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/* the Music Player Daemon (MPD)
* 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 "tag_pool.h"
#include "utils.h"
#define NUM_SLOTS 4096
struct slot {
struct slot *next;
unsigned char ref;
struct tag_item item;
} mpd_packed;
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 != NULL);
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 != NULL);
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 = xmalloc(sizeof(*slot) + length);
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, int length)
{
struct slot **slot_p, *slot;
slot_p = &slots[calc_hash_n(type, value, length) % NUM_SLOTS];
for (slot = *slot_p; slot != NULL; slot = slot->next) {
if (slot->item.type == type &&
strcmp(value, slot->item.value) == 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 != NULL);
}
*slot_p = slot->next;
free(slot);
}
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