DDASReadout::ReferenceCountedBuffer Struct Reference

A reference-counted buffer with dynamic storage. More...

#include <ReferenceCountedBuffer.h>

Public Member Functions
	ReferenceCountedBuffer (size_t initialSize=0)
	Construct the buffer. More...
virtual	~ReferenceCountedBuffer ()
	Destructor. More...
void	reference ()
	Add a reference to the storage. More...
void	dereference ()
	Remove a reference to the storage. More...
bool	isReferenced ()
	Are there references to the object? More...
void	resize (size_t newSize)
	Resize the storage. More...
	operator uint8_t * ()
	operator uint16_t * ()
	operator uint32_t * ()

Public Attributes
size_t	s_size
	Number of bytes of data. More...
size_t	s_references
	Number of references. More...
void *	s_pData
	Data pointer. More...

Detailed Description

A reference-counted buffer with dynamic storage.

The idea is that rather than doing data movement, pointers can be registered with the buffer and unregistered. The buffer can then be queried to determine if it can be released, or put in a free list.

One feature of this buffer is that, if there are not references, it can be resized. Since resizing is only legal if there are no references, the contents of the buffer are not preserved across a resize.

The intended use for this data structure is to provide support for zero copy operations in the DDAS Readout program. The idea is that a block of data can be read from a digitizer into one of these and then pointers to each hit created rather than performing copies into other data structures.

Constructor & Destructor Documentation

ReferenceCountedBuffer()

DDASReadout::ReferenceCountedBuffer::ReferenceCountedBuffer

(

size_t

initialSize = 0

)

Construct the buffer.

Parameters

initialSize

Initial size in bytes allocated to the buffer (default = 0).

Exceptions

std::bad_alloc

Buffer malloc fails for initialSize > 0.

If initailSize is zero (the default) no storage is allocated and the user must do a resize at some point to get storage.

~ReferenceCountedBuffer()

DDASReadout::ReferenceCountedBuffer::~ReferenceCountedBuffer ( )

virtual

Destructor.

It's currently an error to destroy the object if it has references. Otherwise, just free any storage that's been allocated.

Member Function Documentation

dereference()

void DDASReadout::ReferenceCountedBuffer::dereference

(

)

Remove a reference to the storage.

Deincrement the reference counter.

isReferenced()

bool DDASReadout::ReferenceCountedBuffer::isReferenced

(

)

Are there references to the object?

Returns

bool

Return values

true	If the number of references is > 0.
false	Otherwise.

operator uint16_t *()

DDASReadout::ReferenceCountedBuffer::operator uint16_t * ( )

inline

operator uint32_t *()

DDASReadout::ReferenceCountedBuffer::operator uint32_t * ( )

inline

operator uint8_t *()

DDASReadout::ReferenceCountedBuffer::operator uint8_t * ( )

inline

reference()

void DDASReadout::ReferenceCountedBuffer::reference

(

)

Add a reference to the storage.

Increment the reference counter.

resize()

void DDASReadout::ReferenceCountedBuffer::resize

(

size_t

newSize

)

Resize the storage.

Parameters

newSize

The new size in bytes.

Exceptions

std::logic_error	If there are references.
std::bad_alloc	If the memory allocation fails.

This must not be done when there are references as the resize will invalidate all pointers. Therefore if there are references, a std::logic_error is thrown.

Note

If newSize < s_size no resize is done but the exception can still be thrown.

Member Data Documentation

s_pData

void* DDASReadout::ReferenceCountedBuffer::s_pData

Data pointer.

s_references

size_t DDASReadout::ReferenceCountedBuffer::s_references

Number of references.

s_size

size_t DDASReadout::ReferenceCountedBuffer::s_size

Number of bytes of data.

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

• ReferenceCountedBuffer.h
• ReferenceCountedBuffer.cpp