Represent messages queued in the outgoing data path of the TAO_Transport class. More...

#include <Queued_Message.h>

Inheritance diagram for TAO_Queued_Message:

Collaboration diagram for TAO_Queued_Message:

Public Member Functions
	TAO_Queued_Message (TAO_ORB_Core oc, ACE_Allocator alloc=0, bool is_heap_allocated=false)
	Constructor.
virtual	~TAO_Queued_Message (void)
	Destructor.
Intrusive list manipulation
The messages are put in a doubled linked list (for easy insertion and removal). To minimize memory allocations the list is intrusive, i.e. each element in the list contains the pointers for the next and previous element. The following methods are used to manipulate this implicit list. Todo: We should implement this as a base template, something like: template<class T> Intrusive_Node { public: void next (T ); T next () const; private: T* next_; }; and use it as follows: class TAO_Queued_Message : public Intrusive_Node<TAO_Queued_Message> { };
TAO_Queued_Message *	next (void) const
	Set/get the next element in the list.
TAO_Queued_Message *	prev (void) const
	Set/get the previous element in the list.
void	remove_from_list (TAO_Queued_Message &head, TAO_Queued_Message &tail)
	Remove this element from the list.
void	push_back (TAO_Queued_Message &head, TAO_Queued_Message &tail)
	Insert the current element at the tail of the queue.
void	push_front (TAO_Queued_Message &head, TAO_Queued_Message &tail)
	Insert the current element at the head of the queue.
Template Methods
virtual size_t	message_length (void) const =0
	Return the length of the message.
virtual int	all_data_sent (void) const =0
	Return 1 if all the data has been sent.
virtual void	fill_iov (int iovcnt_max, int &iovcnt, iovec iov[]) const =0
	Fill up an io vector using the connects of the message.
virtual void	bytes_transferred (size_t &byte_count)=0
	Update the internal state, data has been sent.
virtual TAO_Queued_Message *	clone (ACE_Allocator *allocator)=0
	Clone this element.
virtual void	destroy (void)=0
	Reclaim resources.
virtual bool	is_expired (const ACE_Time_Value &now) const
	Check for timeout.
virtual void	copy_if_necessary (const ACE_Message_Block *chain)=0
	Provide a hook for copying the underlying data.
Protected Attributes
ACE_Allocator *	allocator_
bool const	is_heap_created_
TAO_ORB_Core *	orb_core_
	Cached copy of ORB_Core pointer.
Private Attributes
TAO_Queued_Message *	next_
	Implement an intrusive double-linked list for the message queue.
TAO_Queued_Message *	prev_

Detailed Description

Represent messages queued in the outgoing data path of the TAO_Transport class.

Please read the documentation in the TAO_Transport class to find out more about the design of the outgoing data path.

In some configurations TAO needs to maintain a per-connection queue of outgoing messages. This queue is drained by the pluggable protocols framework, normally under control of the ACE_Reactor, but other configurations are conceivable. The elements in the queue may be removed early, for example, because the application can specify timeouts for each message, or because the underlying connection is broken.

In many cases the message corresponds to some application request, the application may be blocked waiting for the request to be sent, even more importantly, the ORB can be configured to use the Leader/Followers strategy, in which case one of the waiting threads can be required to wake up before its message completes. Each message may contain a 'Sent_Notifier'

NOTE:

The contents of the ACE_Message_Block may have been allocated from TSS storage, in that case we cannot steal them. However, we do not need to perform a deep copy all the time, for example, in a twoway request the sending thread blocks until the data goes out. The queued message can borrow the memory as it will be deallocated by the sending thread when it finishes. Oneways and asynchronous calls are another story.

Todo:: Change the ORB to allocate oneway and AMI buffer from global memory, to avoid the data copy in this path. What happens if the there is no queueing? Can we check that before allocating the memory?

Constructor & Destructor Documentation

TAO_Queued_Message::TAO_Queued_Message	(	TAO_ORB_Core *	oc,
		ACE_Allocator *	alloc = `0`,
		bool	is_heap_allocated = `false`
	)

Constructor.

TAO_Queued_Message::~TAO_Queued_Message ( void ) [virtual]

Destructor.

Member Function Documentation

virtual int TAO_Queued_Message::all_data_sent ( void ) const [pure virtual]

Return 1 if all the data has been sent.

Implemented in TAO_Asynch_Queued_Message, and TAO_Synch_Queued_Message.

virtual void TAO_Queued_Message::bytes_transferred ( size_t & byte_count ) [pure virtual]

Update the internal state, data has been sent.

After the TAO_Transport class completes a successful (or partially successful) I/O operation it must update the state of all the messages queued. This callback method is used by each message to update its state and determine if all the data has been sent already.

Parameters:

byte_count The number of bytes successfully sent. The TAO_Queued_Message should decrement this value by the number of bytes that must still be sent.

Returns:: Returns 1 if the TAO_Queued_Message has any more data to send.

Implemented in TAO_Asynch_Queued_Message, and TAO_Synch_Queued_Message.

virtual TAO_Queued_Message* TAO_Queued_Message::clone ( ACE_Allocator * allocator ) [pure virtual]

Clone this element.

Implemented in TAO_Asynch_Queued_Message, and TAO_Synch_Queued_Message.

virtual void TAO_Queued_Message::copy_if_necessary ( const ACE_Message_Block * chain ) [pure virtual]

Provide a hook for copying the underlying data.

Parameters:

chain For use in determining origin of underlying data. This parameter must not be modified (through const_cast).

Implemented in TAO_Asynch_Queued_Message, and TAO_Synch_Queued_Message.

virtual void TAO_Queued_Message::destroy ( void ) [pure virtual]

Reclaim resources.

Reliable messages are allocated from the stack, thus they do not be deallocated. Asynchronous (SYNC_NONE) messages are allocated from the heap (or a pool), they need to be reclaimed explicitly.

Implemented in TAO_Asynch_Queued_Message, and TAO_Synch_Queued_Message.

virtual void TAO_Queued_Message::fill_iov	(	int	iovcnt_max,
		int &	iovcnt,
		iovec	iov[]
	)		const `[pure virtual]`

Fill up an io vector using the connects of the message.

Different versions of this class represent the message using either a single buffer, or a message block. This method allows a derived class to fill up the contents of an io vector, the TAO_Transport class uses this method to group as many messages as possible in an iovector before sending them to the OS I/O subsystem.

Parameters:

iovcnt_max	The number of elements in iov
iovcnt	The number of elements already used by iov, this method should update this counter
iov	The io vector

Implemented in TAO_Asynch_Queued_Message, and TAO_Synch_Queued_Message.

bool TAO_Queued_Message::is_expired ( const ACE_Time_Value & now ) const [virtual]

Check for timeout.

Parameters:

now	Pass in the current time using ACE_High_Res_Timer::gettimeofday_hr(). This is a parameter in order to avoid calling gettimeofday_hr() inside of this method (which will be called in a tight loop).