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// -*- C++ -*-
/**
* @file EC_Filter.h
*
* @author Carlos O'Ryan (coryan@cs.wustl.edu)
*
* Based on previous work by Tim Harrison (harrison@cs.wustl.edu) and
* other members of the DOC group. More details can be found in:
*
* http://doc.ece.uci.edu/~coryan/EC/index.html
*/
#ifndef TAO_EC_FILTER_H
#define TAO_EC_FILTER_H
#include /**/ "ace/pre.h"
#include "orbsvcs/RtecEventCommC.h"
#include /**/ "orbsvcs/Event/event_serv_export.h"
#if !defined (ACE_LACKS_PRAGMA_ONCE)
# pragma once
#endif /* ACE_LACKS_PRAGMA_ONCE */
TAO_BEGIN_VERSIONED_NAMESPACE_DECL
class TAO_EC_QOS_Info;
/**
* @class TAO_EC_Filter
*
* @brief Abstract base class for the filter hierarchy.
*
* The per-consumer filtering mechanisms.
* The EC needs to filter data passed to the consumers, so it can
* correctly satisfy its subscription requirements.
* This filtering can include correlations, sequences, timeouts,
* etc. each consumer can request different filtering criteria.
* Different filtering objects are associated with each consumer,
* the filters are organized in a hierarchical structure,
* corresponding to the subscription "expression" that the events
* must satisfy.
* The hierarchy is constructed using the "Builder" pattern.
*
* <H2>Memory Management</H2>
* It does *not* assume ownership of its parent.
*/
class TAO_RTEvent_Serv_Export TAO_EC_Filter
{
public:
/// constructor...
TAO_EC_Filter (void);
/// destructor...
virtual ~TAO_EC_Filter (void);
/// Obtain the parent of this filter.
TAO_EC_Filter* parent (void) const;
/// Become the parent of @a child.
void adopt_child (TAO_EC_Filter* child);
/// Matches two event headers.
/// @todo Should we strategize the algorithm used to match headers?
static int matches (const RtecEventComm::EventHeader& rhs,
const RtecEventComm::EventHeader& lhs);
typedef TAO_EC_Filter* value_type;
typedef TAO_EC_Filter* const const_value_type;
typedef const_value_type* ChildrenIterator;
/**
* STL-like iterators
* Filters follow the Composite pattern. All filters expose the same
* interface as if they all had children, but for simple filters the
* iterators return an empty range.
*/
virtual ChildrenIterator begin (void) const;
virtual ChildrenIterator end (void) const;
virtual int size (void) const;
/**
* Filter this event, returns 1 if the event is accepted, 0
* otherwise.
* Notice that there are two versions of the method, if the event is
* not const then filter can take ownership of the event.
*
* @attention There seems to be a disparity in interfaces: Supplier
* always push event sets of size 1 to the EC_ProxyPushSupplier, and
* EC_Filters do not implement handling of sets of more than 1
* event. Then, why is this not enforced by the interface by having
* EC_ProxyPushSupplier take an event rather than a set?
*/
virtual int filter (const RtecEventComm::EventSet& event,
TAO_EC_QOS_Info& qos_info) = 0;
virtual int filter_nocopy (RtecEventComm::EventSet& event,
TAO_EC_QOS_Info& qos_info) = 0;
/**
* This is called by the children when they accept an event and
* which to pass it up.
* Notice that there are two versions of the method, if the event is
* not const then filter can take ownership of the event.
*/
virtual void push (const RtecEventComm::EventSet& event,
TAO_EC_QOS_Info& qos_info) = 0;
virtual void push_nocopy (RtecEventComm::EventSet& event,
TAO_EC_QOS_Info& qos_info) = 0;
/// Clear any saved state, must reset and assume no events have been
/// received.
virtual void clear (void) = 0;
/// Returns the maximum size of the events pushed by this filter.
virtual CORBA::ULong max_event_size (void) const = 0;
/**
* Returns 0 if an event with that header could never be accepted.
* This can used by the suppliers to filter out consumers that
* couldn't possibly be interested in their events.
* The rt_info and
*/
virtual int can_match (const RtecEventComm::EventHeader& header) const = 0;
/**
* This is used for computing the scheduling dependencies:
*
* Leaf filters check if the header could be matched, similar to the
* can_match() method; if it does they return 1, and 0 otherwise.
* Intermediate nodes always return 0.
*
* This is used to build precise dependencies between the suppliers
* and the leaf of the filters that accept that event. Notice that
* only the nodes doing scheduling recurse through the list, so in
* configurations that do no require scheduling the recursion stops
* fairly soon.
*/
virtual int add_dependencies (const RtecEventComm::EventHeader& header,
const TAO_EC_QOS_Info& qos_info) = 0;
/**
* Obtain the QOS information for this filter, the default
* implementation returns an invalid QOS. Only the filters that
* support scheduling information implement this method.
* @return Returns 0 on success and -1 on failure
*/
virtual void get_qos_info (TAO_EC_QOS_Info& qos_info);
private:
/// The parent...
TAO_EC_Filter* parent_;
};
// ****************************************************************
/**
* @class TAO_EC_Null_Filter
*
* @brief A null filter
*
* This filter accepts any kind of event, it is useful for the
* implementation:
* a) Consumers that accept all events
* b) Consumers that trust the filtering done at the Supplier
* layer.
* c) Event Channels that don't do filtering (such as CosEC
* backends)
*/
class TAO_RTEvent_Serv_Export TAO_EC_Null_Filter : public TAO_EC_Filter
{
public:
/// Constructor.
TAO_EC_Null_Filter (void);
// = The TAO_EC_Filter methods, please check the documentation in
// TAO_EC_Filter.
virtual int filter (const RtecEventComm::EventSet& event,
TAO_EC_QOS_Info& qos_info);
virtual int filter_nocopy (RtecEventComm::EventSet& event,
TAO_EC_QOS_Info& qos_info);
virtual void push (const RtecEventComm::EventSet& event,
TAO_EC_QOS_Info& qos_info);
virtual void push_nocopy (RtecEventComm::EventSet& event,
TAO_EC_QOS_Info& qos_info);
virtual void clear (void);
virtual CORBA::ULong max_event_size (void) const;
virtual int can_match (const RtecEventComm::EventHeader& header) const;
virtual int add_dependencies (const RtecEventComm::EventHeader& header,
const TAO_EC_QOS_Info &qos_info);
};
// ****************************************************************
// @@ Add more types of filters like:
// - Events in a sequence.
// - Events in a sequence with timeouts.
// - Conjunction with timeout [as opposed to disjunction of
// conjunction and a timeout]
// - etc.
// ****************************************************************
TAO_END_VERSIONED_NAMESPACE_DECL
#if defined (__ACE_INLINE__)
#include "orbsvcs/Event/EC_Filter.inl"
#endif /* __ACE_INLINE__ */
#include /**/ "ace/post.h"
#endif /* TAO_EC_FILTER_H */
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