org.entityfs.util
Class NamedReadableFileAdapter

java.lang.Object
  org.entityfs.util.NamedReadableFileAdapter

All Implemented Interfaces:

Lockable, ReadLockable, Named, NamedReadableFile, ReadableFile

public class NamedReadableFileAdapter
extends Object
implements NamedReadableFile

This adapter is used to give a ReadableFile a name, making it a NamedReadableFile. It can for instance be used to pretend that a EFile entity has another name.

Since:

1.0

Author:

Karl Gustafsson

In_jar:

entityfs-util

Constructor Summary

NamedReadableFileAdapter(ReadableFile f, String name)

Method Summary

long	getDataSize() Get the size of the data in the file.
String	getName() Get the name.
EntityLock	getReadLock() Get the read lock without locking it.
long	getSize() Get the size of the file (in bytes).
boolean	isReadLockedByCurrentThread() Does the calling thread hold a read lock for this object? A write lock also qualifies as a read lock.
EntityLock	lockForReading() Lock object for reading and return the lock.
ReadableByteChannel	openChannelForRead() Open a ReadableByteChannel for reading from the file.
InputStream	openForRead() Opens the file for reading.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

NamedReadableFileAdapter

public NamedReadableFileAdapter(ReadableFile f,
                                String name)

Method Detail

getReadLock

public EntityLock getReadLock()

Description copied from interface: ReadLockable

Get the read lock without locking it.

This method always returns a lock, even if the object's file system is not locking or if the object is read only.

Specified by:

getReadLock in interface ReadLockable

Returns:

The lockable's read lock. This might be unlocked or locked by someone else.

lockForReading

public EntityLock lockForReading()

Description copied from interface: ReadLockable

Lock object for reading and return the lock. How the lock is acquired is determined by the EntityLockAdapterFactory and LockAcquiringStrategy used. If this is called on an object that somehow is connected to an entity object, that entity's file system's entity lock adapter factory and lock acquiring strategy is used.

A read lock cannot be upgraded to a write lock (just like how Java's ReadWriteLock works).

For more discussions on locks and locking, see Entity and FileSystem.

This method always returns a lock, even if the object's file system is not locking or if the object is read only.

Specified by:

lockForReading in interface ReadLockable

Returns:

A locked read lock.

isReadLockedByCurrentThread

public boolean isReadLockedByCurrentThread()

Description copied from interface: ReadLockable

Does the calling thread hold a read lock for this object? A write lock also qualifies as a read lock.

Specified by:

isReadLockedByCurrentThread in interface ReadLockable

Returns:

true if the lockable object is read or write locked by the current thread.

getName

public String getName()

Description copied from interface: Named

Get the name. The name of the root directory is /.

Specified by:

getName in interface Named

Returns:

The name of the named object.

openChannelForRead

public ReadableByteChannel openChannelForRead()

Description copied from interface: ReadableFile

Open a ReadableByteChannel for reading from the file. The semantics of this method is the same as for ReadableFile.openForRead().

Although a read lock on the file is required for the execution thread opening the channel, the channel itself is not protected from access by other threads. It can be protected by wrapping it in a LockAwareReadableByteChannel.

Specified by:

openChannelForRead in interface ReadableFile

Returns:

An open ReadableByteChannel. The channel must be closed by the caller. The channel may be a ScatteringByteChannel, but that is not required.

See Also:

ReadableFile.openForRead()

openForRead

public InputStream openForRead()

Description copied from interface: ReadableFile

Opens the file for reading. The caller is responsible for closing the returned stream.

Although a read lock on the file is required for the execution thread opening the stream, the stream itself is not protected from access by other threads. It can be protected by wrapping it in a LockAwareInputStream.

Specified by:

openForRead in interface ReadableFile

Returns:

An InputStream on the file. The stream must be closed by the caller.

getDataSize

public long getDataSize()
                 throws ReadLockRequiredException,
                        AccessDeniedException

Description copied from interface: ReadableFile

Get the size of the data in the file. For compressed files, this is larger than the value returned by ReadableFile.getSize().

Warning: Calculating the data size of a file has the potential of being really slow, depending on the implementation used. The entire file may have to be read through in order to calculate the size of its data.

Implementation note: If the size of the backing file is not known, the StreamUtil.getSizeOfDataInStream(InputStream, int) method can be used to calculate it.

Specified by:

getDataSize in interface ReadableFile

Returns:

The size of data in the file.

Throws:

ReadLockRequiredException - If the client does not have a read lock for the file.

AccessDeniedException - If the client does not have read access to the file.

See Also:

ReadableFile.getSize()

getSize

public long getSize()
             throws ReadLockRequiredException,
                    AccessDeniedException

Description copied from interface: ReadableFile

Get the size of the file (in bytes). This is the number of bytes that the file occupies where it is stored.

Note: Most, but not all, implementations know their sizes. If an implementation does not know its size beforehand, this method will be slow since it has to calculate the file size when it is called.

Implementation note: If the size of the backing file is not known, the StreamUtil.getSizeOfDataInStream(InputStream, int) method can be used to calculate it.

Specified by:

getSize in interface ReadableFile

Returns:

The size of the file, in bytes.

Throws:

ReadLockRequiredException - If the client does not have a read lock for the file.

AccessDeniedException - If the client does not have read access to the file.

See Also:

ReadableFile.getDataSize()