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// -*- C++ -*-
//=============================================================================
/**
* @file LF_Event.h
*
* @author Carlos O'Ryan <coryan@uci.edu>
*/
//=============================================================================
#ifndef TAO_LF_EVENT_H
#define TAO_LF_EVENT_H
#include /**/ "ace/pre.h"
#include /**/ "tao/TAO_Export.h"
#if !defined (ACE_LACKS_PRAGMA_ONCE)
# pragma once
#endif /* ACE_LACKS_PRAGMA_ONCE */
#include /**/ "tao/Versioned_Namespace.h"
TAO_BEGIN_VERSIONED_NAMESPACE_DECL
class TAO_LF_Follower;
class TAO_Leader_Follower;
/**
* @class TAO_LF_Event
*
* @brief Use the Leader/Follower loop to wait for one specific event.
*
* The Leader/Follower event loop is used to wait for incoming
* responses, as well as to wait for all the data to be flushed.
* This class encapsulates this event loop. It uses Template Method to
* parametrize the 'waited for' predicate (i.e. reply received or
* message sent or connection establishment etc.)
*
* @todo Implementing the Leader/Followers loop in this class, as
* well as the callbacks to communicate that an event has completed
* leads to excessive coupling. A better design would use a separate
* class to signal the events, that would allow us to remove the
* Leader/Followers logic from the ORB. However, that requires other
* major changes and it somewhat complicates the design.
*/
class TAO_Export TAO_LF_Event
{
public:
friend class TAO_Leader_Follower;
/// Constructor
TAO_LF_Event (void);
/// Destructor
virtual ~TAO_LF_Event (void);
/// Bind a follower
/**
* An event can be waited on by at most one follower thread, this
* method is used to bind the waiting thread to the event, in order
* to let the event signal any important state changes.
*
* This is virtual to allow the LF_Multi_Event derived type share
* the follower with all the subordinate LF_CH_Events.
*
* @return -1 if the LF_Event is already bound, 0 otherwise
*/
virtual int bind (TAO_LF_Follower *follower);
/// Unbind the follower
virtual int unbind (TAO_LF_Follower *follower);
//@{
/** @name State management
*
* A Leader/Followers event goes through several states during its
* lifetime. We use an enum to represent those states and state
* changes are validated according to the rules defined in the
* concrete classes. We treat the states as finite states in a
* FSM. The possible sequence of states through which the FSM
* migrates is defined in the concrete classes.
*/
enum LFS_STATE {
/// The event is created, and is in initial state
LFS_IDLE = 0,
/// The event is active
LFS_ACTIVE,
/// The event is waiting for connection completion.
LFS_CONNECTION_WAIT,
/// The event has completed successfully
LFS_SUCCESS,
/// A failure has been detected while the event was active
LFS_FAILURE,
/// The event has timed out
LFS_TIMEOUT,
/// The connection was closed.
LFS_CONNECTION_CLOSED
};
/// Accessor to change the state. The state isn't changed unless
/// certain conditions are satisfied.
void state_changed (LFS_STATE new_state, TAO_Leader_Follower &lf);
/// Return true if the condition was satisfied successfully, false if it
/// has not
bool successful (TAO_Leader_Follower &lf) const;
/// Return true if an error was detected while waiting for the
/// event
bool error_detected (TAO_Leader_Follower &lf) const;
/// Check if we should keep waiting.
bool keep_waiting (TAO_Leader_Follower &lf) const;
//@}
/// Reset the state, irrespective of the previous states
void reset_state (LFS_STATE new_state);
static const char *state_name (LFS_STATE st);
protected:
/// Validate the state change
virtual void state_changed_i (LFS_STATE new_state) = 0;
/// Check if we should keep waiting.
bool keep_waiting_i () const;
/// Return true if the condition was satisfied successfully, false if it
/// has not
virtual bool successful_i () const = 0 ;
/// Return true if an error was detected while waiting for the
/// event
virtual bool error_detected_i () const = 0;
/// Check whether we have reached the final state..
virtual bool is_state_final () const = 0;
private:
/// Set the state irrespective of anything.
virtual void set_state (LFS_STATE new_state);
protected:
/// The current state
LFS_STATE state_;
/// The bounded follower
TAO_LF_Follower *follower_;
};
TAO_END_VERSIONED_NAMESPACE_DECL
#if defined (__ACE_INLINE__)
# include "tao/LF_Event.inl"
#endif /* __ACE_INLINE__ */
#include /**/ "ace/post.h"
#endif /* TAO_LF_EVENT_H */
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