Class for IO on a large file descriptor. More...

#include <LargeFiledesIO.h>

Inheritance diagram for casa::LargeFiledesIO:

Public Member Functions
	LargeFiledesIO ()
	Default constructor.
	LargeFiledesIO (int fd, const String &fileName=String())
	Construct from the given file descriptor.
void	attach (int fd, const String &fileName)
	Attach to the given file descriptor.
	~LargeFiledesIO ()
	The destructor does not close the file.
virtual void	write (uInt size, const void *buf)
	Write the number of bytes.
virtual Int	read (uInt size, void *buf, Bool throwException=True)
	Read `size` bytes from the descriptor.
virtual Int64	length ()
	Get the length of the byte stream.
virtual Bool	isReadable () const
	Is the IO stream readable?
virtual Bool	isWritable () const
	Is the IO stream writable?
virtual Bool	isSeekable () const
	Is the IO stream seekable?
const String &	fileName () const
	Get the file name of the file attached.
Static Public Member Functions
static int	create (const Char *name, int mode=0644)
	Some static convenience functions for file create/open/close.
static int	open (const Char *name, Bool writable=False, Bool throwExcp=True)
static void	close (int fd)
Protected Member Functions
int	fd () const

void	detach ()
	Detach from the file descriptor.
void	fillRWFlags (int fd)
	Determine if the file descriptor is readable and/or writable.
void	fillSeekable ()
	Determine if the file is seekable.
virtual Int64	doSeek (Int64 offset, ByteIO::SeekOption)
	Reset the position pointer to the given value.
Private Member Functions
	LargeFiledesIO (const LargeFiledesIO &that)
	Copy constructor, should not be used.
LargeFiledesIO &	operator= (const LargeFiledesIO &that)
	Assignment, should not be used.
Private Attributes
Bool	itsSeekable
Bool	itsReadable
Bool	itsWritable
int	itsFile
String	itsFileName

Detailed Description

Class for IO on a large file descriptor.

Intended use:

Public interface

Review Status

Reviewed By:: Friso Olnon
Date Reviewed:: 1996/11/06
Test programs:: tByteIO

Prerequisite

ByteIO class
file descriptors

Synopsis

This class is a specialization of class ByteIO . It uses a file descriptor to read/write data.

The file associated with the file descriptor has to be opened before hand. The constructor will determine automatically if the file is readable, writable and seekable. Note that on destruction the file descriptor is NOT closed.

Example

This example shows how FiledesIO can be used with an fd. It uses the fd for a regular file, which could be done in an easier way using class RegularFileIO . However, when using pipes or sockets, this would be the only way.

       // Get a file descriptor for the file.
       int fd = open ("file.name");
       // Use that as the source of AipsIO (which will also use CanonicalIO).
       FiledesIO fio (fd);
       AipsIO stream (&fio);
       // Read the data.
       Int vali;
       Bool valb;
       stream >> vali >> valb;

Motivation

Make it possible to use the AIPS++ IO functionality on any file. In this way any device can be hooked to the IO framework.

Definition at line 88 of file LargeFiledesIO.h.

Constructor & Destructor Documentation

casa::LargeFiledesIO::LargeFiledesIO ( )

Default constructor.

A stream can be attached using the attach function.

casa::LargeFiledesIO::LargeFiledesIO	(	int	fd,
		const String &	fileName = `String()`
	)		`[explicit]`

Construct from the given file descriptor.

The file name is only used in possible error messages.

casa::LargeFiledesIO::~LargeFiledesIO ( )

The destructor does not close the file.

casa::LargeFiledesIO::LargeFiledesIO ( const LargeFiledesIO & that ) [private]

Copy constructor, should not be used.

Member Function Documentation

void casa::LargeFiledesIO::attach	(	int	fd,
		const String &	fileName
	)

Attach to the given file descriptor.

An exception is thrown if it is not in a detached state. The file name is only used in error messages.

static void casa::LargeFiledesIO::close ( int fd ) [static]

static int casa::LargeFiledesIO::create	(	const Char *	name,
		int	mode = `0644`
	)		`[static]`

Some static convenience functions for file create/open/close.

void casa::LargeFiledesIO::detach ( ) [protected]

Detach from the file descriptor.

It is not closed.

virtual Int64 casa::LargeFiledesIO::doSeek	(	Int64	offset,
		ByteIO::SeekOption
	)		`[protected, virtual]`

Reset the position pointer to the given value.

It returns the new position.

Implements casa::ByteIO.

Reimplemented in casa::MMapfdIO.

int casa::LargeFiledesIO::fd ( ) const [inline, protected]

Get the file descriptor.

Definition at line 145 of file LargeFiledesIO.h.

References itsFile.

const String& casa::LargeFiledesIO::fileName ( ) const [inline]

Get the file name of the file attached.

Definition at line 131 of file LargeFiledesIO.h.

References itsFileName.

void casa::LargeFiledesIO::fillRWFlags ( int fd ) [protected]

Determine if the file descriptor is readable and/or writable.

void casa::LargeFiledesIO::fillSeekable ( ) [protected]

Determine if the file is seekable.

virtual Bool casa::LargeFiledesIO::isReadable ( ) const [virtual]

Is the IO stream readable?

Implements casa::ByteIO.

virtual Bool casa::LargeFiledesIO::isSeekable ( ) const [virtual]

Is the IO stream seekable?

Implements casa::ByteIO.

virtual Bool casa::LargeFiledesIO::isWritable ( ) const [virtual]

Is the IO stream writable?

Implements casa::ByteIO.

virtual Int64 casa::LargeFiledesIO::length ( ) [virtual]

Get the length of the byte stream.

Implements casa::ByteIO.

static int casa::LargeFiledesIO::open	(	const Char *	name,
		Bool	writable = `False`,
		Bool	throwExcp = `True`
	)		`[static]`

LargeFiledesIO& casa::LargeFiledesIO::operator= ( const LargeFiledesIO & that ) [private]

Assignment, should not be used.

virtual Int casa::LargeFiledesIO::read	(	uInt	size,
		void *	buf,
		Bool	throwException = `True`
	)		`[virtual]`

Read size bytes from the descriptor.

Returns the number of bytes actually read or a negative number if an error occured. Will throw an Exception (AipsError) if the requested number of bytes could not be read, or an error occured, unless throwException is set to False. Will always throw an exception if the descriptor is not readable or the system call returned an undocumented value.

Implements casa::ByteIO.

Reimplemented in casa::MMapfdIO.