panda3d/direct/src/distributed/cConnectionRepository.cxx

// Filename: cConnectionRepository.cxx
// Created by:  drose (17May04)
//
////////////////////////////////////////////////////////////////////
//
// PANDA 3D SOFTWARE
// Copyright (c) 2001 - 2004, Disney Enterprises, Inc.  All rights reserved
//
// All use of this software is subject to the terms of the Panda 3d
// Software license.  You should have received a copy of this license
// along with this source code; you will also find a current copy of
// the license at http://etc.cmu.edu/panda3d/docs/license/ .
//
// To contact the maintainers of this program write to
// panda3d-general@lists.sourceforge.net .
//
////////////////////////////////////////////////////////////////////

#include "cConnectionRepository.h"
#include "dcmsgtypes.h"
#include "dcClass.h"
#include "dcPacker.h"

#include "config_distributed.h"
#include "httpChannel.h"
#include "urlSpec.h"
#include "datagramIterator.h"
#include "throw_event.h"
#include "pStatTimer.h"



const string CConnectionRepository::_overflow_event_name = "CRDatagramOverflow";

#ifndef CPPPARSER
PStatCollector CConnectionRepository::_update_pcollector("App:Show code:readerPollTask:Update");
#endif  // CPPPARSER

////////////////////////////////////////////////////////////////////
//     Function: CConnectionRepository::Constructor
//       Access: Published
//  Description: 
////////////////////////////////////////////////////////////////////
CConnectionRepository::
CConnectionRepository(bool has_owner_view) :
#ifdef HAVE_PYTHON
  _python_repository(NULL),
#endif
#ifdef HAVE_OPENSSL
  _http_conn(NULL),
#endif
#ifdef HAVE_NET
  _cw(&_qcm, 0),
  _qcr(&_qcm, 0),
#endif
#ifdef WANT_NATIVE_NET
  _bdc(0,4096000,4096000,1460),
  _native(false),
#endif
  _client_datagram(true),
  _simulated_disconnect(false),
  _verbose(distributed_cat.is_spam()),
//  _msg_channels(),
  _msg_sender(0),
  _msg_type(0),
  _has_owner_view(has_owner_view)
{
#if defined(HAVE_NET) && defined(SIMULATE_NETWORK_DELAY)
  if (min_lag != 0.0 || max_lag != 0.0) {
    _qcr.start_delay(min_lag, max_lag);
  }
#endif
}

////////////////////////////////////////////////////////////////////
//     Function: CConnectionRepository::Destructor
//       Access: Published
//  Description: 
////////////////////////////////////////////////////////////////////
CConnectionRepository::
~CConnectionRepository() {
  disconnect();
}

#ifdef HAVE_OPENSSL
////////////////////////////////////////////////////////////////////
//     Function: CConnectionRepository::set_connection_http
//       Access: Published
//  Description: Once a connection has been established via the HTTP
//               interface, gets the connection and uses it.  The
//               supplied HTTPChannel object must have a connection
//               available via get_connection().
////////////////////////////////////////////////////////////////////
void CConnectionRepository::
set_connection_http(HTTPChannel *channel) {
  disconnect();
  nassertv(channel->is_connection_ready());
  _http_conn = channel->get_connection();
#ifdef SIMULATE_NETWORK_DELAY
  if (min_lag != 0.0 || max_lag != 0.0) {
    _http_conn->start_delay(min_lag, max_lag);
  }
#endif
}
#endif  // HAVE_OPENSSL

#ifdef HAVE_OPENSSL
////////////////////////////////////////////////////////////////////
//     Function: CConnectionRepository::get_stream
//       Access: Published
//  Description: Returns the SocketStream that internally represents
//               the already-established HTTP connection.  Returns
//               NULL if there is no current HTTP connection.
////////////////////////////////////////////////////////////////////
SocketStream *CConnectionRepository::
get_stream() {
  return _http_conn;
}
#endif  // HAVE_OPENSSL


#ifdef HAVE_NET
////////////////////////////////////////////////////////////////////
//     Function: CConnectionRepository::try_connect_net
//       Access: Published
//  Description: Uses Panda's "net" library to try to connect to the
//               server and port named in the indicated URL.  Returns
//               true if successful, false otherwise.
////////////////////////////////////////////////////////////////////
bool CConnectionRepository::
try_connect_net(const URLSpec &url) {
  disconnect();

  _net_conn = 
    _qcm.open_TCP_client_connection(url.get_server(), url.get_port(),
                                    game_server_timeout_ms);

  if (_net_conn != (Connection *)NULL) {
    _net_conn->set_no_delay(true);
    _qcr.add_connection(_net_conn);
    return true;
  }

  return false;
}
#endif  // HAVE_NET

#ifdef WANT_NATIVE_NET
////////////////////////////////////////////////////////////////////
//     Function: CConnectionRepository::connect_native
//       Access: Published
//  Description: Connects to the server using Panda's low-level and
//               fast "native net" library.
////////////////////////////////////////////////////////////////////
bool CConnectionRepository::
connect_native(const URLSpec &url) {
  _native=true;
  Socket_Address addr;
  addr.set_host(url.get_server(),url.get_port());
  _bdc.ClearAddresses();
  _bdc.AddAddress(addr);
  return _bdc.DoConnect();
}

#endif //WANT NATIVE NET

#ifdef SIMULATE_NETWORK_DELAY
////////////////////////////////////////////////////////////////////
//     Function: CConnectionRepository::start_delay
//       Access: Published
//  Description: Enables a simulated network latency.  All datagrams
//               received from this point on will be held for a random
//               interval of least min_delay seconds, and no more than
//               max_delay seconds, before being visible.  It is as if
//               datagrams suddenly took much longer to arrive.
//
//               This should *only* be called if the underlying socket
//               is non-blocking.  If you call this on a blocking
//               socket, it will force all datagrams to be held up
//               until the socket closes.
//
//               This has no effect if the connection method is via
//               the "native net" library.
////////////////////////////////////////////////////////////////////
void CConnectionRepository::
start_delay(double min_delay, double max_delay) {
  if (min_delay != 0.0 || max_delay != 0.0) {
#ifdef HAVE_NET
    _qcr.start_delay(min_delay, max_delay);
#endif  // HAVE_NET
#ifdef HAVE_OPENSSL
    if (_http_conn != (SocketStream *)NULL) {
      _http_conn->start_delay(min_delay, max_delay);
    }
#endif  // HAVE_OPENSSL
  } else {
    stop_delay();
  }
}
#endif  // SIMULATE_NETWORK_DELAY

#ifdef SIMULATE_NETWORK_DELAY
////////////////////////////////////////////////////////////////////
//     Function: CConnectionRepository::stop_delay
//       Access: Published
//  Description: Disables the simulated network latency started by a
//               previous call to start_delay().  Datagrams will once
//               again be visible as soon as they are received.
////////////////////////////////////////////////////////////////////
void CConnectionRepository::
stop_delay() {
#ifdef HAVE_NET
  _qcr.stop_delay();
#endif  // HAVE_NET
#ifdef HAVE_OPENSSL
  if (_http_conn != (SocketStream *)NULL) {
    _http_conn->stop_delay();
  }
#endif  // HAVE_OPENSSL
}
#endif  // SIMULATE_NETWORK_DELAY

////////////////////////////////////////////////////////////////////
//     Function: CConnectionRepository::check_datagram//       Access: Published
//  Description: Returns true if a new datagram is available, false
//               otherwise.  If the return value is true, the new
//               datagram may be retrieved via get_datagram(), or
//               preferably, with get_datagram_iterator() and
//               get_msg_type().
////////////////////////////////////////////////////////////////////
bool CConnectionRepository::
check_datagram() {
  if (_simulated_disconnect) {
    return false;
  }
  #ifdef WANT_NATIVE_NET
  if(_native)
    _bdc.Flush();
  #endif //WANT_NATIVE_NET
  while (do_check_datagram()) { //Read a datagram
    if (get_verbose()) {
      describe_message(nout, "RECV", _dg);
    }

    // Start breaking apart the datagram.
    _di = DatagramIterator(_dg);

    if (!_client_datagram) 
    {
      unsigned char  wc_cnt;
      wc_cnt = _di.get_uint8();
      _msg_channels.clear();
      for(unsigned char lp1 = 0; lp1 < wc_cnt; lp1++)
      {
            CHANNEL_TYPE  schan  = _di.get_uint64();
            _msg_channels.push_back(schan);
      }
      _msg_sender = _di.get_uint64();
      
#ifdef HAVE_PYTHON
      // For now, we need to stuff this field onto the Python
      // structure, to support legacy code that expects to find it
      // there.
      if (_python_repository != (PyObject *)NULL) {
        PyObject *value = PyLong_FromUnsignedLongLong(_msg_sender);
        PyObject_SetAttrString(_python_repository, "msgSender", value);
        Py_DECREF(value);
      }
#endif  // HAVE_PYTHON
    }

    _msg_type = _di.get_uint16();
    // Is this a message that we can process directly?
    switch (_msg_type) {
#ifdef HAVE_PYTHON
    case CLIENT_OBJECT_UPDATE_FIELD:
    case STATESERVER_OBJECT_UPDATE_FIELD:
      if (_has_owner_view) {
        if (!handle_update_field_owner()) {
          return false;
        }
      } else {
        if (!handle_update_field()) {
          return false;
        }
      }
      break;
#endif  // HAVE_PYTHON

    default:
      // Some unknown message; let the caller deal with it.
      return true;
    }
  }

  // No datagrams available.
  return false;
}

////////////////////////////////////////////////////////////////////
//     Function: CConnectionRepository::is_connected
//       Access: Published
//  Description: Returns true if the connection to the gameserver is
//               established and still good, false if we are not
//               connected.  A false value means either (a) we never
//               successfully connected, (b) we explicitly called
//               disconnect(), or (c) we were connected, but the
//               connection was spontaneously lost.
////////////////////////////////////////////////////////////////////
bool CConnectionRepository::
is_connected() {

#ifdef WANT_NATIVE_NET
  if(_native)
    return (_bdc.IsConnected());
#endif

#ifdef HAVE_NET
  if (_net_conn) {
    if (_qcm.reset_connection_available()) {
      PT(Connection) reset_connection;
      if (_qcm.get_reset_connection(reset_connection)) {
        _qcm.close_connection(reset_connection);
        if (reset_connection == _net_conn) {
          // Whoops, lost our connection.
          _net_conn = NULL;
          return false;
        }
      }
    }
    return true;
  }
#endif  // HAVE_NET

#ifdef HAVE_OPENSSL
  if (_http_conn) {
    if (!_http_conn->is_closed()) {
      return true;
    }

    // Connection lost.
    delete _http_conn;
    _http_conn = NULL;
  }
#endif  // HAVE_OPENSSL

  return false;
}

////////////////////////////////////////////////////////////////////
//     Function: CConnectionRepository::send_datagram
//       Access: Published
//  Description: Queues the indicated datagram for sending to the
//               server.  It may not get send immediately if
//               collect_tcp is in effect; call flush() to guarantee
//               it is sent now.
////////////////////////////////////////////////////////////////////
bool CConnectionRepository::
send_datagram(const Datagram &dg) {
  if (_simulated_disconnect) {
    distributed_cat.warning()
      << "Unable to send datagram during simulated disconnect.\n";
    return false;
  }

  if (get_verbose()) {
    describe_message(nout, "SEND", dg);
  }

#ifdef WANT_NATIVE_NET
  if(_native)
    return _bdc.SendMessage(dg);
#endif

#ifdef HAVE_NET
  if (_net_conn) {
    _cw.send(dg, _net_conn);
    return true;
  }
#endif  // HAVE_NET

#ifdef HAVE_OPENSSL
  if (_http_conn) {
    if (!_http_conn->send_datagram(dg)) {
      distributed_cat.warning()
        << "Could not send datagram.\n";
      return false;
    }

    return true;
  }
#endif  // HAVE_OPENSSL

  distributed_cat.warning()
    << "Unable to send datagram after connection is closed.\n";
  return false;
}

////////////////////////////////////////////////////////////////////
//     Function: CConnectionRepository::consider_flush
//       Access: Published
//  Description: Sends the most recently queued data if enough time
//               has elapsed.  This only has meaning if
//               set_collect_tcp() has been set to true.
////////////////////////////////////////////////////////////////////
bool CConnectionRepository::
consider_flush() {
  if (_simulated_disconnect) {
    return false;
  }

#ifdef WANT_NATIVE_NET
  if(_native)
    return true;  //Maybe we should just flush here for now?
#endif

#ifdef HAVE_NET
  if (_net_conn) {
    return _net_conn->consider_flush();
  }
#endif  // HAVE_NET

#ifdef HAVE_OPENSSL
  if (_http_conn) {
    return _http_conn->consider_flush();
  }
#endif  // HAVE_OPENSSL

  return false;
}

////////////////////////////////////////////////////////////////////
//     Function: CConnectionRepository::flush
//       Access: Published
//  Description: Sends the most recently queued data now.  This only
//               has meaning if set_collect_tcp() has been set to
//               true.
////////////////////////////////////////////////////////////////////
bool CConnectionRepository::
flush() {
  if (_simulated_disconnect) {
    return false;
  }
  #ifdef WANT_NATIVE_NET
  if(_native)
    return _bdc.Flush();
  #endif

  #ifdef HAVE_NET
  if (_net_conn) {
    return _net_conn->flush();
  }
  #endif  // HAVE_NET

  #ifdef HAVE_OPENSSL
  if (_http_conn) {
    return _http_conn->flush();
  }
  #endif  // HAVE_OPENSSL

  return false;
}

////////////////////////////////////////////////////////////////////
//     Function: CConnectionRepository::disconnect
//       Access: Published
//  Description: Closes the connection to the server.
////////////////////////////////////////////////////////////////////
void CConnectionRepository::
disconnect() {
  #ifdef WANT_NATIVE_NET
  if(_native) {
    _bdc.Reset();
    _bdc.ClearAddresses();
  }
  #endif
  #ifdef HAVE_NET
  if (_net_conn) {
    _qcm.close_connection(_net_conn);
    _net_conn = NULL;
  }
  #endif  // HAVE_NET

  #ifdef HAVE_OPENSSL
  if (_http_conn) {
    _http_conn->close();
    delete _http_conn;
    _http_conn = NULL;
  }
  #endif  // HAVE_OPENSSL

  _simulated_disconnect = false;
}

////////////////////////////////////////////////////////////////////
//     Function: CConnectionRepository::do_check_datagram
//       Access: Private
//  Description: The private implementation of check_datagram(), this
//               gets one datagram if it is available.
////////////////////////////////////////////////////////////////////
bool CConnectionRepository::
do_check_datagram() {
  #ifdef WANT_NATIVE_NET
  if(_native) {
    return _bdc.GetMessage(_dg);
  }
  #endif
  #ifdef HAVE_NET
  if (_net_conn) {
    _net_conn->consider_flush();
    if (_qcr.get_overflow_flag()) {
      throw_event(get_overflow_event_name());
      _qcr.reset_overflow_flag();
    }
    return (_qcr.data_available() && _qcr.get_data(_dg));
  }
  #endif  // HAVE_NET

  #ifdef HAVE_OPENSSL
  if (_http_conn) {
    _http_conn->consider_flush();
    return _http_conn->receive_datagram(_dg);
  }
  #endif  // HAVE_OPENSSL


  return false;
}

////////////////////////////////////////////////////////////////////
//     Function: CConnectionRepository::handle_update_field
//       Access: Private
//  Description: Directly handles an update message on a field.
//               Python never touches the datagram; it just gets its
//               distributed method called with the appropriate
//               parameters.  Returns true if everything is ok, false
//               if there was an error processing the field's update
//               method.
////////////////////////////////////////////////////////////////////
bool CConnectionRepository::
handle_update_field() {
  #ifdef HAVE_PYTHON
  PStatTimer timer(_update_pcollector);
  unsigned int do_id = _di.get_uint32();
  if (_python_repository != (PyObject *)NULL) {
    PyObject *doId2do =
      PyObject_GetAttrString(_python_repository, "doId2do");
    nassertr(doId2do != NULL, false);

    #ifdef USE_PYTHON_2_2_OR_EARLIER
    PyObject *doId = PyInt_FromLong(do_id);
    #else
    PyObject *doId = PyLong_FromUnsignedLong(do_id);
    #endif
    PyObject *distobj = PyDict_GetItem(doId2do, doId);
    Py_DECREF(doId);
    Py_DECREF(doId2do);

    if (distobj != NULL) {
      PyObject *dclass_obj = PyObject_GetAttrString(distobj, "dclass");
      nassertr(dclass_obj != NULL, false);

      PyObject *dclass_this = PyObject_GetAttrString(dclass_obj, "this");
      Py_DECREF(dclass_obj);
      nassertr(dclass_this != NULL, false);

      DCClass *dclass = (DCClass *)PyInt_AsLong(dclass_this);
      Py_DECREF(dclass_this);

      // It's a good idea to ensure the reference count to distobj is
      // raised while we call the update method--otherwise, the update
      // method might get into trouble if it tried to delete the
      // object from the doId2do map.
      Py_INCREF(distobj);
      dclass->receive_update(distobj, _di); 
      Py_DECREF(distobj);
      
      if (PyErr_Occurred()) {
        return false;
      }
    }

  }
  #endif  // HAVE_PYTHON  

  return true;
}

////////////////////////////////////////////////////////////////////
//     Function: CConnectionRepository::handle_update_field_owner
//       Access: Private
//  Description: Directly handles an update message on a field.
//               Supports 'owner' views of objects, separate from 'visible'
//               view, and forwards fields to the appropriate view(s) based
//               on DC flags.  Python never touches the datagram; it just
//               gets its distributed method called with the appropriate
//               parameters.  Returns true if everything is ok, false if
//               there was an error processing the field's update method.
////////////////////////////////////////////////////////////////////
bool CConnectionRepository::
handle_update_field_owner() {
  #ifdef HAVE_PYTHON
  PStatTimer timer(_update_pcollector);
  unsigned int do_id = _di.get_uint32();
  if (_python_repository != (PyObject *)NULL) {
    PyObject *doId2do =
      PyObject_GetAttrString(_python_repository, "doId2do");
    nassertr(doId2do != NULL, false);

    PyObject *doId2ownerView =
      PyObject_GetAttrString(_python_repository, "doId2ownerView");
    nassertr(doId2ownerView != NULL, false);

    #ifdef USE_PYTHON_2_2_OR_EARLIER
    PyObject *doId = PyInt_FromLong(do_id);
    #else
    PyObject *doId = PyLong_FromUnsignedLong(do_id);
    #endif

    // pass the update to the owner view first
    PyObject *distobjOV = PyDict_GetItem(doId2ownerView, doId);
    Py_DECREF(doId2ownerView);

    if (distobjOV != NULL) {
      PyObject *dclass_obj = PyObject_GetAttrString(distobjOV, "dclass");
      nassertr(dclass_obj != NULL, false);

      PyObject *dclass_this = PyObject_GetAttrString(dclass_obj, "this");
      Py_DECREF(dclass_obj);
      nassertr(dclass_this != NULL, false);

      DCClass *dclass = (DCClass *)PyInt_AsLong(dclass_this);
      Py_DECREF(dclass_this);

      // check if we should forward this update to the owner view
      DCPacker packer;
      packer.set_unpack_data(_di.get_remaining_bytes());
      int field_id = packer.raw_unpack_uint16();
      DCField *field = dclass->get_field_by_index(field_id);
      if (field->is_ownrecv()) {
        // It's a good idea to ensure the reference count to distobjOV is
        // raised while we call the update method--otherwise, the update
        // method might get into trouble if it tried to delete the
        // object from the doId2do map.
        Py_INCREF(distobjOV);
        // make a copy of the datagram iterator so that we can use the main
        // iterator for the non-owner update
        DatagramIterator _odi(_di);
        dclass->receive_update(distobjOV, _odi); 
        Py_DECREF(distobjOV);
      
        if (PyErr_Occurred()) {
          return false;
        }
      }
    }

    // now pass the update to the visible view
    PyObject *distobj = PyDict_GetItem(doId2do, doId);
    Py_DECREF(doId);
    Py_DECREF(doId2do);

    if (distobj != NULL) {
      PyObject *dclass_obj = PyObject_GetAttrString(distobj, "dclass");
      nassertr(dclass_obj != NULL, false);

      PyObject *dclass_this = PyObject_GetAttrString(dclass_obj, "this");
      Py_DECREF(dclass_obj);
      nassertr(dclass_this != NULL, false);

      DCClass *dclass = (DCClass *)PyInt_AsLong(dclass_this);
      Py_DECREF(dclass_this);

      // check if we should forward this update to the owner view
      DCPacker packer;
      packer.set_unpack_data(_di.get_remaining_bytes());
      int field_id = packer.raw_unpack_uint16();
      DCField *field = dclass->get_field_by_index(field_id);
      if (true) {//field->is_broadcast()) {
        // It's a good idea to ensure the reference count to distobj is
        // raised while we call the update method--otherwise, the update
        // method might get into trouble if it tried to delete the
        // object from the doId2do map.
        Py_INCREF(distobj);
        dclass->receive_update(distobj, _di); 
        Py_DECREF(distobj);
      
        if (PyErr_Occurred()) {
          return false;
        }
      }
    }

  }
  #endif  // HAVE_PYTHON  

  return true;
}

////////////////////////////////////////////////////////////////////
//     Function: CConnectionRepository::describe_message
//       Access: Private
//  Description: Unpacks the message and reformats it for user
//               consumption, writing a description on the indicated
//               output stream.
////////////////////////////////////////////////////////////////////
void CConnectionRepository::
describe_message(ostream &out, const string &prefix, 
                 const Datagram &dg) const {
  DCPacker packer;
  
  packer.set_unpack_data(dg.get_message());
  CHANNEL_TYPE do_id;
  int msg_type;
  bool is_update = false;
  string full_prefix = "CR::" + prefix;

  if (!_client_datagram) 
  {
    unsigned char mcnt = packer.raw_unpack_uint8();
    for( ;mcnt > 0; mcnt--)
        packer.RAW_UNPACK_CHANNEL();  // msg_channel

    packer.RAW_UNPACK_CHANNEL();  // msg_sender
    msg_type = packer.raw_unpack_uint16();
    is_update = (msg_type == STATESERVER_OBJECT_UPDATE_FIELD);
    
  } else {
    msg_type = packer.raw_unpack_uint16();
    is_update = (msg_type == CLIENT_OBJECT_UPDATE_FIELD);
  }

  if (!is_update) {
    // figure out the name of the message
    // TODO: print out the arguments to the message
    string msgName;

    #ifdef HAVE_PYTHON
    if (_python_repository != (PyObject *)NULL) {
      PyObject *msgId = PyLong_FromLong(msg_type);
      nassertv(msgId != NULL);
      PyObject *methodName = PyString_FromString("_getMsgName");
      nassertv(methodName != NULL);

      PyObject *result = PyObject_CallMethodObjArgs(_python_repository, methodName,
						    msgId, NULL);
      nassertv(result != NULL);

      msgName += string(PyString_AsString(result));

      Py_DECREF(methodName);
      Py_DECREF(msgId);
      Py_DECREF(result);
    }
    #endif
    if (msgName.length() == 0) {
      msgName += "unknown message ";
      msgName += msg_type;
      msgName += "\n";
    }
    out << full_prefix << ":" << msgName << "\n";
    dg.dump_hex(out, 2);

  } else {
    // It's an update message.  Figure out what dclass the object is
    // based on its doId, so we can decode the rest of the message.
    do_id = packer.raw_unpack_uint32();
    DCClass *dclass = NULL;

    #ifdef HAVE_PYTHON
    if (_python_repository != (PyObject *)NULL) {
      PyObject *doId2do =
        PyObject_GetAttrString(_python_repository, "doId2do");
      nassertv(doId2do != NULL);

      #ifdef USE_PYTHON_2_2_OR_EARLIER
      PyObject *doId = PyInt_FromLong(do_id);
      #else
      PyObject *doId = PyLong_FromUnsignedLong(do_id);
      #endif
      PyObject *distobj = PyDict_GetItem(doId2do, doId);
      Py_DECREF(doId);
      Py_DECREF(doId2do);

      if (distobj != NULL) {
        PyObject *dclass_obj = PyObject_GetAttrString(distobj, "dclass");
        nassertv(dclass_obj != NULL);

        PyObject *dclass_this = PyObject_GetAttrString(dclass_obj, "this");
        Py_DECREF(dclass_obj);
        nassertv(dclass_this != NULL);
        
        dclass = (DCClass *)PyInt_AsLong(dclass_this);
        Py_DECREF(dclass_this);
      }
    }
    #endif  // HAVE_PYTHON  

    int field_id = packer.raw_unpack_uint16();

    if (dclass == (DCClass *)NULL) {
      out << full_prefix << "update for unknown object " << do_id 
          << ", field " << field_id << "\n";

    } else {
      out << full_prefix <<
        ":" << dclass->get_name() << "(" << do_id << ").";
      DCField *field = dclass->get_field_by_index(field_id);
      if (field == (DCField *)NULL) {
        out << "unknown field " << field_id << "\n";
        
      } else {
        out << field->get_name();
        packer.begin_unpack(field);
        packer.unpack_and_format(out);
        packer.end_unpack();
        out << "\n";
      }
    }
  }
}