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|
/* -*- C++ -*- */
// $Id$
// ============================================================================
//
// = LIBRARY
// ace
//
// = FILENAME
// Message_Queue_T.h
//
// = AUTHOR
// Doug Schmidt
//
// ============================================================================
#if !defined (ACE_MESSAGE_QUEUE_T_H)
#define ACE_MESSAGE_QUEUE_T_H
#include "ace/Synch.h"
#if defined (VXWORKS)
class ACE_Message_Queue_Vx;
#endif /* defined (VXWORKS) */
template <ACE_SYNCH_DECL>
class ACE_Message_Queue : public ACE_Message_Queue_Base
{
// = TITLE
// A threaded message queueing facility, modeled after the
// queueing facilities in System V STREAMs.
//
// = DESCRIPTION
// An <ACE_Message_Queue> is the central queueing facility for
// messages in the ASX framework. If <ACE_SYNCH_DECL> is
// ACE_MT_SYNCH then all operations are thread-safe. Otherwise,
// if it's <ACE_NULL_SYNCH> then there's no locking overhead.
public:
friend class ACE_Message_Queue_Iterator<ACE_SYNCH_USE>;
friend class ACE_Message_Queue_Reverse_Iterator<ACE_SYNCH_USE>;
// = Traits
typedef ACE_Message_Queue_Iterator<ACE_SYNCH_USE> ITERATOR;
typedef ACE_Message_Queue_Reverse_Iterator<ACE_SYNCH_USE> REVERSE_ITERATOR;
// = Initialization and termination methods.
ACE_Message_Queue (size_t hwm = ACE_Message_Queue_Base::DEFAULT_HWM,
size_t lwm = ACE_Message_Queue_Base::DEFAULT_LWM,
ACE_Notification_Strategy * = 0);
// Create a message queue with all the defaults.
virtual int open (size_t hwm = ACE_Message_Queue_Base::DEFAULT_HWM,
size_t lwm = ACE_Message_Queue_Base::DEFAULT_LWM,
ACE_Notification_Strategy * = 0);
// Create a message queue with all the defaults.
virtual int close (void);
// Close down the message queue and release all resources.
virtual ~ACE_Message_Queue (void);
// Close down the message queue and release all resources.
// = Enqueue and dequeue methods.
// For all the following routines if <timeout> == 0, the caller will
// block until action is possible, else will wait until the absolute
// time specified in *<timeout> elapses). These calls will return,
// however, when queue is closed, deactivated, when a signal occurs,
// or if the time specified in timeout elapses, (in which case errno
// = EWOULDBLOCK).
virtual int peek_dequeue_head (ACE_Message_Block *&first_item,
ACE_Time_Value *timeout = 0);
// Retrieve the first <ACE_Message_Block> without removing it.
// Returns -1 on failure, else the number of items still on the
// queue.
virtual int enqueue_prio (ACE_Message_Block *new_item,
ACE_Time_Value *timeout = 0);
// Enqueue an <ACE_Message_Block *> into the <Message_Queue> in
// accordance with its <msg_priority> (0 is lowest priority). FIFO
// order is maintained when messages of the same priority are
// inserted consecutively. Returns -1 on failure, else the number
// of items still on the queue.
virtual int enqueue (ACE_Message_Block *new_item,
ACE_Time_Value *timeout = 0);
// This is an alias for <enqueue_prio>. It's only here for
// backwards compatibility and will go away in a subsequent release.
// Please use <enqueue_prio> instead.
virtual int enqueue_tail (ACE_Message_Block *new_item,
ACE_Time_Value *timeout = 0);
// Enqueue an <ACE_Message_Block *> at the end of the queue.
// Returns -1 on failure, else the number of items still on the
// queue.
virtual int enqueue_head (ACE_Message_Block *new_item,
ACE_Time_Value *timeout = 0);
// Enqueue an <ACE_Message_Block *> at the head of the queue.
// Returns -1 on failure, else the number of items still on the
// queue.
virtual int dequeue_head (ACE_Message_Block *&first_item,
ACE_Time_Value *timeout = 0);
// 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.
// = Check if queue is full/empty.
virtual int is_full (void);
// True if queue is full, else false.
virtual int is_empty (void);
// True if queue is empty, else false.
// = Queue statistic methods.
virtual size_t message_bytes (void);
// Number of total bytes on the queue.
virtual size_t message_count (void);
// Number of total messages on the queue.
// = Flow control routines
virtual size_t high_water_mark (void);
// Get high watermark.
virtual void high_water_mark (size_t hwm);
// Set high watermark.
virtual size_t low_water_mark (void);
// Get low watermark.
virtual void low_water_mark (size_t lwm);
// Set low watermark.
// = Activation control methods.
virtual int deactivate (void);
// Deactivate the queue and wakeup all threads waiting on the queue
// so they can continue. No messages are removed from the queue,
// however. Any other operations called until the queue is
// activated again will immediately return -1 with <errno> ==
// ESHUTDOWN. Returns WAS_INACTIVE if queue was inactive before the
// call and WAS_ACTIVE if queue was active before the call.
virtual int activate (void);
// Reactivate the queue so that threads can enqueue and dequeue
// messages again. Returns WAS_INACTIVE if queue was inactive
// before the call and WAS_ACTIVE if queue was active before the
// call.
virtual int deactivated (void);
// Returns true if <deactivated_> is enabled.
// = Notification hook.
virtual int notify (void);
// This hook is automatically invoked by <enqueue_head>,
// <enqueue_tail>, and <enqueue_prio> when a new item is inserted
// into the queue. Subclasses can override this method to perform
// specific notification strategies (e.g., signaling events for a
// <WFMO_Reactor>, notifying a <Reactor>, etc.). In a
// multi-threaded application with concurrent consumers, there is no
// guarantee that the queue will be still be non-empty by the time
// the notification occurs.
// = Get/set the notification strategy for the <Message_Queue>
virtual ACE_Notification_Strategy *notification_strategy (void);
virtual void notification_strategy (ACE_Notification_Strategy *s);
virtual void dump (void) const;
// Dump the state of an object.
ACE_ALLOC_HOOK_DECLARE;
// Declare the dynamic allocation hooks.
protected:
// = Routines that actually do the enqueueing and dequeueing.
// These routines assume that locks are held by the corresponding
// public methods. Since they are virtual, you can change the
// queueing mechanism by subclassing from <ACE_Message_Queue>.
virtual int enqueue_i (ACE_Message_Block *new_item);
// Enqueue an <ACE_Message_Block *> in accordance with its priority.
virtual int enqueue_tail_i (ACE_Message_Block *new_item);
// Enqueue an <ACE_Message_Block *> at the end of the queue.
virtual int enqueue_head_i (ACE_Message_Block *new_item);
// Enqueue an <ACE_Message_Block *> at the head of the queue.
virtual int dequeue_head_i (ACE_Message_Block *&first_item);
// Dequeue and return the <ACE_Message_Block *> at the head of the
// queue.
// = Check the boundary conditions (assumes locks are held).
virtual int is_full_i (void);
// True if queue is full, else false.
virtual int is_empty_i (void);
// True if queue is empty, else false.
// = Implementation of the public activate() and deactivate() methods above (assumes locks are held).
virtual int deactivate_i (void);
// Deactivate the queue.
virtual int activate_i (void);
// Activate the queue.
// = Helper methods to factor out common #ifdef code.
virtual int wait_not_full_cond (ACE_Guard<ACE_SYNCH_MUTEX_T> &mon,
ACE_Time_Value *timeout);
// Wait for the queue to become non-full.
virtual int wait_not_empty_cond (ACE_Guard<ACE_SYNCH_MUTEX_T> &mon,
ACE_Time_Value *timeout);
// Wait for the queue to become non-empty.
virtual int signal_enqueue_waiters (void);
// Inform any threads waiting to enqueue that they can procede.
virtual int signal_dequeue_waiters (void);
// Inform any threads waiting to dequeue that they can procede.
ACE_Message_Block *head_;
// Pointer to head of ACE_Message_Block list.
ACE_Message_Block *tail_;
// Pointer to tail of ACE_Message_Block list.
size_t low_water_mark_;
// Lowest number before unblocking occurs.
size_t high_water_mark_;
// Greatest number of bytes before blocking.
size_t cur_bytes_;
// Current number of bytes in the queue.
size_t cur_count_;
// Current number of messages in the queue.
int deactivated_;
// Indicates that the queue is inactive.
ACE_Notification_Strategy *notification_strategy_;
// The notification strategy used when a new message is enqueued.
// = Synchronization primitives for controlling concurrent access.
ACE_SYNCH_MUTEX_T lock_;
// Protect queue from concurrent access.
#if defined (ACE_HAS_OPTIMIZED_MESSAGE_QUEUE)
ACE_SYNCH_SEMAPHORE_T not_empty_cond_;
// Used to make threads sleep until the queue is no longer empty.
ACE_SYNCH_SEMAPHORE_T not_full_cond_;
// Used to make threads sleep until the queue is no longer full.
size_t dequeue_waiters_;
// Number of threads waiting to dequeue a <Message_Block>.
size_t enqueue_waiters_;
// Number of threads waiting to enqueue a <Message_Block>.
#else
ACE_SYNCH_CONDITION_T not_empty_cond_;
// Used to make threads sleep until the queue is no longer empty.
ACE_SYNCH_CONDITION_T not_full_cond_;
// Used to make threads sleep until the queue is no longer full.
#endif /* ACE_HAS_OPTIMIZED_MESSAGE_QUEUE */
private:
// = Disallow these operations.
ACE_UNIMPLEMENTED_FUNC (void operator= (const ACE_Message_Queue<ACE_SYNCH_USE> &))
ACE_UNIMPLEMENTED_FUNC (ACE_Message_Queue (const ACE_Message_Queue<ACE_SYNCH_USE> &))
};
template <ACE_SYNCH_DECL>
class ACE_Message_Queue_Iterator
{
// = TITLE
// Iterator for the <ACE_Message_Queue>.
public:
// = Initialization method.
ACE_Message_Queue_Iterator (ACE_Message_Queue <ACE_SYNCH_USE> &queue);
// = Iteration methods.
int next (ACE_Message_Block *&entry);
// Pass back the <entry> that hasn't been seen in the queue.
// Returns 0 when all items have been seen, else 1.
int done (void) const;
// Returns 1 when all items have been seen, else 0.
int advance (void);
// Move forward by one element in the queue. Returns 0 when all the
// items in the set have been seen, else 1.
void dump (void) const;
// Dump the state of an object.
ACE_ALLOC_HOOK_DECLARE;
// Declare the dynamic allocation hooks.
private:
ACE_Message_Queue <ACE_SYNCH_USE> &queue_;
// Message_Queue we are iterating over.
ACE_Message_Block *curr_;
// Keeps track of how far we've advanced...
};
template <ACE_SYNCH_DECL>
class ACE_Message_Queue_Reverse_Iterator
{
// = TITLE
// Reverse Iterator for the <ACE_Message_Queue>.
public:
// = Initialization method.
ACE_Message_Queue_Reverse_Iterator (ACE_Message_Queue <ACE_SYNCH_USE> &queue);
// = Iteration methods.
int next (ACE_Message_Block *&entry);
// Pass back the <entry> that hasn't been seen in the queue.
// Returns 0 when all items have been seen, else 1.
int done (void) const;
// Returns 1 when all items have been seen, else 0.
int advance (void);
// Move forward by one element in the queue. Returns 0 when all the
// items in the set have been seen, else 1.
void dump (void) const;
// Dump the state of an object.
ACE_ALLOC_HOOK_DECLARE;
// Declare the dynamic allocation hooks.
private:
ACE_Message_Queue <ACE_SYNCH_USE> &queue_;
// Message_Queue we are iterating over.
ACE_Message_Block *curr_;
// Keeps track of how far we've advanced...
};
template <ACE_SYNCH_DECL>
class ACE_Dynamic_Message_Queue : public ACE_Message_Queue<ACE_SYNCH_USE>
{
// = TITLE
// 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.
//
// = DESCRIPTION
//
// 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 were made private, but for some
// compilers it is possible to gain access to these methods
// through base class pointers: achieving this may result in
// highly unpredictable results, as expectations about
// where a message starts or remains between method
// invocations may not hold for a dynamically managed
// message queue.
//
public:
// = Initialization and termination methods.
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.
virtual int remove_messages (ACE_Message_Block *&list_head,
ACE_Message_Block *&list_tail,
u_int status_flags);
// 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.
virtual int dequeue_head (ACE_Message_Block *&first_item,
ACE_Time_Value *timeout = 0);
// 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.
virtual void dump (void) const;
// Dump the state of the queue.
ACE_ALLOC_HOOK_DECLARE;
// Declare the dynamic allocation hooks.
protected:
virtual int enqueue_i (ACE_Message_Block *new_item);
// 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.
virtual int sublist_enqueue_i (ACE_Message_Block *new_item,
const ACE_Time_Value ¤t_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
virtual int dequeue_head_i (ACE_Message_Block *&first_item);
// 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.
virtual int refresh_queue (const ACE_Time_Value & current_time);
// Refresh the queue using the strategy
// specific priority status function.
virtual int refresh_pending_queue (const ACE_Time_Value & current_time);
// Refresh the pending queue using the strategy
// specific priority status function.
virtual int refresh_late_queue (const ACE_Time_Value & current_time);
// Refresh the late queue using the strategy
// specific priority status function.
ACE_Message_Block *pending_head_;
// Pointer to head of the pending messages
ACE_Message_Block *pending_tail_;
// Pointer to tail of the pending messages
ACE_Message_Block *late_head_;
// Pointer to head of the late messages
ACE_Message_Block *late_tail_;
// Pointer to tail of the late messages
ACE_Message_Block *beyond_late_head_;
// Pointer to head of the beyond late messages
ACE_Message_Block *beyond_late_tail_;
// Pointer to tail of the beyond late messages
ACE_Dynamic_Message_Strategy &message_strategy_;
// Pointer to a dynamic priority evaluation function.
private:
// = Disallow public access to these operations.
ACE_UNIMPLEMENTED_FUNC (void operator= (const ACE_Dynamic_Message_Queue<ACE_SYNCH_USE> &))
ACE_UNIMPLEMENTED_FUNC (ACE_Dynamic_Message_Queue (const ACE_Dynamic_Message_Queue<ACE_SYNCH_USE> &))
// provide definitions for these (just call base class method),
// but make them private so they're not accessible outside the class
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
virtual int enqueue_tail (ACE_Message_Block *new_item,
ACE_Time_Value *timeout = 0);
// private method to hide public base class method: just calls base class method
virtual int enqueue_head (ACE_Message_Block *new_item,
ACE_Time_Value *timeout = 0);
// private method to hide public base class method: just calls base class method
};
template <ACE_SYNCH_DECL>
class ACE_Message_Queue_Factory
{
// = TITLE
// ACE_Message_Queue_Factory is a static factory class template which
// provides a separate factory method for each of the major kinds of
// priority based message dispatching: static, earliest deadline first
// (EDF), and minimum laxity first (MLF).
//
// = DESCRIPTION
// The ACE_Dynamic_Message_Queue class assumes responsibility for
// releasing the resources of the strategy with which it was
// constructed: the user of a message queue constructed by
// any of these factory methods is only responsible for
// ensuring destruction of the message queue itself.
public:
static ACE_Message_Queue<ACE_SYNCH_USE> *
create_static_message_queue (size_t hwm = ACE_Message_Queue_Base::DEFAULT_HWM,
size_t lwm = ACE_Message_Queue_Base::DEFAULT_LWM,
ACE_Notification_Strategy * = 0);
// factory method for a statically prioritized ACE_Message_Queue
static ACE_Dynamic_Message_Queue<ACE_SYNCH_USE> *
create_deadline_message_queue (size_t hwm = ACE_Message_Queue_Base::DEFAULT_HWM,
size_t lwm = ACE_Message_Queue_Base::DEFAULT_LWM,
ACE_Notification_Strategy * = 0,
u_long static_bit_field_mask = 0x3FFUL, // 2^(10) - 1
u_long static_bit_field_shift = 10, // 10 low order bits
u_long dynamic_priority_max = 0x3FFFFFUL, // 2^(22)-1
u_long dynamic_priority_offset = 0x200000UL); // 2^(22-1)
// factory method for a dynamically prioritized (by time to deadline) ACE_Dynamic_Message_Queue
static ACE_Dynamic_Message_Queue<ACE_SYNCH_USE> *
create_laxity_message_queue (size_t hwm = ACE_Message_Queue_Base::DEFAULT_HWM,
size_t lwm = ACE_Message_Queue_Base::DEFAULT_LWM,
ACE_Notification_Strategy * = 0,
u_long static_bit_field_mask = 0x3FFUL, // 2^(10) - 1
u_long static_bit_field_shift = 10, // 10 low order bits
u_long dynamic_priority_max = 0x3FFFFFUL, // 2^(22)-1
u_long dynamic_priority_offset = 0x200000UL); // 2^(22-1)
// factory method for a dynamically prioritized (by laxity) ACE_Dynamic_Message_Queue
#if defined (VXWORKS)
static ACE_Message_Queue_Vx *
create_Vx_message_queue (size_t max_messages, size_t max_message_length,
ACE_Notification_Strategy *ns = 0);
// factory method for a wrapped VxWorks message queue
#endif /* defined (VXWORKS) */
};
#if defined (__ACE_INLINE__)
#include "ace/Message_Queue_T.i"
#endif /* __ACE_INLINE__ */
#if defined (ACE_TEMPLATES_REQUIRE_SOURCE)
#include "ace/Message_Queue_T.cpp"
#endif /* ACE_TEMPLATES_REQUIRE_SOURCE */
#if defined (ACE_TEMPLATES_REQUIRE_PRAGMA)
#pragma implementation ("Message_Queue_T.cpp")
#endif /* ACE_TEMPLATES_REQUIRE_PRAGMA */
#endif /* ACE_MESSAGE_QUEUE_T_H */
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