LargeFiledesIO.h

Classes

LargeFiledesIO -- Class for IO on a large file descriptor. (full description)

class LargeFiledesIO: public ByteIO

Interface

Public Members

LargeFiledesIO()

explicit LargeFiledesIO (int fd)

void attach (int fd)

~LargeFiledesIO()

virtual void write (uInt size, const void* buf)

virtual Int read (uInt size, void* buf, Bool throwException=True)

virtual Int64 length()

virtual Bool isReadable() const

virtual Bool isWritable() const

virtual Bool isSeekable() const

virtual String fileName() const

static int create (const Char* name, int mode = 0644)

static int open (const Char* name, Bool writable = False, Bool throwExcp = True)

static void close (int fd)

Protected Members

void detach()

void fillRWFlags (int fd)

void fillSeekable()

virtual Int64 doSeek (Int64 offset, ByteIO::ByteIO)

Private Members

LargeFiledesIO (const LargeFiledesIO& that)

LargeFiledesIO& operator= (const LargeFiledesIO& that)

Description

Review Status

Reviewed By:

Friso Olnon

Date Reviewed:

1996/11/06

Programs:

Tests:

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.

Member Description

LargeFiledesIO()

Default constructor. A stream can be attached using the attach function.

explicit LargeFiledesIO (int fd)

Construct from the given file descriptor.

void attach (int fd)

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. 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.

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?

virtual String fileName() const

Get the file name of the file attached.

static int create (const Char* name, int mode = 0644)
static int open (const Char* name, Bool writable = False, Bool throwExcp = True)
static void close (int fd)

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

void detach()

Detach the FILE. Close it when it is owned.

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::ByteIO)

Reset the position pointer to the given value. It returns the new position.

LargeFiledesIO (const LargeFiledesIO& that)

Copy constructor, should not be used.

LargeFiledesIO& operator= (const LargeFiledesIO& that)

Assignment, should not be used.