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/debug.h"
  23 #include "../lib/util/samba_util.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         case SHARE_MODE_LOCK_CACHE:
  57         case GETWD_CACHE:
  58                 result = true;
  59                 break;
  60         default:
  61                 result = false;
  62                 break;
  63         }
  64
  65         return result;
  66 }
  67
  68 static int memcache_destructor(struct memcache *cache) {
  69         struct memcache_element *e, *next;
  70
  71         for (e = cache->mru; e != NULL; e = next) {
  72                 next = e->next;
  73                 TALLOC_FREE(e);
  74         }
  75         return 0;
  76 }
  77
  78 struct memcache *memcache_init(TALLOC_CTX *mem_ctx, size_t max_size)
  79 {
  80         struct memcache *result;
  81
  82         result = talloc_zero(mem_ctx, struct memcache);
  83         if (result == NULL) {
  84                 return NULL;
  85         }
  86         result->max_size = max_size;
  87         talloc_set_destructor(result, memcache_destructor);
  88         return result;
  89 }
  90
  91 void memcache_set_global(struct memcache *cache)
  92 {
  93         TALLOC_FREE(global_cache);
  94         global_cache = cache;
  95 }
  96
  97 static struct memcache_element *memcache_node2elem(struct rb_node *node)
  98 {
  99         return (struct memcache_element *)
 100                 ((char *)node - offsetof(struct memcache_element, rb_node));
 101 }
 102
 103 static void memcache_element_parse(struct memcache_element *e,
 104                                    DATA_BLOB *key, DATA_BLOB *value)
 105 {
 106         key->data = ((uint8_t *)e) + offsetof(struct memcache_element, data);
 107         key->length = e->keylength;
 108         value->data = key->data + e->keylength;
 109         value->length = e->valuelength;
 110 }
 111
 112 static size_t memcache_element_size(size_t key_length, size_t value_length)
 113 {
 114         return sizeof(struct memcache_element) - 1 + key_length + value_length;
 115 }
 116
 117 static int memcache_compare(struct memcache_element *e, enum memcache_number n,
 118                             DATA_BLOB key)
 119 {
 120         DATA_BLOB this_key, this_value;
 121
 122         if ((int)e->n < (int)n) return 1;
 123         if ((int)e->n > (int)n) return -1;
 124
 125         if (e->keylength < key.length) return 1;
 126         if (e->keylength > key.length) return -1;
 127
 128         memcache_element_parse(e, &this_key, &this_value);
 129         return memcmp(this_key.data, key.data, key.length);
 130 }
 131
 132 static struct memcache_element *memcache_find(
 133         struct memcache *cache, enum memcache_number n, DATA_BLOB key)
 134 {
 135         struct rb_node *node;
 136
 137         node = cache->tree.rb_node;
 138
 139         while (node != NULL) {
 140                 struct memcache_element *elem = memcache_node2elem(node);
 141                 int cmp;
 142
 143                 cmp = memcache_compare(elem, n, key);
 144                 if (cmp == 0) {
 145                         return elem;
 146                 }
 147                 node = (cmp < 0) ? node->rb_left : node->rb_right;
 148         }
 149
 150         return NULL;
 151 }
 152
 153 bool memcache_lookup(struct memcache *cache, enum memcache_number n,
 154                      DATA_BLOB key, DATA_BLOB *value)
 155 {
 156         struct memcache_element *e;
 157
 158         if (cache == NULL) {
 159                 cache = global_cache;
 160         }
 161         if (cache == NULL) {
 162                 return false;
 163         }
 164
 165         e = memcache_find(cache, n, key);
 166         if (e == NULL) {
 167                 return false;
 168         }
 169
 170         if (cache->size != 0) {
 171                 DLIST_PROMOTE(cache->mru, e);
 172         }
 173
 174         memcache_element_parse(e, &key, value);
 175         return true;
 176 }
 177
 178 void *memcache_lookup_talloc(struct memcache *cache, enum memcache_number n,
 179                              DATA_BLOB key)
 180 {
 181         DATA_BLOB value;
 182         void *result;
 183
 184         if (!memcache_lookup(cache, n, key, &value)) {
 185                 return NULL;
 186         }
 187
 188         if (value.length != sizeof(result)) {
 189                 return NULL;
 190         }
 191
 192         memcpy(&result, value.data, sizeof(result));
 193
 194         return result;
 195 }
 196
 197 static void memcache_delete_element(struct memcache *cache,
 198                                     struct memcache_element *e)
 199 {
 200         rb_erase(&e->rb_node, &cache->tree);
 201
 202         DLIST_REMOVE(cache->mru, e);
 203
 204         if (memcache_is_talloc(e->n)) {
 205                 DATA_BLOB cache_key, cache_value;
 206                 void *ptr;
 207
 208                 memcache_element_parse(e, &cache_key, &cache_value);
 209                 SMB_ASSERT(cache_value.length == sizeof(ptr));
 210                 memcpy(&ptr, cache_value.data, sizeof(ptr));
 211                 TALLOC_FREE(ptr);
 212         }
 213
 214         cache->size -= memcache_element_size(e->keylength, e->valuelength);
 215
 216         TALLOC_FREE(e);
 217 }
 218
 219 static void memcache_trim(struct memcache *cache)
 220 {
 221         if (cache->max_size == 0) {
 222                 return;
 223         }
 224
 225         while ((cache->size > cache->max_size) && DLIST_TAIL(cache->mru)) {
 226                 memcache_delete_element(cache, DLIST_TAIL(cache->mru));
 227         }
 228 }
 229
 230 void memcache_delete(struct memcache *cache, enum memcache_number n,
 231                      DATA_BLOB key)
 232 {
 233         struct memcache_element *e;
 234
 235         if (cache == NULL) {
 236                 cache = global_cache;
 237         }
 238         if (cache == NULL) {
 239                 return;
 240         }
 241
 242         e = memcache_find(cache, n, key);
 243         if (e == NULL) {
 244                 return;
 245         }
 246
 247         memcache_delete_element(cache, e);
 248 }
 249
 250 void memcache_add(struct memcache *cache, enum memcache_number n,
 251                   DATA_BLOB key, DATA_BLOB value)
 252 {
 253         struct memcache_element *e;
 254         struct rb_node **p;
 255         struct rb_node *parent;
 256         DATA_BLOB cache_key, cache_value;
 257         size_t element_size;
 258
 259         if (cache == NULL) {
 260                 cache = global_cache;
 261         }
 262         if (cache == NULL) {
 263                 return;
 264         }
 265
 266         if (key.length == 0) {
 267                 return;
 268         }
 269
 270         e = memcache_find(cache, n, key);
 271
 272         if (e != NULL) {
 273                 memcache_element_parse(e, &cache_key, &cache_value);
 274
 275                 if (value.length <= cache_value.length) {
 276                         if (memcache_is_talloc(e->n)) {
 277                                 void *ptr;
 278                                 SMB_ASSERT(cache_value.length == sizeof(ptr));
 279                                 memcpy(&ptr, cache_value.data, sizeof(ptr));
 280                                 TALLOC_FREE(ptr);
 281                         }
 282                         /*
 283                          * We can reuse the existing record
 284                          */
 285                         memcpy(cache_value.data, value.data, value.length);
 286                         e->valuelength = value.length;
 287                         return;
 288                 }
 289
 290                 memcache_delete_element(cache, e);
 291         }
 292
 293         element_size = memcache_element_size(key.length, value.length);
 294
 295         e = talloc_size(cache, element_size);
 296         if (e == NULL) {
 297                 DEBUG(0, ("talloc failed\n"));
 298                 return;
 299         }
 300         talloc_set_type(e, struct memcache_element);
 301
 302         e->n = n;
 303         e->keylength = key.length;
 304         e->valuelength = value.length;
 305
 306         memcache_element_parse(e, &cache_key, &cache_value);
 307         memcpy(cache_key.data, key.data, key.length);
 308         memcpy(cache_value.data, value.data, value.length);
 309
 310         parent = NULL;
 311         p = &cache->tree.rb_node;
 312
 313         while (*p) {
 314                 struct memcache_element *elem = memcache_node2elem(*p);
 315                 int cmp;
 316
 317                 parent = (*p);
 318
 319                 cmp = memcache_compare(elem, n, key);
 320
 321                 p = (cmp < 0) ? &(*p)->rb_left : &(*p)->rb_right;
 322         }
 323
 324         rb_link_node(&e->rb_node, parent, p);
 325         rb_insert_color(&e->rb_node, &cache->tree);
 326
 327         DLIST_ADD(cache->mru, e);
 328
 329         cache->size += element_size;
 330         memcache_trim(cache);
 331 }
 332
 333 void memcache_add_talloc(struct memcache *cache, enum memcache_number n,
 334                          DATA_BLOB key, void *pptr)
 335 {
 336         void **ptr = (void **)pptr;
 337         void *p;
 338
 339         if (cache == NULL) {
 340                 cache = global_cache;
 341         }
 342         if (cache == NULL) {
 343                 return;
 344         }
 345
 346         p = talloc_move(cache, ptr);
 347         memcache_add(cache, n, key, data_blob_const(&p, sizeof(p)));
 348 }
 349
 350 void memcache_flush(struct memcache *cache, enum memcache_number n)
 351 {
 352         struct rb_node *node;
 353
 354         if (cache == NULL) {
 355                 cache = global_cache;
 356         }
 357         if (cache == NULL) {
 358                 return;
 359         }
 360
 361         /*
 362          * Find the smallest element of number n
 363          */
 364
 365         node = cache->tree.rb_node;
 366         if (node == NULL) {
 367                 return;
 368         }
 369
 370         /*
 371          * First, find *any* element of number n
 372          */
 373
 374         while (true) {
 375                 struct memcache_element *elem = memcache_node2elem(node);
 376                 struct rb_node *next;
 377
 378                 if ((int)elem->n == (int)n) {
 379                         break;
 380                 }
 381
 382                 if ((int)elem->n < (int)n) {
 383                         next = node->rb_right;
 384                 }
 385                 else {
 386                         next = node->rb_left;
 387                 }
 388                 if (next == NULL) {
 389                         break;
 390                 }
 391                 node = next;
 392         }
 393
 394         /*
 395          * Then, find the leftmost element with number n
 396          */
 397
 398         while (true) {
 399                 struct rb_node *prev = rb_prev(node);
 400                 struct memcache_element *elem;
 401
 402                 if (prev == NULL) {
 403                         break;
 404                 }
 405                 elem = memcache_node2elem(prev);
 406                 if ((int)elem->n != (int)n) {
 407                         break;
 408                 }
 409                 node = prev;
 410         }
 411
 412         while (node != NULL) {
 413                 struct memcache_element *e = memcache_node2elem(node);
 414                 struct rb_node *next = rb_next(node);
 415
 416                 if (e->n != n) {
 417                         break;
 418                 }
 419
 420                 memcache_delete_element(cache, e);
 421                 node = next;
 422         }
 423 }