117 lines
4.2 KiB
C++
117 lines
4.2 KiB
C++
/*
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Copyright (c) 2006-2018, Arvid Norberg
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions
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are met:
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* Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in
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the documentation and/or other materials provided with the distribution.
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* Neither the name of the author nor the names of its
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contributors may be used to endorse or promote products derived
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from this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef TORRENT_FILE_POOL_HPP
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#define TORRENT_FILE_POOL_HPP
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#include <map>
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#include <mutex>
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#include <vector>
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#include "libtorrent/file.hpp"
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#include "libtorrent/aux_/time.hpp"
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#include "libtorrent/units.hpp"
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#include "libtorrent/storage_defs.hpp"
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#include "libtorrent/disk_interface.hpp" // for open_file_state
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namespace libtorrent {
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class file_storage;
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struct open_file_state;
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// this is an internal cache of open file handles. It's primarily used by
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// storage_interface implementations. It provides semi weak guarantees of
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// not opening more file handles than specified. Given multiple threads,
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// each with the ability to lock a file handle (via smart pointer), there
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// may be windows where more file handles are open.
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struct TORRENT_EXPORT file_pool : boost::noncopyable
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{
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// ``size`` specifies the number of allowed files handles
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// to hold open at any given time.
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explicit file_pool(int size = 40);
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~file_pool();
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// return an open file handle to file at ``file_index`` in the
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// file_storage ``fs`` opened at save path ``p``. ``m`` is the
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// file open mode (see file::open_mode_t).
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file_handle open_file(storage_index_t st, std::string const& p
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, file_index_t file_index, file_storage const& fs, open_mode_t m
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, error_code& ec);
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// release all files belonging to the specified storage_interface (``st``)
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// the overload that takes ``file_index`` releases only the file with
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// that index in storage ``st``.
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void release();
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void release(storage_index_t st);
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void release(storage_index_t st, file_index_t file_index);
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// update the allowed number of open file handles to ``size``.
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void resize(int size);
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// returns the current limit of number of allowed open file handles held
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// by the file_pool.
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int size_limit() const { return m_size; }
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// internal
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void set_low_prio_io(bool b) { m_low_prio_io = b; }
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std::vector<open_file_state> get_status(storage_index_t st) const;
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// close the file that was opened least recently (i.e. not *accessed*
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// least recently). The purpose is to make the OS (really just windows)
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// clear and flush its disk cache associated with this file. We don't want
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// any file to stay open for too long, allowing the disk cache to accrue.
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void close_oldest();
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private:
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file_handle remove_oldest(std::unique_lock<std::mutex>&);
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int m_size;
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bool m_low_prio_io = false;
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struct lru_file_entry
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{
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file_handle file_ptr;
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time_point const opened{aux::time_now()};
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time_point last_use{opened};
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open_mode_t mode{};
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};
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// maps storage pointer, file index pairs to the
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// LRU entry for the file
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std::map<std::pair<storage_index_t, file_index_t>, lru_file_entry> m_files;
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mutable std::mutex m_mutex;
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};
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}
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#endif
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