2003-04-10 Havoc Pennington <hp@pobox.com>

[platform/upstream/dbus.git] / dbus / dbus-connection.c

/* -*- mode: C; c-file-style: "gnu" -*- */
/* dbus-connection.c DBusConnection object
 *
 * Copyright (C) 2002, 2003  Red Hat Inc.
 *
 * Licensed under the Academic Free License version 1.2
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 */

#include "dbus-connection.h"
#include "dbus-list.h"
#include "dbus-timeout.h"
#include "dbus-transport.h"
#include "dbus-watch.h"
#include "dbus-connection-internal.h"
#include "dbus-list.h"
#include "dbus-hash.h"
#include "dbus-message-internal.h"
#include "dbus-message-handler.h"
#include "dbus-threads.h"
#include "dbus-protocol.h"
#include "dbus-dataslot.h"

/**
 * @defgroup DBusConnection DBusConnection
 * @ingroup  DBus
 * @brief Connection to another application
 *
 * A DBusConnection represents a connection to another
 * application. Messages can be sent and received via this connection.
 *
 * The connection maintains a queue of incoming messages and a queue
 * of outgoing messages. dbus_connection_pop_message() and friends
 * can be used to read incoming messages from the queue.
 * Outgoing messages are automatically discarded as they are
 * written to the network.
 *
 * In brief a DBusConnection is a message queue associated with some
 * message transport mechanism such as a socket.
 * 
 */

/**
 * @defgroup DBusConnectionInternals DBusConnection implementation details
 * @ingroup  DBusInternals
 * @brief Implementation details of DBusConnection
 *
 * @{
 */

/** default timeout value when waiting for a message reply */
#define DEFAULT_TIMEOUT_VALUE (15 * 1000)

static dbus_bool_t _dbus_modify_sigpipe = TRUE;

/**
 * Implementation details of DBusConnection. All fields are private.
 */
struct DBusConnection
{
  int refcount; /**< Reference count. */

  DBusMutex *mutex; /**< Lock on the entire DBusConnection */

  dbus_bool_t dispatch_acquired; /**< Protects dispatch() */
  DBusCondVar *dispatch_cond;    /**< Protects dispatch() */

  dbus_bool_t io_path_acquired;  /**< Protects transport io path */
  DBusCondVar *io_path_cond;     /**< Protects transport io path */
  
  DBusList *outgoing_messages; /**< Queue of messages we need to send, send the end of the list first. */
  DBusList *incoming_messages; /**< Queue of messages we have received, end of the list received most recently. */

  DBusMessage *message_borrowed; /**< True if the first incoming message has been borrowed */
  DBusCondVar *message_returned_cond; /**< Used with dbus_connection_borrow_message() */
  
  int n_outgoing;              /**< Length of outgoing queue. */
  int n_incoming;              /**< Length of incoming queue. */
  
  DBusTransport *transport;    /**< Object that sends/receives messages over network. */
  DBusWatchList *watches;      /**< Stores active watches. */
  DBusTimeoutList *timeouts;   /**< Stores active timeouts. */
  
  DBusHashTable *handler_table; /**< Table of registered DBusMessageHandler */
  DBusList *filter_list;        /**< List of filters. */

  DBusDataSlotList slot_list;   /**< Data stored by allocated integer ID */

  DBusHashTable *pending_replies;  /**< Hash of message serials and their message handlers. */  
  DBusCounter *connection_counter; /**< Counter that we decrement when finalized */
  
  int client_serial;            /**< Client serial. Increments each time a message is sent  */
  DBusList *disconnect_message_link; /**< Preallocated list node for queueing the disconnection message */

  DBusWakeupMainFunction wakeup_main_function; /**< Function to wake up the mainloop  */
  void *wakeup_main_data; /**< Application data for wakeup_main_function */
  DBusFreeFunction free_wakeup_main_data; /**< free wakeup_main_data */

  DBusDispatchStatusFunction dispatch_status_function; /**< Function on dispatch status changes  */
  void *dispatch_status_data; /**< Application data for dispatch_status_function */
  DBusFreeFunction free_dispatch_status_data; /**< free dispatch_status_data */

  DBusDispatchStatus last_dispatch_status;
};

typedef struct
{
  DBusConnection *connection;
  DBusMessageHandler *handler;
  DBusTimeout *timeout;
  int serial;

  DBusList *timeout_link; /* Preallocated timeout response */
  
  dbus_bool_t timeout_added;
  dbus_bool_t connection_added;
} ReplyHandlerData;

static void reply_handler_data_free (ReplyHandlerData *data);

static void               _dbus_connection_remove_timeout_locked         (DBusConnection     *connection,
                                                                          DBusTimeout        *timeout);
static DBusDispatchStatus _dbus_connection_get_dispatch_status_unlocked  (DBusConnection     *connection);
static void               _dbus_connection_update_dispatch_status_locked (DBusConnection     *connection,
                                                                          DBusDispatchStatus  new_status);


/**
 * Acquires the connection lock.
 *
 * @param connection the connection.
 */
void
_dbus_connection_lock (DBusConnection *connection)
{
  dbus_mutex_lock (connection->mutex);
}

/**
 * Releases the connection lock.
 *
 * @param connection the connection.
 */
void
_dbus_connection_unlock (DBusConnection *connection)
{
  dbus_mutex_unlock (connection->mutex);
}

/**
 * Wakes up the main loop if it is sleeping
 * Needed if we're e.g. queueing outgoing messages
 * on a thread while the mainloop sleeps.
 *
 * @param connection the connection.
 */
static void
_dbus_connection_wakeup_mainloop (DBusConnection *connection)
{
  if (connection->wakeup_main_function)
    (*connection->wakeup_main_function) (connection->wakeup_main_data);
}

/**
 * Adds a message to the incoming message queue, returning #FALSE
 * if there's insufficient memory to queue the message.
 * Does not take over refcount of the message.
 *
 * @param connection the connection.
 * @param message the message to queue.
 * @returns #TRUE on success.
 */
dbus_bool_t
_dbus_connection_queue_received_message (DBusConnection *connection,
                                         DBusMessage    *message)
{
  DBusList *link;

  link = _dbus_list_alloc_link (message);
  if (link == NULL)
    return FALSE;

  dbus_message_ref (message);
  _dbus_connection_queue_received_message_link (connection, link);

  return TRUE;
}

/**
 * Adds a message-containing list link to the incoming message queue,
 * taking ownership of the link and the message's current refcount.
 * Cannot fail due to lack of memory.
 *
 * @param connection the connection.
 * @param link the message link to queue.
 */
void
_dbus_connection_queue_received_message_link (DBusConnection  *connection,
                                              DBusList        *link)
{
  ReplyHandlerData *reply_handler_data;
  dbus_int32_t reply_serial;
  DBusMessage *message;
  
  _dbus_assert (_dbus_transport_get_is_authenticated (connection->transport));
  
  _dbus_list_append_link (&connection->incoming_messages,
                          link);
  message = link->data;
  
  /* If this is a reply we're waiting on, remove timeout for it */
  reply_serial = dbus_message_get_reply_serial (message);
  if (reply_serial != -1)
    {
      reply_handler_data = _dbus_hash_table_lookup_int (connection->pending_replies,
                                                        reply_serial);
      if (reply_handler_data != NULL)
        {
          if (reply_handler_data->timeout_added)
            _dbus_connection_remove_timeout_locked (connection,
                                                    reply_handler_data->timeout);
          reply_handler_data->timeout_added = FALSE;
        }
    }
  
  connection->n_incoming += 1;

  _dbus_connection_wakeup_mainloop (connection);
  
  _dbus_assert (dbus_message_get_name (message) != NULL);
  _dbus_verbose ("Message %p (%s) added to incoming queue %p, %d incoming\n",
                 message, dbus_message_get_name (message),
                 connection,
                 connection->n_incoming);
}

/**
 * Adds a link + message to the incoming message queue.
 * Can't fail. Takes ownership of both link and message.
 *
 * @param connection the connection.
 * @param link the list node and message to queue.
 *
 * @todo This needs to wake up the mainloop if it is in
 * a poll/select and this is a multithreaded app.
 */
static void
_dbus_connection_queue_synthesized_message_link (DBusConnection *connection,
                                                 DBusList *link)
{
  _dbus_list_append_link (&connection->incoming_messages, link);

  connection->n_incoming += 1;

  _dbus_connection_wakeup_mainloop (connection);
  
  _dbus_verbose ("Synthesized message %p added to incoming queue %p, %d incoming\n",
                 link->data, connection, connection->n_incoming);
}


/**
 * Checks whether there are messages in the outgoing message queue.
 *
 * @param connection the connection.
 * @returns #TRUE if the outgoing queue is non-empty.
 */
dbus_bool_t
_dbus_connection_have_messages_to_send (DBusConnection *connection)
{
  return connection->outgoing_messages != NULL;
}

/**
 * Gets the next outgoing message. The message remains in the
 * queue, and the caller does not own a reference to it.
 *
 * @param connection the connection.
 * @returns the message to be sent.
 */ 
DBusMessage*
_dbus_connection_get_message_to_send (DBusConnection *connection)
{
  return _dbus_list_get_last (&connection->outgoing_messages);
}

/**
 * Notifies the connection that a message has been sent, so the
 * message can be removed from the outgoing queue.
 *
 * @param connection the connection.
 * @param message the message that was sent.
 */
void
_dbus_connection_message_sent (DBusConnection *connection,
                               DBusMessage    *message)
{
  _dbus_assert (_dbus_transport_get_is_authenticated (connection->transport));
  _dbus_assert (message == _dbus_list_get_last (&connection->outgoing_messages));
  
  _dbus_list_pop_last (&connection->outgoing_messages);
  
  connection->n_outgoing -= 1;

  _dbus_verbose ("Message %p (%s) removed from outgoing queue %p, %d left to send\n",
                 message, dbus_message_get_name (message),
                 connection, connection->n_outgoing);

  dbus_message_unref (message);
  
  if (connection->n_outgoing == 0)
    _dbus_transport_messages_pending (connection->transport,
                                      connection->n_outgoing);  
}

/**
 * Adds a watch using the connection's DBusAddWatchFunction if
 * available. Otherwise records the watch to be added when said
 * function is available. Also re-adds the watch if the
 * DBusAddWatchFunction changes. May fail due to lack of memory.
 *
 * @param connection the connection.
 * @param watch the watch to add.
 * @returns #TRUE on success.
 */
dbus_bool_t
_dbus_connection_add_watch (DBusConnection *connection,
                            DBusWatch      *watch)
{
  if (connection->watches) /* null during finalize */
    return _dbus_watch_list_add_watch (connection->watches,
                                       watch);
  else
    return FALSE;
}

/**
 * Removes a watch using the connection's DBusRemoveWatchFunction
 * if available. It's an error to call this function on a watch
 * that was not previously added.
 *
 * @param connection the connection.
 * @param watch the watch to remove.
 */
void
_dbus_connection_remove_watch (DBusConnection *connection,
                               DBusWatch      *watch)
{
  if (connection->watches) /* null during finalize */
    _dbus_watch_list_remove_watch (connection->watches,
                                   watch);
}

/**
 * Toggles a watch and notifies app via connection's
 * DBusWatchToggledFunction if available. It's an error to call this
 * function on a watch that was not previously added.
 *
 * @param connection the connection.
 * @param watch the watch to toggle.
 * @param enabled whether to enable or disable
 */
void
_dbus_connection_toggle_watch (DBusConnection *connection,
                               DBusWatch      *watch,
                               dbus_bool_t     enabled)
{
  if (connection->watches) /* null during finalize */
    _dbus_watch_list_toggle_watch (connection->watches,
                                   watch, enabled);
}

/**
 * Adds a timeout using the connection's DBusAddTimeoutFunction if
 * available. Otherwise records the timeout to be added when said
 * function is available. Also re-adds the timeout if the
 * DBusAddTimeoutFunction changes. May fail due to lack of memory.
 * The timeout will fire repeatedly until removed.
 *
 * @param connection the connection.
 * @param timeout the timeout to add.
 * @returns #TRUE on success.
 */
dbus_bool_t
_dbus_connection_add_timeout (DBusConnection *connection,
                              DBusTimeout    *timeout)
{
 if (connection->timeouts) /* null during finalize */
    return _dbus_timeout_list_add_timeout (connection->timeouts,
                                           timeout);
  else
    return FALSE;  
}

/**
 * Removes a timeout using the connection's DBusRemoveTimeoutFunction
 * if available. It's an error to call this function on a timeout
 * that was not previously added.
 *
 * @param connection the connection.
 * @param timeout the timeout to remove.
 */
void
_dbus_connection_remove_timeout (DBusConnection *connection,
                                 DBusTimeout    *timeout)
{
  if (connection->timeouts) /* null during finalize */
    _dbus_timeout_list_remove_timeout (connection->timeouts,
                                       timeout);
}

static void
_dbus_connection_remove_timeout_locked (DBusConnection *connection,
                                        DBusTimeout    *timeout)
{
  dbus_mutex_lock (connection->mutex);
  _dbus_connection_remove_timeout (connection, timeout);
  dbus_mutex_unlock (connection->mutex);
}

/**
 * Toggles a timeout and notifies app via connection's
 * DBusTimeoutToggledFunction if available. It's an error to call this
 * function on a timeout that was not previously added.
 *
 * @param connection the connection.
 * @param timeout the timeout to toggle.
 * @param enabled whether to enable or disable
 */
void
_dbus_connection_toggle_timeout (DBusConnection *connection,
                                 DBusTimeout      *timeout,
                                 dbus_bool_t     enabled)
{
  if (connection->timeouts) /* null during finalize */
    _dbus_timeout_list_toggle_timeout (connection->timeouts,
                                       timeout, enabled);
}

/**
 * Tells the connection that the transport has been disconnected.
 * Results in posting a disconnect message on the incoming message
 * queue.  Only has an effect the first time it's called.
 *
 * @param connection the connection
 */
void
_dbus_connection_notify_disconnected (DBusConnection *connection)
{
  if (connection->disconnect_message_link)
    {
      /* We haven't sent the disconnect message already */
      _dbus_connection_queue_synthesized_message_link (connection,
                                                       connection->disconnect_message_link);
      connection->disconnect_message_link = NULL;
    }
}


/**
 * Acquire the transporter I/O path. This must be done before
 * doing any I/O in the transporter. May sleep and drop the
 * connection mutex while waiting for the I/O path.
 *
 * @param connection the connection.
 * @param timeout_milliseconds maximum blocking time, or -1 for no limit.
 * @returns TRUE if the I/O path was acquired.
 */
static dbus_bool_t
_dbus_connection_acquire_io_path (DBusConnection *connection,
                                  int timeout_milliseconds)
{
  dbus_bool_t res = TRUE;

  if (connection->io_path_acquired)
    {
      if (timeout_milliseconds != -1) 
        res = dbus_condvar_wait_timeout (connection->io_path_cond,
                                         connection->mutex,
                                         timeout_milliseconds);
      else
        dbus_condvar_wait (connection->io_path_cond, connection->mutex);
    }
  
  if (res)
    {
      _dbus_assert (!connection->io_path_acquired);

      connection->io_path_acquired = TRUE;
    }
  
  return res;
}

/**
 * Release the I/O path when you're done with it. Only call
 * after you've acquired the I/O. Wakes up at most one thread
 * currently waiting to acquire the I/O path.
 *
 * @param connection the connection.
 */
static void
_dbus_connection_release_io_path (DBusConnection *connection)
{
  _dbus_assert (connection->io_path_acquired);

  connection->io_path_acquired = FALSE;
  dbus_condvar_wake_one (connection->io_path_cond);
}


/**
 * Queues incoming messages and sends outgoing messages for this
 * connection, optionally blocking in the process. Each call to
 * _dbus_connection_do_iteration() will call select() or poll() one
 * time and then read or write data if possible.
 *
 * The purpose of this function is to be able to flush outgoing
 * messages or queue up incoming messages without returning
 * control to the application and causing reentrancy weirdness.
 *
 * The flags parameter allows you to specify whether to
 * read incoming messages, write outgoing messages, or both,
 * and whether to block if no immediate action is possible.
 *
 * The timeout_milliseconds parameter does nothing unless the
 * iteration is blocking.
 *
 * If there are no outgoing messages and DBUS_ITERATION_DO_READING
 * wasn't specified, then it's impossible to block, even if
 * you specify DBUS_ITERATION_BLOCK; in that case the function
 * returns immediately.
 * 
 * @param connection the connection.
 * @param flags iteration flags.
 * @param timeout_milliseconds maximum blocking time, or -1 for no limit.
 */
void
_dbus_connection_do_iteration (DBusConnection *connection,
                               unsigned int    flags,
                               int             timeout_milliseconds)
{
  if (connection->n_outgoing == 0)
    flags &= ~DBUS_ITERATION_DO_WRITING;

  if (_dbus_connection_acquire_io_path (connection,
                                        (flags & DBUS_ITERATION_BLOCK)?timeout_milliseconds:0))
    {
      _dbus_transport_do_iteration (connection->transport,
                                    flags, timeout_milliseconds);
      _dbus_connection_release_io_path (connection);
    }
}

/**
 * Creates a new connection for the given transport.  A transport
 * represents a message stream that uses some concrete mechanism, such
 * as UNIX domain sockets. May return #NULL if insufficient
 * memory exists to create the connection.
 *
 * @param transport the transport.
 * @returns the new connection, or #NULL on failure.
 */
DBusConnection*
_dbus_connection_new_for_transport (DBusTransport *transport)
{
  DBusConnection *connection;
  DBusWatchList *watch_list;
  DBusTimeoutList *timeout_list;
  DBusHashTable *handler_table, *pending_replies;
  DBusMutex *mutex;
  DBusCondVar *message_returned_cond;
  DBusCondVar *dispatch_cond;
  DBusCondVar *io_path_cond;
  DBusList *disconnect_link;
  DBusMessage *disconnect_message;

  watch_list = NULL;
  connection = NULL;
  handler_table = NULL;
  pending_replies = NULL;
  timeout_list = NULL;
  mutex = NULL;
  message_returned_cond = NULL;
  dispatch_cond = NULL;
  io_path_cond = NULL;
  disconnect_link = NULL;
  disconnect_message = NULL;
  
  watch_list = _dbus_watch_list_new ();
  if (watch_list == NULL)
    goto error;

  timeout_list = _dbus_timeout_list_new ();
  if (timeout_list == NULL)
    goto error;
  
  handler_table =
    _dbus_hash_table_new (DBUS_HASH_STRING,
                          dbus_free, NULL);
  if (handler_table == NULL)
    goto error;

  pending_replies =
    _dbus_hash_table_new (DBUS_HASH_INT,
                          NULL, (DBusFreeFunction)reply_handler_data_free);
  if (pending_replies == NULL)
    goto error;
  
  connection = dbus_new0 (DBusConnection, 1);
  if (connection == NULL)
    goto error;

  mutex = dbus_mutex_new ();
  if (mutex == NULL)
    goto error;
  
  message_returned_cond = dbus_condvar_new ();
  if (message_returned_cond == NULL)
    goto error;
  
  dispatch_cond = dbus_condvar_new ();
  if (dispatch_cond == NULL)
    goto error;
  
  io_path_cond = dbus_condvar_new ();
  if (io_path_cond == NULL)
    goto error;

  disconnect_message = dbus_message_new (NULL, DBUS_MESSAGE_LOCAL_DISCONNECT);
  if (disconnect_message == NULL)
    goto error;

  disconnect_link = _dbus_list_alloc_link (disconnect_message);
  if (disconnect_link == NULL)
    goto error;

  if (_dbus_modify_sigpipe)
    _dbus_disable_sigpipe ();
  
  connection->refcount = 1;
  connection->mutex = mutex;
  connection->dispatch_cond = dispatch_cond;
  connection->io_path_cond = io_path_cond;
  connection->message_returned_cond = message_returned_cond;
  connection->transport = transport;
  connection->watches = watch_list;
  connection->timeouts = timeout_list;
  connection->handler_table = handler_table;
  connection->pending_replies = pending_replies;
  connection->filter_list = NULL;
  connection->last_dispatch_status = DBUS_DISPATCH_COMPLETE; /* so we're notified first time there's data */
  
  _dbus_data_slot_list_init (&connection->slot_list);

  connection->client_serial = 1;

  connection->disconnect_message_link = disconnect_link;
  
  if (!_dbus_transport_set_connection (transport, connection))
    goto error;

  _dbus_transport_ref (transport);  
  
  return connection;
  
 error:
  if (disconnect_message != NULL)
    dbus_message_unref (disconnect_message);
  
  if (disconnect_link != NULL)
    _dbus_list_free_link (disconnect_link);
  
  if (io_path_cond != NULL)
    dbus_condvar_free (io_path_cond);
  
  if (dispatch_cond != NULL)
    dbus_condvar_free (dispatch_cond);
  
  if (message_returned_cond != NULL)
    dbus_condvar_free (message_returned_cond);
  
  if (mutex != NULL)
    dbus_mutex_free (mutex);

  if (connection != NULL)
    dbus_free (connection);

  if (handler_table)
    _dbus_hash_table_unref (handler_table);

  if (pending_replies)
    _dbus_hash_table_unref (pending_replies);
  
  if (watch_list)
    _dbus_watch_list_free (watch_list);

  if (timeout_list)
    _dbus_timeout_list_free (timeout_list);
  
  return NULL;
}

static dbus_int32_t
_dbus_connection_get_next_client_serial (DBusConnection *connection)
{
  int serial;

  serial = connection->client_serial++;

  if (connection->client_serial < 0)
    connection->client_serial = 1;
  
  return serial;
}

/**
 * Used to notify a connection when a DBusMessageHandler is
 * destroyed, so the connection can drop any reference
 * to the handler. This is a private function, but still
 * takes the connection lock. Don't call it with the lock held.
 *
 * @todo needs to check in pending_replies too.
 * 
 * @param connection the connection
 * @param handler the handler
 */
void
_dbus_connection_handler_destroyed_locked (DBusConnection     *connection,
                                           DBusMessageHandler *handler)
{
  DBusHashIter iter;
  DBusList *link;

  dbus_mutex_lock (connection->mutex);
  
  _dbus_hash_iter_init (connection->handler_table, &iter);
  while (_dbus_hash_iter_next (&iter))
    {
      DBusMessageHandler *h = _dbus_hash_iter_get_value (&iter);

      if (h == handler)
        _dbus_hash_iter_remove_entry (&iter);
    }

  link = _dbus_list_get_first_link (&connection->filter_list);
  while (link != NULL)
    {
      DBusMessageHandler *h = link->data;
      DBusList *next = _dbus_list_get_next_link (&connection->filter_list, link);

      if (h == handler)
        _dbus_list_remove_link (&connection->filter_list,
                                link);
      
      link = next;
    }
  dbus_mutex_unlock (connection->mutex);
}

/**
 * Adds the counter used to count the number of open connections.
 * Increments the counter by one, and saves it to be decremented
 * again when this connection is finalized.
 *
 * @param connection a #DBusConnection
 * @param counter counter that tracks number of connections
 */
void
_dbus_connection_set_connection_counter (DBusConnection *connection,
                                         DBusCounter    *counter)
{
  _dbus_assert (connection->connection_counter == NULL);
  
  connection->connection_counter = counter;
  _dbus_counter_ref (connection->connection_counter);
  _dbus_counter_adjust (connection->connection_counter, 1);
}

/** @} */

/**
 * @addtogroup DBusConnection
 *
 * @{
 */

/**
 * Opens a new connection to a remote address.
 *
 * @todo specify what the address parameter is. Right now
 * it's just the name of a UNIX domain socket. It should be
 * something more complex that encodes which transport to use.
 *
 * If the open fails, the function returns #NULL, and provides
 * a reason for the failure in the result parameter. Pass
 * #NULL for the result parameter if you aren't interested
 * in the reason for failure.
 * 
 * @param address the address.
 * @param error address where an error can be returned.
 * @returns new connection, or #NULL on failure.
 */
DBusConnection*
dbus_connection_open (const char     *address,
                      DBusError      *error)
{
  DBusConnection *connection;
  DBusTransport *transport;

  _DBUS_ASSERT_ERROR_IS_CLEAR (error);
  
  transport = _dbus_transport_open (address, error);
  if (transport == NULL)
    {
      _DBUS_ASSERT_ERROR_IS_SET (error);
      return NULL;
    }
  
  connection = _dbus_connection_new_for_transport (transport);

  _dbus_transport_unref (transport);
  
  if (connection == NULL)
    {
      dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);
      return NULL;
    }
  
  return connection;
}

/**
 * Increments the reference count of a DBusConnection.
 *
 * @param connection the connection.
 */
void
dbus_connection_ref (DBusConnection *connection)
{
  dbus_mutex_lock (connection->mutex);
  _dbus_assert (connection->refcount > 0);

  connection->refcount += 1;
  dbus_mutex_unlock (connection->mutex);
}

/**
 * Increments the reference count of a DBusConnection.
 * Requires that the caller already holds the connection lock.
 *
 * @param connection the connection.
 */
void
_dbus_connection_ref_unlocked (DBusConnection *connection)
{
  _dbus_assert (connection->refcount > 0);
  connection->refcount += 1;
}


/* This is run without the mutex held, but after the last reference
 * to the connection has been dropped we should have no thread-related
 * problems
 */
static void
_dbus_connection_last_unref (DBusConnection *connection)
{
  DBusHashIter iter;
  DBusList *link;

  _dbus_verbose ("Finalizing connection %p\n", connection);
  
  _dbus_assert (connection->refcount == 0);
  
  /* You have to disconnect the connection before unref:ing it. Otherwise
   * you won't get the disconnected message.
   */
  _dbus_assert (!_dbus_transport_get_is_connected (connection->transport));
  
  if (connection->connection_counter != NULL)
    {
      /* subtract ourselves from the counter */
      _dbus_counter_adjust (connection->connection_counter, - 1);
      _dbus_counter_unref (connection->connection_counter);
      connection->connection_counter = NULL;
    }

  /* ---- We're going to call various application callbacks here, hope it doesn't break anything... */
  dbus_connection_set_dispatch_status_function (connection, NULL, NULL, NULL);
  dbus_connection_set_wakeup_main_function (connection, NULL, NULL, NULL);
  dbus_connection_set_unix_user_function (connection, NULL, NULL, NULL);
  
  _dbus_watch_list_free (connection->watches);
  connection->watches = NULL;
  
  _dbus_timeout_list_free (connection->timeouts);
  connection->timeouts = NULL;

  _dbus_data_slot_list_free (&connection->slot_list);
  /* ---- Done with stuff that invokes application callbacks */
  
  _dbus_hash_iter_init (connection->handler_table, &iter);
  while (_dbus_hash_iter_next (&iter))
    {
      DBusMessageHandler *h = _dbus_hash_iter_get_value (&iter);
      
      _dbus_message_handler_remove_connection (h, connection);
    }
  
  link = _dbus_list_get_first_link (&connection->filter_list);
  while (link != NULL)
    {
      DBusMessageHandler *h = link->data;
      DBusList *next = _dbus_list_get_next_link (&connection->filter_list, link);
      
      _dbus_message_handler_remove_connection (h, connection);
      
      link = next;
    }

  _dbus_hash_table_unref (connection->handler_table);
  connection->handler_table = NULL;

  _dbus_hash_table_unref (connection->pending_replies);
  connection->pending_replies = NULL;
  
  _dbus_list_clear (&connection->filter_list);
  
  _dbus_list_foreach (&connection->outgoing_messages,
                      (DBusForeachFunction) dbus_message_unref,
                      NULL);
  _dbus_list_clear (&connection->outgoing_messages);
  
  _dbus_list_foreach (&connection->incoming_messages,
                      (DBusForeachFunction) dbus_message_unref,
                      NULL);
  _dbus_list_clear (&connection->incoming_messages);
  
  _dbus_transport_unref (connection->transport);

  if (connection->disconnect_message_link)
    {
      DBusMessage *message = connection->disconnect_message_link->data;
      dbus_message_unref (message);
      _dbus_list_free_link (connection->disconnect_message_link);
    }
  
  dbus_condvar_free (connection->dispatch_cond);
  dbus_condvar_free (connection->io_path_cond);
  dbus_condvar_free (connection->message_returned_cond);
  
  dbus_mutex_free (connection->mutex);
  
  dbus_free (connection);
}

/**
 * Decrements the reference count of a DBusConnection, and finalizes
 * it if the count reaches zero.  It is a bug to drop the last reference
 * to a connection that has not been disconnected.
 *
 * @todo in practice it can be quite tricky to never unref a connection
 * that's still connected; maybe there's some way we could avoid
 * the requirement.
 *
 * @param connection the connection.
 */
void
dbus_connection_unref (DBusConnection *connection)
{
  dbus_bool_t last_unref;
  
  dbus_mutex_lock (connection->mutex);
  
  _dbus_assert (connection != NULL);
  _dbus_assert (connection->refcount > 0);

  connection->refcount -= 1;
  last_unref = (connection->refcount == 0);

#if 0
  printf ("unref() connection %p count = %d\n", connection, connection->refcount);
#endif
  
  dbus_mutex_unlock (connection->mutex);

  if (last_unref)
    _dbus_connection_last_unref (connection);
}

/**
 * Closes the connection, so no further data can be sent or received.
 * Any further attempts to send data will result in errors.  This
 * function does not affect the connection's reference count.  It's
 * safe to disconnect a connection more than once; all calls after the
 * first do nothing. It's impossible to "reconnect" a connection, a
 * new connection must be created.
 *
 * @param connection the connection.
 */
void
dbus_connection_disconnect (DBusConnection *connection)
{
  dbus_mutex_lock (connection->mutex);
  _dbus_transport_disconnect (connection->transport);
  dbus_mutex_unlock (connection->mutex);
}

/**
 * Gets whether the connection is currently connected.  All
 * connections are connected when they are opened.  A connection may
 * become disconnected when the remote application closes its end, or
 * exits; a connection may also be disconnected with
 * dbus_connection_disconnect().
 *
 * @param connection the connection.
 * @returns #TRUE if the connection is still alive.
 */
dbus_bool_t
dbus_connection_get_is_connected (DBusConnection *connection)
{
  dbus_bool_t res;
  
  dbus_mutex_lock (connection->mutex);
  res = _dbus_transport_get_is_connected (connection->transport);
  dbus_mutex_unlock (connection->mutex);
  
  return res;
}

/**
 * Gets whether the connection was authenticated. (Note that
 * if the connection was authenticated then disconnected,
 * this function still returns #TRUE)
 *
 * @param connection the connection
 * @returns #TRUE if the connection was ever authenticated
 */
dbus_bool_t
dbus_connection_get_is_authenticated (DBusConnection *connection)
{
  dbus_bool_t res;
  
  dbus_mutex_lock (connection->mutex);
  res = _dbus_transport_get_is_authenticated (connection->transport);
  dbus_mutex_unlock (connection->mutex);
  
  return res;
}

/**
 * Preallocates resources needed to send a message, allowing the message 
 * to be sent without the possibility of memory allocation failure.
 * Allows apps to create a future guarantee that they can send
 * a message regardless of memory shortages.
 *
 * @param connection the connection we're preallocating for.
 * @returns the preallocated resources, or #NULL
 */
DBusPreallocatedSend*
dbus_connection_preallocate_send (DBusConnection *connection)
{
  /* we store "connection" in the link just to enforce via
   * assertion that preallocated links are only used
   * with the connection they were created for.
   */
  return (DBusPreallocatedSend*) _dbus_list_alloc_link (connection);
}

/**
 * Frees preallocated message-sending resources from
 * dbus_connection_preallocate_send(). Should only
 * be called if the preallocated resources are not used
 * to send a message.
 *
 * @param connection the connection
 * @param preallocated the resources
 */
void
dbus_connection_free_preallocated_send (DBusConnection       *connection,
                                        DBusPreallocatedSend *preallocated)
{
  DBusList *link = (DBusList*) preallocated;
  _dbus_assert (link->data == connection);
  _dbus_list_free_link (link);
}

/**
 * Sends a message using preallocated resources. This function cannot fail.
 * It works identically to dbus_connection_send() in other respects.
 * Preallocated resources comes from dbus_connection_preallocate_send().
 * This function "consumes" the preallocated resources, they need not
 * be freed separately.
 *
 * @param connection the connection
 * @param preallocated the preallocated resources
 * @param message the message to send
 * @param client_serial return location for client serial assigned to the message
 */
void
dbus_connection_send_preallocated (DBusConnection       *connection,
                                   DBusPreallocatedSend *preallocated,
                                   DBusMessage          *message,
                                   dbus_int32_t         *client_serial)
{
  DBusList *link = (DBusList*) preallocated;
  dbus_int32_t serial;
  
  _dbus_assert (link->data == connection);
  _dbus_assert (dbus_message_get_name (message) != NULL);
  
  dbus_mutex_lock (connection->mutex);

  link->data = message;
  _dbus_list_prepend_link (&connection->outgoing_messages,
                           link);

  dbus_message_ref (message);
  connection->n_outgoing += 1;

  _dbus_verbose ("Message %p (%s) added to outgoing queue %p, %d pending to send\n",
                 message,
                 dbus_message_get_name (message),
                 connection,
                 connection->n_outgoing);

  if (dbus_message_get_serial (message) == -1)
    {
      serial = _dbus_connection_get_next_client_serial (connection);
      _dbus_message_set_serial (message, serial);
    }
  
  if (client_serial)
    *client_serial = dbus_message_get_serial (message);
  
  _dbus_message_lock (message);

  if (connection->n_outgoing == 1)
    _dbus_transport_messages_pending (connection->transport,
                                      connection->n_outgoing);
  
  _dbus_connection_wakeup_mainloop (connection);

  dbus_mutex_unlock (connection->mutex);
}

/**
 * Adds a message to the outgoing message queue. Does not block to
 * write the message to the network; that happens asynchronously. To
 * force the message to be written, call dbus_connection_flush().
 * Because this only queues the message, the only reason it can
 * fail is lack of memory. Even if the connection is disconnected,
 * no error will be returned.
 *
 * If the function fails due to lack of memory, it returns #FALSE.
 * The function will never fail for other reasons; even if the
 * connection is disconnected, you can queue an outgoing message,
 * though obviously it won't be sent.
 * 
 * @param connection the connection.
 * @param message the message to write.
 * @param client_serial return location for client serial.
 * @returns #TRUE on success.
 */
dbus_bool_t
dbus_connection_send (DBusConnection *connection,
                      DBusMessage    *message,
                      dbus_int32_t   *client_serial)
{
  DBusPreallocatedSend *preallocated;

  preallocated = dbus_connection_preallocate_send (connection);
  if (preallocated == NULL)
    {
      return FALSE;
    }
  else
    {
      dbus_connection_send_preallocated (connection, preallocated, message, client_serial);
      return TRUE;
    }
}

static dbus_bool_t
reply_handler_timeout (void *data)
{
  DBusConnection *connection;
  ReplyHandlerData *reply_handler_data = data;
  DBusDispatchStatus status;

  connection = reply_handler_data->connection;
  
  dbus_mutex_lock (connection->mutex);
  if (reply_handler_data->timeout_link)
    {
      _dbus_connection_queue_synthesized_message_link (connection,
                                                       reply_handler_data->timeout_link);
      reply_handler_data->timeout_link = NULL;
    }

  _dbus_connection_remove_timeout (connection,
                                   reply_handler_data->timeout);
  reply_handler_data->timeout_added = FALSE;

  status = _dbus_connection_get_dispatch_status_unlocked (connection);
  
  dbus_mutex_unlock (connection->mutex);

  _dbus_connection_update_dispatch_status_locked (connection, status);
  
  return TRUE;
}

static void
reply_handler_data_free (ReplyHandlerData *data)
{
  if (!data)
    return;

  if (data->timeout_added)
    _dbus_connection_remove_timeout_locked (data->connection,
                                            data->timeout);

  if (data->connection_added)
    _dbus_message_handler_remove_connection (data->handler,
                                             data->connection);

  if (data->timeout_link)
    {
      dbus_message_unref ((DBusMessage *)data->timeout_link->data);
      _dbus_list_free_link (data->timeout_link);
    }
  
  dbus_message_handler_unref (data->handler);
  
  dbus_free (data);
}

/**
 * Queues a message to send, as with dbus_connection_send_message(),
 * but also sets up a DBusMessageHandler to receive a reply to the
 * message. If no reply is received in the given timeout_milliseconds,
 * expires the pending reply and sends the DBusMessageHandler a
 * synthetic error reply (generated in-process, not by the remote
 * application) indicating that a timeout occurred.
 *
 * Reply handlers see their replies after message filters see them,
 * but before message handlers added with
 * dbus_connection_register_handler() see them, regardless of the
 * reply message's name. Reply handlers are only handed a single
 * message as a reply, after one reply has been seen the handler is
 * removed. If a filter filters out the reply before the handler sees
 * it, the reply is immediately timed out and a timeout error reply is
 * generated. If a filter removes the timeout error reply then the
 * reply handler will never be called. Filters should not do this.
 * 
 * If #NULL is passed for the reply_handler, the timeout reply will
 * still be generated and placed into the message queue, but no
 * specific message handler will receive the reply.
 *
 * If -1 is passed for the timeout, a sane default timeout is used. -1
 * is typically the best value for the timeout for this reason, unless
 * you want a very short or very long timeout.  There is no way to
 * avoid a timeout entirely, other than passing INT_MAX for the
 * timeout to postpone it indefinitely.
 * 
 * @param connection the connection
 * @param message the message to send
 * @param reply_handler message handler expecting the reply, or #NULL
 * @param timeout_milliseconds timeout in milliseconds or -1 for default
 * @returns #TRUE if the message is successfully queued, #FALSE if no memory.
 *
 */
dbus_bool_t
dbus_connection_send_with_reply (DBusConnection     *connection,
                                 DBusMessage        *message,
                                 DBusMessageHandler *reply_handler,
                                 int                 timeout_milliseconds)
{
  DBusTimeout *timeout;
  ReplyHandlerData *data;
  DBusMessage *reply;
  DBusList *reply_link;
  dbus_int32_t serial = -1;
  
  if (timeout_milliseconds == -1)
    timeout_milliseconds = DEFAULT_TIMEOUT_VALUE;

  data = dbus_new0 (ReplyHandlerData, 1);

  if (!data)
    return FALSE;
  
  timeout = _dbus_timeout_new (timeout_milliseconds, reply_handler_timeout,
                               data, NULL);

  if (!timeout)
    {
      reply_handler_data_free (data);
      return FALSE;
    }

  dbus_mutex_lock (connection->mutex);
  
  /* Add timeout */
  if (!_dbus_connection_add_timeout (connection, timeout))
    {
      reply_handler_data_free (data);
      _dbus_timeout_unref (timeout);
      dbus_mutex_unlock (connection->mutex);
      return FALSE;
    }

  /* The connection now owns the reference to the timeout. */
  _dbus_timeout_unref (timeout);
  
  data->timeout_added = TRUE;
  data->timeout = timeout;
  data->connection = connection;
  
  if (!_dbus_message_handler_add_connection (reply_handler, connection))
    {
      dbus_mutex_unlock (connection->mutex);
      reply_handler_data_free (data);
      return FALSE;
    }
  data->connection_added = TRUE;
  
  /* Assign a serial to the message */
  if (dbus_message_get_serial (message) == -1)
    {
      serial = _dbus_connection_get_next_client_serial (connection);
      _dbus_message_set_serial (message, serial);
    }

  data->handler = reply_handler;
  data->serial = serial;

  dbus_message_handler_ref (reply_handler);

  reply = dbus_message_new_error_reply (message, DBUS_ERROR_NO_REPLY,
                                        "No reply within specified time");
  if (!reply)
    {
      dbus_mutex_unlock (connection->mutex);
      reply_handler_data_free (data);
      return FALSE;
    }

  reply_link = _dbus_list_alloc_link (reply);
  if (!reply)
    {
      dbus_mutex_unlock (connection->mutex);
      dbus_message_unref (reply);
      reply_handler_data_free (data);
      return FALSE;
    }

  data->timeout_link = reply_link;
  
  /* Insert the serial in the pending replies hash. */
  if (!_dbus_hash_table_insert_int (connection->pending_replies, serial, data))
    {
      dbus_mutex_unlock (connection->mutex);
      reply_handler_data_free (data);      
      return FALSE;
    }

  dbus_mutex_unlock (connection->mutex);
  
  if (!dbus_connection_send (connection, message, NULL))
    {
      /* This will free the handler data too */
      _dbus_hash_table_remove_int (connection->pending_replies, serial);
      return FALSE;
    }

  return TRUE;
}


static DBusMessage*
check_for_reply_unlocked (DBusConnection *connection,
                          dbus_int32_t    client_serial)
{
  DBusList *link;
  
  link = _dbus_list_get_first_link (&connection->incoming_messages);

  while (link != NULL)
    {
      DBusMessage *reply = link->data;

      if (dbus_message_get_reply_serial (reply) == client_serial)
        {
          _dbus_list_remove_link (&connection->incoming_messages, link);
          connection->n_incoming  -= 1;
          dbus_message_ref (reply);
          return reply;
        }
      link = _dbus_list_get_next_link (&connection->incoming_messages, link);
    }

  return NULL;
}

/**
 * Sends a message and blocks a certain time period while waiting for a reply.
 * This function does not dispatch any message handlers until the main loop
 * has been reached. This function is used to do non-reentrant "method calls."
 * If a reply is received, it is returned, and removed from the incoming
 * message queue. If it is not received, #NULL is returned and the
 * error is set to #DBUS_ERROR_NO_REPLY. If something else goes
 * wrong, result is set to whatever is appropriate, such as
 * #DBUS_ERROR_NO_MEMORY or #DBUS_ERROR_DISCONNECTED.
 *
 * @todo could use performance improvements (it keeps scanning
 * the whole message queue for example) and has thread issues,
 * see comments in source
 *
 * @param connection the connection
 * @param message the message to send
 * @param timeout_milliseconds timeout in milliseconds or -1 for default
 * @param error return location for error message
 * @returns the message that is the reply or #NULL with an error code if the
 * function fails.
 */
DBusMessage *
dbus_connection_send_with_reply_and_block (DBusConnection     *connection,
                                           DBusMessage        *message,
                                           int                 timeout_milliseconds,
                                           DBusError          *error)
{
  dbus_int32_t client_serial;
  long start_tv_sec, start_tv_usec;
  long end_tv_sec, end_tv_usec;
  long tv_sec, tv_usec;
  DBusDispatchStatus status;

  _DBUS_ASSERT_ERROR_IS_CLEAR (error);
  
  if (timeout_milliseconds == -1)
    timeout_milliseconds = DEFAULT_TIMEOUT_VALUE;

  /* it would probably seem logical to pass in _DBUS_INT_MAX
   * for infinite timeout, but then math below would get
   * all overflow-prone, so smack that down.
   */
  if (timeout_milliseconds > _DBUS_ONE_HOUR_IN_MILLISECONDS * 6)
    timeout_milliseconds = _DBUS_ONE_HOUR_IN_MILLISECONDS * 6;
  
  if (!dbus_connection_send (connection, message, &client_serial))
    {
      _DBUS_SET_OOM (error);
      return NULL;
    }

  message = NULL;
  
  /* Flush message queue */
  dbus_connection_flush (connection);

  dbus_mutex_lock (connection->mutex);

  _dbus_get_current_time (&start_tv_sec, &start_tv_usec);
  end_tv_sec = start_tv_sec + timeout_milliseconds / 1000;
  end_tv_usec = start_tv_usec + (timeout_milliseconds % 1000) * 1000;
  end_tv_sec += end_tv_usec / _DBUS_USEC_PER_SECOND;
  end_tv_usec = end_tv_usec % _DBUS_USEC_PER_SECOND;

  _dbus_verbose ("dbus_connection_send_with_reply_and_block(): will block %d milliseconds for reply serial %d from %ld sec %ld usec to %ld sec %ld usec\n",
                 timeout_milliseconds,
                 client_serial,
                 start_tv_sec, start_tv_usec,
                 end_tv_sec, end_tv_usec);
  
  /* Now we wait... */
  /* THREAD TODO: This is busted. What if a dispatch() or pop_message
   * gets the message before we do?
   */
  /* always block at least once as we know we don't have the reply yet */
  _dbus_connection_do_iteration (connection,
                                 DBUS_ITERATION_DO_READING |
                                 DBUS_ITERATION_BLOCK,
                                 timeout_milliseconds);

 recheck_status:

  /* queue messages and get status */
  status = _dbus_connection_get_dispatch_status_unlocked (connection);

  if (status == DBUS_DISPATCH_DATA_REMAINS)
    {
      DBusMessage *reply;
      
      reply = check_for_reply_unlocked (connection, client_serial);
      if (reply != NULL)
        {          
          status = _dbus_connection_get_dispatch_status_unlocked (connection);
          
          dbus_mutex_unlock (connection->mutex);

          _dbus_verbose ("dbus_connection_send_with_reply_and_block(): got reply %s\n",
                         dbus_message_get_name (reply));

          _dbus_connection_update_dispatch_status_locked (connection, status);
          
          return reply;
        }
    }
  
  _dbus_get_current_time (&tv_sec, &tv_usec);
  
  if (tv_sec < start_tv_sec)
    ; /* clock set backward, bail out */
  else if (connection->disconnect_message_link == NULL)
    ; /* we're disconnected, bail out */
  else if (tv_sec < end_tv_sec ||
           (tv_sec == end_tv_sec && tv_usec < end_tv_usec))
    {
      timeout_milliseconds = (end_tv_sec - tv_sec) * 1000 +
        (end_tv_usec - tv_usec) / 1000;
      _dbus_verbose ("dbus_connection_send_with_reply_and_block(): %d milliseconds remain\n", timeout_milliseconds);
      _dbus_assert (timeout_milliseconds >= 0);
      
      if (status == DBUS_DISPATCH_NEED_MEMORY)
        {
          /* Try sleeping a bit, as we aren't sure we need to block for reading,
           * we may already have a reply in the buffer and just can't process
           * it.
           */
          _dbus_verbose ("dbus_connection_send_with_reply_and_block() waiting for more memory\n");
          
          if (timeout_milliseconds < 100)
            ; /* just busy loop */
          else if (timeout_milliseconds <= 1000)
            _dbus_sleep_milliseconds (timeout_milliseconds / 3);
          else
            _dbus_sleep_milliseconds (1000);
        }
      else
        {          
          /* block again, we don't have the reply buffered yet. */
          _dbus_connection_do_iteration (connection,
                                         DBUS_ITERATION_DO_READING |
                                         DBUS_ITERATION_BLOCK,
                                         timeout_milliseconds);
        }

      goto recheck_status;
    }

  _dbus_verbose ("dbus_connection_send_with_reply_and_block(): Waited %ld milliseconds and got no reply\n",
                 (tv_sec - start_tv_sec) * 1000 + (tv_usec - start_tv_usec) / 1000);
  
  if (dbus_connection_get_is_connected (connection))
    dbus_set_error (error, DBUS_ERROR_NO_REPLY, "Message did not receive a reply");
  else
    dbus_set_error (error, DBUS_ERROR_DISCONNECTED, "Disconnected prior to receiving a reply");
  
  dbus_mutex_unlock (connection->mutex);

  _dbus_connection_update_dispatch_status_locked (connection, status);

  return NULL;
}

/**
 * Blocks until the outgoing message queue is empty.
 *
 * @param connection the connection.
 */
void
dbus_connection_flush (DBusConnection *connection)
{
  /* We have to specify DBUS_ITERATION_DO_READING here because
   * otherwise we could have two apps deadlock if they are both doing
   * a flush(), and the kernel buffers fill up. This could change the
   * dispatch status.
   */
  DBusDispatchStatus status;
  
  dbus_mutex_lock (connection->mutex);
  while (connection->n_outgoing > 0)
    _dbus_connection_do_iteration (connection,
                                   DBUS_ITERATION_DO_READING |
                                   DBUS_ITERATION_DO_WRITING |
                                   DBUS_ITERATION_BLOCK,
                                   -1);

  status = _dbus_connection_get_dispatch_status_unlocked (connection);
  
  dbus_mutex_unlock (connection->mutex);

  _dbus_connection_update_dispatch_status_locked (connection, status);
}

/* Call with mutex held. Will drop it while waiting and re-acquire
 * before returning
 */
static void
_dbus_connection_wait_for_borrowed (DBusConnection *connection)
{
  _dbus_assert (connection->message_borrowed != NULL);

  while (connection->message_borrowed != NULL)
    dbus_condvar_wait (connection->message_returned_cond, connection->mutex);
}

/**
 * Returns the first-received message from the incoming message queue,
 * leaving it in the queue. If the queue is empty, returns #NULL.
 * 
 * The caller does not own a reference to the returned message, and must
 * either return it using dbus_connection_return_message or keep it after
 * calling dbus_connection_steal_borrowed_message. No one can get at the
 * message while its borrowed, so return it as quickly as possible and
 * don't keep a reference to it after returning it. If you need to keep
 * the message, make a copy of it.
 *
 * @param connection the connection.
 * @returns next message in the incoming queue.
 */
DBusMessage*
dbus_connection_borrow_message  (DBusConnection *connection)
{
  DBusMessage *message;
  DBusDispatchStatus status;
  
  /* this is called for the side effect that it queues
   * up any messages from the transport
   */
  status = dbus_connection_get_dispatch_status (connection);
  if (status != DBUS_DISPATCH_DATA_REMAINS)
    return NULL;
  
  dbus_mutex_lock (connection->mutex);

  if (connection->message_borrowed != NULL)
    _dbus_connection_wait_for_borrowed (connection);
  
  message = _dbus_list_get_first (&connection->incoming_messages);

  if (message) 
    connection->message_borrowed = message;
  
  dbus_mutex_unlock (connection->mutex);
  return message;
}

/**
 * @todo docs
 */
void
dbus_connection_return_message (DBusConnection *connection,
                                DBusMessage    *message)
{
  dbus_mutex_lock (connection->mutex);
  
  _dbus_assert (message == connection->message_borrowed);
  
  connection->message_borrowed = NULL;
  dbus_condvar_wake_all (connection->message_returned_cond);
  
  dbus_mutex_unlock (connection->mutex);
}

/**
 * @todo docs
 */
void
dbus_connection_steal_borrowed_message (DBusConnection *connection,
                                        DBusMessage    *message)
{
  DBusMessage *pop_message;
  
  dbus_mutex_lock (connection->mutex);
 
  _dbus_assert (message == connection->message_borrowed);

  pop_message = _dbus_list_pop_first (&connection->incoming_messages);
  _dbus_assert (message == pop_message);
  
  connection->n_incoming -= 1;
 
  _dbus_verbose ("Incoming message %p stolen from queue, %d incoming\n",
                 message, connection->n_incoming);
 
  connection->message_borrowed = NULL;
  dbus_condvar_wake_all (connection->message_returned_cond);
  
  dbus_mutex_unlock (connection->mutex);
}

/* See dbus_connection_pop_message, but requires the caller to own
 * the lock before calling. May drop the lock while running.
 */
static DBusList*
_dbus_connection_pop_message_link_unlocked (DBusConnection *connection)
{
  if (connection->message_borrowed != NULL)
    _dbus_connection_wait_for_borrowed (connection);
  
  if (connection->n_incoming > 0)
    {
      DBusList *link;

      link = _dbus_list_pop_first_link (&connection->incoming_messages);
      connection->n_incoming -= 1;

      _dbus_verbose ("Message %p (%s) removed from incoming queue %p, %d incoming\n",
                     link->data, dbus_message_get_name (link->data),
                     connection, connection->n_incoming);

      return link;
    }
  else
    return NULL;
}

/* See dbus_connection_pop_message, but requires the caller to own
 * the lock before calling. May drop the lock while running.
 */
static DBusMessage*
_dbus_connection_pop_message_unlocked (DBusConnection *connection)
{
  DBusList *link;
  
  link = _dbus_connection_pop_message_link_unlocked (connection);

  if (link != NULL)
    {
      DBusMessage *message;
      
      message = link->data;
      
      _dbus_list_free_link (link);
      
      return message;
    }
  else
    return NULL;
}


/**
 * Returns the first-received message from the incoming message queue,
 * removing it from the queue. The caller owns a reference to the
 * returned message. If the queue is empty, returns #NULL.
 *
 * @param connection the connection.
 * @returns next message in the incoming queue.
 */
DBusMessage*
dbus_connection_pop_message (DBusConnection *connection)
{
  DBusMessage *message;
  DBusDispatchStatus status;

  /* this is called for the side effect that it queues
   * up any messages from the transport
   */
  status = dbus_connection_get_dispatch_status (connection);
  if (status != DBUS_DISPATCH_DATA_REMAINS)
    return NULL;
  
  dbus_mutex_lock (connection->mutex);

  message = _dbus_connection_pop_message_unlocked (connection);

  _dbus_verbose ("Returning popped message %p\n", message);    
  
  dbus_mutex_unlock (connection->mutex);
  
  return message;
}

/**
 * Acquire the dispatcher. This must be done before dispatching
 * messages in order to guarantee the right order of
 * message delivery. May sleep and drop the connection mutex
 * while waiting for the dispatcher.
 *
 * @param connection the connection.
 */
static void
_dbus_connection_acquire_dispatch (DBusConnection *connection)
{
  if (connection->dispatch_acquired)
    dbus_condvar_wait (connection->dispatch_cond, connection->mutex);
  _dbus_assert (!connection->dispatch_acquired);

  connection->dispatch_acquired = TRUE;
}

/**
 * Release the dispatcher when you're done with it. Only call
 * after you've acquired the dispatcher. Wakes up at most one
 * thread currently waiting to acquire the dispatcher.
 *
 * @param connection the connection.
 */
static void
_dbus_connection_release_dispatch (DBusConnection *connection)
{
  _dbus_assert (connection->dispatch_acquired);

  connection->dispatch_acquired = FALSE;
  dbus_condvar_wake_one (connection->dispatch_cond);
}

static void
_dbus_connection_failed_pop (DBusConnection *connection,
                             DBusList *message_link)
{
  _dbus_list_prepend_link (&connection->incoming_messages,
                           message_link);
  connection->n_incoming += 1;
}

static DBusDispatchStatus
_dbus_connection_get_dispatch_status_unlocked (DBusConnection *connection)
{
  if (connection->n_incoming > 0)
    return DBUS_DISPATCH_DATA_REMAINS;
  else if (!_dbus_transport_queue_messages (connection->transport))
    return DBUS_DISPATCH_NEED_MEMORY;
  else
    {
      DBusDispatchStatus status;
      
      status = _dbus_transport_get_dispatch_status (connection->transport);

      if (status != DBUS_DISPATCH_COMPLETE)
        return status;
      else if (connection->n_incoming > 0)
        return DBUS_DISPATCH_DATA_REMAINS;
      else
        return DBUS_DISPATCH_COMPLETE;
    }
}

static void
_dbus_connection_update_dispatch_status_locked (DBusConnection    *connection,
                                                DBusDispatchStatus new_status)
{
  dbus_bool_t changed;
  DBusDispatchStatusFunction function;
  void *data;
  
  dbus_mutex_lock (connection->mutex);
  _dbus_connection_ref_unlocked (connection);

  changed = new_status != connection->last_dispatch_status;

  connection->last_dispatch_status = new_status;

  function = connection->dispatch_status_function;
  data = connection->dispatch_status_data;
  
  dbus_mutex_unlock (connection->mutex);
  
  if (changed && function)
    {
      _dbus_verbose ("Notifying of change to dispatch status of %p now %d (%s)\n",
                     connection, new_status,
                     new_status == DBUS_DISPATCH_COMPLETE ? "complete" :
                     new_status == DBUS_DISPATCH_DATA_REMAINS ? "data remains" :
                     new_status == DBUS_DISPATCH_NEED_MEMORY ? "need memory" :
                     "???");
      (* function) (connection, new_status, data);      
    }
  
  dbus_connection_unref (connection);
}

/**
 * Gets the current state (what we would currently return
 * from dbus_connection_dispatch()) but doesn't actually
 * dispatch any messages.
 * 
 * @param connection the connection.
 * @returns current dispatch status
 */
DBusDispatchStatus
dbus_connection_get_dispatch_status (DBusConnection *connection)
{
  DBusDispatchStatus status;
  
  dbus_mutex_lock (connection->mutex);

  status = _dbus_connection_get_dispatch_status_unlocked (connection);
  
  dbus_mutex_unlock (connection->mutex);

  return status;
}

/**
 * Processes data buffered while handling watches, queueing zero or
 * more incoming messages. Then pops the first-received message from
 * the current incoming message queue, runs any handlers for it, and
 * unrefs the message. Returns a status indicating whether messages/data
 * remain, more memory is needed, or all data has been processed.
 *
 * @param connection the connection
 * @returns dispatch status
 */
DBusDispatchStatus
dbus_connection_dispatch (DBusConnection *connection)
{
  DBusMessageHandler *handler;
  DBusMessage *message;
  DBusList *link, *filter_list_copy, *message_link;
  DBusHandlerResult result;
  ReplyHandlerData *reply_handler_data;
  const char *name;
  dbus_int32_t reply_serial;
  DBusDispatchStatus status;
  
  status = dbus_connection_get_dispatch_status (connection);
  if (status != DBUS_DISPATCH_DATA_REMAINS)
    {
      _dbus_connection_update_dispatch_status_locked (connection, status);
      return status;
    }

  dbus_mutex_lock (connection->mutex);
  
  /* We need to ref the connection since the callback could potentially
   * drop the last ref to it
   */
  _dbus_connection_ref_unlocked (connection);

  _dbus_connection_acquire_dispatch (connection);
  
  /* This call may drop the lock during the execution (if waiting for
   * borrowed messages to be returned) but the order of message
   * dispatch if several threads call dispatch() is still
   * protected by the lock, since only one will get the lock, and that
   * one will finish the message dispatching
   */
  message_link = _dbus_connection_pop_message_link_unlocked (connection);
  if (message_link == NULL)
    {
      /* another thread dispatched our stuff */

      _dbus_connection_release_dispatch (connection);
      dbus_mutex_unlock (connection->mutex);

      status = dbus_connection_get_dispatch_status (connection);

      _dbus_connection_update_dispatch_status_locked (connection, status);
      
      dbus_connection_unref (connection);
      
      return status;
    }

  message = message_link->data;
  
  result = DBUS_HANDLER_RESULT_ALLOW_MORE_HANDLERS;

  reply_serial = dbus_message_get_reply_serial (message);
  reply_handler_data = _dbus_hash_table_lookup_int (connection->pending_replies,
                                                    reply_serial);
  
  if (!_dbus_list_copy (&connection->filter_list, &filter_list_copy))
    {
      _dbus_connection_release_dispatch (connection);
      dbus_mutex_unlock (connection->mutex);
      _dbus_connection_failed_pop (connection, message_link);

      _dbus_connection_update_dispatch_status_locked (connection, DBUS_DISPATCH_NEED_MEMORY);

      dbus_connection_unref (connection);
      
      return DBUS_DISPATCH_NEED_MEMORY;
    }
  
  _dbus_list_foreach (&filter_list_copy,
                      (DBusForeachFunction)dbus_message_handler_ref,
                      NULL);

  /* We're still protected from dispatch() reentrancy here
   * since we acquired the dispatcher
   */
  dbus_mutex_unlock (connection->mutex);
  
  link = _dbus_list_get_first_link (&filter_list_copy);
  while (link != NULL)
    {
      DBusMessageHandler *handler = link->data;
      DBusList *next = _dbus_list_get_next_link (&filter_list_copy, link);

      _dbus_verbose ("  running filter on message %p\n", message);
      result = _dbus_message_handler_handle_message (handler, connection,
                                                     message);

      if (result == DBUS_HANDLER_RESULT_REMOVE_MESSAGE)
        break;

      link = next;
    }

  _dbus_list_foreach (&filter_list_copy,
                      (DBusForeachFunction)dbus_message_handler_unref,
                      NULL);
  _dbus_list_clear (&filter_list_copy);
  
  dbus_mutex_lock (connection->mutex);

  /* Did a reply we were waiting on get filtered? */
  if (reply_handler_data && result == DBUS_HANDLER_RESULT_REMOVE_MESSAGE)
    {
      /* Queue the timeout immediately! */
      if (reply_handler_data->timeout_link)
        {
          _dbus_connection_queue_synthesized_message_link (connection,
                                                           reply_handler_data->timeout_link);
          reply_handler_data->timeout_link = NULL;
        }
      else
        {
          /* We already queued the timeout? Then it was filtered! */
          _dbus_warn ("The timeout error with reply serial %d was filtered, so the reply handler will never be called.\n", reply_serial);
        }
    }
  
  if (result == DBUS_HANDLER_RESULT_REMOVE_MESSAGE)
    goto out;

  if (reply_handler_data)
    {
      dbus_mutex_unlock (connection->mutex);

      _dbus_verbose ("  running reply handler on message %p\n", message);
      
      result = _dbus_message_handler_handle_message (reply_handler_data->handler,
                                                     connection, message);
      reply_handler_data_free (reply_handler_data);
      dbus_mutex_lock (connection->mutex);
      goto out;
    }
  
  name = dbus_message_get_name (message);
  if (name != NULL)
    {
      handler = _dbus_hash_table_lookup_string (connection->handler_table,
                                                name);
      if (handler != NULL)
        {
          /* We're still protected from dispatch() reentrancy here
           * since we acquired the dispatcher
           */
          dbus_mutex_unlock (connection->mutex);

          _dbus_verbose ("  running app handler on message %p (%s)\n",
                         message, dbus_message_get_name (message));
          
          result = _dbus_message_handler_handle_message (handler, connection,
                                                         message);
          dbus_mutex_lock (connection->mutex);
          if (result == DBUS_HANDLER_RESULT_REMOVE_MESSAGE)
            goto out;
        }
    }

  _dbus_verbose ("  done dispatching %p (%s)\n", message,
                 dbus_message_get_name (message));
  
 out:
  _dbus_connection_release_dispatch (connection);
  dbus_mutex_unlock (connection->mutex);
  _dbus_list_free_link (message_link);
  dbus_message_unref (message); /* don't want the message to count in max message limits
                                 * in computing dispatch status
                                 */
  
  status = dbus_connection_get_dispatch_status (connection);

  _dbus_connection_update_dispatch_status_locked (connection, status);
  
  dbus_connection_unref (connection);
  
  return status;
}

/**
 * Sets the watch functions for the connection. These functions are
 * responsible for making the application's main loop aware of file
 * descriptors that need to be monitored for events, using select() or
 * poll(). When using Qt, typically the DBusAddWatchFunction would
 * create a QSocketNotifier. When using GLib, the DBusAddWatchFunction
 * could call g_io_add_watch(), or could be used as part of a more
 * elaborate GSource. Note that when a watch is added, it may
 * not be enabled.
 *
 * The DBusWatchToggledFunction notifies the application that the
 * watch has been enabled or disabled. Call dbus_watch_get_enabled()
 * to check this. A disabled watch should have no effect, and enabled
 * watch should be added to the main loop. This feature is used
 * instead of simply adding/removing the watch because
 * enabling/disabling can be done without memory allocation.  The
 * toggled function may be NULL if a main loop re-queries
 * dbus_watch_get_enabled() every time anyway.
 * 
 * The DBusWatch can be queried for the file descriptor to watch using
 * dbus_watch_get_fd(), and for the events to watch for using
 * dbus_watch_get_flags(). The flags returned by
 * dbus_watch_get_flags() will only contain DBUS_WATCH_READABLE and
 * DBUS_WATCH_WRITABLE, never DBUS_WATCH_HANGUP or DBUS_WATCH_ERROR;
 * all watches implicitly include a watch for hangups, errors, and
 * other exceptional conditions.
 *
 * Once a file descriptor becomes readable or writable, or an exception
 * occurs, dbus_connection_handle_watch() should be called to
 * notify the connection of the file descriptor's condition.
 *
 * dbus_connection_handle_watch() cannot be called during the
 * DBusAddWatchFunction, as the connection will not be ready to handle
 * that watch yet.
 * 
 * It is not allowed to reference a DBusWatch after it has been passed
 * to remove_function.
 *
 * If #FALSE is returned due to lack of memory, the failure may be due
 * to a #FALSE return from the new add_function. If so, the
 * add_function may have been called successfully one or more times,
 * but the remove_function will also have been called to remove any
 * successful adds. i.e. if #FALSE is returned the net result
 * should be that dbus_connection_set_watch_functions() has no effect,
 * but the add_function and remove_function may have been called.
 *
 * @todo We need to drop the lock when we call the
 * add/remove/toggled functions which can be a side effect
 * of setting the watch functions.
 * 
 * @param connection the connection.
 * @param add_function function to begin monitoring a new descriptor.
 * @param remove_function function to stop monitoring a descriptor.
 * @param toggled_function function to notify of enable/disable
 * @param data data to pass to add_function and remove_function.
 * @param free_data_function function to be called to free the data.
 * @returns #FALSE on failure (no memory)
 */
dbus_bool_t
dbus_connection_set_watch_functions (DBusConnection              *connection,
                                     DBusAddWatchFunction         add_function,
                                     DBusRemoveWatchFunction      remove_function,
                                     DBusWatchToggledFunction     toggled_function,
                                     void                        *data,
                                     DBusFreeFunction             free_data_function)
{
  dbus_bool_t retval;
  
  dbus_mutex_lock (connection->mutex);
  /* ref connection for slightly better reentrancy */
  _dbus_connection_ref_unlocked (connection);

  /* FIXME this can call back into user code, and we need to drop the
   * connection lock when it does.
   */
  retval = _dbus_watch_list_set_functions (connection->watches,
                                           add_function, remove_function,
                                           toggled_function,
                                           data, free_data_function);
  
  dbus_mutex_unlock (connection->mutex);
  /* drop our paranoid refcount */
  dbus_connection_unref (connection);

  return retval;
}

/**
 * Sets the timeout functions for the connection. These functions are
 * responsible for making the application's main loop aware of timeouts.
 * When using Qt, typically the DBusAddTimeoutFunction would create a
 * QTimer. When using GLib, the DBusAddTimeoutFunction would call
 * g_timeout_add.
 * 
 * The DBusTimeoutToggledFunction notifies the application that the
 * timeout has been enabled or disabled. Call
 * dbus_timeout_get_enabled() to check this. A disabled timeout should
 * have no effect, and enabled timeout should be added to the main
 * loop. This feature is used instead of simply adding/removing the
 * timeout because enabling/disabling can be done without memory
 * allocation. With Qt, QTimer::start() and QTimer::stop() can be used
 * to enable and disable. The toggled function may be NULL if a main
 * loop re-queries dbus_timeout_get_enabled() every time anyway.
 *
 * The DBusTimeout can be queried for the timer interval using
 * dbus_timeout_get_interval(). dbus_timeout_handle() should
 * be called repeatedly, each time the interval elapses, starting
 * after it has elapsed once. The timeout stops firing when
 * it is removed with the given remove_function.
 *
 * @param connection the connection.
 * @param add_function function to add a timeout.
 * @param remove_function function to remove a timeout.
 * @param toggled_function function to notify of enable/disable
 * @param data data to pass to add_function and remove_function.
 * @param free_data_function function to be called to free the data.
 * @returns #FALSE on failure (no memory)
 */
dbus_bool_t
dbus_connection_set_timeout_functions   (DBusConnection            *connection,
                                         DBusAddTimeoutFunction     add_function,
                                         DBusRemoveTimeoutFunction  remove_function,
                                         DBusTimeoutToggledFunction toggled_function,
                                         void                      *data,
                                         DBusFreeFunction           free_data_function)
{
  dbus_bool_t retval;
  
  dbus_mutex_lock (connection->mutex);
  /* ref connection for slightly better reentrancy */
  _dbus_connection_ref_unlocked (connection);
  
  retval = _dbus_timeout_list_set_functions (connection->timeouts,
                                             add_function, remove_function,
                                             toggled_function,
                                             data, free_data_function);
  
  dbus_mutex_unlock (connection->mutex);
  /* drop our paranoid refcount */
  dbus_connection_unref (connection);

  return retval;
}

/**
 * Sets the mainloop wakeup function for the connection. Thi function is
 * responsible for waking up the main loop (if its sleeping) when some some
 * change has happened to the connection that the mainloop needs to reconsiders
 * (e.g. a message has been queued for writing).
 * When using Qt, this typically results in a call to QEventLoop::wakeUp().
 * When using GLib, it would call g_main_context_wakeup().
 *
 *
 * @param connection the connection.
 * @param wakeup_main_function function to wake up the mainloop
 * @param data data to pass wakeup_main_function
 * @param free_data_function function to be called to free the data.
 */
void
dbus_connection_set_wakeup_main_function (DBusConnection            *connection,
                                          DBusWakeupMainFunction     wakeup_main_function,
                                          void                      *data,
                                          DBusFreeFunction           free_data_function)
{
  void *old_data;
  DBusFreeFunction old_free_data;
  
  dbus_mutex_lock (connection->mutex);
  old_data = connection->wakeup_main_data;
  old_free_data = connection->free_wakeup_main_data;

  connection->wakeup_main_function = wakeup_main_function;
  connection->wakeup_main_data = data;
  connection->free_wakeup_main_data = free_data_function;
  
  dbus_mutex_unlock (connection->mutex);

  /* Callback outside the lock */
  if (old_free_data)
    (*old_free_data) (old_data);
}

/**
 * Set a function to be invoked when the dispatch status changes.
 * If the dispatch status is #DBUS_DISPATCH_DATA_REMAINS, then
 * dbus_connection_dispatch() needs to be called to process incoming
 * messages. However, dbus_connection_dispatch() MUST NOT BE CALLED
 * from inside the DBusDispatchStatusFunction. Indeed, almost
 * any reentrancy in this function is a bad idea. Instead,
 * the DBusDispatchStatusFunction should simply save an indication
 * that messages should be dispatched later, when the main loop
 * is re-entered.
 *
 * @param connection the connection
 * @param function function to call on dispatch status changes
 * @param data data for function
 * @param free_data_function free the function data
 */
void
dbus_connection_set_dispatch_status_function (DBusConnection             *connection,
                                              DBusDispatchStatusFunction  function,
                                              void                       *data,
                                              DBusFreeFunction            free_data_function)
{
  void *old_data;
  DBusFreeFunction old_free_data;
  
  dbus_mutex_lock (connection->mutex);
  old_data = connection->dispatch_status_data;
  old_free_data = connection->free_dispatch_status_data;

  connection->dispatch_status_function = function;
  connection->dispatch_status_data = data;
  connection->free_dispatch_status_data = free_data_function;
  
  dbus_mutex_unlock (connection->mutex);

  /* Callback outside the lock */
  if (old_free_data)
    (*old_free_data) (old_data);
}

/**
 * Called to notify the connection when a previously-added watch
 * is ready for reading or writing, or has an exception such
 * as a hangup.
 *
 * If this function returns #FALSE, then the file descriptor may still
 * be ready for reading or writing, but more memory is needed in order
 * to do the reading or writing. If you ignore the #FALSE return, your
 * application may spin in a busy loop on the file descriptor until
 * memory becomes available, but nothing more catastrophic should
 * happen.
 *
 * @param connection the connection.
 * @param watch the watch.
 * @param condition the current condition of the file descriptors being watched.
 * @returns #FALSE if the IO condition may not have been fully handled due to lack of memory
 */
dbus_bool_t
dbus_connection_handle_watch (DBusConnection              *connection,
                              DBusWatch                   *watch,
                              unsigned int                 condition)
{
  dbus_bool_t retval;
  DBusDispatchStatus status;
  
  dbus_mutex_lock (connection->mutex);
  _dbus_connection_acquire_io_path (connection, -1);
  retval = _dbus_transport_handle_watch (connection->transport,
                                         watch, condition);
  _dbus_connection_release_io_path (connection);

  status = _dbus_connection_get_dispatch_status_unlocked (connection);
  
  dbus_mutex_unlock (connection->mutex);

  _dbus_connection_update_dispatch_status_locked (connection, status);
  
  return retval;
}

/**
 * Gets the UNIX user ID of the connection if any.
 * Returns #TRUE if the uid is filled in.
 * Always returns #FALSE on non-UNIX platforms.
 * Always returns #FALSE prior to authenticating the
 * connection.
 *
 * @param connection the connection
 * @param uid return location for the user ID
 * @returns #TRUE if uid is filled in with a valid user ID
 */
dbus_bool_t
dbus_connection_get_unix_user (DBusConnection *connection,
                               unsigned long  *uid)
{
  dbus_bool_t result;

  dbus_mutex_lock (connection->mutex);

  if (!_dbus_transport_get_is_authenticated (connection->transport))
    result = FALSE;
  else
    result = _dbus_transport_get_unix_user (connection->transport,
                                            uid);
  dbus_mutex_unlock (connection->mutex);

  return result;
}

/**
 * Sets a predicate function used to determine whether a given user ID
 * is allowed to connect. When an incoming connection has
 * authenticated with a particular user ID, this function is called;
 * if it returns #TRUE, the connection is allowed to proceed,
 * otherwise the connection is disconnected.
 *
 * If the function is set to #NULL (as it is by default), then
 * only the same UID as the server process will be allowed to
 * connect.
 *
 * @param connection the connection
 * @param function the predicate
 * @param data data to pass to the predicate
 * @param free_data_function function to free the data
 */
void
dbus_connection_set_unix_user_function (DBusConnection             *connection,
                                        DBusAllowUnixUserFunction   function,
                                        void                       *data,
                                        DBusFreeFunction            free_data_function)
{
  void *old_data = NULL;
  DBusFreeFunction old_free_function = NULL;

  dbus_mutex_lock (connection->mutex);
  _dbus_transport_set_unix_user_function (connection->transport,
                                          function, data, free_data_function,
                                          &old_data, &old_free_function);
  dbus_mutex_unlock (connection->mutex);

  if (old_free_function != NULL)
    (* old_free_function) (old_data);    
}

/**
 * Adds a message filter. Filters are handlers that are run on
 * all incoming messages, prior to the normal handlers
 * registered with dbus_connection_register_handler().
 * Filters are run in the order that they were added.
 * The same handler can be added as a filter more than once, in
 * which case it will be run more than once.
 * Filters added during a filter callback won't be run on the
 * message being processed.
 *
 * @param connection the connection
 * @param handler the handler
 * @returns #TRUE on success, #FALSE if not enough memory.
 */
dbus_bool_t
dbus_connection_add_filter (DBusConnection      *connection,
                            DBusMessageHandler  *handler)
{
  dbus_mutex_lock (connection->mutex);
  if (!_dbus_message_handler_add_connection (handler, connection))
    {
      dbus_mutex_unlock (connection->mutex);
      return FALSE;
    }

  if (!_dbus_list_append (&connection->filter_list,
                          handler))
    {
      _dbus_message_handler_remove_connection (handler, connection);
      dbus_mutex_unlock (connection->mutex);
      return FALSE;
    }

  dbus_mutex_unlock (connection->mutex);
  return TRUE;
}

/**
 * Removes a previously-added message filter. It is a programming
 * error to call this function for a handler that has not
 * been added as a filter. If the given handler was added
 * more than once, only one instance of it will be removed
 * (the most recently-added instance).
 *
 * @param connection the connection
 * @param handler the handler to remove
 *
 */
void
dbus_connection_remove_filter (DBusConnection      *connection,
                               DBusMessageHandler  *handler)
{
  dbus_mutex_lock (connection->mutex);
  if (!_dbus_list_remove_last (&connection->filter_list, handler))
    {
      _dbus_warn ("Tried to remove a DBusConnection filter that had not been added\n");
      dbus_mutex_unlock (connection->mutex);
      return;
    }

  _dbus_message_handler_remove_connection (handler, connection);

  dbus_mutex_unlock (connection->mutex);
}

/**
 * Registers a handler for a list of message names. A single handler
 * can be registered for any number of message names, but each message
 * name can only have one handler at a time. It's not allowed to call
 * this function with the name of a message that already has a
 * handler. If the function returns #FALSE, the handlers were not
 * registered due to lack of memory.
 *
 * @todo the messages_to_handle arg may be more convenient if it's a
 * single string instead of an array. Though right now MessageHandler
 * is sort of designed to say be associated with an entire object with
 * multiple methods, that's why for example the connection only
 * weakrefs it.  So maybe the "manual" API should be different.
 * 
 * @param connection the connection
 * @param handler the handler
 * @param messages_to_handle the messages to handle
 * @param n_messages the number of message names in messages_to_handle
 * @returns #TRUE on success, #FALSE if no memory or another handler already exists
 * 
 **/
dbus_bool_t
dbus_connection_register_handler (DBusConnection     *connection,
                                  DBusMessageHandler *handler,
                                  const char        **messages_to_handle,
                                  int                 n_messages)
{
  int i;

  dbus_mutex_lock (connection->mutex);
  i = 0;
  while (i < n_messages)
    {
      DBusHashIter iter;
      char *key;

      key = _dbus_strdup (messages_to_handle[i]);
      if (key == NULL)
        goto failed;
      
      if (!_dbus_hash_iter_lookup (connection->handler_table,
                                   key, TRUE,
                                   &iter))
        {
          dbus_free (key);
          goto failed;
        }

      if (_dbus_hash_iter_get_value (&iter) != NULL)
        {
          _dbus_warn ("Bug in application: attempted to register a second handler for %s\n",
                      messages_to_handle[i]);
          dbus_free (key); /* won't have replaced the old key with the new one */
          goto failed;
        }

      if (!_dbus_message_handler_add_connection (handler, connection))
        {
          _dbus_hash_iter_remove_entry (&iter);
          /* key has freed on nuking the entry */
          goto failed;
        }
      
      _dbus_hash_iter_set_value (&iter, handler);

      ++i;
    }
  
  dbus_mutex_unlock (connection->mutex);
  return TRUE;
  
 failed:
  /* unregister everything registered so far,
   * so we don't fail partially
   */
  dbus_connection_unregister_handler (connection,
                                      handler,
                                      messages_to_handle,
                                      i);

  dbus_mutex_unlock (connection->mutex);
  return FALSE;
}

/**
 * Unregisters a handler for a list of message names. The handlers
 * must have been previously registered.
 *
 * @param connection the connection
 * @param handler the handler
 * @param messages_to_handle the messages to handle
 * @param n_messages the number of message names in messages_to_handle
 * 
 **/
void
dbus_connection_unregister_handler (DBusConnection     *connection,
                                    DBusMessageHandler *handler,
                                    const char        **messages_to_handle,
                                    int                 n_messages)
{
  int i;

  dbus_mutex_lock (connection->mutex);
  i = 0;
  while (i < n_messages)
    {
      DBusHashIter iter;

      if (!_dbus_hash_iter_lookup (connection->handler_table,
                                   (char*) messages_to_handle[i], FALSE,
                                   &iter))
        {
          _dbus_warn ("Bug in application: attempted to unregister handler for %s which was not registered\n",
                      messages_to_handle[i]);
        }
      else if (_dbus_hash_iter_get_value (&iter) != handler)
        {
          _dbus_warn ("Bug in application: attempted to unregister handler for %s which was registered by a different handler\n",
                      messages_to_handle[i]);
        }
      else
        {
          _dbus_hash_iter_remove_entry (&iter);
          _dbus_message_handler_remove_connection (handler, connection);
        }

      ++i;
    }

  dbus_mutex_unlock (connection->mutex);
}

static DBusDataSlotAllocator slot_allocator;
_DBUS_DEFINE_GLOBAL_LOCK (connection_slots);

/**
 * Allocates an integer ID to be used for storing application-specific
 * data on any DBusConnection. The allocated ID may then be used
 * with dbus_connection_set_data() and dbus_connection_get_data().
 * If allocation fails, -1 is returned. Again, the allocated
 * slot is global, i.e. all DBusConnection objects will
 * have a slot with the given integer ID reserved.
 *
 * @returns -1 on failure, otherwise the data slot ID
 */
int
dbus_connection_allocate_data_slot (void)
{
  return _dbus_data_slot_allocator_alloc (&slot_allocator,
                                          _DBUS_LOCK_NAME (connection_slots));
}

/**
 * Deallocates a global ID for connection data slots.
 * dbus_connection_get_data() and dbus_connection_set_data()
 * may no longer be used with this slot.
 * Existing data stored on existing DBusConnection objects
 * will be freed when the connection is finalized,
 * but may not be retrieved (and may only be replaced
 * if someone else reallocates the slot).
 *
 * @param slot the slot to deallocate
 */
void
dbus_connection_free_data_slot (int slot)
{
  _dbus_data_slot_allocator_free (&slot_allocator, slot);
}

/**
 * Stores a pointer on a DBusConnection, along
 * with an optional function to be used for freeing
 * the data when the data is set again, or when
 * the connection is finalized. The slot number
 * must have been allocated with dbus_connection_allocate_data_slot().
 *
 * @param connection the connection
 * @param slot the slot number
 * @param data the data to store
 * @param free_data_func finalizer function for the data
 * @returns #TRUE if there was enough memory to store the data
 */
dbus_bool_t
dbus_connection_set_data (DBusConnection   *connection,
                          int               slot,
                          void             *data,
                          DBusFreeFunction  free_data_func)
{
  DBusFreeFunction old_free_func;
  void *old_data;
  dbus_bool_t retval;
  
  dbus_mutex_lock (connection->mutex);

  retval = _dbus_data_slot_list_set (&slot_allocator,
                                     &connection->slot_list,
                                     slot, data, free_data_func,
                                     &old_free_func, &old_data);
  
  dbus_mutex_unlock (connection->mutex);

  if (retval)
    {
      /* Do the actual free outside the connection lock */
      if (old_free_func)
        (* old_free_func) (old_data);
    }

  return retval;
}

/**
 * Retrieves data previously set with dbus_connection_set_data().
 * The slot must still be allocated (must not have been freed).
 *
 * @param connection the connection
 * @param slot the slot to get data from
 * @returns the data, or #NULL if not found
 */
void*
dbus_connection_get_data (DBusConnection   *connection,
                          int               slot)
{
  void *res;
  
  dbus_mutex_lock (connection->mutex);

  res = _dbus_data_slot_list_get (&slot_allocator,
                                  &connection->slot_list,
                                  slot);
  
  dbus_mutex_unlock (connection->mutex);

  return res;
}

/**
 * This function sets a global flag for whether dbus_connection_new()
 * will set SIGPIPE behavior to SIG_IGN.
 *
 * @param will_modify_sigpipe #TRUE to allow sigpipe to be set to SIG_IGN
 */
void
dbus_connection_set_change_sigpipe (dbus_bool_t will_modify_sigpipe)
{
  _dbus_modify_sigpipe = will_modify_sigpipe;
}

/**
 * Specifies the maximum size message this connection is allowed to
 * receive. Larger messages will result in disconnecting the
 * connection.
 * 
 * @param connection a #DBusConnection
 * @param size maximum message size the connection can receive, in bytes
 */
void
dbus_connection_set_max_message_size (DBusConnection *connection,
                                      long            size)
{
  dbus_mutex_lock (connection->mutex);
  _dbus_transport_set_max_message_size (connection->transport,
                                        size);
  dbus_mutex_unlock (connection->mutex);
}

/**
 * Gets the value set by dbus_connection_set_max_message_size().
 *
 * @param connection the connection
 * @returns the max size of a single message
 */
long
dbus_connection_get_max_message_size (DBusConnection *connection)
{
  long res;
  dbus_mutex_lock (connection->mutex);
  res = _dbus_transport_get_max_message_size (connection->transport);
  dbus_mutex_unlock (connection->mutex);
  return res;
}

/**
 * Sets the maximum total number of bytes that can be used for all messages
 * received on this connection. Messages count toward the maximum until
 * they are finalized. When the maximum is reached, the connection will
 * not read more data until some messages are finalized.
 *
 * The semantics of the maximum are: if outstanding messages are
 * already above the maximum, additional messages will not be read.
 * The semantics are not: if the next message would cause us to exceed
 * the maximum, we don't read it. The reason is that we don't know the
 * size of a message until after we read it.
 *
 * Thus, the max live messages size can actually be exceeded
 * by up to the maximum size of a single message.
 * 
 * Also, if we read say 1024 bytes off the wire in a single read(),
 * and that contains a half-dozen small messages, we may exceed the
 * size max by that amount. But this should be inconsequential.
 *
 * This does imply that we can't call read() with a buffer larger
 * than we're willing to exceed this limit by.
 *
 * @param connection the connection
 * @param size the maximum size in bytes of all outstanding messages
 */
void
dbus_connection_set_max_live_messages_size (DBusConnection *connection,
                                            long            size)
{
  dbus_mutex_lock (connection->mutex);
  _dbus_transport_set_max_live_messages_size (connection->transport,
                                              size);
  dbus_mutex_unlock (connection->mutex);
}

/**
 * Gets the value set by dbus_connection_set_max_live_messages_size().
 *
 * @param connection the connection
 * @returns the max size of all live messages
 */
long
dbus_connection_get_max_live_messages_size (DBusConnection *connection)
{
  long res;
  dbus_mutex_lock (connection->mutex);
  res = _dbus_transport_get_max_live_messages_size (connection->transport);
  dbus_mutex_unlock (connection->mutex);
  return res;
}

/** @} */