DDASReadout::ZeroCopyHit Class Reference

This class extends RawChannel to produce a raw channel that is zero-copied from a reference counted buffer that comes from a buffer arena. This is a key data structure in the zero-copy DDAS readout. More...

#include <ZeroCopyHit.h>

Inheritance diagram for DDASReadout::ZeroCopyHit:

Collaboration diagram for DDASReadout::ZeroCopyHit:

Public Member Functions
	ZeroCopyHit ()
	Default constructor. More...
	ZeroCopyHit (size_t nWords, void *pHitData, ReferenceCountedBuffer *pBuffer, BufferArena *pArena)
	Construct from parameters. More...
	ZeroCopyHit (const ZeroCopyHit &rhs)
	Copy constructor. More...
ZeroCopyHit &	operator= (const ZeroCopyHit &rhs)
	Assignment operator. More...
virtual	~ZeroCopyHit ()
	Destructor. More...
void	setHit (size_t nWords, void *pHitData, ReferenceCountedBuffer *pBuffer, BufferArena *pArena)
	Sets a new hit. More...
void	freeHit ()
	Free an existing hit. More...
Public Member Functions inherited from DDASReadout::RawChannel
	RawChannel ()
	Default constructor. More...
	RawChannel (size_t nWords)
	Construct a channel for copy-in data. More...
	RawChannel (size_t nWords, void *pZcopyData)
	Constructor initialized with zero-copy hit data. More...
virtual	~RawChannel ()
	Destructor. More...
int	SetTime ()
	Set the 48-bit timestamp data from the hit infomration. More...
int	SetTime (double nsPerTick, bool useExt=false)
	Set time time in ns. More...
int	SetLength ()
	Set the event length from the data. More...
int	SetChannel ()
	Set the channel value from the data. More...
int	Validate (int expecting)
	Determine if a channel has the correct amount of data. More...
void	setData (size_t nWords, void *pZCopyData)
	Set new data. More...
void	copyInData (size_t nWords, const void *pData)
	Copy in data. More...
	RawChannel (const RawChannel &rhs)
	Copy constructor. More...
RawChannel &	operator= (const RawChannel &rhs)
	Assignment operator. More...

Additional Inherited Members
Static Public Member Functions inherited from DDASReadout::RawChannel
static uint32_t	channelLength (void *pData)
	Extract the number of words in a hit. More...
static double	moduleCalibration (uint32_t moduleType)
	Returns the multiplier used to convert the module raw timestamp into nanoseconds. More...
Public Attributes inherited from DDASReadout::RawChannel
uint32_t	s_moduleType
	Type of module this comes from. More...
double	s_time
	Extracted time, possibly calibrated. More...
int	s_chanid
	Channel within module. More...
bool	s_ownData
	True if we own s_data. More...
int	s_ownDataSize
	If we own data, how many uint32_t's. More...
int	s_channelLength
	Number of uint32_t in s_data. More...
uint32_t *	s_data
	Pointer to the hit data. More...

Detailed Description

This class extends RawChannel to produce a raw channel that is zero-copied from a reference counted buffer that comes from a buffer arena. This is a key data structure in the zero-copy DDAS readout.

This acts like a RawChannel, but on destruction, if it is the last reference to the buffer, returns it to the arena from whence it came.

Copy construction and assignment are supported with appropriate semantics to handle proper reference counting.

I'm sure I'm hearing a pile of people ask me why not use std::shared_pointer – The answer is that I don't actually want the buffers to be destroyed as that involves expensive dynamic memory management, I want storage returned to a pre-allocated buffer arena from which it can be quickly re-gotten. Yeah I suppose I could use custom new/delete methods but that seems pretty painful and at least as error prone as this code.

Constructor & Destructor Documentation

ZeroCopyHit() [1/3]

DDASReadout::ZeroCopyHit::ZeroCopyHit

(

)

Default constructor.

Creates a hit. The hit must be initialized with setHit before being accessed.

ZeroCopyHit() [2/3]

DDASReadout::ZeroCopyHit::ZeroCopyHit	(	size_t	nWords,
		void *	pHitData,
		ReferenceCountedBuffer *	pBuffer,
		BufferArena *	pArena
	)

Construct from parameters.

Parameters

nWords	Number of uint32_t's in the hit.
pHitData	Pointer to the hit data.
pBuffer	Underlying reference counted buffer.
pArena	Buffer arena to which the buffer is released when no longer referenced.

Stores stuff away and increments the refrence count on the underlying buffer.

ZeroCopyHit() [3/3]

DDASReadout::ZeroCopyHit::ZeroCopyHit

(

const ZeroCopyHit &

rhs

)

Copy constructor.

Parameters

rhs	Reference ot ZeroCopyHit object to copy.

Copy in the new hit and reference.

~ZeroCopyHit()

DDASReadout::ZeroCopyHit::~ZeroCopyHit ( )

virtual

Destructor.

Dereference.

Member Function Documentation

freeHit()

void DDASReadout::ZeroCopyHit::freeHit

(

)

Free an existing hit.

If this hit is associated with data, disassociates.

operator=()

ZeroCopyHit & DDASReadout::ZeroCopyHit::operator=

(

const ZeroCopyHit &

rhs

)

Assignment operator.

Parameters

rhs	Reference to ZeroCopyHit object assigned to lhs.

Returns

Reference to ZeroCopyHit object.

Dereference, copy in, reference.

setHit()

void DDASReadout::ZeroCopyHit::setHit	(	size_t	nWords,
		void *	pHitData,
		ReferenceCountedBuffer *	pBuffer,
		BufferArena *	pArena
	)

Sets a new hit.

Parameters

nWords	Number of words in the new hit.
pHitData	Pointer to the hit data.
pBuffer	Buffer from whence the hit data came.
pArena	Arena to which the buffer is returned.

If the hit is associated with a zero copy buffer, the reference is released first.

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

• ZeroCopyHit.h
• ZeroCopyHit.cpp