vpr::SemaphoreNSPR Class Reference

Wrapper for semaphores implemented using condition variables. More...

#include <vpr/Sync/Semaphore.h>

Collaboration diagram for vpr::SemaphoreNSPR:

[legend]List of all members.

Public Member Functions
	SemaphoreNSPR (int initialValue=1)
	Custructor.
	~SemaphoreNSPR ()
	Destructor.
vpr::ReturnStatus	acquire ()
	Locks this semaphore.
vpr::ReturnStatus	acquireRead ()
	Acquires a read lock on a resource protected by this semaphore.
vpr::ReturnStatus	acquireWrite ()
	Acquires a write lock on a resource protected by this semaphore.
vpr::ReturnStatus	tryAcquire ()
	Tries to acquire the a resource lock immediately (does not block).
vpr::ReturnStatus	tryAcquireRead ()
	Tries to acquire a read lock on a resource (does not block).
vpr::ReturnStatus	tryAcquireWrite ()
	Tries to acquire a write lock on a resource (does not block).
vpr::ReturnStatus	release ()
	Releases a resource lock.
vpr::ReturnStatus	reset (int val)
	Resets the resource count for this semaphore.
void	dump (FILE *dest=stderr, const char *message="\n------ Semaphore Dump -----\n") const
	Dumps the semaphore debug stuff and current state.
Protected Member Functions
void	operator= (const SemaphoreNSPR &)
	SemaphoreNSPR (const SemaphoreNSPR &)
Protected Attributes
CondVar *	mCondVar
	Semaphore simulator variable for the class.
PRInt32	mValue
	The resource count.

---

Detailed Description

Wrapper for semaphores implemented using condition variables.

This is typedef'd to vpr::Semaphore.

Definition at line 61 of file SemaphoreNSPR.h.

---

Constructor & Destructor Documentation

vpr::SemaphoreNSPR::SemaphoreNSPR

(

int

initialValue = 1

)

[inline]

Custructor.

Postcondition:

The semaphore variable for the class is initilized as an unnamed semaphore.

Parameters:

initialValue

The initial number of resources controlled by the semaphore. If not specified, the default value is 1.

Definition at line 73 of file SemaphoreNSPR.h.

   {
      mCondVar = new CondVar;
      PR_AtomicSet(&mValue, initialValue);
   }

vpr::SemaphoreNSPR::~SemaphoreNSPR

(

)

[inline]

Destructor.

Postcondition:

The resources used by the semaphore variable are freed.

Definition at line 84 of file SemaphoreNSPR.h.

   {
      delete mCondVar;
   }

vpr::SemaphoreNSPR::SemaphoreNSPR

(

const SemaphoreNSPR &

)

[inline, protected]

Definition at line 285 of file SemaphoreNSPR.h.

   {
      /* Do nothing. */ ;
   }

---

Member Function Documentation

vpr::ReturnStatus vpr::SemaphoreNSPR::acquire

(

)

[inline]

Locks this semaphore.

Postcondition:

The calling thread either acquires the semaphore until release() is called, or the caller is put at the tail of a wait and is suspended until such time as it can be freed and allowed to acquire the semaphore itself.

Returns:

vpr::ReturnStatus::Succeed is returned if a resource lock is acquired. vpr::ReturnStatus::Fail is returned otherwise.

Definition at line 100 of file SemaphoreNSPR.h.

   {
      mCondVar->acquire();
      PR_AtomicDecrement(&mValue);

      while ( mValue < 0 )
      {
         mCondVar->wait();
      }
      mCondVar->release();

      return vpr::ReturnStatus();
   }

vpr::ReturnStatus vpr::SemaphoreNSPR::acquireRead

(

)

[inline]

Acquires a read lock on a resource protected by this semaphore.

Postcondition:

The calling thread either acquires the semaphore until release() is called, or the caller is put at the tail of a wait and is suspended until such time as it can be freed and allowed to acquire the semaphore itself.

Returns:

vpr::ReturnStatus::Succeed is returned if a resource read lock is acquired. vpr::ReturnStatus::Fail is returned otherwise.

Note:

There is no special read semaphore for now.

Definition at line 127 of file SemaphoreNSPR.h.

   {
      return this->acquire();
   }

vpr::ReturnStatus vpr::SemaphoreNSPR::acquireWrite

(

)

[inline]

Acquires a write lock on a resource protected by this semaphore.

Postcondition:

The calling thread either acquires the semaphore until release() is called, or the caller is put at the tail of a wait and is suspended until such time as it can be freed and allowed to acquire the semaphore itself.

Returns:

vpr::ReturnStatus::Succeed is returned if a resource write lock is acquired. vpr::ReturnStatus::Fail is returned otherwise.

Note:

There is no special write semaphore for now.

Definition at line 145 of file SemaphoreNSPR.h.

   {
      return this->acquire();
   }

vpr::ReturnStatus vpr::SemaphoreNSPR::tryAcquire

(

)

[inline]

Tries to acquire the a resource lock immediately (does not block).

Postcondition:

If the semaphore could be acquired by the caller, the caller gets control of the semaphore. If the semaphore was already locked, the routine returns immediately without suspending the calling thread.

Returns:

vpr::ReturnStatus::Succeed is returned if a lock is acquired. vpr::ReturnStatus::Fail is returned if no resource could be locked without blocking.

Definition at line 162 of file SemaphoreNSPR.h.

References vpr::ReturnStatus::Fail.

   {
      vpr::ReturnStatus status(vpr::ReturnStatus::Fail);

      if ( mValue >= 0 )
      {
         status = this->acquire();
      }

      return status;
   }

vpr::ReturnStatus vpr::SemaphoreNSPR::tryAcquireRead

(

)

[inline]

Tries to acquire a read lock on a resource (does not block).

Postcondition:

If the semaphore could be acquired by the caller, the caller gets control of the semaphore. If the semaphore was already locked, the routine returns immediately without suspending the calling thread.

Returns:

vpr::ReturnStatus::Succeed is returned if a read lock is acquired. vpr::ReturnStatus::Fail is returned if no resource could be locked without blocking.

Definition at line 186 of file SemaphoreNSPR.h.

   {
      return this->tryAcquire();
   }

vpr::ReturnStatus vpr::SemaphoreNSPR::tryAcquireWrite

(

)

[inline]

Tries to acquire a write lock on a resource (does not block).

Postcondition:

If the semaphore could be acquired by the caller, the caller gets control of the semaphore. If the semaphore was already locked, the routine returns immediately without suspending the calling thread.

Returns:

vpr::ReturnStatus::Succeed is returned if a write lock is acquired. vpr::ReturnStatus::Fail is returned if no resource could be locked without blocking.

Definition at line 203 of file SemaphoreNSPR.h.

   {
      return this->tryAcquire();
   }

vpr::ReturnStatus vpr::SemaphoreNSPR::release

(

)

[inline]

Releases a resource lock.

Precondition:

The semaphore should have been locked before being released.

Postcondition:

The semaphore is released and the thread at the head of the wait queue is allowed to execute again.

Returns:

vpr::ReturnStatus::Succeed is returned if a resource is unlocked successfully. vpr::ReturnStatus::Fail is returned otherwise.

Definition at line 219 of file SemaphoreNSPR.h.

   {
      vpr::ReturnStatus status;

      mCondVar->acquire();
      PR_AtomicIncrement(&mValue);
      status = mCondVar->signal();
      mCondVar->release();

      return status;
   }

vpr::ReturnStatus vpr::SemaphoreNSPR::reset

(

int

val

)

[inline]

Resets the resource count for this semaphore.

Postcondition:

This semaphore's count is set to the specified value.

Parameters:

val

The value to which the semaphore is reset.

Returns:

vpr::ReturnStatus::Succeed is returned if the resource count is reset successfully. vpr::ReturnStatus::Fail is returned otherwise.

Note:

If processes are waiting on the semaphore, the results are undefined.

Definition at line 245 of file SemaphoreNSPR.h.

   {
      vpr::ReturnStatus status;

      mCondVar->acquire();
      PR_AtomicSet(&mValue, val);
      status = mCondVar->broadcast();
      mCondVar->release();

      return status;
   }

void vpr::SemaphoreNSPR::dump	(	FILE *	dest = stderr,
		const char *	message = "\n------ Semaphore Dump -----\n"
	)			const [inline]

Dumps the semaphore debug stuff and current state.

Postcondition:

All important data and debugging information related to this semaphore is dumped to the specified file descriptor (or to stderr if none is given).

Parameters:

	dest	File descriptor to which the output will be written. It defaults to stderr if no descriptor is specified.
	message	Message printed out before the output is dumped.

Definition at line 268 of file SemaphoreNSPR.h.

   {
      fprintf(dest, "%s", message);
      fprintf(dest, "Current semaphore value: %d", mValue);
   }

void vpr::SemaphoreNSPR::operator=

(

const SemaphoreNSPR &

)

[inline, protected]

Definition at line 280 of file SemaphoreNSPR.h.

   {
      /* Do nothing. */ ;
   }

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Member Data Documentation

CondVar* vpr::SemaphoreNSPR::mCondVar [protected]

Semaphore simulator variable for the class.

Definition at line 276 of file SemaphoreNSPR.h.

PRInt32 vpr::SemaphoreNSPR::mValue [protected]

The resource count.

Definition at line 277 of file SemaphoreNSPR.h.

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

• SemaphoreNSPR.h

---