lib/util: move memcache.[ch] to the toplevel 'samba-util' library

This is generic enough that it could be used in all code.

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>

Autobuild-User(master): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(master): Fri Jul 18 15:43:33 CEST 2014 on sn-devel-104

(cherry picked from commit 45807028d478c082fef6f3a3d5a142d96d63fb50)

3 files changed, 532 insertions, 1 deletions

diff --git a/lib/util/memcache.c b/lib/util/memcache.c
new file mode 100644
index 0000000000..50e59fc704
--- /dev/null
+++ b/lib/util/memcache.c
@@ -0,0 +1,421 @@
+/*
+   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 "replace.h"
+#include <talloc.h>
+#include "../lib/util/samba_util.h"
+#include "../lib/util/debug.h"
+#include "../lib/util/dlinklist.h"
+#include "../lib/util/rbtree.h"
+#include "memcache.h"
+
+static struct memcache *global_cache;
+
+struct memcache_element {
+	struct rb_node rb_node;
+	struct memcache_element *prev, *next;
+	size_t keylength, valuelength;
+	uint8_t n;		/* This is really an enum, but save memory */
+	char data[1];		/* placeholder for offsetof */
+};
+
+struct memcache {
+	struct memcache_element *mru;
+	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;
+		TALLOC_FREE(e);
+	}
+	return 0;
+}
+
+struct memcache *memcache_init(TALLOC_CTX *mem_ctx, size_t max_size)
+{
+	struct memcache *result;
+
+	result = talloc_zero(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_t *)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) {
+		DLIST_PROMOTE(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);
+
+	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);
+
+	TALLOC_FREE(e);
+}
+
+static void memcache_trim(struct memcache *cache)
+{
+	if (cache->max_size == 0) {
+		return;
+	}
+
+	while ((cache->size > cache->max_size) && DLIST_TAIL(cache->mru)) {
+		memcache_delete_element(cache, DLIST_TAIL(cache->mru));
+	}
+}
+
+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 = talloc_size(cache, element_size);
+	if (e == NULL) {
+		DEBUG(0, ("talloc failed\n"));
+		return;
+	}
+	talloc_set_type(e, struct memcache_element);
+
+	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);
+
+	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;
+	}
+
+	/*
+	 * 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;
+	}
+}
diff --git a/lib/util/memcache.h b/lib/util/memcache.h
new file mode 100644
index 0000000000..11e59718c9
--- /dev/null
+++ b/lib/util/memcache.h
@@ -0,0 +1,110 @@
+/*
+   Unix SMB/CIFS implementation.
+   In-memory cache
+   Copyright (C) Volker Lendecke 2007-2008
+
+   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/>.
+*/
+
+#ifndef __MEMCACHE_H__
+#define __MEMCACHE_H__
+
+struct memcache;
+
+/*
+ * A memcache can store different subkeys with overlapping keys, the
+ * memcache_number becomes part of the key. Feel free to add caches of your
+ * own here.
+ *
+ * If you add talloc type caches, also note this in the switch statement in
+ * memcache_is_talloc().
+ */
+
+enum memcache_number {
+	STAT_CACHE,
+	GETWD_CACHE,
+	GETPWNAM_CACHE,		/* talloc */
+	MANGLE_HASH2_CACHE,
+	PDB_GETPWSID_CACHE,	/* talloc */
+	SINGLETON_CACHE_TALLOC,	/* talloc */
+	SINGLETON_CACHE,
+	SMB1_SEARCH_OFFSET_MAP
+};
+
+/*
+ * Create a memcache structure. max_size is in bytes, if you set it 0 it will
+ * not forget anything.
+ */
+
+struct memcache *memcache_init(TALLOC_CTX *mem_ctx, size_t max_size);
+
+/*
+ * If you set this global memcache, use it as the default cache when NULL is
+ * passed to the memcache functions below. This is a workaround for many
+ * situations where passing the cache everywhere would be a big hassle.
+ */
+
+void memcache_set_global(struct memcache *cache);
+
+/*
+ * Add a data blob to the cache
+ */
+
+void memcache_add(struct memcache *cache, enum memcache_number n,
+		  DATA_BLOB key, DATA_BLOB value);
+
+/*
+ * Add a talloc object to the cache. The difference to memcache_add() is that
+ * when the objects is to be discared, talloc_free is called for it. Also
+ * talloc_move() ownership of the object to the cache.
+ *
+ * Please note that the current implementation has a fixed relationship
+ * between what cache subtypes store talloc objects and which ones store plain
+ * blobs. We can fix this, but for now we don't have a mixed use of blobs vs
+ * talloc objects in the cache types.
+ */
+
+void memcache_add_talloc(struct memcache *cache, enum memcache_number n,
+			 DATA_BLOB key, void *ptr);
+
+/*
+ * Delete an object from the cache
+ */
+
+void memcache_delete(struct memcache *cache, enum memcache_number n,
+		     DATA_BLOB key);
+
+/*
+ * Look up an object from the cache. Memory still belongs to the cache, so
+ * make a copy of it if needed.
+ */
+
+bool memcache_lookup(struct memcache *cache, enum memcache_number n,
+		     DATA_BLOB key, DATA_BLOB *value);
+
+/*
+ * Look up an object from the cache. Memory still belongs to the cache, so
+ * make a copy of it if needed.
+ */
+
+void *memcache_lookup_talloc(struct memcache *cache, enum memcache_number n,
+			     DATA_BLOB key);
+
+/*
+ * Flush a complete cache subset.
+ */
+
+void memcache_flush(struct memcache *cache, enum memcache_number n);
+
+#endif
diff --git a/lib/util/wscript_build b/lib/util/wscript_build
index 5087116174..f161f96351 100755
--- a/lib/util/wscript_build
+++ b/lib/util/wscript_build
@@ -8,7 +8,7 @@ bld.SAMBA_LIBRARY('samba-util',
                     util_strlist.c util_paths.c idtree.c debug.c fault.c base64.c
                     util_str.c util_str_common.c substitute.c ms_fnmatch.c
                     server_id.c dprintf.c parmlist.c bitmap.c pidfile.c
-                    tevent_debug.c util_process.c''',
+                    tevent_debug.c util_process.c memcache.c''',
                   deps='DYNCONFIG',
                   public_deps='talloc tevent execinfo uid_wrapper pthread LIBCRYPTO charset util_setid systemd-daemon',
                   public_headers='debug.h attr.h byteorder.h data_blob.h memory.h safe_string.h time.h talloc_stack.h xfile.h dlinklist.h samba_util.h string_wrappers.h',