126 lines
2.8 KiB
C
126 lines
2.8 KiB
C
/* ncmpc
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* Copyright (C) 2008 Max Kellermann <max@duempel.org>
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* This project's homepage is: http://www.musicpd.org
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#include "str_pool.h"
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//#include <assert.h>
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#include <stddef.h>
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#include <stdlib.h>
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#include <string.h>
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#define NUM_SLOTS 4096
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struct slot {
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struct slot *next;
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unsigned char ref;
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char value[1];
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} __attribute__((packed));
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struct slot *slots[NUM_SLOTS];
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static inline unsigned
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calc_hash(const char *p)
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{
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unsigned hash = 5381;
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//assert(p != NULL);
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while (*p != 0)
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hash = (hash << 5) + hash + *p++;
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return hash;
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}
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static inline struct slot *
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value_to_slot(const char *value)
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{
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return (struct slot*)(value - offsetof(struct slot, value));
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}
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static struct slot *slot_alloc(struct slot *next, const char *value)
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{
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size_t length = strlen(value);
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struct slot *slot = malloc(sizeof(*slot) + length);
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if (slot == NULL)
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abort(); /* XXX */
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slot->next = next;
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slot->ref = 1;
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memcpy(slot->value, value, length + 1);
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return slot;
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}
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char *str_pool_get(const char *value)
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{
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struct slot **slot_p, *slot;
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slot_p = &slots[calc_hash(value) % NUM_SLOTS];
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for (slot = *slot_p; slot != NULL; slot = slot->next) {
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if (strcmp(value, slot->value) == 0 && slot->ref < 0xff) {
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//assert(slot->ref > 0);
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++slot->ref;
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return slot->value;
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}
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}
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slot = slot_alloc(*slot_p, value);
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*slot_p = slot;
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return slot->value;
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}
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char *str_pool_dup(const char *value)
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{
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struct slot *slot = value_to_slot(value);
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//assert(slot->ref > 0);
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if (slot->ref < 0xff) {
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++slot->ref;
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return (char *) value;
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} else {
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/* the reference counter overflows above 0xff;
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duplicate the value, and start with 1 */
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struct slot **slot_p =
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&slots[calc_hash(slot->value) % NUM_SLOTS];
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slot = slot_alloc(*slot_p, slot->value);
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*slot_p = slot;
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return slot->value;
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}
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}
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void str_pool_put(const char *value)
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{
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struct slot **slot_p, *slot;
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slot = value_to_slot(value);
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//assert(slot->ref > 0);
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--slot->ref;
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if (slot->ref > 0)
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return;
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for (slot_p = &slots[calc_hash(value) % NUM_SLOTS];
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*slot_p != slot;
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slot_p = &(*slot_p)->next) {
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//assert(*slot_p != NULL);
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}
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*slot_p = slot->next;
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free(slot);
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}
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