premiere-libtorrent/include/libtorrent/peer_connection.hpp

/*

Copyright (c) 2003-2014, 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_PEER_CONNECTION_HPP_INCLUDED
#define TORRENT_PEER_CONNECTION_HPP_INCLUDED

#include <ctime>
#include <algorithm>
#include <vector>
#include <string>

#if defined TORRENT_VERBOSE_LOGGING || defined TORRENT_ERROR_LOGGING
#include "libtorrent/debug.hpp"
#endif

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

#include <boost/smart_ptr.hpp>
#include <boost/weak_ptr.hpp>
#include <boost/intrusive_ptr.hpp>
#include <boost/noncopyable.hpp>
#include <boost/array.hpp>
#include <boost/optional.hpp>
#include <boost/cstdint.hpp>
#include <boost/pool/pool.hpp>
#include <boost/aligned_storage.hpp>

#ifdef _MSC_VER
#pragma warning(pop)
#endif

#include "libtorrent/buffer.hpp"
#include "libtorrent/peer_id.hpp"
#include "libtorrent/stat.hpp"
#include "libtorrent/alert.hpp"
#include "libtorrent/peer_request.hpp"
#include "libtorrent/piece_block_progress.hpp"
#include "libtorrent/config.hpp"
#include "libtorrent/bandwidth_limit.hpp"
#include "libtorrent/socket_type_fwd.hpp"
#include "libtorrent/assert.hpp"
#include "libtorrent/chained_buffer.hpp"
#include "libtorrent/disk_buffer_holder.hpp"
#include "libtorrent/bitfield.hpp"
#include "libtorrent/bandwidth_socket.hpp"
#include "libtorrent/socket_type_fwd.hpp"
#include "libtorrent/error_code.hpp"
#include "libtorrent/sliding_average.hpp"
#include "libtorrent/peer_class.hpp"
#include "libtorrent/peer_class_set.hpp"
#include "libtorrent/aux_/session_settings.hpp"
#include "libtorrent/disk_observer.hpp"
#include "libtorrent/connection_interface.hpp"
#include "libtorrent/peer_connection_interface.hpp"
#include "libtorrent/piece_picker.hpp" // for piece_block
#include "libtorrent/socket.hpp" // for tcp::endpoint
#include "libtorrent/io_service_fwd.hpp"

namespace libtorrent
{
	class torrent;
	struct peer_info;
	struct disk_io_job;
	struct disk_interface;
	struct torrent_peer;

#ifndef TORRENT_DISABLE_EXTENSIONS
	struct peer_plugin;
#endif

	namespace aux
	{
		struct session_interface;
	}

	struct pending_block
	{
		pending_block(piece_block const& b)
			: block(b), send_buffer_offset(-1), not_wanted(false)
			, timed_out(false), busy(false), receiving(false)
		{}

		piece_block block;

		// the time we sent this request. This is used to track the round-trip
		// time of receiving the piece. This is not initialized until this
		// pending_block is inserted in the download queue (i.e. not the
		// requst_queue)
		ptime request_time;

		// the number of bytes into the send buffer this request is. Every time
		// some portion of the send buffer is transmitted, this offset is
		// decremented by the number of bytes sent. once this drops below 0, the
		// request_time field is set to the current time.
		// if the request has not been written to the send buffer, this field
		// remoains -1.
		int send_buffer_offset;

		// if any of these are set to true, this block
		// is not allocated
		// in the piece picker anymore, and open for
		// other peers to pick. This may be caused by
		// it either timing out or being received
		// unexpectedly from the peer
		bool not_wanted:1;
		bool timed_out:1;
		
		// the busy flag is set if the block was
		// requested from another peer when this
		// request was queued. We only allow a single
		// busy request at a time in each peer's queue
		bool busy:1;

		// this is true when we first start to receive the resopnse for this
		// request. The first time we read the message header for the piece
		// response is when we calculate the RTT for this request.
		bool receiving:1;

		bool operator==(pending_block const& b)
		{
			return b.block == block
				&& b.not_wanted == not_wanted
				&& b.timed_out == timed_out;
		}
	};

	struct has_block
	{
		has_block(piece_block const& b): block(b) {}
		piece_block const& block;
		bool operator()(pending_block const& pb) const
		{ return pb.block == block; }
	};

	// argument pack passed to peer_connection constructor
	struct peer_connection_args
	{
		aux::session_interface* ses;
		aux::session_settings const* sett;
		counters* stats_counters;
		buffer_allocator_interface* allocator;
		disk_interface* disk_thread;
		io_service* ios;
		boost::weak_ptr<torrent> tor;
		boost::shared_ptr<socket_type> s;
		tcp::endpoint const* endp;
		torrent_peer* peerinfo;
	};

	// internal
	inline void nop(char*, void*, block_cache_reference) {}

	struct peer_connection_hot_members
	{
		// if tor is set, this is an outgoing connection
		peer_connection_hot_members(
			boost::weak_ptr<torrent> t
			, aux::session_interface& ses
			, aux::session_settings const& sett)
			: m_torrent(t)
			, m_ses(ses)
			, m_settings(sett)
			, m_disconnecting(false)
			, m_connecting(!t.expired())
			, m_endgame_mode(false)
			, m_snubbed(false)
			, m_interesting(false)
			, m_choked(true)
			, m_corked(false)
			, m_ignore_stats(false)
			, m_recv_pos(0)
			, m_packet_size(0)
		{}

	protected:

		// the pieces the other end have
		bitfield m_have_piece;

		// this is the torrent this connection is
		// associated with. If the connection is an
		// incoming connection, this is set to zero
		// until the info_hash is received. Then it's
		// set to the torrent it belongs to.

		// TODO: make this a raw pointer (to save size in
		// the first cache line) and make the constructor
		// take a raw pointer. torrent objects should always
		// outlive their peers
		boost::weak_ptr<torrent> m_torrent;
	
	public:

		// a back reference to the session
		// the peer belongs to.
		aux::session_interface& m_ses;

		// settings that apply to this peer
		aux::session_settings const& m_settings;
		
	protected:

		// this is true if this connection has been added
		// to the list of connections that will be closed.
		bool m_disconnecting:1;

		// this is true until this socket has become
		// writable for the first time (i.e. the
		// connection completed). While connecting
		// the timeout will not be triggered. This is
		// because windows XP SP2 may delay connection
		// attempts, which means that the connection
		// may not even have been attempted when the
		// time out is reached.
		bool m_connecting:1;

		// this is set to true if the last time we tried to
		// pick a piece to download, we could only find
		// blocks that were already requested from other
		// peers. In this case, we should not try to pick
		// another piece until the last one we requested is done
		bool m_endgame_mode:1;

		// set to true when a piece request times out. The
		// result is that the desired pending queue size
		// is set to 1
		bool m_snubbed:1;

		// the peer has pieces we are interested in
		bool m_interesting:1;

		// we have choked the upload to the peer
		bool m_choked:1;

		// when this is set, the peer_connection socket is
		// corked, similar to the linux TCP feature TCP_CORK.
		// we won't send anything to the actual socket, just
		// buffer messages up in the application layer send
		// buffer, and send it once we're uncorked.
		bool m_corked:1;

		// when this is set, the transfer stats for this connection
		// is not included in the torrent or session stats
		bool m_ignore_stats:1;

		// the byte offset in m_recv_buffer that we have
		// are passing on to the upper layer. This is
		// always <= m_recv_end
		int m_recv_pos:24;

		// the size (in bytes) of the bittorrent message
		// we're currently receiving
		int m_packet_size;
	};

	class TORRENT_EXTRA_EXPORT peer_connection
		: public peer_connection_hot_members
		, public bandwidth_socket
		, public peer_class_set
		, public disk_observer
		, public connection_interface 
		, public peer_connection_interface 
		, public boost::enable_shared_from_this<peer_connection>
	{
	friend class invariant_access;
	friend struct network_thread_pool;
	friend class torrent;
	public:

		enum connection_type
		{
			bittorrent_connection = 0,
			url_seed_connection = 1,
			http_seed_connection = 2
		};

		virtual int type() const = 0;

		enum channels
		{
			upload_channel,
			download_channel,
			num_channels
		};

		peer_connection(peer_connection_args const& pack);

		// this function is called after it has been constructed and properly
		// reference counted. It is safe to call self() in this function
		// and schedule events with references to itself (that is not safe to
		// do in the constructor).
		virtual void start();

		virtual ~peer_connection();

		void set_peer_info(torrent_peer* pi)
		{
			TORRENT_ASSERT(m_peer_info == 0 || pi == 0 );
			TORRENT_ASSERT(pi != NULL || m_disconnect_started);
			m_peer_info = pi;
		}

		torrent_peer* peer_info_struct() const
		{ return m_peer_info; }
	
		// this is called when the peer object is created, in case
		// it was let in by the connections limit slack. This means
		// the peer needs to, as soon as the handshake is done, either
		// disconnect itself or another peer.
		void peer_exceeds_limit()
		{ m_exceeded_limit = true; }

		// this is called if this peer causes another peer
		// to be disconnected, in which case it has fulfilled
		// its requirement.
		void peer_disconnected_other()
		{ m_exceeded_limit = false; }

		enum peer_speed_t { slow = 1, medium, fast };
		peer_speed_t peer_speed();

		void send_allowed_set();

#ifndef TORRENT_DISABLE_EXTENSIONS
		void add_extension(boost::shared_ptr<peer_plugin>);
		peer_plugin const* find_plugin(char const* type);
#endif

		// this function is called once the torrent associated
		// with this peer connection has retrieved the meta-
		// data. If the torrent was spawned with metadata
		// this is called from the constructor.
		void init();

		// this is called when the metadata is retrieved
		// and the files has been checked
		virtual void on_metadata() {};

		void on_metadata_impl();

		void picker_options(int o)
		{ m_picker_options = o; }

		int prefer_whole_pieces() const
		{
			if (on_parole()) return 1;
			return m_prefer_whole_pieces;
		}

		bool on_parole() const;

		int picker_options() const;

		void prefer_whole_pieces(int num)
		{ m_prefer_whole_pieces = num; }

		bool request_large_blocks() const
		{ return m_request_large_blocks; }

		void request_large_blocks(bool b)
		{ m_request_large_blocks = b; }

		void set_endgame(bool b);
		bool endgame() const { return m_endgame_mode; }

		bool no_download() const { return m_no_download; }
		void no_download(bool b) { m_no_download = b; }

		bool ignore_stats() const { return m_ignore_stats; }
		void ignore_stats(bool b) { m_ignore_stats = b; }

		boost::uint32_t peer_rank() const;

		void fast_reconnect(bool r);
		bool fast_reconnect() const { return m_fast_reconnect; }

		// this is called when we receive a new piece
		// (and it has passed the hash check)
		void received_piece(int index);

		// this adds an announcement in the announcement queue
		// it will let the peer know that we have the given piece
		void announce_piece(int index);
		
		// this will tell the peer to announce the given piece
		// and only allow it to request that piece
		void superseed_piece(int replace_piece, int new_piece);
		bool super_seeded_piece(int index) const
		{
			return m_superseed_piece[0] == index
				|| m_superseed_piece[1] == index;
		}

		// tells if this connection has data it want to send
		// and has enough upload bandwidth quota left to send it.
		bool can_write() const;
		bool can_read();

		bool is_seed() const;
		int num_have_pieces() const { return m_num_pieces; }

		void set_share_mode(bool m);
		bool share_mode() const { return m_share_mode; }

		void set_upload_only(bool u);
		bool upload_only() const { return m_upload_only; }

		void set_holepunch_mode()
		{
			m_holepunch_mode = true;
#ifdef TORRENT_VERBOSE_LOGGING
			peer_log("*** HOLEPUNCH MODE ***");
#endif
		}

		// will send a keep-alive message to the peer
		void keep_alive();

		peer_id const& pid() const { return m_peer_id; }
		void set_pid(const peer_id& peer_id) { m_peer_id = peer_id; }
		bool has_piece(int i) const;

		std::vector<pending_block> const& download_queue() const;
		std::vector<pending_block> const& request_queue() const;
		std::vector<peer_request> const& upload_queue() const;

		void clear_request_queue();

		// estimate of how long it will take until we have
		// received all piece requests that we have sent
		// if extra_bytes is specified, it will include those
		// bytes as if they've been requested
		time_duration download_queue_time(int extra_bytes = 0) const;

		bool is_interesting() const { return m_interesting; }
		bool is_choked() const { return m_choked; }

		bool is_peer_interested() const { return m_peer_interested; }
		bool has_peer_choked() const { return m_peer_choked; }

		void update_interest();

		virtual void get_peer_info(peer_info& p) const;

		// returns the torrent this connection is a part of
		// may be zero if the connection is an incoming connection
		// and it hasn't received enough information to determine
		// which torrent it should be associated with
		boost::weak_ptr<torrent> associated_torrent() const
		{ return m_torrent; }

		stat const& statistics() const { return m_statistics; }
		void add_stat(size_type downloaded, size_type uploaded);
		void sent_bytes(int bytes_payload, int bytes_protocol);
		void received_bytes(int bytes_payload, int bytes_protocol);
		void trancieve_ip_packet(int bytes, bool ipv6);
		void sent_syn(bool ipv6);
		void received_synack(bool ipv6);

		// is called once every second by the main loop
		void second_tick(int tick_interval_ms);

		void timeout_requests();

		boost::shared_ptr<socket_type> get_socket() const { return m_socket; }
		tcp::endpoint const& remote() const { return m_remote; }
		tcp::endpoint local_endpoint() const { return m_local; }

		bitfield const& get_bitfield() const;
		std::vector<int> const& allowed_fast();
		std::vector<int> const& suggested_pieces() const { return m_suggested_pieces; }

		ptime connected_time() const { return m_connect; }
		ptime last_received() const { return m_last_receive; }

		// this will cause this peer_connection to be disconnected.
		virtual void disconnect(error_code const& ec
			, peer_connection_interface::operation_t op, int error = 0);

		// called when a connect attempt fails (not when an
		// established connection fails)
		void connect_failed(error_code const& e);
		bool is_disconnecting() const { return m_disconnecting; }

		// this is called when the connection attempt has succeeded
		// and the peer_connection is supposed to set m_connecting
		// to false, and stop monitor writability
		void on_connection_complete(error_code const& e);

		// returns true if this connection is still waiting to
		// finish the connection attempt
		bool is_connecting() const { return m_connecting; }

		// returns true if the socket of this peer hasn't been
		// attempted to connect yet (i.e. it's queued for
		// connection attempt).
		bool is_queued() const { return m_queued; }
	
		// called when it's time for this peer_conncetion to actually
		// initiate the tcp connection. This may be postponed until
		// the library isn't using up the limitation of half-open
		// tcp connections.	
		// implements connection_interface
		void on_allow_connect(int ticket);
		
		// implements connection_interface. Called by the connection_queue
		void on_connect_timeout();

		// This is called for every peer right after the upload
		// bandwidth has been distributed among them
		// It will reset the used bandwidth to 0.
		void reset_upload_quota();

		// trust management.
		virtual void received_valid_data(int index);
		// returns false if the peer should not be
		// disconnected
		virtual bool received_invalid_data(int index, bool single_peer);

		// a connection is local if it was initiated by us.
		// if it was an incoming connection, it is remote
		bool is_outgoing() const { return m_outgoing; }

		bool received_listen_port() const { return m_received_listen_port; }
		void received_listen_port()
		{ m_received_listen_port = true; }

		bool on_local_network() const;
		bool ignore_unchoke_slots() const;

		bool failed() const { return m_failed; }

		int desired_queue_size() const
		{
			// this peer is in end-game mode we only want
			// one outstanding request
			return (m_endgame_mode || m_snubbed) ? 1 : m_desired_queue_size;
		}

		bool bittyrant_unchoke_compare(
			peer_connection const* p) const;
		// compares this connection against the given connection
		// for which one is more eligible for an unchoke.
		// returns true if this is more eligible
		bool unchoke_compare(peer_connection const* p) const;
		bool upload_rate_compare(peer_connection const* p) const;
		int download_payload_rate() const { return m_statistics.download_payload_rate(); }

		// resets the byte counters that are used to measure
		// the number of bytes transferred within unchoke cycles
		void reset_choke_counters();

		// if this peer connection is useless (neither party is
		// interested in the other), disconnect it
		// returns true if the connection was disconnected
		bool disconnect_if_redundant();

		void increase_est_reciprocation_rate();
		void decrease_est_reciprocation_rate();
		int est_reciprocation_rate() const { return m_est_reciprocation_rate; }

#if defined TORRENT_VERBOSE_LOGGING || defined TORRENT_ERROR_LOGGING
		virtual void peer_log(char const* fmt, ...) const;
		boost::shared_ptr<logger> m_logger;
#endif

#if defined TORRENT_LOGGING || defined TORRENT_ERROR_LOGGING
		ptime m_connect_time;
		ptime m_bitfield_time;
		ptime m_unchoke_time;
#endif

		// the message handlers are called
		// each time a recv() returns some new
		// data, the last time it will be called
		// is when the entire packet has been
		// received, then it will no longer
		// be called. i.e. most handlers need
		// to check how much of the packet they
		// have received before any processing
		void incoming_keepalive();
		void incoming_choke();
		void incoming_unchoke();
		void incoming_interested();
		void incoming_not_interested();
		void incoming_have(int piece_index);
		void incoming_dont_have(int piece_index);
		void incoming_bitfield(bitfield const& bits);
		void incoming_request(peer_request const& r);
		void incoming_piece(peer_request const& p, disk_buffer_holder& data);
		void incoming_piece(peer_request const& p, char const* data);
		void incoming_piece_fragment(int bytes);
		void start_receive_piece(peer_request const& r);
		void incoming_cancel(peer_request const& r);

		bool can_disconnect(error_code const& ec) const;
		void incoming_dht_port(int listen_port);
		
		void incoming_reject_request(peer_request const& r);
		void incoming_have_all();
		void incoming_have_none();
		void incoming_allowed_fast(int index);
		void incoming_suggest(int index);

		void set_has_metadata(bool m) { m_has_metadata = m; }
		bool has_metadata() const { return m_has_metadata; }

		// the following functions appends messages
		// to the send buffer
		bool send_choke();
		bool send_unchoke();
		void send_interested();
		void send_not_interested();
		void send_suggest(int piece);

		void snub_peer();
		// reject any request in the request
		// queue from this piece
		void reject_piece(int index);

		bool can_request_time_critical() const;

		// returns true if the specified block was actually made time-critical.
		// if the block was already time-critical, it returns false.
		bool make_time_critical(piece_block const& block);

		// adds a block to the request queue
		// returns true if successful, false otherwise
		enum flags_t { req_time_critical = 1, req_busy = 2 };
		bool add_request(piece_block const& b, int flags = 0);

		// clears the request queue and sends cancels for all messages
		// in the download queue
		void cancel_all_requests();

		// removes a block from the request queue or download queue
		// sends a cancel message if appropriate
		// refills the request queue, and possibly ignoring pieces requested
		// by peers in the ignore list (to avoid recursion)
		// if force is true, the blocks is also freed from the piece
		// picker, allowing another peer to request it immediately
		void cancel_request(piece_block const& b, bool force = false);
		void send_block_requests();

		void assign_bandwidth(int channel, int amount);

#if TORRENT_USE_INVARIANT_CHECKS
		void check_invariant() const;
#endif

		// is true until we can be sure that the other end
		// speaks our protocol (be it bittorrent or http).
		virtual bool in_handshake() const = 0;

		// returns the block currently being
		// downloaded. And the progress of that
		// block. If the peer isn't downloading
		// a piece for the moment, the boost::optional
		// will be invalid.
		virtual boost::optional<piece_block_progress>
		downloading_piece_progress() const
		{
#ifdef TORRENT_VERBOSE_LOGGING
			peer_log("*** downloading_piece_progress() dispatched to the base class!");
#endif
			return boost::optional<piece_block_progress>();
		}

		// these functions are virtual to let bt_peer_connection hook into them
		// and encrypt the content
		enum message_type_flags { message_type_request = 1 };
		virtual void send_buffer(char const* begin, int size, int flags = 0
			, void (*fun)(char*, int, void*) = 0, void* userdata = 0);
		virtual void setup_send();

		void cork_socket() { TORRENT_ASSERT(!m_corked); m_corked = true; }
		bool is_corked() const { return m_corked; }
		void uncork_socket();

		virtual void append_send_buffer(char* buffer, int size
			, chained_buffer::free_buffer_fun destructor = &nop
			, void* userdata = NULL, block_cache_reference ref
			= block_cache_reference(), bool encrypted = false);

		virtual void append_const_send_buffer(char const* buffer, int size
			, chained_buffer::free_buffer_fun destructor = &nop
			, void* userdata = NULL, block_cache_reference ref
			= block_cache_reference());

#ifndef TORRENT_DISABLE_RESOLVE_COUNTRIES	
		void set_country(char const* c)
		{
			TORRENT_ASSERT(strlen(c) == 2);
			m_country[0] = c[0];
			m_country[1] = c[1];
		}
		bool has_country() const { return m_country[0] != 0; }
#endif

		int outstanding_bytes() const { return m_outstanding_bytes; }

		int send_buffer_size() const
		{ return m_send_buffer.size(); }

		int send_buffer_capacity() const
		{ return m_send_buffer.capacity(); }

		int packet_size() const { return m_packet_size; }

		bool packet_finished() const
		{ return m_packet_size <= m_recv_pos; }

		int receive_pos() const { return m_recv_pos; }

		void max_out_request_queue(int s)
		{ m_max_out_request_queue = s; }
		int max_out_request_queue() const
		{ return m_max_out_request_queue; }

#ifdef TORRENT_DEBUG
		bool piece_failed;
#endif

		time_t last_seen_complete() const { return m_last_seen_complete; }
		void set_last_seen_complete(int ago) { m_last_seen_complete = time(0) - ago; }

		size_type uploaded_in_last_round() const
		{ return m_statistics.total_payload_upload() - m_uploaded_at_last_round; }

		size_type downloaded_in_last_round() const
		{ return m_statistics.total_payload_download() - m_downloaded_at_last_round; }

		size_type uploaded_since_unchoked() const
		{ return m_statistics.total_payload_upload() - m_uploaded_at_last_unchoke; }

		// called when the disk write buffer is drained again, and we can
		// start downloading payload again
		void on_disk();

		void on_allocate_disk_buffer(char* buffer, int buffer_size);

		int num_reading_bytes() const { return m_reading_bytes; }

		enum sync_t { read_async, read_sync };
		void setup_receive(sync_t sync = read_sync);

		boost::shared_ptr<peer_connection> self()
		{
			TORRENT_ASSERT(!m_in_constructor);
			return shared_from_this();
		}

		counters& stats_counters() const { return m_counters; }

	protected:

		size_t try_read(sync_t s, error_code& ec);

		virtual void get_specific_peer_info(peer_info& p) const = 0;

		virtual void write_choke() = 0;
		virtual void write_unchoke() = 0;
		virtual void write_interested() = 0;
		virtual void write_not_interested() = 0;
		virtual void write_request(peer_request const& r) = 0;
		virtual void write_cancel(peer_request const& r) = 0;
		virtual void write_have(int index) = 0;
		virtual void write_dont_have(int index) = 0;
		virtual void write_keepalive() = 0;
		virtual void write_piece(peer_request const& r, disk_buffer_holder& buffer) = 0;
		virtual void write_suggest(int piece) = 0;
		virtual void write_bitfield() = 0;
		
		virtual void write_reject_request(peer_request const& r) = 0;
		virtual void write_allow_fast(int piece) = 0;

		virtual void on_connected() = 0;
		virtual void on_tick() {}
	
		virtual void on_receive(error_code const& error
			, std::size_t bytes_transferred) = 0;
		virtual void on_sent(error_code const& error
			, std::size_t bytes_transferred) = 0;

#ifndef TORRENT_DISABLE_ENCRYPTION
		buffer::interval wr_recv_buffer()
		{
			if (m_recv_buffer.empty())
			{
				TORRENT_ASSERT(m_recv_pos == 0);
				return buffer::interval(0,0);
			}
			TORRENT_ASSERT(!m_disk_recv_buffer);
			TORRENT_ASSERT(m_disk_recv_buffer_size == 0);
			int rcv_pos = (std::min)(m_recv_pos, int(m_recv_buffer.size()));
			return buffer::interval(&m_recv_buffer[0] + m_recv_start
				, &m_recv_buffer[0] + m_recv_start + rcv_pos);
		}

		std::pair<buffer::interval, buffer::interval> wr_recv_buffers(int bytes);
#endif
		
		buffer::const_interval receive_buffer() const
		{
			if (m_recv_buffer.empty())
			{
				TORRENT_ASSERT(m_recv_pos == 0);
				return buffer::interval(0,0);
			}
			int rcv_pos = (std::min)(m_recv_pos, int(m_recv_buffer.size()));
			return buffer::const_interval(&m_recv_buffer[0] + m_recv_start
				, &m_recv_buffer[0] + m_recv_start + rcv_pos);
		}

		bool allocate_disk_receive_buffer(int disk_buffer_size);
		char* release_disk_receive_buffer();
		bool has_disk_receive_buffer() const { return m_disk_recv_buffer; }
		void cut_receive_buffer(int size, int packet_size, int offset = 0);
		void reset_recv_buffer(int packet_size);
		void normalize_receive_buffer();
		void set_soft_packet_size(int size) { m_soft_packet_size = size; }

		// if allow_encrypted is false, and the torrent 'ih' turns out
		// to be an encrypted torrent (AES-256 encrypted) the peer will
		// be disconnected. This is to prevent non-encrypted peers to
		// attach to an encrypted torrent
		void attach_to_torrent(sha1_hash const& ih, bool allow_encrypted);

		bool verify_piece(peer_request const& p) const;

		void update_desired_queue_size();

		// called from the main loop when this connection has any
		// work to do.
		void on_send_data(error_code const& error
			, std::size_t bytes_transferred);
		void on_receive_data(error_code const& error
			, std::size_t bytes_transferred);

		// _nb means null_buffers. i.e. we just know the socket is
		// readable at this point, we don't know how much has been received
		void on_receive_data_nb(error_code const& error
			, std::size_t bytes_transferred);

		void receive_data_impl(error_code const& error
			, std::size_t bytes_transferred, int read_loops);

		virtual int timeout() const;

	private:

		void do_update_interest();
		int preferred_caching() const;
		void fill_send_buffer();
		void on_disk_read_complete(disk_io_job const* j, peer_request r
			, ptime issue_time);
		void on_disk_write_complete(disk_io_job const* j
			, peer_request r, boost::shared_ptr<torrent> t);
		void on_seed_mode_hashed(disk_io_job const* j);

		int wanted_transfer(int channel);
		int request_bandwidth(int channel, int bytes = 0);

		int get_priority(int channel) const;

		boost::shared_ptr<socket_type> m_socket;

		// the queue of blocks we have requested
		// from this peer
		std::vector<pending_block> m_download_queue;

		// the queue of requests we have got
		// from this peer that haven't been issued
		// to the disk thread yet
		std::vector<peer_request> m_requests;

		// this peer's peer info struct. This may
		// be 0, in case the connection is incoming
		// and hasn't been added to a torrent yet.
		torrent_peer* m_peer_info;

		// stats counters
		counters& m_counters;

		// the number of pieces this peer
		// has. Must be the same as
		// std::count(m_have_piece.begin(),
		// m_have_piece.end(), true)
		int m_num_pieces;


	public:
		// upload and download channel state
		// enum from peer_info::bw_state
		char m_channel_state[2];

	protected:

		buffer m_recv_buffer;

		// number of bytes this peer can send and receive
		int m_quota[2];

		// the blocks we have reserved in the piece
		// picker and will request from this peer.
		std::vector<pending_block> m_request_queue;
		
		// the start of the logical receive buffer
		int m_recv_start:24;

		// this is the limit on the number of outstanding requests
		// we have to this peer. This is initialized to the settings
		// in the session_settings structure. But it may be lowered
		// if the peer is known to require a smaller limit (like BitComet).
		// or if the extended handshake sets a limit.
		// web seeds also has a limit on the queue size.
		int m_max_out_request_queue;

		// this is the peer we're actually talking to
		// it may not necessarily be the peer we're
		// connected to, in case we use a proxy
		tcp::endpoint m_remote;

	public:
		chained_buffer m_send_buffer;
	private:

		// the disk thread to use to issue disk jobs to
		disk_interface& m_disk_thread;

	public:
		buffer_allocator_interface& m_allocator;
	private:

		// io service
		io_service& m_ios;

	public:
#ifndef TORRENT_DISABLE_EXTENSIONS
		typedef std::list<boost::shared_ptr<peer_plugin> > extension_list_t;
		extension_list_t m_extensions;
#endif
	private:

		// the average rate of receiving complete piece messages
		sliding_average<20> m_piece_rate;
		sliding_average<20> m_send_rate;

		// the round-trip time of piece requests and the corresponding piece
		// message
		sliding_average<50> m_rtt;

		// keep the io_service running as long as we
		// have peer connections
		io_service::work m_work;

		// the time when we last got a part of a
		// piece packet from this peer
		ptime m_last_piece;

		// the time we sent a request to
		// this peer the last time
		ptime m_last_request;
		// the time we received the last
		// piece request from the peer
		ptime m_last_incoming_request;
		// the time when we unchoked this peer
		ptime m_last_unchoke;

		// if we're unchoked by this peer, this
		// was the time
		ptime m_last_unchoked;

		// the time we last choked this peer. min_time() in
		// case we never unchoked it
		ptime m_last_choke;

		// timeouts
		ptime m_last_receive;
		ptime m_last_sent;

		// the time when the first entry in the
		// request queue was requested, increased
		// for each entry that is popped from the
		// download queue. Used for request timeout
		ptime m_requested;

		// a timestamp when the remote download rate
		// was last updated
		ptime m_remote_dl_update;

		// the time when async_connect was called
		// or when the incoming connection was established
		ptime m_connect;

		// the time when this peer sent us a not_interested message
		// the last time.
		ptime m_became_uninterested;

		// the time when we sent a not_interested message to
		// this peer the last time.
		ptime m_became_uninteresting;

		// the total payload download bytes
		// at the last unchoke round. This is used to
		// measure the number of bytes transferred during
		// an unchoke cycle, to unchoke peers the more bytes
		// they sent us
		size_type m_downloaded_at_last_round;
		size_type m_uploaded_at_last_round;

		// this is the number of bytes we had uploaded the
		// last time this peer was unchoked. This does not
		// reset each unchoke interval/round. This is used to
		// track upload across rounds, for the full duration of
		// the peer being unchoked. Specifically, it's used
		// for the round-robin unchoke algorithm.
		size_type m_uploaded_at_last_unchoke;

		// some messages needs to be read from the socket
		// buffer in multiple stages. This soft packet
		// size limits the read size between message handler
		// dispatch. Ignored when set to 0
		int m_soft_packet_size;

		// the number of bytes that the other
		// end has to send us in order to respond
		// to all outstanding piece requests we
		// have sent to it
		int m_outstanding_bytes;

		template <std::size_t Size>
		struct handler_storage
		{
#ifdef TORRENT_DEBUG
			handler_storage()
			  : used(false)
			{}

			bool used;
#else
			handler_storage() {}
#endif
			boost::aligned_storage<Size> bytes;
		private:
			handler_storage(handler_storage const&);
		};

		handler_storage<TORRENT_READ_HANDLER_MAX_SIZE> m_read_handler_storage;
		handler_storage<TORRENT_WRITE_HANDLER_MAX_SIZE> m_write_handler_storage;

#ifndef TORRENT_DISABLE_GEO_IP
		std::string m_inet_as_name;
#endif

		// if this peer is receiving a piece, this
		// points to a disk buffer that the data is
		// read into. This eliminates a memcopy from
		// the receive buffer into the disk buffer
		disk_buffer_holder m_disk_recv_buffer;

		// we have suggested these pieces to the peer
		// don't suggest it again
		bitfield m_sent_suggested_pieces;

		// the pieces we will send to the peer
		// if requested (regardless of choke state)
		std::vector<int> m_accept_fast;

		// a sent-piece counter for the allowed fast set
		// to avoid exploitation. Each slot is a counter
		// for one of the pieces from the allowed-fast set
		std::vector<boost::uint16_t> m_accept_fast_piece_cnt;

		// the pieces the peer will send us if
		// requested (regardless of choke state)
		std::vector<int> m_allowed_fast;

		// pieces that has been suggested to be
		// downloaded from this peer
		std::vector<int> m_suggested_pieces;

		// the time when this peer last saw a complete copy
		// of this torrent
		time_t m_last_seen_complete;

		// the block we're currently receiving. Or
		// (-1, -1) if we're not receiving one
		piece_block m_receiving_block;

		// the local endpoint for this peer, i.e. our address
		// and our port. If this is set for outgoing connections
		// before the connection completes, it means we want to
		// force the connection to be bound to the specified interface.
		// if it ends up being bound to a different local IP, the connection
		// is closed.
		tcp::endpoint m_local;
		
		// remote peer's id
		peer_id m_peer_id;

		// the bandwidth channels, upload and download
		// keeps track of the current quotas
		bandwidth_channel m_bandwidth_channel[num_channels];

	private:
		// statistics about upload and download speeds
		// and total amount of uploads and downloads for
		// this peer
		// TODO: factor this out into its own class with a virtual interface
		// torrent and session should implement this interface
		stat m_statistics;
	protected:

		// if the timeout is extended for the outstanding
		// requests, this is the number of seconds it was
		// extended.
		int m_timeout_extend;

		// the number of outstanding bytes expected
		// to be received by extensions
		int m_extension_outstanding_bytes;

		// the number of time critical requests
		// queued up in the m_request_queue that
		// soon will be committed to the download
		// queue. This is included in download_queue_time()
		// so that it can be used while adding more
		// requests and take the previous requests
		// into account without submitting it all
		// immediately
		int m_queued_time_critical;

		// the number of valid, received bytes in m_recv_buffer
		int m_recv_end:24;

//#error 1 byte

		// recv_buf.begin (start of actual receive buffer)
		// |
		// |      m_recv_start (logical start of current
		// |      |  receive buffer, as perceived by upper layers)
		// |      |
		// |      |    m_recv_pos (number of bytes consumed
		// |      |    |  by upper layer, from logical receive buffer)
		// |      |    |
		// |      x---------x
		// |      |         |        recv_buf.end (end of actual receive buffer)
		// |      |         |        |
		// v      v         v        v
		// *------==========---------
		//                     ^
		//                     |
		//                     |
		// ------------------->x  m_recv_end (end of received data,
		//                          beyond this point is garbage)
		// m_recv_buffer

		// when not using contiguous receive buffers, there
		// may be a disk_recv_buffer in the mix as well. Whenever
		// m_disk_recv_buffer_size > 0 (and presumably also
		// m_disk_recv_buffer != NULL) the disk buffer is imagined
		// to be appended to the receive buffer right after m_recv_end.

		int m_disk_recv_buffer_size;

		// the number of bytes we are currently reading
		// from disk, that will be added to the send
		// buffer as soon as they complete
		int m_reading_bytes;
		
		// options used for the piece picker. These flags will
		// be augmented with flags controlled by other settings
		// like sequential download etc. These are here to
		// let plugins control flags that should always be set
		int m_picker_options;
		
		// the number of invalid piece-requests
		// we have got from this peer. If the request
		// queue gets empty, and there have been
		// invalid requests, we can assume the
		// peer is waiting for those pieces.
		// we can then clear its download queue
		// by sending choke, unchoke.
		int m_num_invalid_requests;

		// the ticket id from the connection queue.
		// This is used to identify the connection
		// so that it can be removed from the queue
		// once the connection completes
		int m_connection_ticket;

		// if [0] is -1, superseeding is not active. If it is >= 0
		// this is the piece that is available to this peer. Only
		// these two pieces can be downloaded from us by this peer.
		// This will remain the current piece for this peer until
		// another peer sends us a have message for this piece
		int m_superseed_piece[2];

		// pieces downloaded since last second
		// timer timeout; used for determining 
		// approx download rate
		int m_remote_pieces_dled;

		// approximate peer download rate
		int m_remote_dl_rate;

		// the number of bytes send to the disk-io
		// thread that hasn't yet been completely written.
		int m_outstanding_writing_bytes;

		// max transfer rates seen on this peer
		int m_download_rate_peak;
		int m_upload_rate_peak;

		// when using the BitTyrant choker, this is our
		// estimated reciprocation rate. i.e. the rate
		// we need to send to this peer for it to unchoke
		// us
		int m_est_reciprocation_rate;

		// the number of request we should queue up
		// at the remote end.
		boost::uint16_t m_desired_queue_size;

#ifndef TORRENT_DISABLE_RESOLVE_COUNTRIES	
		// in case the session settings is set
		// to resolve countries, this is set to
		// the two character country code this
		// peer resides in.
		char m_country[2];
#endif

		// this is a measurement of how fast the peer
		// it allows some variance without changing
		// back and forth between states. values are enums
		// from peer_speed_t.
		boost::uint8_t m_speed;

		// if set to non-zero, this peer will always prefer
		// to request entire n pieces, rather than blocks.
		// where n is the value of this variable.
		// if it is 0, the download rate limit setting
		// will be used to determine if whole pieces
		// are preferred.
		boost::uint8_t m_prefer_whole_pieces;
		
		// this is the number of times this peer has had
		// a request rejected because of a disk I/O failure.
		// once this reaches a certain threshold, the
		// peer is disconnected in order to avoid infinite
		// loops of consistent failures
		boost::uint8_t m_disk_read_failures;

		// this is used in seed mode whenever we trigger a hash check
		// for a piece, before we read it. It's used to throttle
		// the hash checks to just a few per peer at a time.
		boost::uint8_t m_outstanding_piece_verification:3;
		
		// is true if it was we that connected to the peer
		// and false if we got an incoming connection
		// could be considered: true = local, false = remote
		bool m_outgoing:1;

		// is true if we learn the incoming connections listening
		// during the extended handshake
		bool m_received_listen_port:1;

		// if this is true, the disconnection
		// timestamp is not updated when the connection
		// is closed. This means the time until we can
		// reconnect to this peer is shorter, and likely
		// immediate.
		bool m_fast_reconnect:1;
		
		// this is set to true if the connection timed
		// out or closed the connection. In that
		// case we will not try to reconnect to
		// this peer
		bool m_failed:1;

		// this is set to true if the connection attempt
		// succeeded. i.e. the TCP 3-way handshake
		bool m_connected:1;

		// This is true until connect is called on the
		// peer_connection's socket. It is false on incoming
		// connections.
		bool m_queued:1;

		// if this is true, the blocks picked by the piece
		// picker will be merged before passed to the
		// request function. i.e. subsequent blocks are
		// merged into larger blocks. This is used by
		// the http-downloader, to request whole pieces
		// at a time.
		bool m_request_large_blocks:1;

		// set to true if this peer is in share mode		
		bool m_share_mode:1;

		// set to true when this peer is only uploading
		bool m_upload_only:1;

		// this is set to true once the bitfield is received
		bool m_bitfield_received:1;

		// if this is set to true, the client will not
		// pick any pieces from this peer
		bool m_no_download:1;

		// set to true when we've sent the first round of suggests
		bool m_sent_suggests:1;

		// set to true while we're trying to holepunch
		bool m_holepunch_mode:1;

		// the other side has told us that it won't send anymore
		// data to us for a while
		bool m_peer_choked:1;

		// this is set to true when a have_all
		// message is received. This information
		// is used to fill the bitmask in init()
		bool m_have_all:1;

		// other side says that it's interested in downloading
		// from us.
		bool m_peer_interested:1;

		// set to true when we should recalculate interest
		// for this peer. Since this is a fairly expensive
		// operation, it's delayed until the second_tick is
		// fired, so that multiple events that wants to recalc
		// interest are coalesced into only triggering it once
		// the actual computation is done in do_update_interest().
		bool m_need_interest_update:1;
		
		// set to true if this peer has metadata, and false
		// otherwise.
		bool m_has_metadata:1;

		// this is true while this connection is queued
		// in the connection_queue. We may not destruct
		// the connection while it is, since it's not
		// held by an owning pointer, just a plain one
		bool m_queued_for_connection:1;

		// this is set to true if this peer was accepted exceeding
		// the connection limit. It means it has to disconnect
		// itself, or some other peer, as soon as it's completed
		// the handshake. We need to wait for the handshake in
		// order to know which torrent it belongs to, to know which
		// other peers to compare it to.
		bool m_exceeded_limit:1;

		template <class Handler, std::size_t Size>
		struct allocating_handler
		{
			allocating_handler(
				Handler const& h, handler_storage<Size>& s
			)
			  : handler(h)
			  , storage(s)
			{}

			template <class A0>
			void operator()(A0 const& a0) const
			{
				handler(a0);
			}

			template <class A0, class A1>
			void operator()(A0 const& a0, A1 const& a1) const
			{
				handler(a0, a1);
			}

			template <class A0, class A1, class A2>
			void operator()(A0 const& a0, A1 const& a1, A2 const& a2) const
			{
				handler(a0, a1, a2);
			}

			friend void* asio_handler_allocate(
			    std::size_t size, allocating_handler<Handler, Size>* ctx)
			{
				TORRENT_ASSERT(size <= Size);
#ifdef TORRENT_DEBUG
				TORRENT_ASSERT(!ctx->storage.used);
				ctx->storage.used = true;
#endif
				return &ctx->storage.bytes;
			}

			friend void asio_handler_deallocate(
				void*, std::size_t, allocating_handler<Handler, Size>* ctx)
			{
#ifdef TORRENT_DEBUG
				ctx->storage.used = false;
#endif
			}

			Handler handler;
			handler_storage<Size>& storage;
		};

		template <class Handler>
		allocating_handler<Handler, TORRENT_READ_HANDLER_MAX_SIZE>
			make_read_handler(Handler const& handler)
		{
			return allocating_handler<Handler, TORRENT_READ_HANDLER_MAX_SIZE>(
				handler, m_read_handler_storage
			);
		}

		template <class Handler>
		allocating_handler<Handler, TORRENT_WRITE_HANDLER_MAX_SIZE>
			make_write_handler(Handler const& handler)
		{
			return allocating_handler<Handler, TORRENT_WRITE_HANDLER_MAX_SIZE>(
				handler, m_write_handler_storage
			);
		}

#if TORRENT_USE_ASSERTS
	public:
		bool m_in_constructor;
		bool m_disconnect_started;
		bool m_initialized;
		int m_in_use;
		int m_received_in_piece;
		bool m_destructed;
		// this is true while there is an outstanding
		// async write job on the socket
		bool m_socket_is_writing;
#endif
	};

	struct cork
	{
		cork(peer_connection& p): m_pc(p), m_need_uncork(false)
		{
			if (m_pc.is_corked()) return;
			m_pc.cork_socket();
			m_need_uncork = true;
		}
		~cork() { if (m_need_uncork) m_pc.uncork_socket(); }
		peer_connection& m_pc;
		bool m_need_uncork;
	};

}

#endif // TORRENT_PEER_CONNECTION_HPP_INCLUDED