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/*
* Copyright 2003-2019 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.
*/
#ifndef MPD_INPUT_CACHE_MANAGER_HXX
#define MPD_INPUT_CACHE_MANAGER_HXX
#include "thread/Mutex.hxx"
#include "util/Compiler.h"
#include <boost/intrusive/set.hpp>
#include <boost/intrusive/list.hpp>
class InputStream;
class InputCacheItem;
class InputCacheLease;
struct InputCacheConfig;
/**
* A class which caches files in RAM. It is supposed to prefetch
* files before they are played.
*/
class InputCacheManager {
const size_t max_total_size;
mutable Mutex mutex;
size_t total_size = 0;
struct ItemCompare {
gcc_pure
bool operator()(const InputCacheItem &a,
const char *b) const noexcept;
gcc_pure
bool operator()(const char *a,
const InputCacheItem &b) const noexcept;
gcc_pure
bool operator()(const InputCacheItem &a,
const InputCacheItem &b) const noexcept;
};
boost::intrusive::list<InputCacheItem,
boost::intrusive::base_hook<boost::intrusive::list_base_hook<boost::intrusive::link_mode<boost::intrusive::auto_unlink>>>,
boost::intrusive::constant_time_size<false>> items_by_time;
using UriMap =
boost::intrusive::set<InputCacheItem,
boost::intrusive::base_hook<boost::intrusive::set_base_hook<boost::intrusive::link_mode<boost::intrusive::normal_link>>>,
boost::intrusive::compare<ItemCompare>,
boost::intrusive::constant_time_size<false>>;
UriMap items_by_uri;
public:
explicit InputCacheManager(const InputCacheConfig &config) noexcept;
~InputCacheManager() noexcept;
gcc_pure
bool Contains(const char *uri) noexcept;
/**
* Throws if opening the #InputStream fails.
*
* @param create if true, then the cache item will be created
* if it did not exist
* @return a lease of the new item or nullptr if the file is
* not eligible for caching
*/
InputCacheLease Get(const char *uri, bool create);
/**
* Shortcut for "Get(uri,true)", discarding the returned
* lease.
*/
void Prefetch(const char *uri);
private:
/**
* Check whether the given #InputStream can be stored in this
* cache.
*/
bool IsEligible(const InputStream &input) noexcept;
void Remove(InputCacheItem &item) noexcept;
void Delete(InputCacheItem *item) noexcept;
InputCacheItem *FindOldestUnused() noexcept;
/**
* @return true if one item has been evicted, false if no
* unused item was found
*/
bool EvictOldestUnused() noexcept;
};
#endif
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