de.enough.polish.content.storage
Class StorageIndex

java.lang.Object
  de.enough.polish.content.storage.StorageIndex

All Implemented Interfaces:

Comparator

Direct Known Subclasses:

RmsStorageIndex

public class StorageIndex
extends Object
implements Comparator

Serves as an index for stored contents

Author:

Andre Schmidt

Field Summary

protected ArrayList	index the index list
protected long	maxCacheSize the maximum cache size

Constructor Summary

StorageIndex(long maxCacheSize)
Creates a new StorageIndex instance

Method Summary

void	addReference(StorageReference reference) Adds a reference to the index and stores the index
void	applyOrder() Applies the clean order to this index by the use of the internal index array and the compareTo() method
int	compare(Object first, Object second) Compares two objects.
long	getAvailableCacheSize() Returns the maximum possible number of bytes that can be stored.
long	getCacheSize() Returns the current cache size
int	getDisposableIndex() Returns the index of the first disposable content.
StorageReference	getReference(ContentDescriptor descriptor) Returns the reference for the specified descriptor if it is present in the index
StorageReference	getReference(int i) Returns the reference at position i
boolean	isCleanNeeded() Returns true, if the current cache size is greater than the threshold, otherwise false
boolean	isCleanNeeded(int extraBytes) Returns true, if the current cache size is not enough to store an additional extraBytes bytes, otherwise false
boolean	isDisposableTo(StorageReference reference, StorageReference master) Returns true, if the reference is disposable to the specified master, otherwise false
boolean	isPrepared() Returns true, if the index is prepared, otherwise false
protected ArrayList	load() Loads the ArrayList representing the index.
void	prepare() Prepares this index by calling load and adding the loaded references to the index
void	removeReference(StorageReference reference) Removes a reference from the index and stores the index
void	shutdown() Called when a content storage is shutdown.
int	size() Returns the number of the references in this index
protected void	store(ArrayList index) Stores the ArrayList representing the index.
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

index

protected ArrayList index

the index list

maxCacheSize

protected final long maxCacheSize

the maximum cache size

Constructor Detail

StorageIndex

public StorageIndex(long maxCacheSize)

Creates a new StorageIndex instance

Parameters:

maxCacheSize - the maximum cache size for this instances

Method Detail

prepare

public void prepare()

Prepares this index by calling load and adding the loaded references to the index

isPrepared

public boolean isPrepared()

Returns true, if the index is prepared, otherwise false

Returns:

true, if the index is prepared, otherwise false

addReference

public void addReference(StorageReference reference)

Adds a reference to the index and stores the index

Parameters:

reference - the reference

removeReference

public void removeReference(StorageReference reference)

Removes a reference from the index and stores the index

Parameters:

reference - the reference

getDisposableIndex

public int getDisposableIndex()

Returns the index of the first disposable content.

Returns:

the index of the first disposable content.

getReference

public StorageReference getReference(int i)

Returns the reference at position i

Parameters:

i - the position

Returns:

the reference at the specified position

size

public int size()

Returns the number of the references in this index

Returns:

the number of the references in this index

getCacheSize

public long getCacheSize()

Returns the current cache size

Returns:

the current cache size

getAvailableCacheSize

public long getAvailableCacheSize()

Returns the maximum possible number of bytes that can be stored. This takes into consideration both user-specified limitations (e.g. maximum cache size) and platform-specific limitations (e.g. storage space).

Returns:

the maximum possible number of bytes that can be stored in the cache.

load

protected ArrayList load()

Loads the ArrayList representing the index. It is encouraged to overwrite this method for persistence of the index.

Returns:

the ArrayList representing the index

store

protected void store(ArrayList index)

Stores the ArrayList representing the index. It is encouraged to overwrite this method for persistence of the index.

Parameters:

index - the ArrayList representing the index

getReference

public StorageReference getReference(ContentDescriptor descriptor)

Returns the reference for the specified descriptor if it is present in the index

Parameters:

descriptor - the content descriptor

Returns:

the found reference or null

isCleanNeeded

public boolean isCleanNeeded()

Returns true, if the current cache size is greater than the threshold, otherwise false

Returns:

true, if the current cache size is greater than the threshold, otherwise false

isCleanNeeded

public boolean isCleanNeeded(int extraBytes)

Returns true, if the current cache size is not enough to store an additional extraBytes bytes, otherwise false

Parameters:

extraBytes - the number of extra bytes to store

Returns:

true, if the current cache size is greater than the threshold, otherwise false

compare

public int compare(Object first,
                   Object second)

Description copied from interface: Comparator

Compares two objects. In the foregoing description, the notation sgn(expression) designates the mathematical signum function, which is defined to return one of -1, 0, or 1 according to whether the value of expression is negative, zero or positive. The implementor must ensure that sgn(compare(x, y)) == -sgn(compare(y, x)) for all x and y. (This implies that compare(x, y) must throw an exception if and only if compare(y, x) throws an exception.) The implementor must also ensure that the relation is transitive: ((compare(x, y)>0) && (compare(y, z)>0)) implies compare(x, z)>0. Finally, the implementor must ensure that compare(x, y)==0 implies that sgn(compare(x, z))==sgn(compare(y, z)) for all z. It is generally the case, but not strictly required that (compare(x, y)==0) == (x.equals(y)). Generally speaking, any comparator that violates this condition should clearly indicate this fact. The recommended language is "Note: this comparator imposes orderings that are inconsistent with equals."

Specified by:

compare in interface Comparator

Parameters:

first - the first object

second - the object that is compared with o1

Returns:

a negative integer, zero, or a positive integer as the first argument is less than, equal to, or greater than the second.

isDisposableTo

public boolean isDisposableTo(StorageReference reference,
                              StorageReference master)

Returns true, if the reference is disposable to the specified master, otherwise false

Parameters:

reference - the reference

master - the master

Returns:

true, if the reference is disposable to the specified master, otherwise false

applyOrder

public void applyOrder()

Applies the clean order to this index by the use of the internal index array and the compareTo() method

shutdown

public void shutdown()

Called when a content storage is shutdown. Overwrite this to implements shutdown behaviour.

toString

public String toString()

Overrides:

toString in class Object