/samba-3.5.6/source3/lib/memcache.c
C | 436 lines | 317 code | 86 blank | 33 comment | 87 complexity | 5bcd4c67f5e2eeb7c171ecd484154c7a MD5 | raw file
- /*
- Unix SMB/CIFS implementation.
- In-memory cache
- Copyright (C) Volker Lendecke 2007
- This program is free software; you can redistribute it and/or modify
- it under the terms of the GNU General Public License as published by
- the Free Software Foundation; either version 3 of the License, or
- (at your option) any later version.
- This program is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- GNU General Public License for more details.
- You should have received a copy of the GNU General Public License
- along with this program. If not, see <http://www.gnu.org/licenses/>.
- */
- #include "memcache.h"
- #include "../lib/util/rbtree.h"
- static struct memcache *global_cache;
- struct memcache_element {
- struct rb_node rb_node;
- struct memcache_element *prev, *next;
- size_t keylength, valuelength;
- uint8 n; /* This is really an enum, but save memory */
- char data[1]; /* placeholder for offsetof */
- };
- struct memcache {
- struct memcache_element *mru, *lru;
- struct rb_root tree;
- size_t size;
- size_t max_size;
- };
- static void memcache_element_parse(struct memcache_element *e,
- DATA_BLOB *key, DATA_BLOB *value);
- static bool memcache_is_talloc(enum memcache_number n)
- {
- bool result;
- switch (n) {
- case GETPWNAM_CACHE:
- case PDB_GETPWSID_CACHE:
- case SINGLETON_CACHE_TALLOC:
- result = true;
- break;
- default:
- result = false;
- break;
- }
- return result;
- }
- static int memcache_destructor(struct memcache *cache) {
- struct memcache_element *e, *next;
- for (e = cache->mru; e != NULL; e = next) {
- next = e->next;
- SAFE_FREE(e);
- }
- return 0;
- }
- struct memcache *memcache_init(TALLOC_CTX *mem_ctx, size_t max_size)
- {
- struct memcache *result;
- result = TALLOC_ZERO_P(mem_ctx, struct memcache);
- if (result == NULL) {
- return NULL;
- }
- result->max_size = max_size;
- talloc_set_destructor(result, memcache_destructor);
- return result;
- }
- void memcache_set_global(struct memcache *cache)
- {
- TALLOC_FREE(global_cache);
- global_cache = cache;
- }
- static struct memcache_element *memcache_node2elem(struct rb_node *node)
- {
- return (struct memcache_element *)
- ((char *)node - offsetof(struct memcache_element, rb_node));
- }
- static void memcache_element_parse(struct memcache_element *e,
- DATA_BLOB *key, DATA_BLOB *value)
- {
- key->data = ((uint8 *)e) + offsetof(struct memcache_element, data);
- key->length = e->keylength;
- value->data = key->data + e->keylength;
- value->length = e->valuelength;
- }
- static size_t memcache_element_size(size_t key_length, size_t value_length)
- {
- return sizeof(struct memcache_element) - 1 + key_length + value_length;
- }
- static int memcache_compare(struct memcache_element *e, enum memcache_number n,
- DATA_BLOB key)
- {
- DATA_BLOB this_key, this_value;
- if ((int)e->n < (int)n) return 1;
- if ((int)e->n > (int)n) return -1;
- if (e->keylength < key.length) return 1;
- if (e->keylength > key.length) return -1;
- memcache_element_parse(e, &this_key, &this_value);
- return memcmp(this_key.data, key.data, key.length);
- }
- static struct memcache_element *memcache_find(
- struct memcache *cache, enum memcache_number n, DATA_BLOB key)
- {
- struct rb_node *node;
- node = cache->tree.rb_node;
- while (node != NULL) {
- struct memcache_element *elem = memcache_node2elem(node);
- int cmp;
- cmp = memcache_compare(elem, n, key);
- if (cmp == 0) {
- return elem;
- }
- node = (cmp < 0) ? node->rb_left : node->rb_right;
- }
- return NULL;
- }
- bool memcache_lookup(struct memcache *cache, enum memcache_number n,
- DATA_BLOB key, DATA_BLOB *value)
- {
- struct memcache_element *e;
- if (cache == NULL) {
- cache = global_cache;
- }
- if (cache == NULL) {
- return false;
- }
- e = memcache_find(cache, n, key);
- if (e == NULL) {
- return false;
- }
- if (cache->size != 0) {
- /*
- * Do LRU promotion only when we will ever shrink
- */
- if (e == cache->lru) {
- cache->lru = e->prev;
- }
- DLIST_PROMOTE(cache->mru, e);
- if (cache->mru == NULL) {
- cache->mru = e;
- }
- }
- memcache_element_parse(e, &key, value);
- return true;
- }
- void *memcache_lookup_talloc(struct memcache *cache, enum memcache_number n,
- DATA_BLOB key)
- {
- DATA_BLOB value;
- void *result;
- if (!memcache_lookup(cache, n, key, &value)) {
- return NULL;
- }
- if (value.length != sizeof(result)) {
- return NULL;
- }
- memcpy(&result, value.data, sizeof(result));
- return result;
- }
- static void memcache_delete_element(struct memcache *cache,
- struct memcache_element *e)
- {
- rb_erase(&e->rb_node, &cache->tree);
- if (e == cache->lru) {
- cache->lru = e->prev;
- }
- DLIST_REMOVE(cache->mru, e);
- if (memcache_is_talloc(e->n)) {
- DATA_BLOB cache_key, cache_value;
- void *ptr;
- memcache_element_parse(e, &cache_key, &cache_value);
- SMB_ASSERT(cache_value.length == sizeof(ptr));
- memcpy(&ptr, cache_value.data, sizeof(ptr));
- TALLOC_FREE(ptr);
- }
- cache->size -= memcache_element_size(e->keylength, e->valuelength);
- SAFE_FREE(e);
- }
- static void memcache_trim(struct memcache *cache)
- {
- if (cache->max_size == 0) {
- return;
- }
- while ((cache->size > cache->max_size) && (cache->lru != NULL)) {
- memcache_delete_element(cache, cache->lru);
- }
- }
- void memcache_delete(struct memcache *cache, enum memcache_number n,
- DATA_BLOB key)
- {
- struct memcache_element *e;
- if (cache == NULL) {
- cache = global_cache;
- }
- if (cache == NULL) {
- return;
- }
- e = memcache_find(cache, n, key);
- if (e == NULL) {
- return;
- }
- memcache_delete_element(cache, e);
- }
- void memcache_add(struct memcache *cache, enum memcache_number n,
- DATA_BLOB key, DATA_BLOB value)
- {
- struct memcache_element *e;
- struct rb_node **p;
- struct rb_node *parent;
- DATA_BLOB cache_key, cache_value;
- size_t element_size;
- if (cache == NULL) {
- cache = global_cache;
- }
- if (cache == NULL) {
- return;
- }
- if (key.length == 0) {
- return;
- }
- e = memcache_find(cache, n, key);
- if (e != NULL) {
- memcache_element_parse(e, &cache_key, &cache_value);
- if (value.length <= cache_value.length) {
- if (memcache_is_talloc(e->n)) {
- void *ptr;
- SMB_ASSERT(cache_value.length == sizeof(ptr));
- memcpy(&ptr, cache_value.data, sizeof(ptr));
- TALLOC_FREE(ptr);
- }
- /*
- * We can reuse the existing record
- */
- memcpy(cache_value.data, value.data, value.length);
- e->valuelength = value.length;
- return;
- }
- memcache_delete_element(cache, e);
- }
- element_size = memcache_element_size(key.length, value.length);
- e = (struct memcache_element *)SMB_MALLOC(element_size);
- if (e == NULL) {
- DEBUG(0, ("malloc failed\n"));
- return;
- }
- e->n = n;
- e->keylength = key.length;
- e->valuelength = value.length;
- memcache_element_parse(e, &cache_key, &cache_value);
- memcpy(cache_key.data, key.data, key.length);
- memcpy(cache_value.data, value.data, value.length);
- parent = NULL;
- p = &cache->tree.rb_node;
- while (*p) {
- struct memcache_element *elem = memcache_node2elem(*p);
- int cmp;
- parent = (*p);
- cmp = memcache_compare(elem, n, key);
- p = (cmp < 0) ? &(*p)->rb_left : &(*p)->rb_right;
- }
- rb_link_node(&e->rb_node, parent, p);
- rb_insert_color(&e->rb_node, &cache->tree);
- DLIST_ADD(cache->mru, e);
- if (cache->lru == NULL) {
- cache->lru = e;
- }
- cache->size += element_size;
- memcache_trim(cache);
- }
- void memcache_add_talloc(struct memcache *cache, enum memcache_number n,
- DATA_BLOB key, void *pptr)
- {
- void **ptr = (void **)pptr;
- void *p;
- if (cache == NULL) {
- cache = global_cache;
- }
- if (cache == NULL) {
- return;
- }
- p = talloc_move(cache, ptr);
- memcache_add(cache, n, key, data_blob_const(&p, sizeof(p)));
- }
- void memcache_flush(struct memcache *cache, enum memcache_number n)
- {
- struct rb_node *node;
- if (cache == NULL) {
- cache = global_cache;
- }
- if (cache == NULL) {
- return;
- }
- /*
- * Find the smallest element of number n
- */
- node = cache->tree.rb_node;
- if (node == NULL) {
- return;
- }
- /*
- * First, find *any* element of number n
- */
- while (true) {
- struct memcache_element *elem = memcache_node2elem(node);
- struct rb_node *next;
- if ((int)elem->n == (int)n) {
- break;
- }
- if ((int)elem->n < (int)n) {
- next = node->rb_right;
- }
- else {
- next = node->rb_left;
- }
- if (next == NULL) {
- break;
- }
- node = next;
- }
- if (node == NULL) {
- return;
- }
- /*
- * Then, find the leftmost element with number n
- */
- while (true) {
- struct rb_node *prev = rb_prev(node);
- struct memcache_element *elem;
- if (prev == NULL) {
- break;
- }
- elem = memcache_node2elem(prev);
- if ((int)elem->n != (int)n) {
- break;
- }
- node = prev;
- }
- while (node != NULL) {
- struct memcache_element *e = memcache_node2elem(node);
- struct rb_node *next = rb_next(node);
- if (e->n != n) {
- break;
- }
- memcache_delete_element(cache, e);
- node = next;
- }
- }