peer_connection_leech.cc

LibTorrent is a BitTorrent library written in C++ for *nix, with a focus on high performance and goo

  // beginning of the buffer. Or do we use position? Propably best,
  // therefor ProtocolBuffer::position() points to the beginning of
  // the unused data.

  try {
    
    // Normal read.
    //
    // We rarely will read zero bytes as the read of 64 bytes will
    // almost always either not fill up or it will require additional
    // reads.
    //
    // Only loop when end hits 64.

    do {

      switch (m_down->get_state()) {
      case ProtocolRead::IDLE:
        if (m_down->buffer()->size_end() == read_size)
          throw internal_error("PeerConnectionLeech::event_read() m_down->buffer()->size_end() == read_size.");

        m_down->buffer()->move_end(read_stream_throws(m_down->buffer()->end(), read_size - m_down->buffer()->size_end()));
        
        while (read_message());
        
        if (m_down->buffer()->size_end() == read_size) {
          read_buffer_move_unused();
          break;
        } else {
          read_buffer_move_unused();
          return;
        }

      case ProtocolRead::READ_PIECE:
        if (!download_queue()->is_downloading())
          throw internal_error("ProtocolRead::READ_PIECE state but RequestList is not downloading");

        if (!m_downloadQueue.transfer()->is_valid() || !m_downloadQueue.transfer()->is_leader()) {
          m_down->set_state(ProtocolRead::READ_SKIP_PIECE);
          break;
        }

        if (!down_chunk())
          return;

        m_tryRequest = true;
        m_down->set_state(ProtocolRead::IDLE);
        down_chunk_finished();
        break;

      case ProtocolRead::READ_SKIP_PIECE:
        if (download_queue()->transfer()->is_leader()) {
          m_down->set_state(ProtocolRead::READ_PIECE);
          m_download->download_throttle()->insert(m_peerChunks.download_throttle());
          break;
        }

        if (!down_chunk_skip())
          return;

        m_tryRequest = true;
        m_down->set_state(ProtocolRead::IDLE);
        down_chunk_finished();
        break;

      default:
        throw internal_error("PeerConnectionLeech::event_read() wrong state.");
      }

      // Figure out how to get rid of the shouldLoop boolean.
    } while (true);

  // Exception handlers:

  } catch (close_connection& e) {
    m_download->connection_list()->erase(this, 0);

  } catch (blocked_connection& e) {
    m_download->info()->signal_network_log().emit("Momentarily blocked read connection.");
    m_download->connection_list()->erase(this, 0);

  } catch (network_error& e) {
    m_download->info()->signal_network_log().emit(e.what());

    m_download->connection_list()->erase(this, 0);

  } catch (storage_error& e) {
    m_download->info()->signal_storage_error().emit(e.what());
    m_download->connection_list()->erase(this, 0);

  } catch (base_error& e) {
    std::stringstream s;
    s << "Connection read fd(" << get_fd().get_fd() << ',' << m_down->get_state() << ',' << m_down->last_command() << ") \"" << e.what() << '"';

    e.set(s.str());

    throw;
  }
}

inline void
PeerConnectionLeech::fill_write_buffer() {
  // No need to use delayed choke as we are a leecher.
  if (m_sendChoked && m_up->can_write_choke()) {
    m_sendChoked = false;
    m_up->write_choke(m_up->choked());

    if (m_up->choked()) {
      m_download->upload_throttle()->erase(m_peerChunks.upload_throttle());
      up_chunk_release();
      m_peerChunks.upload_queue()->clear();

    } else {
      m_download->upload_throttle()->insert(m_peerChunks.upload_throttle());
    }
  }

  // Send the interested state before any requests as some clients,
  // e.g. BitTornado 0.7.14 and uTorrent 0.3.0, disconnect if a
  // request has been received while uninterested. The problem arises
  // as they send unchoke before receiving interested.
  if (m_sendInterested && m_up->can_write_interested()) {
    m_up->write_interested(m_up->interested());
    m_sendInterested = false;
  }

  if (m_tryRequest &&

      !(m_tryRequest = !should_request()) &&
      !(m_tryRequest = try_request_pieces()) &&

      !download_queue()->is_interested_in_active()) {
    m_sendInterested = true;
    m_up->set_interested(false);
  }

  while (!m_peerChunks.have_queue()->empty() && m_up->can_write_have()) {
    m_up->write_have(m_peerChunks.have_queue()->front());
    m_peerChunks.have_queue()->pop_front();
  }

  if (!m_up->choked() &&
      !m_peerChunks.upload_queue()->empty() &&
      m_up->can_write_piece())
    write_prepare_piece();
}

void
PeerConnectionLeech::event_write() {
  try {
  
    do {

      switch (m_up->get_state()) {
      case ProtocolWrite::IDLE:

        // We might have buffered keepalive message or similar, but
        // 'end' should remain at the start of the buffer.
        if (m_up->buffer()->size_end() != 0)
          throw internal_error("PeerConnectionLeech::event_write() ProtocolWrite::IDLE in a wrong state.");

        // Fill up buffer.
        fill_write_buffer();

        if (m_up->buffer()->size_position() == 0) {
          manager->poll()->remove_write(this);
          return;
        }

        m_up->set_state(ProtocolWrite::MSG);
        m_up->buffer()->prepare_end();

      case ProtocolWrite::MSG:
        m_up->buffer()->move_position(write_stream_throws(m_up->buffer()->position(), m_up->buffer()->remaining()));

        if (m_up->buffer()->remaining())
          return;

        m_up->buffer()->reset();

        if (m_up->last_command() != ProtocolBase::PIECE) {
          // Break or loop? Might do an ifelse based on size of the
          // write buffer. Also the write buffer is relatively large.
          m_up->set_state(ProtocolWrite::IDLE);
          break;
        }

        // We're uploading a piece.
        load_up_chunk();
        m_up->set_state(ProtocolWrite::WRITE_PIECE);

      case ProtocolWrite::WRITE_PIECE:
        if (!up_chunk())
          return;

        m_up->set_state(ProtocolWrite::IDLE);

        break;

      default:
        throw internal_error("PeerConnectionLeech::event_write() wrong state.");
      }

    } while (true);

  } catch (close_connection& e) {
    m_download->connection_list()->erase(this, 0);

  } catch (blocked_connection& e) {
    m_download->info()->signal_network_log().emit("Momentarily blocked write connection.");
    m_download->connection_list()->erase(this, 0);

  } catch (network_error& e) {
    m_download->info()->signal_network_log().emit(e.what());
    m_download->connection_list()->erase(this, 0);

  } catch (storage_error& e) {
    m_download->info()->signal_storage_error().emit(e.what());
    m_download->connection_list()->erase(this, 0);

  } catch (base_error& e) {
    std::stringstream s;
    s << "Connection write fd(" << get_fd().get_fd() << ',' << m_up->get_state() << ',' << m_up->last_command() << ") \"" << e.what() << '"';

    e.set(s.str());

    throw;
  }
}

void
PeerConnectionLeech::read_have_chunk(uint32_t index) {
  if (index >= m_peerChunks.bitfield()->size_bits())
    throw network_error("Peer sent HAVE message with out-of-range index.");

  if (m_peerChunks.bitfield()->get(index))
    return;

  m_download->chunk_statistics()->received_have_chunk(&m_peerChunks, index, m_download->content()->chunk_size());

  if (m_peerChunks.bitfield()->is_all_set())
    if (m_download->content()->is_done())
      throw close_connection();
    else
      set_remote_not_interested();

  if (m_download->content()->is_done())
    return;

  if (is_up_interested()) {

    if (!m_tryRequest && m_download->chunk_selector()->received_have_chunk(&m_peerChunks, index)) {
      m_tryRequest = true;
      write_insert_poll_safe();
    }

  } else {

    if (m_download->chunk_selector()->received_have_chunk(&m_peerChunks, index)) {
      m_sendInterested = true;
      m_up->set_interested(true);
      
      // Is it enough to insert into write here? Make the interested
      // check branch to include insert_write, even when not sending
      // interested.
      m_tryRequest = true;
      write_insert_poll_safe();
    }
  }
}

}