cAsyncMemoryBlock

Thread safe smart pointer for raw memory blocks. More...

Public Member Functions
	cAsyncMemoryBlock ()
	Default constructor.
virtual	~cAsyncMemoryBlock ()
	Destructor.
tResult	Alloc (tInt nSize)
	Allocates new memory for the MemoryBlock *. More...
tResult	Assign (void *pMem, tInt nSize)
	Assigns memory to the MemoryBlock object which has already been allocated. More...
tResult	Free ()
	Lock MemoryBlock and free memory is allocated and not assigned *. More...
tResult	ReadLock (void **ppMem, const tBool bWait=tTrue)
	Try to lock memory for read access. More...
tResult	WriteLock (void **ppMem, const tBool bWait=tTrue)
	Try to lock memory for write access. More...
tResult	Unlock (void)
	Unlock MemoryBlock. More...
tResult	Copy (cAsyncMemoryBlock &oSrc)
	Copies the content of the source MemoryBlock. More...
tInt	Compare (cAsyncMemoryBlock &oSrc)
	Compares size and content with another MemoryBlock. More...
tInt	GetSize ()
	Get size of MemoryBlock. More...
tResult	WaitNewData (tInt nTimeout=-1)
	Wait for the NewDataEvent which is set by unlocking a write access. More...

Private Attributes
void *	m_pMem
tBool	m_bMemAssigned
	memory pointer
tInt	m_nSize
	memory assigned not alloced (not to be freed afterwards)
tInt	m_nReaderCount
	memory size
tBool	m_bWriteAccess
	count of active readers
tInt	m_nWriterWaitCount
	write access currently active
std::recursive_mutex	m_oMutexChangeState
	number of writers which are waiting
std::mutex	m_mutexLock
	mutex for short locks (like counter increments)
std::mutex	m_mutexNoReader
	mutex for locking MemoryBlock for other access
std::mutex	m_mutexNewData
	Mutex for locking the condVariable depending on 'noReader'.
std::condition_variable	m_CondEventNoReader
	Mutex for locking the conditional variable depending on 'newData'.
std::condition_variable	m_CondNewData
	condition_variable to signal a waiting writer that all readers finished
std::condition_variable	m_CondMutexLock
	event to signal new data

Detailed Description

Thread safe smart pointer for raw memory blocks.

Definition at line 21 of file asyncmemoryblock.h.

Member Function Documentation

Alloc()

tResult Alloc

(

tInt

nSize

)

Allocates new memory for the MemoryBlock *.

Parameters

nSize

[in] memory size

Return values

ERR_NOERROR	no Error
ERR_RESOURCE_IN_USE	memory already allocated or assigned
ERR_MEMORY	no memory available

Assign()

tResult Assign	(	void *	pMem,
		tInt	nSize
	)

Assigns memory to the MemoryBlock object which has already been allocated.

Parameters

pMem	[in] memory pointer
nSize	[in] memory size

Return values

ERR_NOERROR	no Error
ERR_RESOURCE_IN_USE	memory already allocated or assigned

This method is real-time safe.\nSee @ref page_real_time_safe.\n

Compare()

tInt Compare

(

cAsyncMemoryBlock &

oSrc

)

Compares size and content with another MemoryBlock.

Parameters

oSrc	[in] Source MemoryBlock to be copied

Return values

0	equal
<0	lower
>0	greater

Copy()

tResult Copy

(

cAsyncMemoryBlock &

oSrc

)

Copies the content of the source MemoryBlock.

The size of the destination is adjusted to the source.

Parameters

oSrc	[in] Source MemoryBlock to be copied

Return values

STATUS_OK	no error
ERR_MEMORY	memory error

Free()

tResult Free

(

)

Lock MemoryBlock and free memory is allocated and not assigned *.

Return values

STATUS_OK	no Error
ERR_MEMORY	no memory allocated or assigned

GetSize()

tInt GetSize

(

)

Get size of MemoryBlock.

Returns

Size of MemoryBlock

This method is real-time safe.\nSee @ref page_real_time_safe.\n

ReadLock()

tResult ReadLock	(	void **	ppMem,
		const tBool	bWait = tTrue
	)

Try to lock memory for read access.

Multiple read access is allowed. Wait (send thread to sleep) if MemoryBlock is locked by a write access. If parameter bWait == tFalse this method returns STATUS_ERROR without waiting if no immediate access is possible. Memory pointer of the Block is returned in the parameter ppMem. Calling ReadLock after WriteLock on the same thread will not block. Only calls from different threads will block.

Parameters

bWait	[in] tTrue: wait if access is locked
ppMem	[out] Memory pointer of this MemoryBlock

Return values

STATUS_OK	no Error
ERR_POINTER	ppMem is nullptr
ERR_UNEXPECTED	no memory is allocated
ERR_RESOURCE_IN_USE	if memory is locked and bWait is tFalse

Unlock()

tResult Unlock

(

void

)

Unlock MemoryBlock.

If currently write access: allow read and write access. If currently read access: decrement reader counter and allow write access if no more reader active.

Return values

STATUS_OK	no Error
ERR_UNEXPECTED	no access active or no memory allocated

WaitNewData()

tResult WaitNewData

(

tInt

nTimeout = -1

)

Wait for the NewDataEvent which is set by unlocking a write access.

Parameters

nTimeout

[in] Timeout, default = -1 (INFINITE)

Return values

STATUS_OK	no error
ERR_TIMEOUT	wait error / timeout

WriteLock()

tResult WriteLock	(	void **	ppMem,
		const tBool	bWait = tTrue
	)

Try to lock memory for write access.

Only one writer and no reader is allowed. Wait (send thread to sleep) if other write or read access is active. If parameter bWait == tFalse this method returns STATUS_ERROR without waiting if no immediate access is possible. Memory pointer of the MemoryBlock is returned in the parameter ppMem. Calling WriteLock will not block if it is called repeatedly from the same thread. Only calls from different threads will result in a block.

Parameters

bWait	[in] tTrue: wait if access is locked
ppMem	[out] Memory pointer of this MemoryBlock

Return values

STATUS_OK	no Error
ERR_POINTER	ppMem is nullptr
ERR_UNEXPECTED	no memory is allocated
ERR_RESOURCE_IN_USE	if memory is locked and bWait is tFalse