuelength;
 108 }
 109
 110 static size_t memcache_element_size(size_t key_length, size_t value_length)
 111 {
 112         return sizeof(struct memcache_element) - 1 + key_length + value_length;
 113 }
 114
 115 static int memcache_compare(struct memcache_element *e, enum memcache_number n,
 116                             DATA_BLOB key)
 117 {
 118         DATA_BLOB this_key, this_value;
 119
 120         if ((int)e->n < (int)n) return 1;
 121         if ((int)e->n > (int)n) return -1;
 122
 123         if (e->keylength < key.length) return 1;
 124         if (e->keylength > key.length) return -1;
 125
 126         memcache_element_parse(e, &this_key, &this_value);
 127         return memcmp(this_key.data, key.data, key.length);
 128 }
 129
 130 static struct memcache_element *memcache_find(
 131         struct memcache *cache, enum memcache_number n, DATA_BLOB key)
 132 {
 133         struct rb_node *node;
 134
 135         node = cache->tree.rb_node;
 136
 137         while (node != NULL) {
 138                 struct memcache_element *elem = memcache_node2elem(node);
 139                 int cmp;
 140
 141                 cmp = memcache_compare(elem, n, key);
 142                 if (cmp == 0) {
 143                         return elem;
 144                 }
 145                 node = (cmp < 0) ? node->rb_left : node->rb_right;
 146         }
 147
 148         return NULL;
 149 }
 150
 151 bool memcache_lookup(struct memcache *cache, enum memcache_number n,
 152                      DATA_BLOB key, DATA_BLOB *value)
 153 {
 154         struct memcache_element *e;
 155
 156         if (cache == NULL) {
 157                 cache = global_cache;
 158         }
 159         if (cache == NULL) {
 160                 return false;
 161         }
 162
 163         e = memcache_find(cache, n, key);
 164         if (e == NULL) {
 165                 return false;
 166         }
 167
 168         if (cache->size != 0) {
 169                 DLIST_PROMOTE(cache->mru, e);
 170         }
 171
 172         memcache_element_parse(e, &key, value);
 173         return true;
 174 }
 175
 176 void *memcache_lookup_talloc(struct memcache *cache, enum memcache_number n,
 177                              DATA_BLOB key)
 178 {
 179         DATA_BLOB value;
 180         void *result;
 181
 182         if (!memcache_lookup(cache, n, key, &value)) {
 183                 return NULL;
 184         }
 185
 186         if (value.length != sizeof(result)) {
 187                 return NULL;
 188         }
 189
 190         memcpy(&result, value.data, sizeof(result));
 191
 192         return result;
 193 }
 194
 195 static void memcache_delete_element(struct memcache *cache,
 196                                     struct memcache_element *e)
 197 {
 198         rb_erase(&e->rb_node, &cache->tree);
 199
 200         DLIST_REMOVE(cache->mru, e);
 201
 202         if (memcache_is_talloc(e->n)) {
 203                 DATA_BLOB cache_key, cache_value;
 204                 void *ptr;
 205
 206                 memcache_element_parse(e, &cache_key, &cache_value);
 207                 SMB_ASSERT(cache_value.length == sizeof(ptr));
 208                 memcpy(&ptr, cache_value.data, sizeof(ptr));
 209                 TALLOC_FREE(ptr);
 210         }
 211
 212         cache->size -= memcache_element_size(e->keylength, e->valuelength);
 213
 214         TALLOC_FREE(e);
 215 }
 216
 217 static void memcache_trim(struct memcache *cache)
 218 {
 219         if (cache->max_size == 0) {
 220                 return;
 221         }
 222
 223         while ((cache->size > cache->max_size) && DLIST_TAIL(cache->mru)) {
 224                 memcache_delete_element(cache, DLIST_TAIL(cache->mru));
 225         }
 226 }
 227
 228 void memcache_delete(struct memcache *cache, enum memcache_number n,
 229                      DATA_BLOB key)
 230 {
 231         struct memcache_element *e;
 232
 233         if (cache == NULL) {
 234                 cache = global_cache;
 235         }
 236         if (cache == NULL) {
 237                 return;
 238         }
 239
 240         e = memcache_find(cache, n, key);
 241         if (e == NULL) {
 242                 return;
 243         }
 244
 245         memcache_delete_element(cache, e);
 246 }
 247
 248 void memcache_add(struct memcache *cache, enum memcache_number n,
 249                   DATA_BLOB key, DATA_BLOB value)
 250 {
 251         struct memcache_element *e;
 252         struct rb_node **p;
 253         struct rb_node *parent;
 254         DATA_BLOB cache_key, cache_value;
 255         size_t element_size;
 256
 257         if (cache == NULL) {
 258                 cache = global_cache;
 259         }
 260         if (cache == NULL) {
 261                 return;
 262         }
 263
 264         if (key.length == 0) {
 265                 return;
 266         }
 267
 268         e = memcache_find(cache, n, key);
 269
 270         if (e != NULL) {
 271                 memcache_element_parse(e, &cache_key, &cache_value);
 272
 273                 if (value.length <= cache_value.length) {
 274                         if (memcache_is_talloc(e->n)) {
 275                                 void *ptr;
 276                                 SMB_ASSERT(cache_value.length == sizeof(ptr));
 277                                 memcpy(&ptr, cache_value.data, sizeof(ptr));
 278                                 TALLOC_FREE(ptr);
 279                         }
 280                         /*
 281                          * We can reuse the existing record
 282                          */
 283                         memcpy(cache_value.data, value.data, value.length);
 284                         e->valuelength = value.length;
 285                         return;
 286                 }
 287
 288                 memcache_delete_element(cache, e);
 289         }
 290
 291         element_size = memcache_element_size(key.length, value.length);
 292
 293         e = talloc_size(cache, element_size);
 294         if (e == NULL) {
 295                 DEBUG(0, ("talloc failed\n"));
 296                 return;
 297         }
 298         talloc_set_type(e, struct memcache_element);
 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
 327         cache->size += element_size;
 328         memcache_trim(cache);
 329 }
 330
 331 void memcache_add_talloc(struct memcache *cache, enum memcache_number n,
 332                          DATA_BLOB key, void *pptr)
 333 {
 334         void **ptr = (void **)pptr;
 335         void *p;
 336
 337         if (cache == NULL) {
 338                 cache = global_cache;
 339         }
 340         if (cache == NULL) {
 341                 return;
 342         }
 343
 344         p = talloc_move(cache, ptr);
 345         memcache_add(cache, n, key, data_blob_const(&p, sizeof(p)));
 346 }
 347
 348 void memcache_flush(struct memcache *cache, enum memcache_number n)
 349 {
 350         struct rb_node *node;
 351
 352         if (cache == NULL) {
 353                 cache = global_cache;
 354         }
 355         if (cache == NULL) {
 356                 return;
 357         }
 358
 359         /*
 360          * Find the smallest element of number n
 361          */
 362
 363         node = cache->tree.rb_node;
 364         if (node == NULL) {
 365                 return;
 366         }
 367
 368         /*
 369          * First, find *any* element of number n
 370          */
 371
 372         while (true) {
 373                 struct memcache_element *elem = memcache_node2elem(node);
 374                 struct rb_node *next;
 375
 376                 if ((int)elem->n == (int)n) {
 377                         break;
 378                 }
 379
 380                 if ((int)elem->n < (int)n) {
 381                         next = node->rb_right;
 382                 }
 383                 else {
 384                         next = node->rb_left;
 385                 }
 386                 if (next == NULL) {
 387                         break;
 388                 }
 389                 node = next;
 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 }