1 files changed, 125 insertions, 0 deletions
diff --git a/src/str_pool.c b/src/str_pool.c
new file mode 100644
index 000000000..74839b59d
--- /dev/null
+++ b/src/str_pool.c
@@ -0,0 +1,125 @@
+/* ncmpc
+ * Copyright (C) 2008 Max Kellermann <max@duempel.org>
+ * This project's homepage is: 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include "str_pool.h"
+
+#include <assert.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define NUM_SLOTS 4096
+
+struct slot {
+	struct slot *next;
+	unsigned char ref;
+	char value[1];
+} __attribute__((packed));
+
+struct slot *slots[NUM_SLOTS];
+
+static inline unsigned
+calc_hash(const char *p)
+{
+	unsigned hash = 5381;
+
+	assert(p != NULL);
+
+	while (*p != 0)
+		hash = (hash << 5) + hash + *p++;
+
+	return hash;
+}
+
+static inline struct slot *
+value_to_slot(char *value)
+{
+	return (struct slot*)(value - offsetof(struct slot, value));
+}
+
+static struct slot *slot_alloc(struct slot *next, const char *value)
+{
+	size_t length = strlen(value);
+	struct slot *slot = malloc(sizeof(*slot) + length);
+	if (slot == NULL)
+		abort(); /* XXX */
+
+	slot->next = next;
+	slot->ref = 1;
+	memcpy(slot->value, value, length + 1);
+	return slot;
+}
+
+char *str_pool_get(const char *value)
+{
+	struct slot **slot_p, *slot;
+
+	slot_p = &slots[calc_hash(value) % NUM_SLOTS];
+	for (slot = *slot_p; slot != NULL; slot = slot->next) {
+		if (strcmp(value, slot->value) == 0 && slot->ref < 0xff) {
+			assert(slot->ref > 0);
+			++slot->ref;
+			return slot->value;
+		}
+	}
+
+	slot = slot_alloc(*slot_p, value);
+	*slot_p = slot;
+	return slot->value;
+}
+
+char *str_pool_dup(char *value)
+{
+	struct slot *slot = value_to_slot(value);
+
+	assert(slot->ref > 0);
+
+	if (slot->ref < 0xff) {
+		++slot->ref;
+		return value;
+	} else {
+		/* the reference counter overflows above 0xff;
+		   duplicate the value, and start with 1 */
+		struct slot **slot_p =
+			&slots[calc_hash(slot->value) % NUM_SLOTS];
+		slot = slot_alloc(*slot_p, slot->value);
+		*slot_p = slot;
+		return slot->value;
+	}
+}
+
+void str_pool_put(char *value)
+{
+	struct slot **slot_p, *slot;
+
+	slot = value_to_slot(value);
+	assert(slot->ref > 0);
+	--slot->ref;
+
+	if (slot->ref > 0)
+		return;
+
+	for (slot_p = &slots[calc_hash(value) % NUM_SLOTS];
+	     *slot_p != slot;
+	     slot_p = &(*slot_p)->next) {
+		assert(*slot_p != NULL);
+	}
+
+	*slot_p = slot->next;
+	free(slot);
+}