summaryrefslogtreecommitdiff
path: root/source3/lib/cache.c
diff options
context:
space:
mode:
Diffstat (limited to 'source3/lib/cache.c')
-rw-r--r--source3/lib/cache.c298
1 files changed, 298 insertions, 0 deletions
diff --git a/source3/lib/cache.c b/source3/lib/cache.c
new file mode 100644
index 0000000000..baf2fe3984
--- /dev/null
+++ b/source3/lib/cache.c
@@ -0,0 +1,298 @@
+/*
+ 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 "cache.h"
+#include "rbtree.h"
+
+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 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;
+}
+
+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;
+
+ 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;
+}
+
+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);
+
+ 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;
+
+ 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 (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) {
+ /*
+ * 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_flush(struct memcache *cache, enum memcache_number n)
+{
+ struct rb_node *node;
+
+ /*
+ * Find the smallest element of number n
+ */
+
+ node = cache->tree.rb_node;
+ if (node == NULL) {
+ return;
+ }
+
+ while (true) {
+ struct memcache_element *elem = memcache_node2elem(node);
+ struct rb_node *next;
+
+ if ((int)elem->n < (int)n) {
+ next = node->rb_right;
+ }
+ else {
+ next = node->rb_left;
+ }
+ if (next == NULL) {
+ break;
+ }
+ node = next;
+ }
+
+ node = rb_next(node);
+ if (node == NULL) {
+ return;
+ }
+
+ while (node != NULL) {
+ struct memcache_element *e = memcache_node2elem(node);
+ struct rb_node *next = rb_next(node);
+
+ memcache_delete_element(cache, e);
+ node = next;
+ }
+}