casacore::BucketMapped Class Reference

Use file mapping for buckets in a part of a file. More...

#include <BucketMapped.h>

Inheritance diagram for casacore::BucketMapped:

Public Member Functions
	BucketMapped (BucketFile *file, Int64 startOffset, uInt bucketSize, uInt nrOfBuckets)
	Create the cache for (part of) a file.
	~BucketMapped ()
	Unmap the file.
const char *	getBucket (uInt bucketNr)
	Get a readonly pointer to the given bucket in memory.
char *	getrwBucket (uInt bucketNr)
	Get a writable pointer to the given bucket in memory.
Private Member Functions
	BucketMapped (const BucketMapped &)
	Copy constructor is not possible.
BucketMapped &	operator= (const BucketMapped &)
	Assignment is not possible.
virtual void	doFlush ()
	Flush the file.
virtual void	doResync ()
	Do the actual resync-ing.
virtual void	doExtend (uInt nrBucket)
	Extend the file with the given number of buckets.
virtual void	initializeBuckets (uInt bucketNr)
	Initialize the bucket buffer.

Detailed Description

Use file mapping for buckets in a part of a file.

Intended use:

Public interface

Review Status

Reviewed By:: UNKNOWN
Date Reviewed:: before2004/08/25

Prerequisite

BucketFile

Etymology

BucketMapped uses memory-mapped files for bucket access.

Synopsis

BucketMapped is similar to class BucketCache and is meant to be used by the storage managers of the Table System.

It gives access to buckets in a file by means of memory-mapped files. However, its functionality is a subset of BucketCache and is only meant to be used by the Tiled Storage Managers. If The Standard and Incremental Storage Manager also want to use it, functions like extend needs to be added to this class. Also support for a free bucket list needs to be added.

Motivation

Use of BucketCache is sub-optimal when having large buckets and more or less random IO. Memory-mapping behaves much better.

Definition at line 76 of file BucketMapped.h.

Constructor & Destructor Documentation

casacore::BucketMapped::BucketMapped	(	BucketFile *	file,
		Int64	startOffset,
		uInt	bucketSize,
		uInt	nrOfBuckets
	)

Create the cache for (part of) a file.

The file part mapped into memory starts at startOffset. Its length is bucketSize*nrOfBuckets bytes. If the file is smaller, the remainder is indicated as an extension similarly to the behaviour of function extend.

casacore::BucketMapped::~BucketMapped ( )

Unmap the file.

casacore::BucketMapped::BucketMapped ( const BucketMapped & ) [private]

Copy constructor is not possible.