twister-core/libtorrent/src/web_peer_connection.cpp

/*

Copyright (c) 2003-2012, 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.

*/

#include "libtorrent/pch.hpp"

#include <vector>
#include <boost/limits.hpp>
#include <boost/bind.hpp>
#include <stdlib.h>

#include "libtorrent/web_peer_connection.hpp"
#include "libtorrent/session.hpp"
#include "libtorrent/identify_client.hpp"
#include "libtorrent/entry.hpp"
#include "libtorrent/bencode.hpp"
#include "libtorrent/alert_types.hpp"
#include "libtorrent/invariant_check.hpp"
#include "libtorrent/io.hpp"
#include "libtorrent/version.hpp"
#include "libtorrent/aux_/session_impl.hpp"
#include "libtorrent/parse_url.hpp"
#include "libtorrent/peer_info.hpp"

using boost::shared_ptr;
using libtorrent::aux::session_impl;

namespace libtorrent
{
	enum
	{
		request_size_overhead = 5000
	};

	web_peer_connection::web_peer_connection(
		session_impl& ses
		, boost::weak_ptr<torrent> t
		, boost::shared_ptr<socket_type> s
		, tcp::endpoint const& remote
		, std::string const& url
		, policy::peer* peerinfo
		, std::string const& auth
		, web_seed_entry::headers_t const& extra_headers)
		: web_connection_base(ses, t, s, remote, url, peerinfo, auth, extra_headers)
		, m_url(url)
		, m_received_body(0)
		, m_range_pos(0)
		, m_block_pos(0)
		, m_chunk_pos(0)
		, m_partial_chunk_header(0)
	{
		INVARIANT_CHECK;

		if (!ses.settings().report_web_seed_downloads)
			ignore_stats(true);

		shared_ptr<torrent> tor = t.lock();
		TORRENT_ASSERT(tor);

		// we always prefer downloading 1 MiB chunks
		// from web seeds, or whole pieces if pieces
		// are larger than a MiB
		prefer_whole_pieces((std::max)((1024 * 1024) / tor->torrent_file().piece_length(), 1));
		
		// we want large blocks as well, so
		// we can request more bytes at once
		// this setting will merge adjacent requests
		// into single larger ones
		request_large_blocks(true);

#ifdef TORRENT_VERBOSE_LOGGING
		peer_log("*** web_peer_connection %s", url.c_str());
#endif
	}

	void web_peer_connection::disconnect(error_code const& ec, int error)
	{
		boost::shared_ptr<torrent> t = associated_torrent().lock();
		peer_connection::disconnect(ec, error);
		if (t) t->disconnect_web_seed(this);
	}
	
	boost::optional<piece_block_progress>
	web_peer_connection::downloading_piece_progress() const
	{
		if (m_requests.empty())
			return boost::optional<piece_block_progress>();

		boost::shared_ptr<torrent> t = associated_torrent().lock();
		TORRENT_ASSERT(t);

		piece_block_progress ret;

		ret.piece_index = m_requests.front().piece;
		ret.bytes_downloaded = m_block_pos % t->block_size();
		// this is used to make sure that the block_index stays within
		// bounds. If the entire piece is downloaded, the block_index
		// would otherwise point to one past the end
		int correction = m_block_pos ? -1 : 0;
		ret.block_index = (m_requests.front().start + m_block_pos + correction) / t->block_size();
		TORRENT_ASSERT(ret.block_index < int(piece_block::invalid.block_index));
		TORRENT_ASSERT(ret.piece_index < int(piece_block::invalid.piece_index));

		ret.full_block_bytes = t->block_size();
		const int last_piece = t->torrent_file().num_pieces() - 1;
		if (ret.piece_index == last_piece && ret.block_index
			== t->torrent_file().piece_size(last_piece) / t->block_size())
			ret.full_block_bytes = t->torrent_file().piece_size(last_piece) % t->block_size();
		return ret;
	}

	void web_peer_connection::write_request(peer_request const& r)
	{
		INVARIANT_CHECK;

		boost::shared_ptr<torrent> t = associated_torrent().lock();
		TORRENT_ASSERT(t);

		TORRENT_ASSERT(t->valid_metadata());

		bool single_file_request = t->torrent_file().num_files() == 1;

		if (!single_file_request)
		{
			// handle incorrect .torrent files which are multi-file
			// but have web seeds not ending with a slash
			if (m_path.empty() || m_path[m_path.size() - 1] != '/') m_path += "/";
			if (m_url.empty() || m_url[m_url.size() - 1] != '/') m_url += "/";
		}
		else
		{
			// handle .torrent files that don't include the filename in the url
			if (m_path.empty()) m_path += "/" + t->torrent_file().name();
			else if (m_path[m_path.size() - 1] == '/')
			{
				std::string tmp = t->torrent_file().files().at(0).path;
#ifdef TORRENT_WINDOWS
				convert_path_to_posix(tmp);
#endif
				m_path += tmp;
			}
			else if (!m_url.empty() && m_url[m_url.size() - 1] == '/')
			{
				std::string tmp = t->torrent_file().files().at(0).path;
#ifdef TORRENT_WINDOWS
				convert_path_to_posix(tmp);
#endif
				m_url += tmp;
			}
		}

		torrent_info const& info = t->torrent_file();
		
		std::string request;
		request.reserve(400);

		int size = r.length;
		const int block_size = t->block_size();
		const int piece_size = t->torrent_file().piece_length();
		peer_request pr;
		while (size > 0)
		{
			int request_offset = r.start + r.length - size;
			pr.start = request_offset % piece_size;
			pr.length = (std::min)(block_size, size);
			pr.piece = r.piece + request_offset / piece_size;
			m_requests.push_back(pr);
			size -= pr.length;
		}

		proxy_settings const& ps = m_ses.proxy();
		bool using_proxy = (ps.type == proxy_settings::http
			|| ps.type == proxy_settings::http_pw) && !m_ssl;

		if (single_file_request)
		{
			request += "GET ";
			// do not encode single file paths, they are 
			// assumed to be encoded in the torrent file
			request += using_proxy ? m_url : m_path;
			request += " HTTP/1.1\r\n";
			add_headers(request, ps, using_proxy);
			request += "\r\nRange: bytes=";
			request += to_string(size_type(r.piece) * info.piece_length() + r.start).elems;
			request += "-";
			request += to_string(size_type(r.piece) * info.piece_length() + r.start + r.length - 1).elems;
			request += "\r\n\r\n";
			m_first_request = false;
			m_file_requests.push_back(0);
		}
		else
		{
			std::vector<file_slice> files = info.orig_files().map_block(r.piece, r.start
				, r.length);

			for (std::vector<file_slice>::iterator i = files.begin();
				i != files.end(); ++i)
			{
				file_slice const& f = *i;
				if (info.orig_files().internal_at(f.file_index).pad_file)
				{
					m_file_requests.push_back(f.file_index);
					continue;
				}

				request += "GET ";
				if (using_proxy)
				{
					request += m_url;
					std::string path = info.orig_files().file_path(info.orig_files().internal_at(f.file_index));
#ifdef TORRENT_WINDOWS
					convert_path_to_posix(path);
#endif
					request += escape_path(path.c_str(), path.length());
				}
				else
				{
					std::string path = m_path;
					path += info.orig_files().file_path(info.orig_files().internal_at(f.file_index));
#ifdef TORRENT_WINDOWS
					convert_path_to_posix(path);
#endif
					request += escape_path(path.c_str(), path.length());
				}
				request += " HTTP/1.1\r\n";
				add_headers(request, ps, using_proxy);
				request += "\r\nRange: bytes=";
				request += to_string(f.offset).elems;
				request += "-";
				request += to_string(f.offset + f.size - 1).elems;
				request += "\r\n\r\n";
				m_first_request = false;
				TORRENT_ASSERT(f.file_index >= 0);
				m_file_requests.push_back(f.file_index);
			}
		}

#ifdef TORRENT_VERBOSE_LOGGING
		peer_log("==> %s", request.c_str());
#endif

		send_buffer(request.c_str(), request.size(), message_type_request);
	}

	// --------------------------
	// RECEIVE DATA
	// --------------------------

	namespace
	{
		bool range_contains(peer_request const& range, peer_request const& req, int piece_size)
		{
			size_type range_start = size_type(range.piece) * piece_size + range.start;
			size_type req_start = size_type(req.piece) * piece_size + req.start;
			return range_start <= req_start
				&& range_start + range.length >= req_start + req.length;
		}
	}

	bool web_peer_connection::maybe_harvest_block()
	{
		peer_request const& front_request = m_requests.front();

		if (int(m_piece.size()) < front_request.length) return false;
		TORRENT_ASSERT(int(m_piece.size() == front_request.length));

		// each call to incoming_piece() may result in us becoming
		// a seed. If we become a seed, all seeds we're connected to
		// will be disconnected, including this web seed. We need to
		// check for the disconnect condition after the call.

		boost::shared_ptr<torrent> t = associated_torrent().lock();
		TORRENT_ASSERT(t);
		buffer::const_interval recv_buffer = receive_buffer();

		incoming_piece(front_request, &m_piece[0]);
		m_requests.pop_front();
		if (associated_torrent().expired()) return false;
		TORRENT_ASSERT(m_block_pos >= front_request.length);
		m_block_pos -= front_request.length;
		cut_receive_buffer(m_body_start, t->block_size() + request_size_overhead);
		m_body_start = 0;
		recv_buffer = receive_buffer();
//		TORRENT_ASSERT(m_received_body <= range_end - range_start);
		m_piece.clear();
		TORRENT_ASSERT(m_piece.empty());
		return true;
	}

	bool web_peer_connection::received_invalid_data(int index, bool single_peer)
	{
		if (!single_peer) return peer_connection::received_invalid_data(index, single_peer);

		// when a web seed fails a hash check, do the following:
		// 1. if the whole piece only overlaps a single file, mark that file as not
		//    have for this peer
		// 2. if the piece overlaps more than one file, mark the piece as not have
		//    for this peer
		// 3. if it's a single file torrent, just ban it right away
		// this handles the case where web seeds may have some files updated but not other

		boost::shared_ptr<torrent> t = associated_torrent().lock();
		file_storage const& fs = t->torrent_file().files();

		// single file torrent
		if (fs.num_files() == 1) return peer_connection::received_invalid_data(index, single_peer);

		std::vector<file_slice> files = fs.map_block(index, 0, fs.piece_size(index));

		if (files.size() == 1)
		{
			// assume the web seed has a different copy of this specific file
			// than what we expect, and pretend not to have it.
			int fi = files[0].file_index;
			int first_piece = fs.file_offset(fi) / fs.piece_length();
			// one past last piece
			int end_piece = (fs.file_offset(fi) + fs.file_size(fi) + 1) / fs.piece_length();
			for (int i = first_piece; i < end_piece; ++i)
				incoming_dont_have(i);
		}
		else
		{
			incoming_dont_have(index);
		}

		peer_connection::received_invalid_data(index, single_peer);

		// if we don't think we have any of the files, allow banning the web seed
		if (num_have_pieces() == 0) return true;

		// don't disconnect, we won't request anything from this file again
		return false;
	}

	void web_peer_connection::on_receive(error_code const& error
		, std::size_t bytes_transferred)
	{
		INVARIANT_CHECK;

#ifdef TORRENT_DEBUG
		TORRENT_ASSERT(m_statistics.last_payload_downloaded()
			+ m_statistics.last_protocol_downloaded() + bytes_transferred < size_t(INT_MAX));
		int dl_target = m_statistics.last_payload_downloaded()
			+ m_statistics.last_protocol_downloaded() + bytes_transferred;
#endif

		if (error)
		{
			m_statistics.received_bytes(0, bytes_transferred);
#ifdef TORRENT_VERBOSE_LOGGING
			peer_log("*** web_peer_connection error: %s", error.message().c_str());
#endif
#ifdef TORRENT_DEBUG
			TORRENT_ASSERT(m_statistics.last_payload_downloaded()
				+ m_statistics.last_protocol_downloaded()
				== dl_target);
#endif
			return;
		}

		boost::shared_ptr<torrent> t = associated_torrent().lock();
		TORRENT_ASSERT(t);

		for (;;)
		{
#ifdef TORRENT_DEBUG
			TORRENT_ASSERT(m_statistics.last_payload_downloaded()
				+ m_statistics.last_protocol_downloaded() + int(bytes_transferred)
				== dl_target);
#endif

			buffer::const_interval recv_buffer = receive_buffer();

			int payload;
			int protocol;
			bool header_finished = m_parser.header_finished();
			if (!header_finished)
			{
				bool failed = false;
				boost::tie(payload, protocol) = m_parser.incoming(recv_buffer, failed);
				m_statistics.received_bytes(0, protocol);
				TORRENT_ASSERT(int(bytes_transferred) >= protocol);
				bytes_transferred -= protocol;

				if (failed)
				{
					m_statistics.received_bytes(0, bytes_transferred);
#ifdef TORRENT_VERBOSE_LOGGING
					peer_log("*** %s", std::string(recv_buffer.begin, recv_buffer.end).c_str());
#endif
					disconnect(errors::http_parse_error, 2);
#ifdef TORRENT_DEBUG
					TORRENT_ASSERT(m_statistics.last_payload_downloaded()
						+ m_statistics.last_protocol_downloaded()
						== dl_target);
#endif
					return;
				}

				TORRENT_ASSERT(recv_buffer.left() == 0 || *recv_buffer.begin == 'H');
			
				TORRENT_ASSERT(recv_buffer.left() <= packet_size());
				
				// this means the entire status line hasn't been received yet
				if (m_parser.status_code() == -1)
				{
					TORRENT_ASSERT(payload == 0);
					TORRENT_ASSERT(bytes_transferred == 0);
#ifdef TORRENT_DEBUG
					TORRENT_ASSERT(m_statistics.last_payload_downloaded()
						+ m_statistics.last_protocol_downloaded() + int(bytes_transferred)
						== dl_target);
#endif
					break;
				}

				if (!m_parser.header_finished())
				{
					TORRENT_ASSERT(payload == 0);
					TORRENT_ASSERT(bytes_transferred == 0);
#ifdef TORRENT_DEBUG
					TORRENT_ASSERT(m_statistics.last_payload_downloaded()
						+ m_statistics.last_protocol_downloaded() + int(bytes_transferred)
						== dl_target);
#endif
					break;
				}

				m_body_start = m_parser.body_start();
				m_received_body = 0;
			}

			// we just completed reading the header
			if (!header_finished)
			{
#ifdef TORRENT_VERBOSE_LOGGING
				peer_log("*** STATUS: %d %s", m_parser.status_code(), m_parser.message().c_str());
				std::multimap<std::string, std::string> const& headers = m_parser.headers();
				for (std::multimap<std::string, std::string>::const_iterator i = headers.begin()
					, end(headers.end()); i != end; ++i)
					peer_log("   %s: %s", i->first.c_str(), i->second.c_str());
#endif
				// if the status code is not one of the accepted ones, abort
				if (!is_ok_status(m_parser.status_code()))
				{
					int retry_time = atoi(m_parser.header("retry-after").c_str());
					if (retry_time <= 0) retry_time = 5 * 60;
					// temporarily unavailable, retry later
					t->retry_web_seed(this, retry_time);
					std::string error_msg = to_string(m_parser.status_code()).elems
						+ (" " + m_parser.message());
					if (m_ses.m_alerts.should_post<url_seed_alert>())
					{
						m_ses.m_alerts.post_alert(url_seed_alert(t->get_handle(), m_url
							, error_msg));
					}
					m_statistics.received_bytes(0, bytes_transferred);
					disconnect(error_code(m_parser.status_code(), get_http_category()), 1);
#ifdef TORRENT_DEBUG
					TORRENT_ASSERT(m_statistics.last_payload_downloaded()
						+ m_statistics.last_protocol_downloaded()
						== dl_target);
#endif
					return;
				}
				if (is_redirect(m_parser.status_code()))
				{
					// this means we got a redirection request
					// look for the location header
					std::string location = m_parser.header("location");
					m_statistics.received_bytes(0, bytes_transferred);

					if (location.empty())
					{
						// we should not try this server again.
						t->remove_web_seed(this);
						disconnect(errors::missing_location, 2);
#ifdef TORRENT_DEBUG
						TORRENT_ASSERT(m_statistics.last_payload_downloaded()
							+ m_statistics.last_protocol_downloaded()
							== dl_target);
#endif
						return;
					}
					
					bool single_file_request = false;
					if (!m_path.empty() && m_path[m_path.size() - 1] != '/')
						single_file_request = true;

					// add the redirected url and remove the current one
					if (!single_file_request)
					{
						TORRENT_ASSERT(!m_file_requests.empty());
						int file_index = m_file_requests.front();

						torrent_info const& info = t->torrent_file();
						std::string path = info.orig_files().file_path(info.orig_files().at(file_index));
#ifdef TORRENT_WINDOWS
						convert_path_to_posix(path);
#endif
						path = escape_path(path.c_str(), path.length());
						size_t i = location.rfind(path);
						if (i == std::string::npos)
						{
							t->remove_web_seed(this);
							disconnect(errors::invalid_redirection, 2);
#ifdef TORRENT_DEBUG
							TORRENT_ASSERT(m_statistics.last_payload_downloaded()
								+ m_statistics.last_protocol_downloaded()
								== dl_target);
#endif
							return;
						}
						location.resize(i);
					}
					t->add_web_seed(location, web_seed_entry::url_seed, m_external_auth, m_extra_headers);
					t->remove_web_seed(this);
					disconnect(errors::redirecting, 2);
#ifdef TORRENT_DEBUG
					TORRENT_ASSERT(m_statistics.last_payload_downloaded()
						+ m_statistics.last_protocol_downloaded()
						== dl_target);
#endif
					return;
				}

				std::string const& server_version = m_parser.header("server");
				if (!server_version.empty())
				{
					m_server_string = "URL seed @ ";
					m_server_string += m_host;
					m_server_string += " (";
					m_server_string += server_version;
					m_server_string += ")";
				}

				m_body_start = m_parser.body_start();
				m_received_body = 0;
				m_range_pos = 0;
			}

			recv_buffer.begin += m_body_start;

			// we only received the header, no data
			if (recv_buffer.left() == 0)
			{
#ifdef TORRENT_DEBUG
				TORRENT_ASSERT(m_statistics.last_payload_downloaded()
					+ m_statistics.last_protocol_downloaded()
					== dl_target);
#endif
				break;
			}

			size_type range_start;
			size_type range_end;
			if (m_parser.status_code() == 206)
			{
				boost::tie(range_start, range_end) = m_parser.content_range();
				if (range_start < 0 || range_end < range_start)
				{
					m_statistics.received_bytes(0, bytes_transferred);
					// we should not try this server again.
					t->remove_web_seed(this);
					disconnect(errors::invalid_range);
#ifdef TORRENT_DEBUG
					TORRENT_ASSERT(m_statistics.last_payload_downloaded()
						+ m_statistics.last_protocol_downloaded()
						== dl_target);
#endif
					return;
				}
				// the http range is inclusive
				range_end++;
			}
			else
			{
				range_start = 0;
				range_end = m_parser.content_length();
				if (range_end == -1)
				{
					m_statistics.received_bytes(0, bytes_transferred);
					// we should not try this server again.
					t->remove_web_seed(this);
					disconnect(errors::no_content_length, 2);
#ifdef TORRENT_DEBUG
					TORRENT_ASSERT(m_statistics.last_payload_downloaded()
						+ m_statistics.last_protocol_downloaded()
						== dl_target);
#endif
					return;
				}
			}

			if (m_requests.empty() || m_file_requests.empty())
			{
				m_statistics.received_bytes(0, bytes_transferred);
				disconnect(errors::http_error, 2);
#ifdef TORRENT_DEBUG
				TORRENT_ASSERT(m_statistics.last_payload_downloaded()
					+ m_statistics.last_protocol_downloaded()
					== dl_target);
#endif
				return;
			}

			// =========================
			// === CHUNKED ENCODING  ===
			// =========================
			while (m_parser.chunked_encoding()
				&& m_chunk_pos >= 0
				&& m_chunk_pos < recv_buffer.left())
			{
				int header_size = 0;
				size_type chunk_size = 0;
				buffer::const_interval chunk_start = recv_buffer;
				chunk_start.begin += m_chunk_pos;
				TORRENT_ASSERT(chunk_start.begin[0] == '\r' || is_hex(chunk_start.begin, 1));
				bool ret = m_parser.parse_chunk_header(chunk_start, &chunk_size, &header_size);
				if (!ret)
				{
					TORRENT_ASSERT(int(bytes_transferred) >= chunk_start.left() - m_partial_chunk_header);
					bytes_transferred -= chunk_start.left() - m_partial_chunk_header;
					m_statistics.received_bytes(0, chunk_start.left() - m_partial_chunk_header);
					m_partial_chunk_header = chunk_start.left();
					if (bytes_transferred == 0) return;
					break;
				}
				else
				{
#ifdef TORRENT_VERBOSE_LOGGING
					peer_log("*** parsed chunk: %d header_size: %d", chunk_size, header_size);
#endif
					TORRENT_ASSERT(int(bytes_transferred) >= header_size - m_partial_chunk_header);
					bytes_transferred -= header_size - m_partial_chunk_header;
					m_statistics.received_bytes(0, header_size - m_partial_chunk_header);
					m_partial_chunk_header = 0;
					TORRENT_ASSERT(chunk_size != 0 || chunk_start.left() <= header_size || chunk_start.begin[header_size] == 'H');
					// cut out the chunk header from the receive buffer
					TORRENT_ASSERT(m_body_start + m_chunk_pos < INT_MAX);
					cut_receive_buffer(header_size, t->block_size() + request_size_overhead, int(m_body_start + m_chunk_pos));
					recv_buffer = receive_buffer();
					recv_buffer.begin += m_body_start;
					m_chunk_pos += chunk_size;
					if (chunk_size == 0)
					{
#ifdef TORRENT_DEBUG
						chunk_start = recv_buffer;
						chunk_start.begin += m_chunk_pos;
						TORRENT_ASSERT(chunk_start.left() == 0 || chunk_start.begin[0] == 'H');
#endif
						m_chunk_pos = -1;
					}
				}
			}

			size_type left_in_response = range_end - range_start - m_range_pos;
			int payload_transferred = int((std::min)(left_in_response, size_type(bytes_transferred)));

			torrent_info const& info = t->torrent_file();

			peer_request front_request = m_requests.front();

			TORRENT_ASSERT(m_block_pos >= 0);

#ifdef TORRENT_VERBOSE_LOGGING
			peer_log("*** payload_transferred: %d [ %d:%d = %d ]"
				, payload_transferred, front_request.piece
				, front_request.start, front_request.length);
#endif
			m_statistics.received_bytes(payload_transferred, 0);
			TORRENT_ASSERT(int(bytes_transferred) >= payload_transferred);
			bytes_transferred -= payload_transferred;
			m_range_pos += payload_transferred;
			m_block_pos += payload_transferred;
			if (m_range_pos > range_end - range_start) m_range_pos = range_end - range_start;

#if 0
			std::cerr << "REQUESTS: m_requests: " << m_requests.size()
				<< " file_requests: " << m_file_requests.size() << std::endl;
#endif

			int file_index = m_file_requests.front();
			peer_request in_range = info.orig_files().map_file(file_index, range_start
				, int(range_end - range_start));

			// request start
			size_type rs = size_type(in_range.piece) * info.piece_length() + in_range.start;
			// request end
			size_type re = rs + in_range.length;
			// file start
			size_type fs = size_type(front_request.piece) * info.piece_length() + front_request.start;
#if 0
			size_type fe = fs + front_request.length;

			std::cerr << "RANGE: r = (" << rs << ", " << re << " ) "
				"f = (" << fs << ", " << fe << ") "
				"file_index = " << file_index << " received_body = " << m_received_body << std::endl;
#endif

			// the http response body consists of 3 parts
			// 1. the middle of a block or the ending of a block
			// 2. a number of whole blocks
			// 3. the start of a block
			// in that order, these parts are parsed.

			bool range_overlaps_request = re > fs + int(m_piece.size());

			if (!range_overlaps_request)
			{
				incoming_piece_fragment((std::min)(payload_transferred
					, front_request.length - m_block_pos));
				m_statistics.received_bytes(0, bytes_transferred);
				// this means the end of the incoming request ends _before_ the
				// first expected byte (fs + m_piece.size())
				disconnect(errors::invalid_range, 2);
				return;
			}

			// if the request is contained in the range (i.e. the entire request
			// fits in the range) we should not start a partial piece, since we soon
			// will receive enough to call incoming_piece() and pass the read buffer
			// directly (in the next loop below).
			if (range_overlaps_request && !range_contains(in_range, front_request, info.piece_length()))
			{
				// the start of the next block to receive is stored
				// in m_piece. We need to append the rest of that
				// block from the http receive buffer and then
				// (if it completed) call incoming_piece() with
				// m_piece as buffer.
				
				int piece_size = int(m_piece.size());
				int copy_size = (std::min)((std::min)(front_request.length - piece_size
					, recv_buffer.left()), int(range_end - range_start - m_received_body));
				if (copy_size > m_chunk_pos && m_chunk_pos > 0) copy_size = m_chunk_pos;
				if (copy_size > 0)
				{
					TORRENT_ASSERT(m_piece.size() == m_received_in_piece);
					m_piece.resize(piece_size + copy_size);
					std::memcpy(&m_piece[0] + piece_size, recv_buffer.begin, copy_size);
					TORRENT_ASSERT(int(m_piece.size()) <= front_request.length);
					recv_buffer.begin += copy_size;
					m_received_body += copy_size;
					m_body_start += copy_size;
					if (m_chunk_pos > 0)
					{
						TORRENT_ASSERT(m_chunk_pos >= copy_size);
						m_chunk_pos -= copy_size;
					}
					TORRENT_ASSERT(m_received_body <= range_end - range_start);
					TORRENT_ASSERT(int(m_piece.size()) <= front_request.length);
					incoming_piece_fragment(copy_size);
					TORRENT_ASSERT(m_piece.size() == m_received_in_piece);
				}

				if (maybe_harvest_block())
					recv_buffer = receive_buffer();
				if (associated_torrent().expired()) return;
			}

			// report all received blocks to the bittorrent engine
			while (!m_requests.empty()
				&& range_contains(in_range, m_requests.front(), info.piece_length())
				&& m_block_pos >= m_requests.front().length)
			{
				peer_request r = m_requests.front();
				TORRENT_ASSERT(recv_buffer.left() >= r.length);

				incoming_piece_fragment(r.length);
				incoming_piece(r, recv_buffer.begin);
				m_requests.pop_front();
				if (associated_torrent().expired()) return;
				TORRENT_ASSERT(m_block_pos >= r.length);
				m_block_pos -= r.length;
				m_received_body += r.length;
				TORRENT_ASSERT(receive_buffer().begin + m_body_start == recv_buffer.begin);
				TORRENT_ASSERT(m_received_body <= range_end - range_start);
				cut_receive_buffer(m_body_start + r.length, t->block_size() + request_size_overhead);
				if (m_chunk_pos > 0)
				{
					TORRENT_ASSERT(m_chunk_pos >= r.length);
					m_chunk_pos -= r.length;
				}
				m_body_start = 0;
				recv_buffer = receive_buffer();
			}

			if (!m_requests.empty())
			{
				if (in_range.start + in_range.length < m_requests.front().start + m_requests.front().length
					&& (m_received_body + recv_buffer.left() >= range_end - range_start))
				{
					int piece_size = int(m_piece.size());
					int copy_size = (std::min)((std::min)(m_requests.front().length - piece_size
						, recv_buffer.left()), int(range_end - range_start - m_received_body));
					TORRENT_ASSERT(copy_size >= 0);
					if (copy_size > 0)
					{
						TORRENT_ASSERT(m_piece.size() == m_received_in_piece);
						m_piece.resize(piece_size + copy_size);
						std::memcpy(&m_piece[0] + piece_size, recv_buffer.begin, copy_size);
						recv_buffer.begin += copy_size;
						m_received_body += copy_size;
						m_body_start += copy_size;
						incoming_piece_fragment(copy_size);
						TORRENT_ASSERT(m_piece.size() == m_received_in_piece);
					}
					TORRENT_ASSERT(m_received_body == range_end - range_start);
				}
			}

			TORRENT_ASSERT(m_received_body <= range_end - range_start);
			// if we're in chunked encoding mode, we have to wait for the complete
			// tail header before we can consider have received the block, otherwise
			// we'll get out of sync with the next http response. m_chunk_pos is set
			// to -1 when the tail header has been received
			if (m_received_body == range_end - range_start
				&& (!m_parser.chunked_encoding() || m_chunk_pos == -1))
			{
				int size_to_cut = recv_buffer.begin - receive_buffer().begin;

				TORRENT_ASSERT(receive_buffer().left() < size_to_cut + 1
					|| receive_buffer()[size_to_cut] == 'H');

				cut_receive_buffer(size_to_cut, t->block_size() + request_size_overhead);
				if (m_chunk_pos > 0)
				{
					TORRENT_ASSERT(m_chunk_pos >= size_to_cut);
					m_chunk_pos -= size_to_cut;
				}
				recv_buffer = receive_buffer();
				m_file_requests.pop_front();
				m_parser.reset();
				m_body_start = 0;
				m_received_body = 0;
				m_chunk_pos = 0;
				m_partial_chunk_header = 0;
				
				torrent_info const& info = t->torrent_file();
				while (!m_file_requests.empty()
					&& info.orig_files().internal_at(m_file_requests.front()).pad_file)
				{
					// the next file is a pad file. We didn't actually send
					// a request for this since it most likely doesn't exist on
					// the web server anyway. Just pretend that we received a
					// bunch of zeroes here and pop it again
					int file_index = m_file_requests.front();
					m_file_requests.pop_front();
					size_type file_size = info.orig_files().file_size(info.orig_files().internal_at(file_index));
					TORRENT_ASSERT(m_block_pos < front_request.length);
					int pad_size = (std::min)(file_size, size_type(front_request.length - m_block_pos));

					// insert zeroes to represent the pad file
					m_piece.resize(m_piece.size() + pad_size, 0);
					m_block_pos += pad_size;
					incoming_piece_fragment(pad_size);

					if (maybe_harvest_block())
						recv_buffer = receive_buffer();
					if (associated_torrent().expired()) return;
				}
				continue;
			}
			if (bytes_transferred == 0 || payload_transferred == 0)
			{
#ifdef TORRENT_DEBUG
				TORRENT_ASSERT(m_statistics.last_payload_downloaded()
					+ m_statistics.last_protocol_downloaded()
					== dl_target);
#endif
				break;
			}
			TORRENT_ASSERT(payload_transferred > 0);
		}
		TORRENT_ASSERT(bytes_transferred == 0);
#ifdef TORRENT_DEBUG
		TORRENT_ASSERT(m_statistics.last_payload_downloaded()
			+ m_statistics.last_protocol_downloaded() == dl_target);
#endif
	}

	void web_peer_connection::get_specific_peer_info(peer_info& p) const
	{
		web_connection_base::get_specific_peer_info(p);
		p.flags |= peer_info::local_connection;
		p.connection_type = peer_info::web_seed;
	}

}