casacore::MultiFileBase Class Reference

Abstract base class to combine multiple files in a single one. More...

#include <MultiFileBase.h>

Inheritance diagram for casacore::MultiFileBase:

Public Member Functions
	MultiFileBase (const String &name, Int blockSize=0)
	Open or create a MultiFileBase with the given name.
virtual	~MultiFileBase ()
	The destructor flushes and closes the file.
Int	fileId (const String &name, Bool throwExcp=True) const
	Return the file id of a file in the MultiFileBase object.
Int	addFile (const String &name)
	Add a file to the MultiFileBase object.
void	deleteFile (Int fileId)
	Delete a file.
Int64	read (Int fileId, void *buffer, Int64 size, Int64 offset)
	Read a block at the given offset.
Int64	write (Int fileId, const void *buffer, Int64 size, Int64 offset)
	Write a block at the given offset.
void	flush ()
	Flush the file by writing all dirty data and all header info.
void	resync ()
	Resync with another process by clearing the buffers and rereading the header.
virtual void	reopenRW ()=0
	Reopen the underlying file for read/write access.
virtual void	fsync ()=0
	Fsync the file (i.e., force the data to be physically written).
String	fileName () const
	Get the file name of the MultiFileBase.
Bool	isWritable () const
	Is the file writable?
Int64	blockSize () const
	Get the block size used.
uInt	nfile () const
	Get the nr of virtual files.
Int64	size () const
	Get the total nr of data blocks used.
const vector< MultiFileInfo > &	info () const
	Get the info object (for test purposes mainly).
const vector< Int64 > &	freeBlocks () const
	Get the free blocks (for test purposes mainly).
Protected Member Functions
void	setNewFile ()
	Set the flags and blockSize for a new MultiFile/HDF5.
Protected Attributes
String	itsName
Int64	itsBlockSize
Int64	itsNrBlock
Int64	itsHdrCounter
vector< MultiFileInfo >	itsInfo
Bool	itsWritable
Bool	itsChanged
vector< Int64 >	itsFreeBlocks
Private Member Functions
void	writeDirty (MultiFileInfo &info)
virtual void	doAddFile (MultiFileInfo &)=0
	Do the class-specific actions on adding a file.
virtual void	doDeleteFile (MultiFileInfo &)=0
	Do the class-specific actions on deleting a file.
virtual void	flushFile ()=0
	Flush the file itself.
virtual void	close ()=0
	Flush and close the file.
virtual void	writeHeader ()=0
	Write the header info.
virtual void	readHeader (Bool always=True)=0
	Read the header info.
virtual void	extend (MultiFileInfo &info, Int64 lastblk)=0
	Extend the virtual file to fit lastblk.
virtual void	writeBlock (MultiFileInfo &info, Int64 blknr, const void *buffer)=0
	Write a data block.
virtual void	readBlock (MultiFileInfo &info, Int64 blknr, void *buffer)=0
	Read a data block.

Detailed Description

Abstract base class to combine multiple files in a single one.

Intended use:

Public interface

Review Status

Test programs:: tMultiFile

Synopsis

This class is a container file holding multiple virtual files. It is primarily meant as a container file for the storage manager files of a table to reduce the number of files used (especially for Lustre) and to reduce the number of open files (especially when concatenating tables).
A secondary goal is offering the ability to use an IO buffer size that matches the file system well (large buffer size for e.g. ZFS).

The SetupNewTable constructor has a StorageOption argument to define if a MultiFile has to be used and if so, the buffer size to use. It is also possible to specify that through aipsrc variables.

A virtual file is spread over multiple (fixed size) data blocks in the MultiFile. A data block is never shared by multiple files. For each virtual file MultiFile keeps a MultiFileInfo object telling the file size and the blocks numbers used for the file. When flushing the MultiFile, this meta info is written into a header block and, if needed, continuation blocks. On open and resync, it is read back.

A virtual file is represented by an MFFileIO object, which is derived from ByteIO and as such part of the casacore IO framework. It makes it possible for applications to access a virtual file in the same way as a regular file.

It is possible to delete a virtual file. Its blocks will be added to the free block list (which is also stored in the meta info).

Example

In principle it is possible to use the MultiFile functions directly. However, in general it is much easier to use an MFFileIO object per virtual file as shown below.

 // Create a new MultiFile using a block size of 1 MB.
 MultiFile mfile("file.mf', ByteIO::New, 1048576);
 // Create a virtual file in it.
 MFFileIO mf1(mfile, "mf1", ByteIO::New);
 // Use it (for example) as the sink of AipsIO.
 AipsIO stream (&mf1);
 // Write values.
 stream << (Int)10;
 stream << True;
 // Seek to beginning of file and read data in.
 stream.setpos (0);
 Int vali;
 Bool valb;
 stream >> vali >> valb;

To Do

write headers at alternating file positions (for robustness)
possibly write headers entirely at the end if larger than blocksize

Definition at line 134 of file MultiFileBase.h.

Constructor & Destructor Documentation

casacore::MultiFileBase::MultiFileBase	(	const String &	name,
		Int	blockSize = `0`
	)

Open or create a MultiFileBase with the given name.

Upon creation the block size can be given. If 0, it uses the block size of the file system the file is on.

virtual casacore::MultiFileBase::~MultiFileBase ( ) [virtual]

The destructor flushes and closes the file.

Member Function Documentation

Int casacore::MultiFileBase::addFile ( const String & name )

Add a file to the MultiFileBase object.

It returns the file id. Only the base name of the given file name is used. In this way the MultiFileBase container file can be moved.

Int64 casacore::MultiFileBase::blockSize ( ) const [inline]

Get the block size used.

Definition at line 189 of file MultiFileBase.h.

References itsBlockSize.

virtual void casacore::MultiFileBase::close ( ) [private, pure virtual]

Flush and close the file.

Implemented in casacore::MultiFile, and casacore::MultiHDF5.

void casacore::MultiFileBase::deleteFile ( Int fileId )

Delete a file.

It adds its blocks to the free block list.

virtual void casacore::MultiFileBase::doAddFile ( MultiFileInfo & ) [private, pure virtual]

Do the class-specific actions on adding a file.

Implemented in casacore::MultiFile, and casacore::MultiHDF5.

virtual void casacore::MultiFileBase::doDeleteFile ( MultiFileInfo & ) [private, pure virtual]

Do the class-specific actions on deleting a file.

Implemented in casacore::MultiFile, and casacore::MultiHDF5.

virtual void casacore::MultiFileBase::extend	(	MultiFileInfo &	info,
		Int64	lastblk
	)			`[private, pure virtual]`

Extend the virtual file to fit lastblk.

Implemented in casacore::MultiFile, and casacore::MultiHDF5.

Int casacore::MultiFileBase::fileId	(	const String &	name,
		Bool	throwExcp = `True`
	)			const

Return the file id of a file in the MultiFileBase object.

If the name is unknown, an exception is thrown if throwExcp is set. Otherwise it returns -1.

String casacore::MultiFileBase::fileName ( ) const [inline]

Get the file name of the MultiFileBase.

Definition at line 181 of file MultiFileBase.h.

References itsName.

void casacore::MultiFileBase::flush ( )

Flush the file by writing all dirty data and all header info.

virtual void casacore::MultiFileBase::flushFile ( ) [private, pure virtual]

Flush the file itself.

Implemented in casacore::MultiFile, and casacore::MultiHDF5.

const vector<Int64>& casacore::MultiFileBase::freeBlocks ( ) const [inline]

Get the free blocks (for test purposes mainly).

Definition at line 204 of file MultiFileBase.h.

References itsFreeBlocks.

virtual void casacore::MultiFileBase::fsync ( ) [pure virtual]

Fsync the file (i.e., force the data to be physically written).

Implemented in casacore::MultiFile, and casacore::MultiHDF5.

const vector<MultiFileInfo>& casacore::MultiFileBase::info ( ) const [inline]

Get the info object (for test purposes mainly).

Definition at line 200 of file MultiFileBase.h.

References itsInfo.

Bool casacore::MultiFileBase::isWritable ( ) const [inline]

Is the file writable?

Definition at line 185 of file MultiFileBase.h.

References itsWritable.

uInt casacore::MultiFileBase::nfile ( ) const

Get the nr of virtual files.

Int64 casacore::MultiFileBase::read	(	Int	fileId,
		void *	buffer,
		Int64	size,
		Int64	offset
	)

Read a block at the given offset.

It returns the actual size read.

virtual void casacore::MultiFileBase::readBlock	(	MultiFileInfo &	info,
		Int64	blknr,
		void *	buffer
	)			`[private, pure virtual]`

Read a data block.

Implemented in casacore::MultiFile, and casacore::MultiHDF5.

virtual void casacore::MultiFileBase::readHeader ( Bool always = True ) [private, pure virtual]

Read the header info.

If always==False, the info is only read if the header counter has changed.

Implemented in casacore::MultiFile, and casacore::MultiHDF5.

virtual void casacore::MultiFileBase::reopenRW ( ) [pure virtual]

Reopen the underlying file for read/write access.

Nothing will be done if the file is writable already. Otherwise it will be reopened and an exception will be thrown if it is not possible to reopen it for read/write access.

Implemented in casacore::MultiFile, and casacore::MultiHDF5.

void casacore::MultiFileBase::resync ( )

Resync with another process by clearing the buffers and rereading the header.

The header is only read if its counter has changed.

void casacore::MultiFileBase::setNewFile ( ) [protected]

Set the flags and blockSize for a new MultiFile/HDF5.

Int64 casacore::MultiFileBase::size ( ) const [inline]

Get the total nr of data blocks used.

Definition at line 196 of file MultiFileBase.h.

References itsNrBlock.