ACE_RW_Token Class Reference

Class that acquires, renews, and releases a process-local synchronization token. More...

#include <Local_Tokens.h>

Inheritance diagram for ACE_RW_Token:

Collaboration diagram for ACE_RW_Token:

List of all members.

Public Types
enum	PROXY_TYPE { READER, WRITER }
	These are the types that proxies can be. More...
Public Member Functions
	ACE_RW_Token (const ACE_TCHAR *name)
	Constructor.
virtual	~ACE_RW_Token (void)
	Destructor.
virtual int	acquire (ACE_TPQ_Entry *caller, int ignore_deadlock, int notify)
virtual int	tryacquire (ACE_TPQ_Entry *caller)
	Same as acquire except fails on would block.
virtual int	renew (ACE_TPQ_Entry *caller, int requeue_position)
virtual int	release (ACE_TPQ_Entry *caller)
void	dump (void) const
	Dump the state of the class.
virtual int	type (void) const
	Returns READER or WRITER.
virtual int	owners (OWNER_STACK &o, const ACE_TCHAR *id)
virtual int	is_waiting_for (const ACE_TCHAR *id)
	Returns 1 if id is waiting for this token. 0 otherwise.
virtual int	is_owner (const ACE_TCHAR *id)
	Returns 1 if id is an owner of this token. 0 otherwise.
Protected Member Functions
void	notify_new_owner (ACE_TPQ_Entry *caller)
	Sets the new owner.
Protected Attributes
int	num_writers_
	The number of waiting writers.
ACE_TOKEN_CONST::MUTEX	lock_
	ACE_Mutex_Token used to lock internal data structures.

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Detailed Description

Class that acquires, renews, and releases a process-local synchronization token.

Not a public interface. This class is a more general-purpose synchronization mechanism than SunOS 5.x mutexes. For example, it implements "recursive mutex" semantics, where a thread that owns the token can reacquire it without deadlocking. In addition, threads that are blocked awaiting the token are serviced in strict FIFO order as other threads release the token (SunOS 5.x mutexes don't strictly enforce an acquisition order).

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Member Enumeration Documentation

enum ACE_RW_Token::PROXY_TYPE

These are the types that proxies can be.

Enumerator:

READER
WRITER

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Constructor & Destructor Documentation

ACE_RW_Token::ACE_RW_Token

(

const ACE_TCHAR *

name

)

[explicit]

Constructor.

ACE_RW_Token::~ACE_RW_Token

(

void

)

[virtual]

Destructor.

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Member Function Documentation

int ACE_RW_Token::acquire	(	ACE_TPQ_Entry *	caller,
		int	ignore_deadlock,
		int	notify
	)		[virtual]

Returns 0 on success, -1 on failure with <ACE_Log_Msg::errnum> as the reason. If errnum == EWOULDBLOCK, and notify == 1, <ACE_Token_Proxy::sleep_hook> has been called on the current owner of the token. If ignore_deadlock is passed as 1 and errnum == EDEADLK, then deadlock was detected via ACE_Token_Manager.

Implements ACE_Tokens.

void ACE_RW_Token::dump

(

void

)

const

Dump the state of the class.

Reimplemented from ACE_Tokens.

int ACE_RW_Token::is_owner

(

const ACE_TCHAR *

id

)

[virtual]

Returns 1 if id is an owner of this token. 0 otherwise.

Implements ACE_Tokens.

int ACE_RW_Token::is_waiting_for

(

const ACE_TCHAR *

id

)

[virtual]

Returns 1 if id is waiting for this token. 0 otherwise.

Implements ACE_Tokens.

void ACE_RW_Token::notify_new_owner

(

ACE_TPQ_Entry *

caller

)

[protected]

Sets the new owner.

int ACE_RW_Token::owners	(	OWNER_STACK &	o,
		const ACE_TCHAR *	id
	)		[virtual]

Returns a stack of the current owners. Returns -1 on error, 0 on success. If id is non-zero, returns 1 if id is an owner.

Implements ACE_Tokens.

int ACE_RW_Token::release

(

ACE_TPQ_Entry *

caller

)

[virtual]

Relinquish the token. If there are any waiters then the next one in line gets it. If the caller is not the owner, caller is removed from the waiter list.

Implements ACE_Tokens.

int ACE_RW_Token::renew	(	ACE_TPQ_Entry *	caller,
		int	requeue_position
	)		[virtual]

An optimized method that efficiently reacquires the token if no other threads are waiting. This is useful for situations where you don't want to degrade the quality of service if there are other threads waiting to get the token. If <requeue_position> == -1 and there are other threads waiting to obtain the token we are queued at the end of the list of waiters. If <requeue_position> > -1 then it indicates how many entries to skip over before inserting our thread into the list of waiters (e.g., <requeue_position> == 0 means "insert at front of the queue"). Renew has the rather odd semantics such that if there are other waiting threads it will give up the token even if the nesting_level_ > 1. I'm not sure if this is really the right thing to do (since it makes it possible for shared data to be changed unexpectedly) so use with caution... Returns 0 on success, -1 on failure with <ACE_Log_Msg::errnum> as the reason. If errnum == EWOULDBLOCK, and notify == 1, <ACE_Token_Proxy::sleep_hook> has been called on the current owner of the token.

Implements ACE_Tokens.

int ACE_RW_Token::tryacquire

(

ACE_TPQ_Entry *

caller

)

[virtual]

Same as acquire except fails on would block.

Implements ACE_Tokens.

int ACE_RW_Token::type

(

void

)

const [virtual]

Returns READER or WRITER.

Implements ACE_Tokens.

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Member Data Documentation

ACE_TOKEN_CONST::MUTEX ACE_RW_Token::lock_ [protected]

ACE_Mutex_Token used to lock internal data structures.

int ACE_RW_Token::num_writers_ [protected]

The number of waiting writers.

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The documentation for this class was generated from the following files:

• Local_Tokens.h
• Local_Tokens.cpp