A derived class which adapts the ACE_Message_Queue class in order to maintain dynamic priorities for enqueued <ACE_Message_Blocks> and manage the queue order according to these dynamic priorities. More...

#include <Message_Queue_T.h>

Inheritance diagram for ACE_Dynamic_Message_Queue< ACE_SYNCH_DECL, TIME_POLICY >:

[legend]

Collaboration diagram for ACE_Dynamic_Message_Queue< ACE_SYNCH_DECL, TIME_POLICY >:

[legend]

Public Member Functions
	ACE_Dynamic_Message_Queue (ACE_Dynamic_Message_Strategy &message_strategy, size_t hwm=ACE_Message_Queue_Base::DEFAULT_HWM, size_t lwm=ACE_Message_Queue_Base::DEFAULT_LWM, ACE_Notification_Strategy *=0)

virtual	~ACE_Dynamic_Message_Queue (void)
	Close down the message queue and release all resources. More...

virtual int	remove_messages (ACE_Message_Block &list_head, ACE_Message_Block &list_tail, u_int status_flags)

virtual int	dequeue_head (ACE_Message_Block &first_item, ACE_Time_Value timeout=0)

virtual void	dump (void) const
	Dump the state of the queue. More...

virtual int	enqueue_tail (ACE_Message_Block new_item, ACE_Time_Value timeout=0)

virtual int	enqueue_head (ACE_Message_Block new_item, ACE_Time_Value timeout=0)

Public Member Functions inherited from ACE_Message_Queue< ACE_SYNCH_USE, TIME_POLICY >
virtual int	close (void)

virtual	~ACE_Message_Queue (void)
	Releases all resources from the message queue and marks it deactivated. More...

virtual int	flush (void)

virtual int	flush_i (void)

virtual ACE_SYNCH_MUTEX_T &	lock (void)
	Returns a reference to the lock used by the ACE_Message_Queue. More...

ACE_Time_Value_T< TIME_POLICY >	gettimeofday (void) const

void	set_time_policy (TIME_POLICY const &time_policy)

	ACE_Message_Queue (size_t hwm=ACE_Message_Queue_Base::DEFAULT_HWM, size_t lwm=ACE_Message_Queue_Base::DEFAULT_LWM, ACE_Notification_Strategy *ns=0)

virtual int	open (size_t hwm=ACE_Message_Queue_Base::DEFAULT_HWM, size_t lwm=ACE_Message_Queue_Base::DEFAULT_LWM, ACE_Notification_Strategy *ns=0)

virtual int	enqueue_prio (ACE_Message_Block new_item, ACE_Time_Value timeout=0)

virtual int	enqueue_deadline (ACE_Message_Block new_item, ACE_Time_Value timeout=0)

virtual int	enqueue (ACE_Message_Block new_item, ACE_Time_Value timeout=0)

virtual int	dequeue (ACE_Message_Block &first_item, ACE_Time_Value timeout=0)
	This method is an alias for the dequeue_head() method. More...

virtual int	dequeue_prio (ACE_Message_Block &first_item, ACE_Time_Value timeout=0)

virtual int	dequeue_tail (ACE_Message_Block &dequeued, ACE_Time_Value timeout=0)

virtual int	dequeue_deadline (ACE_Message_Block &dequeued, ACE_Time_Value timeout=0)

virtual bool	is_full (void)
	True if queue is full, else false. More...

virtual bool	is_empty (void)
	True if queue is empty, else false. More...

virtual size_t	message_bytes (void)

virtual void	message_bytes (size_t new_size)

virtual size_t	message_length (void)

virtual void	message_length (size_t new_length)

virtual size_t	message_count (void)

virtual size_t	high_water_mark (void)

virtual void	high_water_mark (size_t hwm)

virtual size_t	low_water_mark (void)

virtual void	low_water_mark (size_t lwm)

virtual int	deactivate (void)

virtual int	activate (void)

virtual int	pulse (void)

virtual int	state (void)

virtual int	deactivated (void)

virtual int	notify (void)

virtual ACE_Notification_Strategy *	notification_strategy (void)
	Get the notification strategy for the <Message_Queue> More...

virtual void	notification_strategy (ACE_Notification_Strategy *s)
	Set the notification strategy for the <Message_Queue> More...

Public Member Functions inherited from ACE_Message_Queue_Base
	ACE_Message_Queue_Base (void)

virtual	~ACE_Message_Queue_Base (void)
	Close down the message queue and release all resources. More...

Public Attributes
	ACE_ALLOC_HOOK_DECLARE
	Declare the dynamic allocation hooks. More...

Public Attributes inherited from ACE_Message_Queue< ACE_SYNCH_USE, TIME_POLICY >
	ACE_ALLOC_HOOK_DECLARE
	Declare the dynamic allocation hooks. More...

Public Attributes inherited from ACE_Message_Queue_Base
	ACE_ALLOC_HOOK_DECLARE
	Declare the dynamic allocation hooks. More...

Protected Member Functions
virtual int	enqueue_i (ACE_Message_Block *new_item)

virtual int	sublist_enqueue_i (ACE_Message_Block new_item, const ACE_Time_Value &current_time, ACE_Message_Block &sublist_head, ACE_Message_Block *&sublist_tail, ACE_Dynamic_Message_Strategy::Priority_Status status)
	Enqueue a message in priority order within a given priority status sublist. More...

virtual int	dequeue_head_i (ACE_Message_Block *&first_item)

virtual int	refresh_queue (const ACE_Time_Value &current_time)

virtual int	refresh_pending_queue (const ACE_Time_Value &current_time)

virtual int	refresh_late_queue (const ACE_Time_Value &current_time)

Protected Member Functions inherited from ACE_Message_Queue< ACE_SYNCH_USE, TIME_POLICY >
virtual int	enqueue_deadline_i (ACE_Message_Block *new_item)
	Enqueue an <ACE_Message_Block *> in accordance with its deadline time. More...

virtual int	enqueue_tail_i (ACE_Message_Block *new_item)
	Enqueue an <ACE_Message_Block *> at the end of the queue. More...

virtual int	enqueue_head_i (ACE_Message_Block *new_item)
	Enqueue an <ACE_Message_Block *> at the head of the queue. More...

virtual int	dequeue_prio_i (ACE_Message_Block *&dequeued)

virtual int	dequeue_tail_i (ACE_Message_Block *&first_item)

virtual int	dequeue_deadline_i (ACE_Message_Block *&first_item)

virtual bool	is_full_i (void)
	True if queue is full, else false. More...

virtual bool	is_empty_i (void)
	True if queue is empty, else false. More...

virtual int	deactivate_i (int pulse=0)

virtual int	activate_i (void)
	Activate the queue. More...

virtual int	wait_not_full_cond (ACE_Time_Value *timeout)
	Wait for the queue to become non-full. More...

virtual int	wait_not_empty_cond (ACE_Time_Value *timeout)
	Wait for the queue to become non-empty. More...

virtual int	signal_enqueue_waiters (void)
	Inform any threads waiting to enqueue that they can procede. More...

virtual int	signal_dequeue_waiters (void)
	Inform any threads waiting to dequeue that they can procede. More...

Protected Attributes
ACE_Message_Block *	pending_head_
	Pointer to head of the pending messages. More...

ACE_Message_Block *	pending_tail_
	Pointer to tail of the pending messages. More...

ACE_Message_Block *	late_head_
	Pointer to head of the late messages. More...

ACE_Message_Block *	late_tail_
	Pointer to tail of the late messages. More...

ACE_Message_Block *	beyond_late_head_
	Pointer to head of the beyond late messages. More...

ACE_Message_Block *	beyond_late_tail_
	Pointer to tail of the beyond late messages. More...

ACE_Dynamic_Message_Strategy &	message_strategy_
	Pointer to a dynamic priority evaluation function. More...

Protected Attributes inherited from ACE_Message_Queue< ACE_SYNCH_USE, TIME_POLICY >
ACE_Message_Block *	head_
	Pointer to head of ACE_Message_Block list. More...

ACE_Message_Block *	tail_
	Pointer to tail of ACE_Message_Block list. More...

size_t	low_water_mark_
	Lowest number before unblocking occurs. More...

size_t	high_water_mark_
	Greatest number of bytes before blocking. More...

size_t	cur_bytes_
	Current number of bytes in the queue. More...

size_t	cur_length_
	Current length of messages in the queue. More...

size_t	cur_count_
	Current number of messages in the queue. More...

ACE_Notification_Strategy *	notification_strategy_
	The notification strategy used when a new message is enqueued. More...

ACE_SYNCH_MUTEX_T	lock_
	Protect queue from concurrent access. More...

ACE_Condition_Attributes_T< TIME_POLICY >	cond_attr_
	Attributes to initialize conditions with. More...

ACE_SYNCH_CONDITION_T	not_empty_cond_
	Used to make threads sleep until the queue is no longer empty. More...

ACE_SYNCH_CONDITION_T	not_full_cond_
	Used to make threads sleep until the queue is no longer full. More...

TIME_POLICY	time_policy_
	The policy to return the current time of day. More...

Protected Attributes inherited from ACE_Message_Queue_Base
int	state_

Private Member Functions
void	operator= (const ACE_Dynamic_Message_Queue< _ACE_SYNCH, TIME_POLICY > &)

	ACE_Dynamic_Message_Queue (const ACE_Dynamic_Message_Queue< _ACE_SYNCH, TIME_POLICY > &)

virtual int	peek_dequeue_head (ACE_Message_Block &first_item, ACE_Time_Value timeout=0)
	Private method to hide public base class method: just calls base class method. More...

Additional Inherited Members
Public Types inherited from ACE_Message_Queue< ACE_SYNCH_USE, TIME_POLICY >
typedef ACE_Message_Queue_Iterator< ACE_SYNCH_USE, TIME_POLICY >	ITERATOR

typedef ACE_Message_Queue_Reverse_Iterator< ACE_SYNCH_USE, TIME_POLICY >	REVERSE_ITERATOR

Public Types inherited from ACE_Message_Queue_Base
enum	{ DEFAULT_HWM = 16 * 1024, DEFAULT_LWM = 16 * 1024, ACTIVATED = 1, DEACTIVATED = 2, PULSED = 3 }

Detailed Description

template<ACE_SYNCH_DECL, class TIME_POLICY = ACE_System_Time_Policy>
class ACE_Dynamic_Message_Queue< ACE_SYNCH_DECL, TIME_POLICY >

A derived class which adapts the ACE_Message_Queue class in order to maintain dynamic priorities for enqueued <ACE_Message_Blocks> and manage the queue order according to these dynamic priorities.

The messages in the queue are managed so as to preserve a logical ordering with minimal overhead per enqueue and dequeue operation. For this reason, the actual order of messages in the linked list of the queue may differ from their priority order. As time passes, a message may change from pending status to late status, and eventually to beyond late status. To minimize reordering overhead under this design force, three separate boundaries are maintained within the linked list of messages. Messages are dequeued preferentially from the head of the pending portion, then the head of the late portion, and finally from the head of the beyond late portion. In this way, only the boundaries need to be maintained (which can be done efficiently, as aging messages maintain the same linked list order as they progress from one status to the next), with no reordering of the messages themselves, while providing correct priority ordered dequeueing semantics. Head and tail enqueue methods inherited from ACE_Message_Queue are made private to prevent out-of-order messages from confusing management of the various portions of the queue. Messages in the pending portion of the queue whose priority becomes late (according to the specific dynamic strategy) advance into the late portion of the queue. Messages in the late portion of the queue whose priority becomes later than can be represented advance to the beyond_late portion of the queue. These behaviors support a limited schedule overrun, with pending messages prioritized ahead of late messages, and late messages ahead of beyond late messages. These behaviors can be modified in derived classes by providing alternative definitions for the appropriate virtual methods. When filled with messages, the queue's linked list should look like: H T | | B - B - B - B - L - L - L - P - P - P - P - P | | | | | | BH BT LH LT PH PT Where the symbols are as follows: H = Head of the entire list T = Tail of the entire list B = Beyond late message BH = Beyond late messages Head BT = Beyond late messages Tail L = Late message LH = Late messages Head LT = Late messages Tail P = Pending message PH = Pending messages Head PT = Pending messages Tail Caveat: the virtual methods enqueue_tail, enqueue_head, and peek_dequeue_head have semantics for the static message queues that cannot be guaranteed for dynamic message queues. The peek_dequeue_head method just calls the base class method, while the two enqueue methods call the priority enqueue method. The order of messages in the dynamic queue is a function of message deadlines and how long they are in the queues. You can manipulate these in some cases to ensure the correct semantics, but that is not a very stable or portable approach (discouraged).

Constructor & Destructor Documentation

template<ACE_SYNCH_DECL , class TIME_POLICY >

ACE_Dynamic_Message_Queue< ACE_SYNCH_DECL, TIME_POLICY >::ACE_Dynamic_Message_Queue	(	ACE_Dynamic_Message_Strategy &	message_strategy,
		size_t	hwm = `ACE_Message_Queue_Base::DEFAULT_HWM`,
		size_t	lwm = `ACE_Message_Queue_Base::DEFAULT_LWM`,
		ACE_Notification_Strategy *	ns = `0`
	)

template<ACE_SYNCH_DECL , class TIME_POLICY >

ACE_Dynamic_Message_Queue< ACE_SYNCH_DECL, TIME_POLICY >::~ACE_Dynamic_Message_Queue ( void )

virtual

Close down the message queue and release all resources.

template<ACE_SYNCH_DECL , class TIME_POLICY = ACE_System_Time_Policy>

ACE_Dynamic_Message_Queue< ACE_SYNCH_DECL, TIME_POLICY >::ACE_Dynamic_Message_Queue ( const ACE_Dynamic_Message_Queue< _ACE_SYNCH, TIME_POLICY > & )

private

Member Function Documentation

template<ACE_SYNCH_DECL , class TIME_POLICY >

int ACE_Dynamic_Message_Queue< ACE_SYNCH_DECL, TIME_POLICY >::dequeue_head	(	ACE_Message_Block *&	first_item,
		ACE_Time_Value *	timeout = `0`
	)

virtual

Dequeue and return the <ACE_Message_Block *> at the head of the queue. Returns -1 on failure, else the number of items still on the queue.

Reimplemented from ACE_Message_Queue< ACE_SYNCH_USE, TIME_POLICY >.

template<ACE_SYNCH_DECL , class TIME_POLICY >

int ACE_Dynamic_Message_Queue< ACE_SYNCH_DECL, TIME_POLICY >::dequeue_head_i ( ACE_Message_Block *& first_item )

protectedvirtual

Dequeue and return the <ACE_Message_Block *> at the head of the logical queue. Attempts first to dequeue from the pending portion of the queue, or if that is empty from the late portion, or if that is empty from the beyond late portion, or if that is empty just sets the passed pointer to zero and returns -1.

Reimplemented from ACE_Message_Queue< ACE_SYNCH_USE, TIME_POLICY >.

template<ACE_SYNCH_DECL , class TIME_POLICY >

void ACE_Dynamic_Message_Queue< ACE_SYNCH_DECL, TIME_POLICY >::dump ( void ) const

virtual

Dump the state of the queue.

Reimplemented from ACE_Message_Queue< ACE_SYNCH_USE, TIME_POLICY >.

template<ACE_SYNCH_DECL , class TIME_POLICY >

int ACE_Dynamic_Message_Queue< ACE_SYNCH_DECL, TIME_POLICY >::enqueue_head	(	ACE_Message_Block *	new_item,
		ACE_Time_Value *	timeout = `0`
	)

virtual

Just call priority enqueue method: head enqueue semantics for dynamic message queues are unstable: the message may or may not be where it was placed after the queue is refreshed prior to the next enqueue or dequeue operation.

Reimplemented from ACE_Message_Queue< ACE_SYNCH_USE, TIME_POLICY >.

template<ACE_SYNCH_DECL , class TIME_POLICY >

int ACE_Dynamic_Message_Queue< ACE_SYNCH_DECL, TIME_POLICY >::enqueue_i ( ACE_Message_Block * new_item )

protectedvirtual

Enqueue an <ACE_Message_Block *> in accordance with its priority. priority may be dynamic or static or a combination or both It calls the priority evaluation function passed into the Dynamic Message Queue constructor to update the priorities of all enqueued messages.

Reimplemented from ACE_Message_Queue< ACE_SYNCH_USE, TIME_POLICY >.

template<ACE_SYNCH_DECL , class TIME_POLICY >

int ACE_Dynamic_Message_Queue< ACE_SYNCH_DECL, TIME_POLICY >::enqueue_tail	(	ACE_Message_Block *	new_item,
		ACE_Time_Value *	timeout = `0`
	)

virtual

Just call priority enqueue method: tail enqueue semantics for dynamic message queues are unstable: the message may or may not be where it was placed after the queue is refreshed prior to the next enqueue or dequeue operation.

Reimplemented from ACE_Message_Queue< ACE_SYNCH_USE, TIME_POLICY >.

template<ACE_SYNCH_DECL , class TIME_POLICY = ACE_System_Time_Policy>

void ACE_Dynamic_Message_Queue< ACE_SYNCH_DECL, TIME_POLICY >::operator= ( const ACE_Dynamic_Message_Queue< _ACE_SYNCH, TIME_POLICY > & )

private

template<ACE_SYNCH_DECL , class TIME_POLICY >

int ACE_Dynamic_Message_Queue< ACE_SYNCH_DECL, TIME_POLICY >::peek_dequeue_head	(	ACE_Message_Block *&	first_item,
		ACE_Time_Value *	timeout = `0`
	)

privatevirtual

Private method to hide public base class method: just calls base class method.

Reimplemented from ACE_Message_Queue< ACE_SYNCH_USE, TIME_POLICY >.

template<ACE_SYNCH_DECL , class TIME_POLICY >

int ACE_Dynamic_Message_Queue< ACE_SYNCH_DECL, TIME_POLICY >::refresh_late_queue ( const ACE_Time_Value & current_time )

protectedvirtual

Refresh the late queue using the strategy specific priority status function.

template<ACE_SYNCH_DECL , class TIME_POLICY >

int ACE_Dynamic_Message_Queue< ACE_SYNCH_DECL, TIME_POLICY >::refresh_pending_queue ( const ACE_Time_Value & current_time )

protectedvirtual

Refresh the pending queue using the strategy specific priority status function.

template<ACE_SYNCH_DECL , class TIME_POLICY >

int ACE_Dynamic_Message_Queue< ACE_SYNCH_DECL, TIME_POLICY >::refresh_queue ( const ACE_Time_Value & current_time )

protectedvirtual

Refresh the queue using the strategy specific priority status function.

template<ACE_SYNCH_DECL , class TIME_POLICY >

int ACE_Dynamic_Message_Queue< ACE_SYNCH_DECL, TIME_POLICY >::remove_messages	(	ACE_Message_Block *&	list_head,
		ACE_Message_Block *&	list_tail,
		u_int	status_flags
	)

virtual

Detach all messages with status given in the passed flags from the queue and return them by setting passed head and tail pointers to the linked list they comprise. This method is intended primarily as a means of periodically harvesting messages that have missed their deadlines, but is available in its most general form. All messages are returned in priority order, from head to tail, as of the time this method was called.

template<ACE_SYNCH_DECL , class TIME_POLICY >

int ACE_Dynamic_Message_Queue< ACE_SYNCH_DECL, TIME_POLICY >::sublist_enqueue_i	(	ACE_Message_Block *	new_item,
		const ACE_Time_Value &	current_time,
		ACE_Message_Block *&	sublist_head,
		ACE_Message_Block *&	sublist_tail,
		ACE_Dynamic_Message_Strategy::Priority_Status	status
	)