path: root/ace/Message_Queue.h

/* -*- C++ -*- */
// $Id$

// ============================================================================
//
// = LIBRARY
//    ace
//
// = FILENAME
//    Message_Queue.h
//
// = AUTHOR
//    Doug Schmidt
//
// ============================================================================

#ifndef ACE_MESSAGE_QUEUE_H
#define ACE_MESSAGE_QUEUE_H

#include "ace/Message_Block.h"

#if !defined (ACE_LACKS_PRAGMA_ONCE)
# pragma once
#endif /* ACE_LACKS_PRAGMA_ONCE */

#include "ace/IO_Cntl_Msg.h"

// Forward decls.
class ACE_Notification_Strategy;
template <ACE_SYNCH_DECL> class ACE_Message_Queue_Iterator;
template <ACE_SYNCH_DECL> class ACE_Message_Queue_Reverse_Iterator;

class ACE_Export ACE_Message_Queue_Base
{
  // = TITLE
  //   Workaround HP/C++ compiler bug with enums in templates.
  //
  // = DESCRIPTION
  //   The ever lamest HP/C++ compiler seems to fail if enums are
  //   defined inside a template, hence we have to move them into a
  //   base class.
public:
  // = Default high and low water marks.
  enum
  {
    DEFAULT_HWM = 16 * 1024,
    // Default high watermark (16 K).
    DEFAULT_LWM = 16 * 1024,
    // Default low watermark (same as high water mark).
    WAS_ACTIVE = 1,
    // Message queue was active before activate() or deactivate().
    WAS_INACTIVE = 2
    // Message queue was inactive before activate() or deactivate().
  };

  ACE_Message_Queue_Base (void);

  virtual int close (void) = 0;
  // Close down the message queue and release all resources.

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

  // = Enqueue and dequeue methods.

  // For the following enqueue and dequeue methods 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 enqueue_tail (ACE_Message_Block *new_item,
                            ACE_Time_Value *timeout = 0) = 0;
  virtual int enqueue (ACE_Message_Block *new_item,
                       ACE_Time_Value *timeout = 0) = 0;
  // Enqueue a <ACE_Message_Block *> into the tail of the queue.
  // Return -1 on failure, number of items in queue otherwise.

  virtual int dequeue_head (ACE_Message_Block *&first_item,
                            ACE_Time_Value *timeout = 0) = 0;
  virtual int dequeue (ACE_Message_Block *&first_item,
                       ACE_Time_Value *timeout = 0) = 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) = 0;
  // True if queue is full, else false.
  virtual int is_empty (void) = 0;
  // True if queue is empty, else false.

  // = Queue statistic methods.
  virtual size_t message_bytes (void) = 0;
  // Number of total bytes on the queue.
  virtual size_t message_count (void) = 0;
  // Number of total messages on the queue.

  // = Activation control methods.

  virtual int deactivate (void) = 0;
  // 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) = 0;
  // 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) = 0;
  // Returns true if <deactivated_> is enabled.

  // = Notification hook.

  virtual void dump (void) const = 0;
  // Dump the state of an object.

  ACE_ALLOC_HOOK_DECLARE;
  // Declare the dynamic allocation hooks.

private:
  // = Disallow these operations.
  ACE_UNIMPLEMENTED_FUNC (void operator= (const ACE_Message_Queue_Base &))
  ACE_UNIMPLEMENTED_FUNC (ACE_Message_Queue_Base (const ACE_Message_Queue_Base &))
};

// Include the templates here.
#include "ace/Message_Queue_T.h"

#if defined (VXWORKS)
# include /**/ <msgQLib.h>

class ACE_Message_Queue_Vx : public ACE_Message_Queue<ACE_NULL_SYNCH>
{
  // = TITLE
  //     Wrapper for VxWorks message queues.
  //
  // = DESCRIPTION
  //     Specialization of ACE_Message_Queue to simply wrap VxWorks
  //     MsgQ.  It does not use any synchronization, because it relies
  //     on the native MsgQ implementation to take care of that.  The
  //     only system calls that it uses are VxWorks msgQLib calls, so
  //     it is suitable for use in interrupt service routines.
  //
  //     NOTE: *Many* ACE_Message_Queue features are not supported with
  //     this specialization, including:
  //     * The two size arguments to the constructor and open () are
  //       interpreted differently.  The first is interpreted as the
  //       maximum number of bytes in a message.  The second is
  //       interpreted as the maximum number of messages that can be
  //       queued.
  //     * dequeue_head () *requires* that the ACE_Message_Block
  //       pointer argument point to an ACE_Message_Block that was
  //       allocated by the caller.  It must be big enough to support
  //       the received message, without using continutation.  The
  //       pointer argument is not modified.
  //     * Message priority.  MSG_Q_FIFO is hard-coded.
  //     * enqueue method timeouts.
  //     * peek_dequeue_head ().
  //     * ACE_Message_Queue_Iterators.
  //     * The ability to change low and high water marks after creation.
  //     * Message_Block chains.  The continuation field of ACE_Message_Block
  //     *   is ignored; only the first block of a fragment chain is
  //     *   recognized.
public:
  // = Initialization and termination methods.
  ACE_Message_Queue_Vx (size_t max_messages,
                        size_t max_message_length,
                        ACE_Notification_Strategy * = 0);

  // Create a message queue with all the defaults.
  virtual int open (size_t max_messages,
                    size_t max_message_length,
                    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_Vx (void);
  // Close down the message queue and release all resources.

  // = 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.

  void dump (void) const;
  // Dump the state of an object.

  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.

  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_Null_Mutex> &mon,
                                  ACE_Time_Value *tv);
  // Wait for the queue to become non-full.

  virtual int wait_not_empty_cond (ACE_Guard<ACE_Null_Mutex> &mon,
                                   ACE_Time_Value *tv);
  // 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.

  MSG_Q_ID msgq (void);
  // Access the underlying msgQ.

private:
  int max_messages_;
  // Maximum number of messages that can be queued.

  int max_message_length_;
  // Maximum message size, in bytes.

  int options_;
  // Native message queue options.

  // = Disallow these operations.
  ACE_UNIMPLEMENTED_FUNC (void operator= (const ACE_Message_Queue_Vx &))
  ACE_UNIMPLEMENTED_FUNC (ACE_Message_Queue_Vx (const ACE_Message_Queue_Vx &))

  ACE_UNIMPLEMENTED_FUNC (virtual int peek_dequeue_head
                            (ACE_Message_Block *&first_item,
                             ACE_Time_Value *tv = 0))
};
#endif /* VXWORKS */

#if defined (ACE_WIN32) && (ACE_HAS_WINNT4 != 0)
class ACE_Export ACE_Message_Queue_NT : public ACE_Message_Queue_Base
{
  // = TITLE
  //     Message Queue implementation using IO completion port on NT.
  //
  // = DESCRIPTION
  //     Implementation of a strip-downed ACE_Message_Queue using NT's
  //     IO completion port mechanism.
  //
  //     NOTE: *Many* ACE_Message_Queue features are not supported with
  //     this implementation, including:
  //     * open method have different signatures.
  //     * dequeue_head () *requires* that the ACE_Message_Block
  //       pointer argument point to an ACE_Message_Block that was
  //       allocated by the caller.
  //     * peek_dequeue_head ().
  //     * ACE_Message_Queue_Iterators.
  //     * No flow control.
public:
  // = Initialization and termination methods.
  ACE_Message_Queue_NT (size_t max_threads = ACE_Message_Queue_Base::DEFAULT_HWM);

  virtual int open (size_t max_threads = ACE_Message_Queue_Base::DEFAULT_HWM);
  // Initialize the Message Queue by creating a new NT I/O completion
  // port.  The first arguemnt specifies the number of threads
  // released by the MQ that are allowed to run concurrently.  Return
  // 0 when succeeds, -1 otherwise.

  virtual int close (void);
  // Close down the underlying I/O completion port.  You need to
  // re-open the MQ after this function is executed.

  virtual ~ACE_Message_Queue_NT (void);
  // Close down the message queue and release all resources.

  // = Enqueue and dequeue methods.

  virtual int enqueue_tail (ACE_Message_Block *new_item,
                            ACE_Time_Value *timeout = 0);
  virtual int enqueue (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 dequeue_head (ACE_Message_Block *&first_item,
                            ACE_Time_Value *timeout = 0);
  virtual int dequeue (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);
  // Always return false.
  virtual int is_empty (void);
  // True if queue is empty, else false.  Notice the return value is
  // only transient.

  // = Queue statistic methods (transient.)
  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.

  virtual size_t max_threads (void);
  // Get the max concurrent thread number.

  // = Activation control methods.

  virtual int deactivate (void);
  // Deactivate the queue and wakeup all threads waiting on the queue
  // so they can continue.  Messages already in the queue get removed.
  // If there are more messages in the queue than there are threads
  // waiting on the queue, the left over messages will not be removed.
  // Any other enqueue/dequeue 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 void dump (void) const;
  // Dump the state of an object.

  virtual ACE_HANDLE completion_port (void);
  // Get the handle to the underlying completion port.

  ACE_ALLOC_HOOK_DECLARE;
  // Declare the dynamic allocation hooks.

private:
  // = Internal states.

  size_t max_cthrs_;
  // Maximum threads that can be released (and run) concurrently.

  size_t cur_thrs_;
  // Current number of threads waiting to dequeue messages.

  size_t cur_bytes_;
  // Current number of bytes in queue.

  size_t cur_count_;
  // Current number of messages in the queue.

  ACE_Thread_Mutex lock_;
  // Synchronizer.  This should really be an ACE_Recursive_Thread_Mutex
  // but since this class is only supported on NT, it's okay to use
  // ACE_Thread_Mutex here.

  int deactivated_;
  // Indicates that the queue is inactive.

  ACE_HANDLE completion_port_;
  // Underlying NT IoCompletionPort.

  // = Disallow these operations.
  ACE_UNIMPLEMENTED_FUNC (void operator= (const ACE_Message_Queue_NT &))
  ACE_UNIMPLEMENTED_FUNC (ACE_Message_Queue_NT (const ACE_Message_Queue_NT &))
};
#endif /* ACE_WIN32 && ACE_HAS_WINNT4 != 0 */

// This must go here to avoid problems with circular includes.
#include "ace/Strategies.h"

#if defined (__ACE_INLINE__)
#include "ace/Message_Queue.i"
#endif /* __ACE_INLINE__ */

#endif /* ACE_MESSAGE_QUEUE_H */