premiere-libtorrent/include/libtorrent/disk_io_job.hpp

/*

Copyright (c) 2010-2016, Arvid Norberg
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      from this software without specific prior written permission.

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*/

#ifndef TORRENT_DISK_IO_JOB_HPP
#define TORRENT_DISK_IO_JOB_HPP

#include "libtorrent/error_code.hpp"
#include "libtorrent/tailqueue.hpp"
#include "libtorrent/peer_request.hpp"
#include "libtorrent/aux_/block_cache_reference.hpp"
#include "libtorrent/sha1_hash.hpp"

#include "libtorrent/aux_/disable_warnings_push.hpp"
#include <boost/variant/variant.hpp>
#include "libtorrent/aux_/disable_warnings_pop.hpp"

#include <string>
#include <vector>
#include <memory>
#include <functional>

namespace libtorrent
{
	struct storage_interface;
	struct cached_piece_entry;
	class torrent_info;
	struct add_torrent_params;

	// disk_io_jobs are allocated in a pool allocator in disk_io_thread
	// they are always allocated from the network thread, posted
	// (as pointers) to the disk I/O thread, and then passed back
	// to the network thread for completion handling and to be freed.
	// each disk_io_job can belong to one tailqueue. The job queue
	// in the disk thread, is one, the jobs waiting on completion
	// on a cache piece (in block_cache) is another, and a job
	// waiting for a storage fence to be lowered is another. Jobs
	// are never in more than one queue at a time. Only passing around
	// pointers and chaining them back and forth into lists saves
	// a lot of heap allocation churn of using general purpose
	// containers.
	struct TORRENT_EXTRA_EXPORT disk_io_job : tailqueue_node<disk_io_job>
	{
		disk_io_job();
		~disk_io_job();
		disk_io_job(disk_io_job const&) = delete;
		disk_io_job& operator=(disk_io_job const&) = delete;

		void call_callback();

		enum action_t
		{
			read
			, write
			, hash
			, move_storage
			, release_files
			, delete_files
			, check_fastresume
			, rename_file
			, stop_torrent
			, flush_piece
			, flush_hashed
			, flush_storage
			, trim_cache
			, file_priority
			, clear_piece
			, resolve_links
			, num_job_ids
		};

		enum flags_t
		{
			sequential_access = 0x1,

			// force making a copy of the cached block, rather
			// than getting a reference to the block already in
			// the cache.
			force_copy = 0x4,

			// this is set by the storage object when a fence is raised
			// for this job. It means that this no other jobs on the same
			// storage will execute in parallel with this one. It's used
			// to lower the fence when the job has completed
			fence = 0x8,

			// don't keep the read block in cache
			volatile_read = 0x10,

			// this job is currently being performed, or it's hanging
			// on a cache piece that may be flushed soon
			in_progress = 0x20
		};

		// for write jobs, returns true if its block
		// is not dirty anymore
		bool completed(cached_piece_entry const* pe, int block_size);

		// unique identifier for the peer when reading
		void* requester = nullptr;

		// for write, this points to the data to write,
		// for read, the data read is returned here
		// for other jobs, it may point to other job-specific types
		// for move_storage and rename_file this is a string allocated
		// with malloc()
		// for get_cache_info this points to a cache_status object which
		// is filled in
		union
		{
			char* disk_block;
			char* string;
			add_torrent_params const* check_resume_data;
			std::vector<std::uint8_t>* priorities;
			int delete_options;
		} buffer;

		// the disk storage this job applies to (if applicable)
		std::shared_ptr<storage_interface> storage;

		// this is called when operation completes

		using read_handler = std::function<void(aux::block_cache_reference ref
			, char* block, int flags, storage_error const& se)>;
		using write_handler = std::function<void(storage_error const&)>;
		using hash_handler = std::function<void(int, int, sha1_hash const&, storage_error const&)>;
		using move_handler = std::function<void(int, std::string const&, storage_error const&)>;
		using release_handler = std::function<void()>;
		using check_handler = std::function<void(int, storage_error const&)>;
		using rename_handler = std::function<void(std::string const&, int, storage_error const&)>;
		using clear_piece_handler = std::function<void(int)>;

		boost::variant<read_handler
			, write_handler
			, hash_handler
			, move_handler
			, release_handler
			, check_handler
			, rename_handler
			, clear_piece_handler> callback;

		// the error code from the file operation
		// on error, this also contains the path of the
		// file the disk operation failed on
		storage_error error;

		union
		{
			// result for hash jobs
			char piece_hash[20];

			// this is used for check_fastresume to pass in a vector of hard-links
			// to create. Each element corresponds to a file in the file_storage.
			// The string is the absolute path of the identical file to create
			// the hard link to.
			std::vector<std::string>* links;

			struct io_args
			{
			// if this is set, the read operation is required to
			// release the block references once it's done sending
			// the buffer. For aligned block requests (by far the
			// most common) the buffers are not actually copied
			// into the send buffer, but simply referenced. When this
			// is set in a response to a read, the buffer needs to
			// be de-referenced by sending a reclaim_block message
			// back to the disk thread
			aux::block_cache_reference ref;

			// for read and write, the offset into the piece
			// the read or write should start
			// for hash jobs, this is the first block the hash
			// job is still holding a reference to. The end of
			// the range of blocks a hash jobs holds references
			// to is always the last block in the piece.
			std::uint32_t offset;

			// number of bytes 'buffer' points to. Used for read & write
			std::uint16_t buffer_size;
			} io;
		} d;

		// arguments used for read and write
		// the piece this job applies to
		std::uint32_t piece:24;

		// the type of job this is
		std::uint32_t action:8;

		enum { operation_failed = -1 };

		// return value of operation
		std::int32_t ret = 0;

		// flags controlling this job
		std::uint8_t flags = 0;

#if TORRENT_USE_ASSERTS
		bool in_use = false;

		// set to true when the job is added to the completion queue.
		// to make sure we don't add it twice
		mutable bool job_posted = false;

		// set to true when the callback has been called once
		// used to make sure we don't call it twice
		mutable bool callback_called = false;

		// this is true when the job is blocked by a storage_fence
		mutable bool blocked = false;
#endif
	};

}

#endif // TORRENT_DISK_IO_JOB_HPP