171 lines
3.7 KiB
C++
171 lines
3.7 KiB
C++
/*
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* Copyright (C) 2003-2015 The Music Player Daemon Project
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* 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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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include "config.h"
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#include "TagPool.hxx"
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#include "TagItem.hxx"
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#include "util/Cast.hxx"
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#include "util/VarSize.hxx"
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#include "util/StringView.hxx"
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#include <assert.h>
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#include <string.h>
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#include <stdlib.h>
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Mutex tag_pool_lock;
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static constexpr size_t NUM_SLOTS = 4096;
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struct TagPoolSlot {
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TagPoolSlot *next;
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unsigned char ref;
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TagItem item;
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TagPoolSlot(TagPoolSlot *_next, TagType type,
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StringView value)
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:next(_next), ref(1) {
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item.type = type;
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memcpy(item.value, value.data, value.size);
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item.value[value.size] = 0;
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}
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static TagPoolSlot *Create(TagPoolSlot *_next, TagType type,
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StringView value);
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} gcc_packed;
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TagPoolSlot *
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TagPoolSlot::Create(TagPoolSlot *_next, TagType type,
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StringView value)
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{
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TagPoolSlot *dummy;
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return NewVarSize<TagPoolSlot>(sizeof(dummy->item.value),
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value.size + 1,
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_next, type,
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value);
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}
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static TagPoolSlot *slots[NUM_SLOTS];
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static inline unsigned
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calc_hash(TagType type, StringView p)
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{
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unsigned hash = 5381;
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for (auto ch : p)
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hash = (hash << 5) + hash + ch;
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return hash ^ type;
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}
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static inline unsigned
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calc_hash(TagType type, const char *p)
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{
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unsigned hash = 5381;
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assert(p != nullptr);
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while (*p != 0)
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hash = (hash << 5) + hash + *p++;
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return hash ^ type;
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}
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#if CLANG_OR_GCC_VERSION(4,7)
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constexpr
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#endif
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static inline TagPoolSlot *
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tag_item_to_slot(TagItem *item)
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{
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return &ContainerCast(*item, &TagPoolSlot::item);
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}
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static inline TagPoolSlot **
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tag_value_slot_p(TagType type, StringView value)
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{
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return &slots[calc_hash(type, value) % NUM_SLOTS];
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}
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static inline TagPoolSlot **
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tag_value_slot_p(TagType type, const char *value)
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{
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return &slots[calc_hash(type, value) % NUM_SLOTS];
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}
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TagItem *
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tag_pool_get_item(TagType type, StringView value)
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{
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auto slot_p = tag_value_slot_p(type, value);
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for (auto slot = *slot_p; slot != nullptr; slot = slot->next) {
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if (slot->item.type == type &&
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value.Equals(slot->item.value) &&
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slot->ref < 0xff) {
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assert(slot->ref > 0);
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++slot->ref;
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return &slot->item;
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}
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}
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auto slot = TagPoolSlot::Create(*slot_p, type, value);
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*slot_p = slot;
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return &slot->item;
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}
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TagItem *
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tag_pool_dup_item(TagItem *item)
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{
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TagPoolSlot *slot = tag_item_to_slot(item);
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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 item;
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} else {
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/* the reference counter overflows above 0xff;
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duplicate the item, and start with 1 */
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auto slot_p = tag_value_slot_p(item->type, item->value);
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slot = TagPoolSlot::Create(*slot_p, item->type,
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item->value);
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*slot_p = slot;
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return &slot->item;
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}
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}
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void
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tag_pool_put_item(TagItem *item)
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{
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TagPoolSlot **slot_p, *slot;
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slot = tag_item_to_slot(item);
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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 = tag_value_slot_p(item->type, item->value);
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*slot_p != slot;
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slot_p = &(*slot_p)->next) {
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assert(*slot_p != nullptr);
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}
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*slot_p = slot->next;
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DeleteVarSize(slot);
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}
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