org.planx.io
Class MultiFileSystem

java.lang.Object
  org.planx.io.MultiFileSystem

All Implemented Interfaces:

FileSystem

public class MultiFileSystem
extends Object
implements FileSystem

Combines several FileSystems into one providing transparent access to all of them. Operations involving lookup of a file system based on a Locator have O(N) performance where N is the number of FileSystems associated with this MultiFileSystem. The lookup is done by calling FileSystem.isContained(Locator) on every file system until a file system returns true.

Subclasses may override the lookup(Locator) method to change the lookup implementation.

Author:

Thomas Ambus

Constructor Summary

MultiFileSystem()
Creates an empty MultiFileSystem.

MultiFileSystem(FileSystem allocFs)
Creates a MultiFileSystem using the specified file system for allocation of new data.

Method Summary

void	addFileSystem(FileSystem fs) Adds the specified file system to this MultiFileSystem.
Bound	all() Allocates data in the file system designated for new allocations.
Bound	allocate() Allocates data in the file system designated for new allocations.
Bound	allocate(long size) Allocates data in the file system designated for new allocations.
void	clear() Frees all data in this FileSystem.
void	clearModified() Clears the modified status of all the file systems.
void	close() Closes all the contained file systems.
void	free(Bound l) Frees the space occupied by the specified Bound.
FileSystem	getAllocationFileSystem() Returns the file system designated for new allocations of data or null if none exists.
PositionalData	getData(Locator l) Returns a PositionalData for reading and writing to the FileSystem at the specified location.
Bound	getMeta() Unsupported - returns null.
SourceId	id() Returns the SourceId of the allocation file system.
boolean	isContained(Locator l) Returns true if and only if the specified locator is contained in any of the file systems associated with this MultiFileSystem.
boolean	isModified() Returns true if any of the file systems are modified.
boolean	isReadOnly() Returns true only if all the file systems are read-only.
FileSystem	lookup(Locator l) Returns the FileSystem containing the specified locator or returns null if none of the file systems contains the locator.
void	removeFileSystem(FileSystem fs) Removes the specified file system from this MultiFileSystem.
void	setAllocationFileSystem(FileSystem allocFs) Sets the file system designated for new allocations of data.
void	setMeta(Bound b) Unsupported.
void	setReadOnly(boolean isReadOnly) Sets the read-only status of all the file systems.
long	size() Returns the total size of all associated file systems.
String	toString()

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

MultiFileSystem

public MultiFileSystem()

Creates an empty MultiFileSystem. Allocation operations will not be supported.

MultiFileSystem

public MultiFileSystem(FileSystem allocFs)

Creates a MultiFileSystem using the specified file system for allocation of new data. That file system will also be considered part of this file system.

Method Detail

addFileSystem

public void addFileSystem(FileSystem fs)

Adds the specified file system to this MultiFileSystem.

removeFileSystem

public void removeFileSystem(FileSystem fs)

Removes the specified file system from this MultiFileSystem.

getAllocationFileSystem

public FileSystem getAllocationFileSystem()

Returns the file system designated for new allocations of data or null if none exists.

setAllocationFileSystem

public void setAllocationFileSystem(FileSystem allocFs)

Sets the file system designated for new allocations of data. The file system will automatically be added to the systems contained in this MultiFileSystem. Any previous allocation file system will not be removed automatically.

id

public SourceId id()
            throws IOException

Returns the SourceId of the allocation file system.

Specified by:

id in interface FileSystem

Throws:

IOException

allocate

public Bound allocate()
               throws IOException

Allocates data in the file system designated for new allocations.

Specified by:

allocate in interface FileSystem

Throws:

IOException - if an I/O error occurred.

allocate

public Bound allocate(long size)
               throws IOException

Allocates data in the file system designated for new allocations.

Specified by:

allocate in interface FileSystem

Throws:

IOException - if an I/O error occurred or the specified amount of bytes could not be allocated.

all

public Bound all()
          throws IOException

Allocates data in the file system designated for new allocations.

Specified by:

all in interface FileSystem

Throws:

IOException - if an I/O error occurred.

free

public void free(Bound l)
          throws IOException

Description copied from interface: FileSystem

Frees the space occupied by the specified Bound.

Specified by:

free in interface FileSystem

Throws:

IOException - if an I/O error occurred.

InvalidSourceIdException - if the file system identifier of the locator is invalid.

OutOfBoundsException - if the locator is out of bounds.

getMeta

public Bound getMeta()
              throws IOException

Unsupported - returns null.

Specified by:

getMeta in interface FileSystem

Throws:

IOException

setMeta

public void setMeta(Bound b)
             throws IOException

Unsupported.

Specified by:

setMeta in interface FileSystem

Throws:

IOException

clear

public void clear()
           throws IOException

Description copied from interface: FileSystem

Frees all data in this FileSystem.

Specified by:

clear in interface FileSystem

Throws:

IOException

getData

public PositionalData getData(Locator l)
                       throws IOException

Description copied from interface: FileSystem

Returns a PositionalData for reading and writing to the FileSystem at the specified location.

Specified by:

getData in interface FileSystem

Throws:

IOException - if an I/O error occurred.

InvalidSourceIdException - if the file system identifier of the locator is invalid.

OutOfBoundsException - if the locator is out of bounds.

size

public long size()
          throws IOException

Returns the total size of all associated file systems.

Specified by:

size in interface FileSystem

Throws:

IOException - if an I/O error occurred.

isModified

public boolean isModified()
                   throws IOException

Returns true if any of the file systems are modified.

Specified by:

isModified in interface FileSystem

Throws:

IOException

clearModified

public void clearModified()
                   throws IOException

Clears the modified status of all the file systems.

Specified by:

clearModified in interface FileSystem

Throws:

IOException

isReadOnly

public boolean isReadOnly()
                   throws IOException

Returns true only if all the file systems are read-only.

Specified by:

isReadOnly in interface FileSystem

Throws:

IOException

setReadOnly

public void setReadOnly(boolean isReadOnly)
                 throws IOException

Sets the read-only status of all the file systems.

Specified by:

setReadOnly in interface FileSystem

Throws:

IOException

close

public void close()
           throws IOException

Closes all the contained file systems.

Specified by:

close in interface FileSystem

Throws:

IOException - if an I/O error occurred.

isContained

public boolean isContained(Locator l)

Returns true if and only if the specified locator is contained in any of the file systems associated with this MultiFileSystem.

Specified by:

isContained in interface FileSystem

lookup

public FileSystem lookup(Locator l)
                  throws IOException

Returns the FileSystem containing the specified locator or returns null if none of the file systems contains the locator. Subclasses may override this method to change lookup implementation.

Throws:

IOException

toString

public String toString()

Overrides:

toString in class Object