1 files changed, 164 insertions, 0 deletions
diff --git a/src/dict/dict-init-cache.c b/src/dict/dict-init-cache.c
new file mode 100644
index 0000000..ed76940
--- /dev/null
+++ b/src/dict/dict-init-cache.c
@@ -0,0 +1,164 @@
+/* Copyright (c) 2021 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "ioloop.h"
+#include "dict.h"
+#include "dict-private.h"
+#include "dict-init-cache.h"
+#include "llist.h"
+
+/* How many seconds to keep dict opened for reuse after it's been closed */
+#define DICT_CACHE_TIMEOUT_SECS 30
+/* How many closed dicts to keep */
+#define DICT_CACHE_MAX_COUNT 10
+
+struct dict_init_cache_list {
+	struct dict_init_cache_list *prev, *next;
+
+	struct dict *dict;
+	char *dict_name;
+	int refcount;
+
+	time_t destroy_time;
+};
+
+static struct dict_init_cache_list *dicts = NULL;
+static struct timeout *to_dict = NULL;
+
+static struct dict_init_cache_list *
+dict_init_cache_add(const char *dict_name, struct dict *dict)
+{
+	struct dict_init_cache_list *list;
+
+	list = i_new(struct dict_init_cache_list, 1);
+	list->refcount = 1;
+	list->dict = dict;
+	list->dict_name = i_strdup(dict_name);
+
+	DLLIST_PREPEND(&dicts, list);
+
+	return list;
+}
+
+static void dict_init_cache_list_free(struct dict_init_cache_list *list)
+{
+	i_assert(list->refcount == 0);
+
+	DLLIST_REMOVE(&dicts, list);
+	dict_deinit(&list->dict);
+	i_free(list->dict_name);
+	i_free(list);
+}
+
+static struct dict_init_cache_list *dict_init_cache_find(const char *dict_name)
+{
+	struct dict_init_cache_list *listp = dicts, *next = NULL, *match = NULL;
+	unsigned int ref0_count = 0;
+
+	while (listp != NULL) {
+                next = listp->next;
+		if (match != NULL) {
+			/* already found the dict. we're just going through
+			   the rest of them to drop 0 refcounts */
+		} else if (strcmp(dict_name, listp->dict_name) == 0)
+			match = listp;
+
+		if (listp->refcount == 0 && listp != match) {
+			if (listp->destroy_time <= ioloop_time ||
+			    ref0_count >= DICT_CACHE_MAX_COUNT - 1)
+				dict_init_cache_list_free(listp);
+			else
+				ref0_count++;
+		}
+                listp = next;
+	}
+	return match;
+}
+
+int dict_init_cache_get(const char *dict_name, const char *uri,
+			const struct dict_settings *set,
+			struct dict **dict_r, const char **error_r)
+{
+	struct dict_init_cache_list *match;
+	int ret = 0;
+
+	match = dict_init_cache_find(dict_name);
+	if (match == NULL) {
+		if (dict_init(uri, set, dict_r, error_r) < 0)
+			return -1;
+		match = dict_init_cache_add(dict_name, *dict_r);
+	} else {
+		match->refcount++;
+		*dict_r = match->dict;
+	}
+	i_assert(match->dict != NULL);
+	return ret;
+}
+
+static void destroy_unrefed(void)
+{
+	struct dict_init_cache_list *listp, *next = NULL;
+	bool seen_ref0 = FALSE;
+
+	for (listp = dicts; listp != NULL; listp = next) {
+		next = listp->next;
+
+		i_assert(listp->refcount >= 0);
+		if (listp->refcount > 0)
+			;
+		else if (listp->destroy_time <= ioloop_time)
+			dict_init_cache_list_free(listp);
+		else
+			seen_ref0 = TRUE;
+	}
+
+	if (!seen_ref0 && to_dict != NULL)
+		timeout_remove(&to_dict);
+}
+
+static void dict_removal_timeout(void *context ATTR_UNUSED)
+{
+	destroy_unrefed();
+}
+
+void dict_init_cache_unref(struct dict **_dict)
+{
+	struct dict *dict = *_dict;
+	struct dict_init_cache_list *listp;
+
+	if (dict == NULL)
+		return;
+
+	*_dict = NULL;
+	for (listp = dicts; listp != NULL; listp = listp->next) {
+		if (listp->dict == dict)
+			break;
+	}
+
+	i_assert(listp != NULL && listp->dict == dict);
+	i_assert(listp->refcount > 0);
+
+	listp->refcount--;
+	listp->destroy_time = ioloop_time + DICT_CACHE_TIMEOUT_SECS;
+
+	if (to_dict == NULL) {
+		to_dict = timeout_add_to(io_loop_get_root(),
+					 DICT_CACHE_TIMEOUT_SECS*1000/2,
+					 dict_removal_timeout, NULL);
+	}
+}
+
+void dict_init_cache_wait_all(void)
+{
+	struct dict_init_cache_list *listp;
+
+	for (listp = dicts; listp != NULL; listp = listp->next)
+		dict_wait(listp->dict);
+}
+
+void dict_init_cache_destroy_all(void)
+{
+	timeout_remove(&to_dict);
+	while (dicts != NULL)
+		dict_init_cache_list_free(dicts);
+}