Class for IO on a tape device. More...
#include <TapeIO.h>
Public Member Functions | |
TapeIO () | |
Default constructor. | |
TapeIO (int fd) | |
Construct from the given file descriptor. | |
TapeIO (const Path &device, Bool writable=False) | |
Construct from the given device. | |
virtual | ~TapeIO () |
The destructor will only close the file if the appropriate constructor, or attach function, was used. | |
void | attach (int fd) |
Attach to the given file descriptor. | |
void | attach (const Path &device, Bool writable=False) |
Attach to the given tape device. | |
virtual void | write (Int64 size, const void *buf) |
Write the specified number of bytes. | |
virtual Int64 | read (Int64 size, void *buf, Bool throwException=True) |
Read size bytes from the tape. | |
virtual void | rewind () |
Rewind the tape device to the beginning. | |
virtual void | skip (uInt howMany=1) |
skip the specified number of files (ie tape marks) on the tape. | |
virtual void | mark (uInt howMany=1) |
write the specified number of filemarks. | |
Bool | fixedBlocks () const |
returns True if the tape device is configured to use a fixed block size | |
uInt | fixedBlockSize () const |
returns the block size in bytes. | |
void | setFixedBlockSize (uInt sizeInBytes) |
Configure the tape device to use fixed length blocks of the specified size. | |
void | setVariableBlockSize () |
Configure the tape device to use variable length blocks. | |
virtual Int64 | length () |
Get the length of the tape device. | |
virtual Bool | isReadable () const |
Is the tape device readable? | |
virtual Bool | isWritable () const |
Is the tape device writable? | |
virtual Bool | isSeekable () const |
Is the tape device seekable? | |
virtual String | fileName () const |
Get the name of the attached device or return a zero length string if it cannot be determined. | |
Static Public Member Functions | |
static int | open (const Path &device, Bool writable=False) |
Some static convenience functions for file descriptor opening & closing. | |
static void | close (int fd) |
Protected Member Functions | |
void | detach () |
Detach the FILE. | |
void | fillRWFlags () |
Determine if the file 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 | |
TapeIO (const TapeIO &that) | |
The following functions are made private so that the compiler does not generate default ones. | |
TapeIO & | operator= (const TapeIO &that) |
void | setBlockSize (uInt sizeInBytes) |
uInt | getBlockSize () const |
Private Attributes | |
int | itsDevice |
Bool | itsOwner |
Bool | itsReadable |
Bool | itsWritable |
Bool | itsSeekable |
String | itsDeviceName |
Class for IO on a tape device.
Public interface
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.
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;
Make it possible to use the Casacore IO functionality on any file. In this way any device can be hooked to the IO framework.
Definition at line 87 of file TapeIO.h.
casacore::TapeIO::TapeIO | ( | ) |
Default constructor.
A stream can be attached using the attach function.
casacore::TapeIO::TapeIO | ( | int | fd | ) | [explicit] |
Construct from the given file descriptor.
The file descriptor must have been obtained using the TapeIO::open static function. When constructed this way the class will not take over the file descriptor and hence not close the Tape device when this class is destroyed.
Construct from the given device.
The device must point to a tape device and if requested it is checked if the device is writeable. Throws an exception if the device could not be opened correctly. When constructed this way the class will close the Tape device when this class is destroyed or the TapeIO object is attached to a new file descriptor.
virtual casacore::TapeIO::~TapeIO | ( | ) | [virtual] |
The destructor will only close the file if the appropriate constructor, or attach function, was used.
casacore::TapeIO::TapeIO | ( | const TapeIO & | that | ) | [private] |
The following functions are made private so that the compiler does not generate default ones.
They cannot be used and are not defined.
Attach to the given tape device.
The tape will be closed when this class is destroyed or the TapeIO object is attached to a new descriptor.
void casacore::TapeIO::attach | ( | int | fd | ) |
static void casacore::TapeIO::close | ( | int | fd | ) | [static] |
void casacore::TapeIO::detach | ( | ) | [protected] |
Detach the FILE.
Close it when it is owned.
virtual Int64 casacore::TapeIO::doSeek | ( | Int64 | offset, | |
ByteIO::SeekOption | ||||
) | [protected, virtual] |
Reset the position pointer to the given value.
It returns the new position. May not work on all Tape devices use the isSeekable(0 member function to see if this function is usuable. Otherwise an Exception (AipsError) is thrown.
Implements casacore::ByteIO.
virtual String casacore::TapeIO::fileName | ( | ) | const [virtual] |
Get the name of the attached device or return a zero length string if it cannot be determined.
Reimplemented from casacore::ByteIO.
void casacore::TapeIO::fillRWFlags | ( | ) | [protected] |
Determine if the file is readable and/or writable.
void casacore::TapeIO::fillSeekable | ( | ) | [protected] |
Determine if the file is seekable.
Bool casacore::TapeIO::fixedBlocks | ( | ) | const |
returns True if the tape device is configured to use a fixed block size
uInt casacore::TapeIO::fixedBlockSize | ( | ) | const |
returns the block size in bytes.
Returns zero if the device is configured to use variable length blocks.
uInt casacore::TapeIO::getBlockSize | ( | ) | const [private] |
virtual Bool casacore::TapeIO::isReadable | ( | ) | const [virtual] |
Is the tape device readable?
Implements casacore::ByteIO.
virtual Bool casacore::TapeIO::isSeekable | ( | ) | const [virtual] |
Is the tape device seekable?
Implements casacore::ByteIO.
virtual Bool casacore::TapeIO::isWritable | ( | ) | const [virtual] |
Is the tape device writable?
Implements casacore::ByteIO.
virtual Int64 casacore::TapeIO::length | ( | ) | [virtual] |
Get the length of the tape device.
Not a meaningful function for this class and this function always returns -1.
Implements casacore::ByteIO.
virtual void casacore::TapeIO::mark | ( | uInt | howMany = 1 |
) | [virtual] |
write the specified number of filemarks.
Reimplemented from casacore::ByteIO.
virtual Int64 casacore::TapeIO::read | ( | Int64 | size, | |
void * | buf, | |||
Bool | throwException = True | |||
) | [virtual] |
Read size
bytes from the tape.
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 tape is not readable or the system call returns an undocumented value. Returns zero if the tape is at the end of the current file (and size is non-zero and throwException is False).
Implements casacore::ByteIO.
virtual void casacore::TapeIO::rewind | ( | ) | [virtual] |
Rewind the tape device to the beginning.
void casacore::TapeIO::setBlockSize | ( | uInt | sizeInBytes | ) | [private] |
void casacore::TapeIO::setFixedBlockSize | ( | uInt | sizeInBytes | ) |
Configure the tape device to use fixed length blocks of the specified size.
The size must be bigger than zero (dugh!). Values bigger than 64k may cause problems on some systems. Currently this function only does anything under Solaris and Linux systems.
void casacore::TapeIO::setVariableBlockSize | ( | ) |
Configure the tape device to use variable length blocks.
Currently this function only does anything under Solaris and Linux systems.
virtual void casacore::TapeIO::skip | ( | uInt | howMany = 1 |
) | [virtual] |
skip the specified number of files (ie tape marks) on the tape.
Throws an exception if you try to skip past the last filemark.
virtual void casacore::TapeIO::write | ( | Int64 | size, | |
const void * | buf | |||
) | [virtual] |
Write the specified number of bytes.
Implements casacore::ByteIO.
int casacore::TapeIO::itsDevice [private] |
String casacore::TapeIO::itsDeviceName [private] |
Bool casacore::TapeIO::itsOwner [private] |
Bool casacore::TapeIO::itsReadable [private] |
Bool casacore::TapeIO::itsSeekable [private] |
Bool casacore::TapeIO::itsWritable [private] |