premiere-libtorrent/src/session.cpp

/*

Copyright (c) 2003, Arvid Norberg, Magnus Jonsson
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.

*/

#include <ctime>
#include <iostream>
#include <fstream>
#include <iomanip>
#include <iterator>
#include <algorithm>
#include <set>
#include <cctype>
#include <algorithm>

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

#include <boost/lexical_cast.hpp>
#include <boost/filesystem/convenience.hpp>
#include <boost/filesystem/exception.hpp>
#include <boost/limits.hpp>
#include <boost/bind.hpp>

#ifdef _MSC_VER
#pragma warning(pop)
#endif

#include "libtorrent/peer_id.hpp"
#include "libtorrent/torrent_info.hpp"
#include "libtorrent/tracker_manager.hpp"
#include "libtorrent/bencode.hpp"
#include "libtorrent/hasher.hpp"
#include "libtorrent/entry.hpp"
#include "libtorrent/session.hpp"
#include "libtorrent/fingerprint.hpp"
#include "libtorrent/entry.hpp"
#include "libtorrent/alert_types.hpp"
#include "libtorrent/invariant_check.hpp"
#include "libtorrent/file.hpp"
#include "libtorrent/allocate_resources.hpp"
#include "libtorrent/peer_connection.hpp"

#if defined(_MSC_VER) && _MSC_VER < 1300
namespace std
{
	using ::srand;
	using ::isprint;
};
#endif

namespace
{
/*
	int saturated_add(int a, int b)
	{
		assert(a>=0);
		assert(b>=0);

		int sum=a+b;
		if(sum<0)
			sum=std::numeric_limits<int>::max();

		assert(sum>=a && sum>=b);
		return sum;
	}
*/
	// adjusts the upload rates of every peer connection
	// to make sure the sum of all send quotas equals
	// the given upload_limit. An upload limit of
	// std::numeric_limits<int>::max() means unlimited upload
	// rate, but the rates of each peer has to be set anyway,
	// since it depends on the download rate from the peer.
/*
	void control_upload_rates(
		int upload_limit,
		libtorrent::detail::session_impl::connection_map connections)
	{
		assert(upload_limit >= 0);

		using namespace libtorrent;
		std::vector<resource_request *> requests;

		for (detail::session_impl::connection_map::iterator c = connections.begin();
			c != connections.end(); ++c)
		{
			boost::shared_ptr<peer_connection> p = c->second;
			requests.push_back(p->upload_bandwidth_quota());
		}

		allocate_resources(upload_limit, requests);

		for (detail::session_impl::connection_map::iterator c = connections.begin();
			c != connections.end(); ++c)
		{
			boost::shared_ptr<peer_connection> p = c->second;
			p->update_send_quota_left();
		}
	}
*/
/*
	void control_number_of_connections(
		int connections_limit,
		libtorrent::detail::session_impl::torrent_map hash_list)
	{
		assert(connections_limit >= 0);

		using namespace libtorrent;
		std::vector<resource_consumer> torrents;

		for (detail::session_impl::torrent_map::iterator c = hash_list.begin();
			c != hash_list.end(); ++c)
		{
			boost::shared_ptr<torrent> t = c->second;

			int estimated_capacity=t->num_peers()+1;
			int limit =t->get_policy().get_max_connections();
			if(limit==-1)
				limit=std::numeric_limits<int>::max();

			torrents.push_back(resource_consumer(t,limit,estimated_capacity));
		}

		allocate_resources(connections_limit, torrents);

		for (std::vector<resource_consumer>::iterator r=torrents.begin();
			r!=torrents.end(); ++r)
		{
			// TODO: inform torrent of how many connections it's allowed.
//			boost::any_cast<boost::shared_ptr<torrent> >
//				(r->who())->set_send_quota(r->allowed_use());
		}
	}
*/
}

namespace libtorrent { namespace detail
{

	// This is the checker thread
	// it is looping in an infinite loop
	// until the session is aborted. It will
	// normally just block in a wait() call,
	// waiting for a signal from session that
	// there's a new torrent to check.

	void checker_impl::operator()()
	{
		eh_initializer();
		for (;;)
		{
			piece_checker_data* t = 0;
			{
				boost::mutex::scoped_lock l(m_mutex);

				// if the job queue is empty and
				// we shouldn't abort
				// wait for a signal
				if (m_torrents.empty() && !m_abort)
					m_cond.wait(l);

				if (m_abort) return;

				assert(!m_torrents.empty());
				
				t = &m_torrents.front();
				if (t->abort)
				{
					m_torrents.pop_front();
					continue;
				}
			}

			try
			{
				assert(t != 0);
				t->torrent_ptr->check_files(*t, m_mutex);
				// lock the session to add the new torrent

				boost::mutex::scoped_lock l(m_mutex);
				if (!t->abort)
				{
					boost::mutex::scoped_lock l(m_ses.m_mutex);

					m_ses.m_torrents.insert(
						std::make_pair(t->info_hash, t->torrent_ptr)).first;

					peer_id id;
					std::fill(id.begin(), id.end(), 0);
					for (std::vector<address>::const_iterator i = t->peers.begin();
						i != t->peers.end();
						++i)
					{
						t->torrent_ptr->get_policy().peer_from_tracker(*i, id);
					}
				}
			}
			catch(const std::exception& e)
			{
				// This will happen if the storage fails to initialize
				boost::mutex::scoped_lock l(m_ses.m_mutex);
				if (m_ses.m_alerts.should_post(alert::fatal))
				{
					m_ses.m_alerts.post_alert(
						file_error_alert(
							t->torrent_ptr->get_handle()
							, e.what()));
				}
			}
			catch(...)
			{
#ifndef NDEBUG
				std::cerr << "error while checking files\n";
#endif
				assert(false);
			}

			// remove ourself from the 'checking'-list
			// (we're no longer in the checking state)
			boost::mutex::scoped_lock l(m_mutex);
			m_torrents.pop_front();
		}
	}

	detail::piece_checker_data* checker_impl::find_torrent(const sha1_hash& info_hash)
	{
		for (std::deque<piece_checker_data>::iterator i
			= m_torrents.begin();
			i != m_torrents.end();
			++i)
		{
			if (i->info_hash == info_hash) return &(*i);
		}
		return 0;
	}

	session_impl::session_impl(
		std::pair<int, int> listen_port_range
		, const fingerprint& cl_fprint
		, const char* listen_interface = 0)
		: m_tracker_manager(m_settings)
		, m_listen_port_range(listen_port_range)
		, m_listen_interface(listen_interface, listen_port_range.first)
		, m_abort(false)
		, m_upload_rate(-1)
		, m_incoming_connection(false)
	{
		assert(listen_port_range.first > 0);
		assert(listen_port_range.first < listen_port_range.second);
		assert(m_listen_interface.port > 0);

		// ---- generate a peer id ----

		std::srand((unsigned int)std::time(0));

		m_key = rand() + (rand() << 15) + (rand() << 30);
		std::string print = cl_fprint.to_string();
		assert(print.length() == 8);

		// the client's fingerprint
		std::copy(
			print.begin()
			, print.begin() + print.length()
			, m_peer_id.begin());

		// the random number
		for (unsigned char* i = m_peer_id.begin() + print.length();
			i != m_peer_id.end();
			++i)
		{
			*i = rand();
		}
	}

	void session_impl::purge_connections()
	{
		while (!m_disconnect_peer.empty())
		{
			m_connections.erase(m_disconnect_peer.back());
			m_disconnect_peer.pop_back();
			assert(m_selector.count_read_monitors() == (int)m_connections.size() + (bool)m_listen_socket);
		}
	}

	void session_impl::open_listen_port()
	{
		try
		{
			// create listener socket
			m_listen_socket = boost::shared_ptr<socket>(new socket(socket::tcp, false));

			for(;;)
			{
				try
				{
					m_listen_socket->listen(m_listen_interface, 10);
					break;
				}
				catch (network_error& e)
				{
					if (e.error_code() == socket::address_not_available)
					{
						std::string msg = "cannot listen on the given interface '" + m_listen_interface.as_string() + "'";
						m_alerts.post_alert(listen_failed_alert(msg));
#ifndef NDEBUG
						(*m_logger) << msg << "\n";
#endif
						m_listen_socket.reset();
						break;
					}
					m_listen_interface.port++;
					if (m_listen_interface.port > m_listen_port_range.second)
					{
						std::stringstream msg;
						msg << "none of the ports in the range ["
							<< m_listen_port_range.first
							<< ", " << m_listen_port_range.second
							<< "] could be opened for listening";
						m_alerts.post_alert(listen_failed_alert(msg.str()));
#ifndef NDEBUG
						(*m_logger) << msg.str() << "\n";
#endif
						m_listen_socket.reset();
						break;
					}
				}
			}
		}
		catch (network_error& e)
		{
			m_alerts.post_alert(listen_failed_alert(e.what()));
		}

#ifndef NDEBUG
		if (m_listen_socket)
		{
			(*m_logger) << "listening on port: " << m_listen_interface.port << "\n";
		}
#endif
		if (m_listen_socket)
		{
			m_selector.monitor_readability(m_listen_socket);
			m_selector.monitor_errors(m_listen_socket);
		}
	}


	void session_impl::operator()()
	{
		eh_initializer();
#ifndef NDEBUG
		m_logger = create_log("main session");

		try
		{
#endif

		open_listen_port();

		std::vector<boost::shared_ptr<socket> > readable_clients;
		std::vector<boost::shared_ptr<socket> > writable_clients;
		std::vector<boost::shared_ptr<socket> > error_clients;
		boost::posix_time::ptime timer = boost::posix_time::second_clock::local_time();

#ifndef NDEBUG
		int loops_per_second = 0;
#endif
		for(;;)
		{

#ifndef NDEBUG
			check_invariant("loops_per_second++");
			loops_per_second++;
#endif


			// if nothing happens within 500000 microseconds (0.5 seconds)
			// do the loop anyway to check if anything else has changed
			m_selector.wait(500000, readable_clients, writable_clients, error_clients);

#ifndef NDEBUG
			for (std::vector<boost::shared_ptr<libtorrent::socket> >::iterator i =
				writable_clients.begin();
				i != writable_clients.end();
				++i)
			{
				assert((*i)->is_writable());
			}
#endif
			boost::mutex::scoped_lock l(m_mutex);

			assert(m_selector.count_read_monitors() == (int)m_connections.size() + (bool)m_listen_socket);

			if (m_abort)
			{
				m_tracker_manager.abort_all_requests();
				for (std::map<sha1_hash, boost::shared_ptr<torrent> >::iterator i =
						m_torrents.begin();
					i != m_torrents.end();
					++i)
				{
					i->second->abort();
					tracker_request req = i->second->generate_tracker_request();
					req.listen_port = m_listen_interface.port;
					req.key = m_key;
					m_tracker_manager.queue_request(req);
				}
				m_connections.clear();
				m_torrents.clear();
				break;
			}

#ifndef NDEBUG
			check_invariant("before SEND SOCKETS");
#endif

			// ************************
			// SEND SOCKETS
			// ************************

			// let the writable connections send data
			for (std::vector<boost::shared_ptr<socket> >::iterator i
				= writable_clients.begin();
				i != writable_clients.end();
				++i)
			{
				assert((*i)->is_writable());
				connection_map::iterator p = m_connections.find(*i);
				// the connection may have been disconnected in the receive phase
				if (p == m_connections.end())
				{
					m_selector.remove(*i);
				}
				else
				{
					try
					{
						assert(m_selector.is_writability_monitored(p->first));
						assert(p->second->has_data());
						assert(p->second->get_socket()->is_writable());
						p->second->send_data();
					}
					catch (file_error& e)
					{
						torrent* t = p->second->associated_torrent();
						assert(t != 0);

						if (m_alerts.should_post(alert::fatal))
						{
							m_alerts.post_alert(
								file_error_alert(
								t->get_handle()
								, e.what()));
						}

						// pause the torrent
						t->pause();
						assert(m_selector.count_read_monitors() == (int)m_connections.size() + (bool)m_listen_socket);
					}
					catch (std::exception& e)
					{
						// the connection wants to disconnect for some reason,
						// remove it from the connection-list
						if (m_alerts.should_post(alert::debug))
						{
							m_alerts.post_alert(
								peer_error_alert(p->first->sender(), e.what()));
						}

						p->second->set_failed();
						m_selector.remove(*i);
						m_connections.erase(p);
						assert(m_selector.count_read_monitors() == (int)m_connections.size() + (bool)m_listen_socket);
					}
				}
			}
			purge_connections();

#ifndef NDEBUG
			check_invariant("after SEND SOCKETS");
#endif
			// ************************
			// RECEIVE SOCKETS
			// ************************

			// let the readable clients receive data
			for (std::vector<boost::shared_ptr<socket> >::iterator i = readable_clients.begin();
				i != readable_clients.end();
				++i)
			{
				// special case for m_listen_socket socket
				if (*i == m_listen_socket)
				{
					assert(m_listen_socket);
					boost::shared_ptr<libtorrent::socket> s = (*i)->accept();
					if (s)
					{
						s->set_blocking(false);
						// we got a connection request!
						m_incoming_connection = true;
#ifndef NDEBUG
						(*m_logger) << s->sender().as_string() << " <== INCOMING CONNECTION\n";
#endif
						// TODO: filter ip:s

						boost::shared_ptr<peer_connection> c(
							new peer_connection(*this, m_selector, s));

/*						if (m_upload_rate != -1)
						{
							c->upload_bandwidth_quota()->given = 0;
							c->update_send_quota_left();
						}
*/
						m_connections.insert(std::make_pair(s, c));
						m_selector.monitor_readability(s);
						m_selector.monitor_errors(s);
					}
					continue;
				}
				connection_map::iterator p = m_connections.find(*i);
				if(p == m_connections.end())
				{
					m_selector.remove(*i);
				}
				else
				{
					try
					{
						p->second->receive_data();
					}
					catch (file_error& e)
					{
						torrent* t = p->second->associated_torrent();
						assert(t != 0);

						if (m_alerts.should_post(alert::fatal))
						{
							m_alerts.post_alert(
								file_error_alert(
								t->get_handle()
								, e.what()));
						}

						assert(m_selector.count_read_monitors() == (int)m_connections.size() + (bool)m_listen_socket);
						t->pause();
					}
					catch (std::exception& e)
					{
						if (m_alerts.should_post(alert::debug))
						{
							m_alerts.post_alert(
								peer_error_alert(p->first->sender(), e.what()));
						}
						// the connection wants to disconnect for some reason, remove it
						// from the connection-list
						p->second->set_failed();
						m_selector.remove(*i);
						m_connections.erase(p);
						assert(m_selector.count_read_monitors() == (int)m_connections.size() + (bool)m_listen_socket);
					}
				}
			}
			purge_connections();
#ifndef NDEBUG
			check_invariant("after RECEIVE SOCKETS");
#endif

			// ************************
			// ERROR SOCKETS
			// ************************


			// disconnect the one we couldn't connect to
			for (std::vector<boost::shared_ptr<socket> >::iterator i = error_clients.begin();
				i != error_clients.end();
				++i)
			{
				connection_map::iterator p = m_connections.find(*i);
				if (m_alerts.should_post(alert::debug))
				{
					m_alerts.post_alert(
						peer_error_alert(
							p->first->sender()
							, "socket received an exception"));
				}

				m_selector.remove(*i);
				// the connection may have been disconnected in the receive or send phase
				if (p != m_connections.end())
				{
					p->second->set_failed();
					m_connections.erase(p);
					assert(m_selector.count_read_monitors() == (int)m_connections.size() + (bool)m_listen_socket);
				}
			}

#ifndef NDEBUG
			check_invariant("after ERROR SOCKETS");
#endif

			boost::posix_time::time_duration d = boost::posix_time::second_clock::local_time() - timer;
			if (d.seconds() < 1) continue;
			timer = boost::posix_time::second_clock::local_time();

			// ************************
			// THE SECTION BELOW IS EXECUTED ONCE EVERY SECOND
			// ************************

#ifndef NDEBUG
			// std::cout << "\n\nloops: " << loops_per_second << "\n";
			loops_per_second = 0;
#endif

			// do the second_tick() on each connection
			// this will update their statistics (download and upload speeds)
			// also purge sockets that have timed out
			// and keep sockets open by keeping them alive.
			for (connection_map::iterator i = m_connections.begin();
				i != m_connections.end();)
			{
				connection_map::iterator j = i;
				++i;
				// if this socket has timed out
				// close it.
				if (j->second->has_timed_out())
				{
					if (m_alerts.should_post(alert::debug))
					{
						m_alerts.post_alert(
							peer_error_alert(j->first->sender(), "connection timed out"));
					}
					j->second->set_failed();
					m_selector.remove(j->first);
					m_connections.erase(j);
					assert(m_selector.count_read_monitors() == (int)m_connections.size() + (bool)m_listen_socket);
					continue;
				}

				j->second->keep_alive();
			}

			// check each torrent for abortion or
			// tracker updates
			for (std::map<sha1_hash, boost::shared_ptr<torrent> >::iterator i
				= m_torrents.begin(); i != m_torrents.end();)
			{
				if (i->second->is_aborted())
				{
					tracker_request req = i->second->generate_tracker_request();
					req.listen_port = m_listen_interface.port;
					req.key = m_key;
					m_tracker_manager.queue_request(req);
					i->second->disconnect_all();
					purge_connections();
#ifndef NDEBUG
					sha1_hash i_hash = i->second->torrent_file().info_hash();
#endif
					m_torrents.erase(i++);
					assert(m_torrents.find(i_hash) == m_torrents.end());
					continue;
				}
				else if (i->second->should_request())
				{
					tracker_request req = i->second->generate_tracker_request();
					req.listen_port = m_listen_interface.port;
					req.key = m_key;
					m_tracker_manager.queue_request(
						req
						, boost::get_pointer(i->second));
				}

				// tick() will set the used upload quota
				i->second->second_tick();
				++i;
			}
			purge_connections();

			// distribute the maximum upload rate among the torrents

			allocate_resources(m_upload_rate == -1
				? std::numeric_limits<int>::max()
				: m_upload_rate
				, m_torrents
				, &torrent::m_upload_bandwidth_quota);

			for (std::map<sha1_hash, boost::shared_ptr<torrent> >::iterator i
				= m_torrents.begin(); i != m_torrents.end(); ++i)
			{
				i->second->distribute_resources();
			}

			m_tracker_manager.tick();
		}

		while (!m_tracker_manager.send_finished())
		{
			m_tracker_manager.tick();
			boost::xtime t;
			boost::xtime_get(&t, boost::TIME_UTC);
			t.nsec += 100000000;
			boost::thread::sleep(t);
		}

#ifndef NDEBUG
		}
		catch (std::bad_cast& e)
		{
			std::cerr << e.what() << "\n";
			assert(false);
		}
		catch (std::exception& e)
		{
			std::cerr << e.what() << "\n";
			assert(false);
		}
		catch (...)
		{
			std::cerr << "error!\n";
			assert(false);
		}
#endif
	}


	// the return value from this function is valid only as long as the
	// session is locked!
	torrent* session_impl::find_torrent(const sha1_hash& info_hash)
	{
		std::map<sha1_hash, boost::shared_ptr<torrent> >::iterator i
			= m_torrents.find(info_hash);
#ifndef NDEBUG
		for (std::map<sha1_hash, boost::shared_ptr<torrent> >::iterator j
			= m_torrents.begin();
			j != m_torrents.end();
			++j)
		{
			torrent* p = boost::get_pointer(j->second);
		}
#endif
		if (i != m_torrents.end()) return boost::get_pointer(i->second);
		return 0;
	}

#ifndef NDEBUG
	boost::shared_ptr<logger> session_impl::create_log(std::string name)
	{
		name = "libtorrent_log_" + name + ".log";
		// current options are file_logger and cout_logger
#if defined(TORRENT_VERBOSE_LOGGING)
		return boost::shared_ptr<logger>(new file_logger(name.c_str()));
#else
		return boost::shared_ptr<logger>(new null_logger());
#endif
	}
#endif

#ifndef NDEBUG
	void session_impl::check_invariant(const char *place)
	{
		assert(place);

		for (connection_map::iterator i = m_connections.begin();
			i != m_connections.end();
			++i)
		{
			if (i->second->has_data() != m_selector.is_writability_monitored(i->first))
			{
				std::ofstream error_log("error.log", std::ios_base::app);
				boost::shared_ptr<peer_connection> p = i->second;
				error_log << "session_imple::check_invariant()\n"
					"peer_connection::has_data() != is_writability_monitored()\n";
				error_log << "peer_connection::has_data() " << p->has_data() << "\n";
				error_log << "peer_connection::send_quota_left " << p->send_quota_left() << "\n";
				error_log << "peer_connection::upload_bandwidth_quota()->given " << p->upload_bandwidth_quota()->given << "\n";
				error_log << "peer_connection::get_peer_id " << p->get_peer_id() << "\n";
				error_log << "place: " << place << "\n";
				error_log.flush();
				assert(false);
			}
			if (i->second->associated_torrent())
			{
				assert(i->second->associated_torrent()
					->get_policy().has_connection(boost::get_pointer(i->second)));
			}
		}
	}
#endif

}}

namespace libtorrent
{

	session::session(
		std::pair<int, int> listen_port_range
		, const fingerprint& id
		, const char* listen_interface)
		: m_impl(listen_port_range, id, listen_interface)
		, m_checker_impl(m_impl)
		, m_thread(boost::ref(m_impl))
		, m_checker_thread(boost::ref(m_checker_impl))
	{
		assert(listen_port_range.first > 0);
		assert(listen_port_range.first < listen_port_range.second);
#ifndef NDEBUG
		// this test was added after it came to my attention
		// that devstudios managed c++ failed to generate
		// correct code for boost.function
		boost::function0<void> test = boost::ref(m_impl);
		assert(!test.empty());
#endif
	}

	session::session(std::pair<int, int> listen_port_range)
		: m_impl(listen_port_range, fingerprint("LT",0,0,1,0))
		, m_checker_impl(m_impl)
		, m_thread(boost::ref(m_impl))
		, m_checker_thread(boost::ref(m_checker_impl))
	{
		assert(listen_port_range.first > 0);
		assert(listen_port_range.first < listen_port_range.second);
#ifndef NDEBUG
		boost::function0<void> test = boost::ref(m_impl);
		assert(!test.empty());
#endif
	}

	// TODO: add a check to see if filenames are accepted on the
	// current platform.
	// if the torrent already exists, this will throw duplicate_torrent
	torrent_handle session::add_torrent(
		const torrent_info& ti
		, const boost::filesystem::path& save_path
		, const entry& resume_data)
	{

		{
			// lock the session
			boost::mutex::scoped_lock l(m_impl.m_mutex);

			// is the torrent already active?
			if (m_impl.find_torrent(ti.info_hash()))
				throw duplicate_torrent();
		}

		{
			// lock the checker_thread
			boost::mutex::scoped_lock l(m_checker_impl.m_mutex);

			// is the torrent currently being checked?
			if (m_checker_impl.find_torrent(ti.info_hash()))
				throw duplicate_torrent();
		}

		// create the torrent and the data associated with
		// the checker thread and store it before starting
		// the thread
		boost::shared_ptr<torrent> torrent_ptr(
			new torrent(m_impl, ti, save_path, m_impl.m_listen_interface));

		detail::piece_checker_data d;
		d.torrent_ptr = torrent_ptr;
		d.save_path = save_path;
		d.info_hash = ti.info_hash();
		d.parse_resume_data(resume_data, torrent_ptr->torrent_file());
		
		// lock the checker thread
		boost::mutex::scoped_lock l(m_checker_impl.m_mutex);

		// add the torrent to the queue to be checked
		m_checker_impl.m_torrents.push_back(d);
		// and notify the thread that it got another
		// job in its queue
		m_checker_impl.m_cond.notify_one();

		return torrent_handle(&m_impl, &m_checker_impl, ti.info_hash());
	}

	void session::remove_torrent(const torrent_handle& h)
	{
		if (h.m_ses != &m_impl) return;
		assert(h.m_chk == &m_checker_impl || h.m_chk == 0);
		assert(h.m_ses != 0);

		{
			boost::mutex::scoped_lock l(m_impl.m_mutex);
			torrent* t = m_impl.find_torrent(h.m_info_hash);
			if (t != 0)
			{
				t->abort();
				return;
			}
		}

		if (h.m_chk)
		{
			boost::mutex::scoped_lock l(m_checker_impl.m_mutex);

			detail::piece_checker_data* d = m_checker_impl.find_torrent(h.m_info_hash);
			if (d != 0)
			{
				d->abort = true;
				return;
			}
		}
	}

	bool session::listen_on(
		std::pair<int, int> const& port_range
		, const char* net_interface)
	{
		boost::mutex::scoped_lock l(m_impl.m_mutex);

		if (m_impl.m_listen_socket)
		{
			m_impl.m_selector.remove(m_impl.m_listen_socket);
			m_impl.m_listen_socket.reset();
		}

		m_impl.m_listen_port_range = port_range;
		m_impl.m_listen_interface = address(net_interface, port_range.first);
		m_impl.open_listen_port();
		return m_impl.m_listen_socket;
	}

	unsigned short session::listen_port() const
	{
		boost::mutex::scoped_lock l(m_impl.m_mutex);
		return m_impl.m_listen_interface.port;
	}

	bool session::is_listening() const
	{
		boost::mutex::scoped_lock l(m_impl.m_mutex);
		return m_impl.m_listen_socket;
	}

	void session::set_http_settings(const http_settings& s)
	{
		boost::mutex::scoped_lock l(m_impl.m_mutex);
		m_impl.m_settings = s;
	}

	session::~session()
	{
		{
			boost::mutex::scoped_lock l(m_impl.m_mutex);
			m_impl.m_abort = true;
		}

		{
			boost::mutex::scoped_lock l(m_checker_impl.m_mutex);
			// abort the checker thread
			m_checker_impl.m_abort = true;

			// abort the currently checking torrent
			if (!m_checker_impl.m_torrents.empty())
			{
				m_checker_impl.m_torrents.front().abort = true;
			}
			m_checker_impl.m_cond.notify_one();
		}

		m_thread.join();
		m_checker_thread.join();
	}

	void session::set_upload_rate_limit(int bytes_per_second)
	{
		assert(bytes_per_second > 0 || bytes_per_second == -1);
		boost::mutex::scoped_lock l(m_impl.m_mutex);
		m_impl.m_upload_rate = bytes_per_second;
		if (m_impl.m_upload_rate != -1 || !m_impl.m_connections.empty())
			return;

		for (detail::session_impl::connection_map::iterator i
			= m_impl.m_connections.begin();
			i != m_impl.m_connections.end();)
		{
			i->second->upload_bandwidth_quota()->given = std::numeric_limits<int>::max();
//			i->second->update_send_quota_left();
		}

	}

	std::auto_ptr<alert> session::pop_alert()
	{
		if (m_impl.m_alerts.pending())
			return m_impl.m_alerts.get();
		else
			return std::auto_ptr<alert>(0);
	}

	void session::set_severity_level(alert::severity_t s)
	{
		m_impl.m_alerts.set_severity(s);
	}

	void detail::piece_checker_data::parse_resume_data(
		const entry& resume_data
		, const torrent_info& info)
	{
		// if we don't have any resume data, return
		if (resume_data.type() == entry::undefined_t) return;

		entry rd = resume_data;

		try
		{
			if (rd["file-format"].string() != "libtorrent resume file")
				return;

			if (rd["file-version"].integer() != 1)
				return;

			// verify info_hash
			const std::string &hash = rd["info-hash"].string();
			std::string real_hash((char*)info.info_hash().begin(), (char*)info.info_hash().end());
			if (hash != real_hash)
				return;

			// the peers

			entry::list_type& peer_list = rd["peers"].list();

			std::vector<address> tmp_peers;
			tmp_peers.reserve(peer_list.size());
			for (entry::list_type::iterator i = peer_list.begin();
				i != peer_list.end();
				++i)
			{
				address a(
					(*i)["ip"].string().c_str()
					, (unsigned short)(*i)["port"].integer());
				tmp_peers.push_back(a);
			}

			peers.swap(tmp_peers);



			// read piece map
			const entry::list_type& slots = rd["slots"].list();
			if ((int)slots.size() > info.num_pieces())
				return;

			std::vector<int> tmp_pieces;
			tmp_pieces.reserve(slots.size());
			for (entry::list_type::const_iterator i = slots.begin();
				i != slots.end();
				++i)
			{
				int index = (int)i->integer();
				if (index >= info.num_pieces() || index < -2)
					return;
				tmp_pieces.push_back(index);
			}


			int num_blocks_per_piece = (int)rd["blocks per piece"].integer();
			if (num_blocks_per_piece != info.piece_length() / torrent_ptr->block_size())
				return;

			// the unfinished pieces

			entry::list_type& unfinished = rd["unfinished"].list();

			std::vector<piece_picker::downloading_piece> tmp_unfinished;
			tmp_unfinished.reserve(unfinished.size());
			for (entry::list_type::iterator i = unfinished.begin();
				i != unfinished.end();
				++i)
			{
				piece_picker::downloading_piece p;

				p.index = (int)(*i)["piece"].integer();
				if (p.index < 0 || p.index >= info.num_pieces())
					return;

				const std::string& bitmask = (*i)["bitmask"].string();

				const int num_bitmask_bytes = std::max(num_blocks_per_piece / 8, 1);
				if ((int)bitmask.size() != num_bitmask_bytes) return;
				for (int j = 0; j < num_bitmask_bytes; ++j)
				{
					unsigned char bits = bitmask[j];
					for (int k = 0; k < 8; ++k)
					{
						const int bit = j * 8 + k;
						if (bits & (1 << k))
							p.finished_blocks[bit] = true;
					}
				}

				if (p.finished_blocks.count() == 0) continue;

				std::vector<int>::iterator slot_iter
					= std::find(tmp_pieces.begin(), tmp_pieces.end(), p.index);
				if (slot_iter == tmp_pieces.end())
				{
					// this piece is marked as unfinished
					// but doesn't have any storage
					return;
				}

				assert(*slot_iter == p.index);
				int slot_index = static_cast<int>(slot_iter - tmp_pieces.begin());
				unsigned long adler
					= torrent_ptr->filesystem().piece_crc(
						slot_index
						, torrent_ptr->block_size()
						, p.finished_blocks);

				const entry& ad = (*i)["adler32"];

				// crc's didn't match, don't use the resume data
				if (ad.integer() != adler)
					return;

				tmp_unfinished.push_back(p);
			}

			// verify file sizes

			std::vector<size_type> file_sizes;
			entry::list_type& l = rd["file sizes"].list();

#if defined(_MSC_VER) && _MSC_VER < 1300
			for (entry::list_type::iterator i = l.begin();
				i != l.end();
				++i)
			{
				file_sizes.push_back(i->integer());
			}
#else
			typedef entry::integer_type const& (entry::*mem_fun_type)() const;

			std::transform(
				l.begin()
				, l.end()
				, std::back_inserter(file_sizes)
				, boost::bind((mem_fun_type)&entry::integer, _1));
#endif
			if (!match_filesizes(info, save_path, file_sizes))
				return;

			piece_map.swap(tmp_pieces);
			unfinished_pieces.swap(tmp_unfinished);
		}
		catch (invalid_encoding)
		{
			return;
		}
		catch (type_error)
		{
			return;
		}
		catch (file_error)
		{
			return;
		}
	}
}