ACE_Semaphore Class Reference

Wrapper for Dijkstra style general semaphores. More...

#include <Semaphore.h>

List of all members.

Public Member Functions
	ACE_Semaphore (unsigned int count=1, int type=USYNC_THREAD, const ACE_TCHAR *name=0, void *=0, int max=0x7fffffff)
	Initialize the semaphore, with initial value of "count".
	~ACE_Semaphore (void)
	Implicitly destroy the semaphore.
int	remove (void)
int	acquire (void)
int	acquire (ACE_Time_Value &tv)
int	acquire (ACE_Time_Value *tv)
int	tryacquire (void)
int	release (void)
int	release (unsigned int release_count)
int	acquire_read (void)
int	acquire_write (void)
int	tryacquire_read (void)
int	tryacquire_write (void)
int	tryacquire_write_upgrade (void)
void	dump (void) const
	Dump the state of an object.
const ACE_sema_t &	lock (void) const
	Return the underlying lock.
Public Attributes
	ACE_ALLOC_HOOK_DECLARE
	Declare the dynamic allocation hooks.
Protected Attributes
ACE_sema_t	semaphore_
bool	removed_
Private Member Functions
void	operator= (const ACE_Semaphore &)
	ACE_Semaphore (const ACE_Semaphore &)

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Detailed Description

Wrapper for Dijkstra style general semaphores.

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Constructor & Destructor Documentation

ACE_Semaphore::ACE_Semaphore	(	unsigned int	count = 1,
		int	type = USYNC_THREAD,
		const ACE_TCHAR *	name = 0,
		void *	arg = 0,
		int	max = 0x7fffffff
	)

Initialize the semaphore, with initial value of "count".

ACE_Semaphore::~ACE_Semaphore

(

void

)

Implicitly destroy the semaphore.

ACE_Semaphore::ACE_Semaphore

(

const ACE_Semaphore &

)

[private]

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Member Function Documentation

ACE_INLINE int ACE_Semaphore::remove

(

void

)

Explicitly destroy the semaphore. Note that only one thread should call this method since it doesn't protect against race conditions.

ACE_INLINE int ACE_Semaphore::acquire

(

void

)

Block the thread until the semaphore count becomes greater than 0, then decrement it.

ACE_INLINE int ACE_Semaphore::acquire

(

ACE_Time_Value &

tv

)

Block the thread until the semaphore count becomes greater than 0 (at which point it is decremented) or until tv times out (in which case -1 is returned and errno == ETIME). Note that tv is assumed to be in "absolute" rather than "relative" time. The value of tv is updated upon return to show the actual (absolute) acquisition time.

Note:

Solaris threads do not support timed semaphores. Therefore, if you're running on Solaris you might want to consider using the ACE POSIX pthreads implementation instead, which can be enabled by compiling ACE with -DACE_HAS_PTHREADS, rather than -DACE_HAS_STHREADS or -DACE_HAS_POSIX_SEM.

ACE_INLINE int ACE_Semaphore::acquire

(

ACE_Time_Value *

tv

)

If tv == 0 then call <acquire()> directly. Otherwise, Block the thread until the semaphore count becomes greater than 0 (at which point it is decremented) or until tv times out (in which case -1 is returned and errno == ETIME). Note that <*tv> is assumed to be in "absolute" rather than "relative" time. The value of <*tv> is updated upon return to show the actual (absolute) acquisition time.

Note:

Solaris threads do not support timed semaphores. Therefore, if you're running on Solaris you might want to consider using the ACE POSIX pthreads implementation instead, which can be enabled by compiling ACE with -DACE_HAS_PTHREADS, rather than -DACE_HAS_STHREADS or -DACE_HAS_POSIX_SEM.

ACE_INLINE int ACE_Semaphore::tryacquire

(

void

)

Conditionally decrement the semaphore if count is greater than 0 (i.e., won't block). Returns -1 on failure. If we "failed" because someone else already had the lock, errno is set to EBUSY.

ACE_INLINE int ACE_Semaphore::release

(

void

)

Increment the semaphore by 1, potentially unblocking a waiting thread.

ACE_INLINE int ACE_Semaphore::release

(

unsigned int

release_count

)

Increment the semaphore by release_count, potentially unblocking waiting threads.

ACE_INLINE int ACE_Semaphore::acquire_read

(

void

)

Acquire semaphore ownership. This calls <acquire> and is only here to make the ACE_Semaphore interface consistent with the other synchronization APIs.

ACE_INLINE int ACE_Semaphore::acquire_write

(

void

)

Acquire semaphore ownership. This calls <acquire> and is only here to make the ACE_Semaphore interface consistent with the other synchronization APIs.

ACE_INLINE int ACE_Semaphore::tryacquire_read

(

void

)

Conditionally acquire semaphore (i.e., won't block). This calls <tryacquire> and is only here to make the ACE_Semaphore interface consistent with the other synchronization APIs. Returns -1 on failure. If we "failed" because someone else already had the lock, errno is set to EBUSY.

ACE_INLINE int ACE_Semaphore::tryacquire_write

(

void

)

Conditionally acquire semaphore (i.e., won't block). This calls <tryacquire> and is only here to make the ACE_Semaphore interface consistent with the other synchronization APIs. Returns -1 on failure. If we "failed" because someone else already had the lock, errno is set to EBUSY.

ACE_INLINE int ACE_Semaphore::tryacquire_write_upgrade

(

void

)

This is only here to make the ACE_Semaphore interface consistent with the other synchronization APIs. Assumes the caller has already acquired the semaphore using one of the above calls, and returns 0 (success) always.

ACE_BEGIN_VERSIONED_NAMESPACE_DECL void ACE_Semaphore::dump

(

void

)

const

Dump the state of an object.

ACE_BEGIN_VERSIONED_NAMESPACE_DECL ACE_INLINE const ACE_sema_t & ACE_Semaphore::lock

(

void

)

const

Return the underlying lock.

void ACE_Semaphore::operator=

(

const ACE_Semaphore &

)

[private]

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Member Data Documentation

ACE_Semaphore::ACE_ALLOC_HOOK_DECLARE

Declare the dynamic allocation hooks.

ACE_sema_t ACE_Semaphore::semaphore_ [protected]

bool ACE_Semaphore::removed_ [protected]

Keeps track of whether remove() has been called yet to avoid multiple remove() calls, e.g., explicitly and implicitly in the destructor. This flag isn't protected by a lock, so make sure that you don't have multiple threads simultaneously calling remove () on the same object, which is a bad idea anyway...

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

• Semaphore.h
• Semaphore.cpp
• Semaphore.inl