A time-based thread-safe in-memory cache thing. Called em_cache 'cause

2004-01-13  Not Zed  <NotZed@Ximian.com>

        * e-msgport.c (em_cache*): A time-based thread-safe in-memory
        cache thing.  Called em_cache 'cause there's an e_cache in gal.

svn path=/trunk/; revision=24213

3 files changed, 237 insertions, 0 deletions

diff --git a/e-util/ChangeLog b/e-util/ChangeLog
index e4a25d11f5..0ed9ae50a8 100644
--- a/e-util/ChangeLog
+++ b/e-util/ChangeLog
@@ -1,3 +1,8 @@
+2004-01-13  Not Zed  <NotZed@Ximian.com>
+
+	* e-msgport.c (em_cache*): A time-based thread-safe in-memory
+	cache thing.  Called em_cache 'cause there's an e_cache in gal.
+
 2004-01-05  Not Zed  <NotZed@Ximian.com>
 
 	* e-memory.c (e_mempool_destroy): Fix from Zan Lynx
diff --git a/e-util/e-msgport.c b/e-util/e-msgport.c
index 36ea6cfe8d..f360a3f157 100644
--- a/e-util/e-msgport.c
+++ b/e-util/e-msgport.c
@@ -43,6 +43,7 @@
 
 #define m(x)			/* msgport debug */
 #define t(x) 			/* thread debug */
+#define c(x)			/* cache debug */
 
 void e_dlist_init(EDList *v)
 {
@@ -125,6 +126,214 @@ int e_dlist_length(EDList *l)
 	return count;
 }
 
+struct _EMCache {
+	GMutex *lock;
+	GHashTable *key_table;
+	EDList lru_list;
+	size_t node_size;
+	int node_count;
+	time_t timeout;
+	GFreeFunc node_free;
+};
+
+/**
+ * em_cache_new:
+ * @timeout: 
+ * @nodesize: 
+ * @nodefree: 
+ * 
+ * Setup a new timeout cache.  @nodesize is the size of nodes in the
+ * cache, and @nodefree will be called to free YOUR content.
+ * 
+ * Return value: 
+ **/
+EMCache *
+em_cache_new(time_t timeout, size_t nodesize, GFreeFunc nodefree)
+{
+	struct _EMCache *emc;
+
+	emc = g_malloc0(sizeof(*emc));
+	emc->node_size = nodesize;
+	emc->key_table = g_hash_table_new(g_str_hash, g_str_equal);
+	emc->node_free = nodefree;
+	e_dlist_init(&emc->lru_list);
+	emc->lock = g_mutex_new();
+	emc->timeout = timeout;
+
+	return emc;
+}
+
+/**
+ * em_cache_destroy:
+ * @emc: 
+ * 
+ * destroy the cache, duh.
+ **/
+void
+em_cache_destroy(EMCache *emc)
+{
+	em_cache_clear(emc);
+	g_mutex_free(emc->lock);
+	g_free(emc);
+}
+
+/**
+ * em_cache_lookup:
+ * @emc: 
+ * @key: 
+ * 
+ * Lookup a cache node.  once you're finished with it, you need to
+ * unref it.
+ * 
+ * Return value: 
+ **/
+EMCacheNode *
+em_cache_lookup(EMCache *emc, const char *key)
+{
+	EMCacheNode *n;
+
+	g_mutex_lock(emc->lock);
+	n = g_hash_table_lookup(emc->key_table, key);
+	if (n) {
+		e_dlist_remove((EDListNode *)n);
+		e_dlist_addhead(&emc->lru_list, (EDListNode *)n);
+		n->stamp = time(0);
+		n->ref_count++;
+	}
+	g_mutex_unlock(emc->lock);
+
+	c(printf("looking up '%s' %s\n", key, n?"found":"not found"));
+
+	return n;
+}
+
+/**
+ * em_cache_node_new:
+ * @emc: 
+ * @key: 
+ * 
+ * Create a new key'd cache node.  The node will not be added to the
+ * cache until you insert it.
+ * 
+ * Return value: 
+ **/
+EMCacheNode *
+em_cache_node_new(EMCache *emc, const char *key)
+{
+	EMCacheNode *n;
+
+	/* this could use memchunks, but its probably overkill */
+	n = g_malloc0(emc->node_size);
+	n->key = g_strdup(key);
+
+	return n;
+}
+
+/**
+ * em_cache_node_unref:
+ * @emc: 
+ * @n: 
+ * 
+ * unref a cache node, you can only unref nodes which have been looked
+ * up.
+ **/
+void
+em_cache_node_unref(EMCache *emc, EMCacheNode *n)
+{
+	g_mutex_lock(emc->lock);
+	g_assert(n->ref_count > 0);
+	n->ref_count--;
+	g_mutex_unlock(emc->lock);
+}
+
+/**
+ * em_cache_add:
+ * @emc: 
+ * @n: 
+ * 
+ * Add a cache node to the cache, once added the memory is owned by
+ * the cache.  If there are conflicts and the old node is still in
+ * use, then the new node is not added, otherwise it is added and any
+ * nodes older than the expire time are flushed.
+ **/
+void
+em_cache_add(EMCache *emc, EMCacheNode *n)
+{
+	EMCacheNode *old, *prev;
+	EDList old_nodes;
+
+	e_dlist_init(&old_nodes);
+
+	g_mutex_lock(emc->lock);
+	old = g_hash_table_lookup(emc->key_table, n->key);
+	if (old != NULL) {
+		if (old->ref_count == 0) {
+			g_hash_table_remove(emc->key_table, old->key);
+			e_dlist_remove((EDListNode *)old);
+			e_dlist_addtail(&old_nodes, (EDListNode *)old);
+			goto insert;
+		} else {
+			e_dlist_addtail(&old_nodes, (EDListNode *)n);
+		}
+	} else {
+		time_t now;
+	insert:
+		now = time(0);
+		g_hash_table_insert(emc->key_table, n->key, n);
+		e_dlist_addhead(&emc->lru_list, (EDListNode *)n);
+		n->stamp = now;
+		emc->node_count++;
+
+		c(printf("inserting node %s\n", n->key));
+
+		old = (EMCacheNode *)emc->lru_list.tailpred;
+		prev = old->prev;
+		while (prev && old->stamp < now - emc->timeout) {
+			if (old->ref_count == 0) {
+				c(printf("expiring node %s\n", old->key));
+				g_hash_table_remove(emc->key_table, old->key);
+				e_dlist_remove((EDListNode *)old);
+				e_dlist_addtail(&old_nodes, (EDListNode *)old);
+			}
+			old = prev;
+			prev = prev->prev;
+		}
+	}
+
+	g_mutex_unlock(emc->lock);
+
+	while ((old = (EMCacheNode *)e_dlist_remhead(&old_nodes))) {
+		emc->node_free(old);
+		g_free(old->key);
+		g_free(old);
+	}
+}
+
+/**
+ * em_cache_clear:
+ * @emc: 
+ * 
+ * clear the cache.  just for api completeness.
+ **/
+void
+em_cache_clear(EMCache *emc)
+{
+	EMCacheNode *node;
+	EDList old_nodes;
+
+	e_dlist_init(&old_nodes);
+	g_mutex_lock(emc->lock);
+	while ((node = (EMCacheNode *)e_dlist_remhead(&emc->lru_list)))
+		e_dlist_addtail(&old_nodes, (EDListNode *)node);
+	g_mutex_unlock(emc->lock);
+
+	while ((node = (EMCacheNode *)e_dlist_remhead(&old_nodes))) {
+		emc->node_free(node);
+		g_free(node->key);
+		g_free(node);
+	}
+}
+
 struct _EMsgPort {
 	EDList queue;
 	int condwait;		/* how many waiting in condwait */
diff --git a/e-util/e-msgport.h b/e-util/e-msgport.h
index 8d4e0c20f7..6347564c0f 100644
--- a/e-util/e-msgport.h
+++ b/e-util/e-msgport.h
@@ -2,6 +2,9 @@
 #ifndef _E_MSGPORT_H
 #define _E_MSGPORT_H
 
+#include <time.h>
+#include <glib.h>
+
 /* double-linked list yeah another one, deal */
 typedef struct _EDListNode {
 	struct _EDListNode *next;
@@ -25,6 +28,26 @@ EDListNode *e_dlist_remtail(EDList *l);
 int e_dlist_empty(EDList *l);
 int e_dlist_length(EDList *l);
 
+/* a time-based cache */
+typedef struct _EMCache EMCache;
+typedef struct _EMCacheNode EMCacheNode;
+
+/* subclass this for your data nodes, EMCache is opaque */
+struct _EMCacheNode {
+	struct _EMCacheNode *next, *prev;
+	char *key;
+	int ref_count;
+	time_t stamp;
+};
+
+EMCache *em_cache_new(time_t timeout, size_t nodesize, GFreeFunc nodefree);
+void em_cache_destroy(EMCache *emc);
+EMCacheNode *em_cache_lookup(EMCache *emc, const char *key);
+EMCacheNode *em_cache_node_new(EMCache *emc, const char *key);
+void em_cache_node_unref(EMCache *emc, EMCacheNode *n);
+void em_cache_add(EMCache *emc, EMCacheNode *n);
+void em_cache_clear(EMCache *emc);
+
 /* message ports - a simple inter-thread 'ipc' primitive */
 /* opaque handle */
 typedef struct _EMsgPort EMsgPort;