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;
+	}
+}