piece_picker.hpp

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/*

Copyright (c) 2003, 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
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*/
#ifndef TORRENT_PIECE_PICKER_HPP_INCLUDED
#define TORRENT_PIECE_PICKER_HPP_INCLUDED

#include <algorithm>
#include <vector>
#include <bitset>
#include <utility>

#ifdef _MSC_VER
#pragma warning(push, 1)
#endif

#include <boost/static_assert.hpp>

#ifdef _MSC_VER
#pragma warning(pop)
#endif

#include "libtorrent/peer_id.hpp"
#include "libtorrent/socket.hpp"
#include "libtorrent/session_settings.hpp"
#include "libtorrent/config.hpp"
#include "libtorrent/assert.hpp"

namespace libtorrent
{

	class torrent;
	class peer_connection;

	struct TORRENT_EXPORT piece_block
	{
		piece_block(int p_index, int b_index)
			: piece_index(p_index)
			, block_index(b_index)
		{}
		int piece_index;
		int block_index;

		bool operator<(piece_block const& b) const
		{
			if (piece_index < b.piece_index) return true;
			if (piece_index == b.piece_index) return block_index < b.block_index;
			return false;
		}

		bool operator==(piece_block const& b) const
		{ return piece_index == b.piece_index && block_index == b.block_index; }

		bool operator!=(piece_block const& b) const
		{ return piece_index != b.piece_index || block_index != b.block_index; }

	};

	class TORRENT_EXPORT piece_picker
	{
	public:

		struct block_info
		{
			block_info(): peer(0), num_peers(0), state(state_none) {}
			// the peer this block was requested or
			// downloaded from. This is a pointer to
			// a policy::peer object
			void* peer;
			// the number of peers that has this block in their
			// download or request queues
			unsigned num_peers:14;
			// the state of this block
			enum { state_none, state_requested, state_writing, state_finished };
			unsigned state:2;
		};

		// the peers that are downloading this piece
		// are considered fast peers or slow peers.
		// none is set if the blocks were downloaded
		// in a previous session
		enum piece_state_t
		{ none, slow, medium, fast };

		struct downloading_piece
		{
			downloading_piece(): finished(0), writing(0), requested(0) {}
			piece_state_t state;

			// the index of the piece
			int index;
			// info about each block
			// this is a pointer into the m_block_info
			// vector owned by the piece_picker
			block_info* info;
			// the number of blocks in the finished state
			boost::int16_t finished;
			// the number of blocks in the writing state
			boost::int16_t writing;
			// the number of blocks in the requested state
			boost::int16_t requested;
		};

		piece_picker(int blocks_per_piece
			, int total_num_blocks);

		void get_availability(std::vector<int>& avail) const;

		void set_sequenced_download_threshold(int sequenced_download_threshold);

		// the vector tells which pieces we already have
		// and which we don't have.
		void files_checked(
			std::vector<bool> const& pieces
			, std::vector<downloading_piece> const& unfinished
			, std::vector<int>& verify_pieces);

		// increases the peer count for the given piece
		// (is used when a HAVE or BITFIELD message is received)
		void inc_refcount(int index);

		// decreases the peer count for the given piece
		// (used when a peer disconnects)
		void dec_refcount(int index);
		
		// these will increase and decrease the peer count
		// of all pieces. They are used when seeds join
		// or leave the swarm.
		void inc_refcount_all();
		void dec_refcount_all();

		// This indicates that we just received this piece
		// it means that the refcounter will indicate that
		// we are not interested in this piece anymore
		// (i.e. we don't have to maintain a refcount)
		void we_have(int index);

		// sets the priority of a piece.
		// returns true if the priority was changed from 0 to non-0
		// or vice versa
		bool set_piece_priority(int index, int prio);

		// returns the priority for the piece at 'index'
		int piece_priority(int index) const;

		// returns the current piece priorities for all pieces
		void piece_priorities(std::vector<int>& pieces) const;

		// ========== start deprecation ==============

		// fills the bitmask with 1's for pieces that are filtered
		void filtered_pieces(std::vector<bool>& mask) const;

		// ========== end deprecation ==============

		// pieces should be the vector that represents the pieces a
		// client has. It returns a list of all pieces that this client
		// has and that are interesting to download. It returns them in
		// priority order. It doesn't care about the download flag.
		// The user of this function must lookup if any piece is
		// marked as being downloaded. If the user of this function
		// decides to download a piece, it must mark it as being downloaded
		// itself, by using the mark_as_downloading() member function.
		// THIS IS DONE BY THE peer_connection::send_request() MEMBER FUNCTION!
		// The last argument is the policy::peer pointer for the peer that
		// we'll download from.
		void pick_pieces(std::vector<bool> const& pieces
			, std::vector<piece_block>& interesting_blocks
			, int num_pieces, int prefer_whole_pieces
			, void* peer, piece_state_t speed
			, bool rarest_first, bool on_parole
			, std::vector<int> const& suggested_pieces) const;

		// picks blocks from each of the pieces in the piece_list
		// vector that is also in the piece bitmask. The blocks
		// are added to interesting_blocks, and busy blocks are
		// added to backup_blocks. num blocks is the number of
		// blocks to be picked. Blocks are not picked from pieces
		// that are being downloaded
		int add_blocks(std::vector<int> const& piece_list
			, const std::vector<bool>& pieces
			, std::vector<piece_block>& interesting_blocks
			, int num_blocks, int prefer_whole_pieces
			, void* peer, std::vector<int> const& ignore) const;

		// picks blocks only from downloading pieces
		int add_blocks_downloading(
			std::vector<bool> const& pieces
			, std::vector<piece_block>& interesting_blocks
			, std::vector<piece_block>& backup_blocks
			, int num_blocks, int prefer_whole_pieces
			, void* peer, piece_state_t speed
			, bool on_parole) const;

		// clears the peer pointer in all downloading pieces with this
		// peer pointer
		void clear_peer(void* peer);

		// returns true if any client is currently downloading this
		// piece-block, or if it's queued for downloading by some client
		// or if it already has been successfully downloaded
		bool is_requested(piece_block block) const;
		// returns true if the block has been downloaded
		bool is_downloaded(piece_block block) const;
		// returns true if the block has been downloaded and written to disk