1 files changed, 151 insertions, 0 deletions
diff --git a/src/TagPool.cxx b/src/TagPool.cxx
new file mode 100644
index 00000000..a9b89284
--- /dev/null
+++ b/src/TagPool.cxx
@@ -0,0 +1,151 @@
+/*
+ * Copyright (C) 2003-2013 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * 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 2 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, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "config.h"
+#include "TagPool.hxx"
+
+#include <glib.h>
+
+#include <assert.h>
+
+Mutex tag_pool_lock;
+
+#define NUM_SLOTS 4096
+
+struct slot {
+	struct slot *next;
+	unsigned char ref;
+	struct tag_item item;
+} mpd_packed;
+
+static struct slot *slots[NUM_SLOTS];
+
+static inline unsigned
+calc_hash_n(enum tag_type type, const char *p, size_t length)
+{
+	unsigned hash = 5381;
+
+	assert(p != nullptr);
+
+	while (length-- > 0)
+		hash = (hash << 5) + hash + *p++;
+
+	return hash ^ type;
+}
+
+static inline unsigned
+calc_hash(enum tag_type type, const char *p)
+{
+	unsigned hash = 5381;
+
+	assert(p != nullptr);
+
+	while (*p != 0)
+		hash = (hash << 5) + hash + *p++;
+
+	return hash ^ type;
+}
+
+static inline struct slot *
+tag_item_to_slot(struct tag_item *item)
+{
+	return (struct slot*)(((char*)item) - offsetof(struct slot, item));
+}
+
+static struct slot *slot_alloc(struct slot *next,
+			       enum tag_type type,
+			       const char *value, int length)
+{
+	struct slot *slot;
+
+	slot = (struct slot *)
+		g_malloc(sizeof(*slot) - sizeof(slot->item.value) + length + 1);
+	slot->next = next;
+	slot->ref = 1;
+	slot->item.type = type;
+	memcpy(slot->item.value, value, length);
+	slot->item.value[length] = 0;
+	return slot;
+}
+
+struct tag_item *
+tag_pool_get_item(enum tag_type type, const char *value, size_t length)
+{
+	struct slot **slot_p, *slot;
+
+	slot_p = &slots[calc_hash_n(type, value, length) % NUM_SLOTS];
+	for (slot = *slot_p; slot != nullptr; slot = slot->next) {
+		if (slot->item.type == type &&
+		    length == strlen(slot->item.value) &&
+		    memcmp(value, slot->item.value, length) == 0 &&
+		    slot->ref < 0xff) {
+			assert(slot->ref > 0);
+			++slot->ref;
+			return &slot->item;
+		}
+	}
+
+	slot = slot_alloc(*slot_p, type, value, length);
+	*slot_p = slot;
+	return &slot->item;
+}
+
+struct tag_item *tag_pool_dup_item(struct tag_item *item)
+{
+	struct slot *slot = tag_item_to_slot(item);
+
+	assert(slot->ref > 0);
+
+	if (slot->ref < 0xff) {
+		++slot->ref;
+		return item;
+	} else {
+		/* the reference counter overflows above 0xff;
+		   duplicate the item, and start with 1 */
+		size_t length = strlen(item->value);
+		struct slot **slot_p =
+			&slots[calc_hash_n(item->type, item->value,
+					   length) % NUM_SLOTS];
+		slot = slot_alloc(*slot_p, item->type,
+				  item->value, strlen(item->value));
+		*slot_p = slot;
+		return &slot->item;
+	}
+}
+
+void tag_pool_put_item(struct tag_item *item)
+{
+	struct slot **slot_p, *slot;
+
+	slot = tag_item_to_slot(item);
+	assert(slot->ref > 0);
+	--slot->ref;
+
+	if (slot->ref > 0)
+		return;
+
+	for (slot_p = &slots[calc_hash(item->type, item->value) % NUM_SLOTS];
+	     *slot_p != slot;
+	     slot_p = &(*slot_p)->next) {
+		assert(*slot_p != nullptr);
+	}
+
+	*slot_p = slot->next;
+	g_free(slot);
+}