Store data in dynamically allocated buffers. More...

#include <DynBuffer.h>

Public Member Functions
	DynBuffer (uInt nrOfBytes=4096)
	Allocate a first buffer of the specified number of bytes (default 4096). More...

	~DynBuffer ()
	Remove the whole buffer, i.e. More...

void	allocstart ()
	Prepare for storing data (re-initialize the buffer) More...

uInt	alloc (uInt nrOfValues, uInt valueSize, Char *&ptr)
	Allocate buffer space for `nrOfValues` values of size `valueSize` bytes, and return the pointer `ptr` to the buffer and the number of values that fit in the buffer. More...

void	remove (uInt nrOfBuffer=1)
	Remove buffer `nrOfBuffer` and the buffers appended to it, and re-initialize the current buffer. More...

void	nextstart ()
	Prepare for data retrieval (set up for looping through the buffers). More...

Bool	next (uInt &usedLength, Char *&ptr)
	Get the pointer to the next buffer and its used length in bytes. More...

Private Member Functions
uInt	newbuf (uInt nrOfValues, uInt valueSize)
	Get the next buffer for storing `nrOfValues` values of size `valueSize` bytes, and return the number of values that can be stored in the free space of that buffer (maybe less than `nrOfValues`). More...

Private Attributes
uInt	bufsz_p
	size of 1st buffer and min. More...

Int	nextbuf_p
	buffernr for next function More...

Int	curbuf_p
	current buffernr More...

Int	nrbuf_p
	nr of buffers allocated More...

Int	maxnrbuf_p
	size of Blocks More...

Block< uInt >	uselen_p
	used length per buffer More...

Block< uInt >	totlen_p
	total length per buffer More...

PtrBlock< Char * >	bufptr_p
	pointer to buffer More...

uInt	curuselen_p
	used length of current buffer More...

uInt	curtotlen_p
	total length of current buffer More...

Char *	curbufptr_p
	pointer to current buffer More...

Detailed Description

Store data in dynamically allocated buffers.

Intended use:

Public interface

Review Status

Reviewed By:: Friso Olnon
Date Reviewed:: 1995/03/16
Test programs:: tDynBuffer

Synopsis

DynBuffer allows one to store data in dynamically allocated buffers. When a buffer is full, an additional buffer can be allocated and "linked" to the existing one; so, the data may not be stored contiguously You can loop through all the linked buffers and get their individual addresses and sizes, so that you can access the data.

Example

Example (without exception handling):

 uInt nrOfValues, nrNeeded, nrAvailable;// nr of data values
 float* pData = floatarr;               // ptr to data to be handled
 Char* pBuffer;                         // ptr to buffer
 
 DynBuffer buffer;                      // create buffer
 buffer.allocstart();                   // prepare for storing
 nrNeeded = nrOfValues;                 // nr of values to store
 // copy data into dynamic buffer
 while (nrNeeded > 0) {
 nrAvailable = buffer.alloc (nrNeeded, sizeof(float), pBuffer);
 // get buffer space:
 // room for nrAvailable values
 memcpy (pBuffer, pData, nrAvailable*sizeof(float));
 // copy that many data values
 nrNeeded -= nrAvailable;           // how much more needed?
 pData += nrAvailable;              // pointer to as yet unstored data
 }
 // Maybe store more values
.
.
 // Retrieve all the data values from the buffers and write them
 buffer.nextstart();                    // goto buffer start
 while (buffer.next (nrAvailable, pBuffer)) {
 // get next buffer
 write (fd, nrAvailable, pBuffer);  // write data from that buffer
 }

Motivation

This class is developed as an intermediate buffer for class AipsIO, but it may serve other purposes as well.

Definition at line 92 of file DynBuffer.h.

Constructor & Destructor Documentation

casacore::DynBuffer::DynBuffer ( uInt nrOfBytes = 4096 )

Allocate a first buffer of the specified number of bytes (default 4096).

When the allocation fails, an exception is thrown.

casacore::DynBuffer::~DynBuffer ( )

Remove the whole buffer, i.e.

the first buffer and all the buffers appended to it.

Member Function Documentation

uInt casacore::DynBuffer::alloc	(	uInt	nrOfValues,
		uInt	valueSize,
		Char *&	ptr
	)

inline

Allocate buffer space for nrOfValues values of size valueSize bytes, and return the pointer ptr to the buffer and the number of values that fit in the buffer.

When not all values fit in the current buffer, new buffer space is added (probably non-contiguous). If that allocation fails an exception is thrown.

Definition at line 177 of file DynBuffer.h.

References curbufptr_p, curtotlen_p, curuselen_p, and newbuf().

void casacore::DynBuffer::allocstart ( )

Prepare for storing data (re-initialize the buffer)

uInt casacore::DynBuffer::newbuf	(	uInt	nrOfValues,
		uInt	valueSize
	)

private

Get the next buffer for storing nrOfValues values of size valueSize bytes, and return the number of values that can be stored in the free space of that buffer (maybe less than nrOfValues).

The new current buffer can be the present one (if it has free space), the next buffer already allocated (if there is one), or a newly allocated and linked-in buffer. If, in the last case, the allocation fails an exception is thrown.

Referenced by alloc().

Bool casacore::DynBuffer::next	(	uInt &	usedLength,
		Char *&	ptr
	)

Get the pointer to the next buffer and its used length in bytes.

The function returns a False value if there are no more buffers.

void casacore::DynBuffer::nextstart ( )

Prepare for data retrieval (set up for looping through the buffers).

void casacore::DynBuffer::remove ( uInt nrOfBuffer = 1 )

Remove buffer nrOfBuffer and the buffers appended to it, and re-initialize the current buffer.

By default we keep the first buffer (i.e. the one numbered 0).

The idea is that you may want to free intermediate storage space taken up by data that you no longer need, and that the first buffer is often big enough to hold further data. So, you only remove the first buffer in special cases.

Member Data Documentation

PtrBlock<Char*> casacore::DynBuffer::bufptr_p

private

pointer to buffer

Definition at line 162 of file DynBuffer.h.

uInt casacore::DynBuffer::bufsz_p

private

size of 1st buffer and min.

bufsize

Definition at line 148 of file DynBuffer.h.

Int casacore::DynBuffer::curbuf_p

private

current buffernr

Definition at line 152 of file DynBuffer.h.

Char* casacore::DynBuffer::curbufptr_p

private

pointer to current buffer

Definition at line 168 of file DynBuffer.h.

Referenced by alloc().

uInt casacore::DynBuffer::curtotlen_p

private

total length of current buffer

Definition at line 166 of file DynBuffer.h.

Referenced by alloc().

uInt casacore::DynBuffer::curuselen_p

private

used length of current buffer

Definition at line 164 of file DynBuffer.h.

Referenced by alloc().

Int casacore::DynBuffer::maxnrbuf_p

private

size of Blocks

Definition at line 156 of file DynBuffer.h.

Int casacore::DynBuffer::nextbuf_p

private

buffernr for next function

Definition at line 150 of file DynBuffer.h.

Int casacore::DynBuffer::nrbuf_p

private

nr of buffers allocated

Definition at line 154 of file DynBuffer.h.

Block<uInt> casacore::DynBuffer::totlen_p

private

total length per buffer

Definition at line 160 of file DynBuffer.h.

Block<uInt> casacore::DynBuffer::uselen_p

private

used length per buffer

Definition at line 158 of file DynBuffer.h.

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

casa/Utilities/DynBuffer.h

Public Member Functions

Private Member Functions

Private Attributes

Detailed Description

Intended use:

Review Status

Synopsis

Example

Motivation

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation