premiere-libtorrent/include/libtorrent/disk_io_thread.hpp

/*

Copyright (c) 2007, Arvid Norberg
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:

    * Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in
      the documentation and/or other materials provided with the distribution.
    * Neither the name of the author nor the names of its
      contributors may be used to endorse or promote products derived
      from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.

*/

#ifndef TORRENT_DISK_IO_THREAD
#define TORRENT_DISK_IO_THREAD

#ifdef TORRENT_DISK_STATS
#include <fstream>
#endif

#include "libtorrent/storage.hpp"
#include <boost/thread/thread.hpp>
#include <boost/function.hpp>
#include <boost/thread/mutex.hpp>
#include <boost/bind.hpp>
#include <boost/pool/pool.hpp>
#include <boost/noncopyable.hpp>
#include <boost/shared_array.hpp>
#include <deque>
#include "libtorrent/config.hpp"

namespace libtorrent
{

	struct cached_piece_info
	{
		int piece;
		std::vector<bool> blocks;
		ptime last_use;
	};
	
	struct disk_io_job
	{
		disk_io_job()
			: action(read)
			, buffer(0)
			, buffer_size(0)
			, piece(0)
			, offset(0)
			, priority(0)
		{}

		enum action_t
		{
			read
			, write
			, hash
			, move_storage
			, release_files
			, delete_files
		};

		action_t action;

		char* buffer;
		size_type buffer_size;
		boost::intrusive_ptr<piece_manager> storage;
		// arguments used for read and write
		int piece, offset;
		// used for move_storage. On errors, this is set
		// to the error message
		std::string str;

		// priority decides whether or not this
		// job will skip entries in the queue or
		// not. It always skips in front of entries
		// with lower priority
		int priority;

		// this is called when operation completes
		boost::function<void(int, disk_io_job const&)> callback;
	};

	struct cache_status
	{
		cache_status()
			: blocks_written(0)
			, writes(0)
			, blocks_read(0)
			, blocks_read_hit(0)
			, reads(0)
			, cache_size(0)
			, read_cache_size(0)
		{}

		// the number of 16kB blocks written
		size_type blocks_written;
		// the number of write operations used
		size_type writes;
		// (blocks_written - writes) / blocks_written represents the
		// "cache hit" ratio in the write cache
		// the number of blocks read

		// the number of blocks passed back to the bittorrent engine
		size_type blocks_read;
		// the number of blocks that was just copied from the read cache
		size_type blocks_read_hit;
		// the number of read operations used
		size_type reads;

		// the number of blocks in the cache (both read and write)
		int cache_size;

		// the number of blocks in the cache used for read cache
		int read_cache_size;
	};
	
	// this is a singleton consisting of the thread and a queue
	// of disk io jobs
	struct disk_io_thread : boost::noncopyable
	{
		disk_io_thread(asio::io_service& ios, int block_size = 16 * 1024);
		~disk_io_thread();

#ifdef TORRENT_STATS
		int disk_allocations() const
		{ return m_allocations; }
#endif

		void join();

		// aborts read operations
		void stop(boost::intrusive_ptr<piece_manager> s);
		void add_job(disk_io_job const& j
			, boost::function<void(int, disk_io_job const&)> const& f
			= boost::function<void(int, disk_io_job const&)>());

#ifndef NDEBUG
		disk_io_job find_job(boost::intrusive_ptr<piece_manager> s
			, int action, int piece) const;
#endif
		// keep track of the number of bytes in the job queue
		// at any given time. i.e. the sum of all buffer_size.
		// this is used to slow down the download global download
		// speed when the queue buffer size is too big.
		size_type queue_buffer_size() const
		{ return m_queue_buffer_size; }

		void get_cache_info(sha1_hash const& ih
			, std::vector<cached_piece_info>& ret) const;

		cache_status status() const;
		void set_cache_size(int s);
		void set_cache_expiry(int ex);

		void operator()();

		char* allocate_buffer();
		void free_buffer(char* buf);

#ifndef NDEBUG
		void check_invariant() const;
#endif
		
	private:

		typedef boost::recursive_mutex mutex_t;

		struct cached_piece_entry
		{
			int piece;
			// storage this piece belongs to
			boost::intrusive_ptr<piece_manager> storage;
			// the last time a block was writting to this piece
			ptime last_use;
			// the number of blocks in the cache for this piece
			int num_blocks;
			// the pointers to the block data
			boost::shared_array<char*> blocks;
		};

		char* allocate_buffer(mutex_t::scoped_lock& l);
		void free_buffer(char* buf, mutex_t::scoped_lock& l);

		// cache operations
		std::vector<cached_piece_entry>::iterator find_cached_piece(
			std::vector<cached_piece_entry>& cache, disk_io_job const& j
			, mutex_t::scoped_lock& l);

		// write cache operations
		void flush_oldest_piece(mutex_t::scoped_lock& l);
		void flush_expired_pieces(mutex_t::scoped_lock& l);
		void flush_and_remove(std::vector<cached_piece_entry>::iterator i, mutex_t::scoped_lock& l);
		void flush(std::vector<cached_piece_entry>::iterator i, mutex_t::scoped_lock& l);
		void cache_block(disk_io_job& j, mutex_t::scoped_lock& l);

		// read cache operations
		bool clear_oldest_read_piece(mutex_t::scoped_lock& l);
		int read_into_piece(cached_piece_entry& p, int start_block, mutex_t::scoped_lock& l);
		int cache_read_block(disk_io_job const& j, mutex_t::scoped_lock& l);
		void free_piece(cached_piece_entry& p, mutex_t::scoped_lock& l);
		bool make_room(int num_blocks, mutex_t::scoped_lock& l);
		int try_read_from_cache(disk_io_job const& j, mutex_t::scoped_lock& l);

		mutable mutex_t m_mutex;
		boost::condition m_signal;
		bool m_abort;
		std::deque<disk_io_job> m_jobs;
		size_type m_queue_buffer_size;

		// write cache
		std::vector<cached_piece_entry> m_pieces;
		
		// read cache
		std::vector<cached_piece_entry> m_read_pieces;

		// total number of blocks in use by both the read
		// and the write cache. This is not supposed to
		// exceed m_cache_size
		cache_status m_cache_stats;
		int m_num_cached_blocks;

		// in (16kB) blocks
		int m_cache_size;

		// expiration time of cache entries in seconds
		int m_cache_expiry;

		// if set to true, each piece flush will allocate
		// one piece worth of temporary memory on the heap
		// and copy the block data into it, and then perform
		// a single write operation from that buffer.
		// if memory is constrained, that temporary buffer
		// might is avoided by setting this to false.
		// in case the allocation fails, the piece flush
		// falls back to writing each block separately.
		bool m_coalesce_writes;
		bool m_coalesce_reads;
		bool m_use_read_cache;

		// memory pool for read and write operations
		// and disk cache
		boost::pool<> m_pool;

		// number of bytes per block. The BitTorrent
		// protocol defines the block size to 16 KiB.
		int m_block_size;
#ifndef NDEBUG
		disk_io_job m_current;
#endif

#ifdef TORRENT_DISK_STATS
		std::ofstream m_log;
#endif
#ifdef TORRENT_STATS
		int m_allocations;
#endif

		size_type m_writes;
		size_type m_blocks_written;

		asio::io_service& m_ios;

		// thread for performing blocking disk io operations
		boost::thread m_disk_io_thread;
	};

}

#endif