org.entityfs.util.io
Class GZipReadableFile

java.lang.Object
  org.entityfs.util.io.GZipReadableFile

All Implemented Interfaces:

Lockable, ReadLockable, ReadableFile

public class GZipReadableFile
extends Object
implements ReadableFile

This is a ReadableFile that transparently decompresses the contents of a wrapped file using gzip compression. The gzip input stream is opened on a buffered stream, whose buffer size can be set.

A ReadableFile can be made into a NamedReadableFile using the NamedReadableFileAdapter.

Since:

1.1

Author:

Karl Gustafsson

See Also:

GZipWritableFile

Constructor Summary

GZipReadableFile(ReadableFile adapted)
Create a new adapter.

GZipReadableFile(ReadableFile adapted, int bufferSize)
Create a new adapter.

Method Summary

long	getDataSize() Get the size of the data in the file.
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

GZipReadableFile

public GZipReadableFile(ReadableFile adapted)

Create a new adapter. The buffered stream will use the default buffer size of BufferedInputStream.

Parameters:

adapted - The adapted file.

GZipReadableFile

public GZipReadableFile(ReadableFile adapted,
                        int bufferSize)
                 throws IllegalArgumentException

Create a new adapter.

Parameters:

adapted - The adapted file.

bufferSize - The buffer size for the buffered stream that the gzip stream is opened on.

Throws:

IllegalArgumentException - If the buffer size is <= 0.

Method Detail

openChannelForRead

public ReadableByteChannel openChannelForRead()
                                       throws ReadLockRequiredException,
                                              AccessDeniedException

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.

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.openForRead()

openForRead

public InputStream openForRead()
                        throws ReadLockRequiredException,
                               AccessDeniedException

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.

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.

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.

isReadLockedByCurrentThread

public boolean isReadLockedByCurrentThread()
                                    throws IllegalStateException

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.

Throws:

IllegalStateException - If this is called on a disconnected entity view.

lockForReading

public EntityLock lockForReading()
                          throws LockTimeoutException

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.

Throws:

LockTimeoutException - If the lock acquiring timed out. (It is up to the LockAcquiringStrategy to decide if lock acquiring can time out.)

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()