org.nuxeo.common.file

Class LRUFileCache

java.lang.Object

org.nuxeo.common.file.LRUFileCache

All Implemented Interfaces:

FileCache

public class LRUFileCache
extends Object
implements FileCache

A LRU cache of Files with capped filesystem size.

When a new file is put in the cache, if the total size becomes more that the maximum size then least recently access entries are removed until the new file fits.

A file will never be actually removed from the filesystem while the File object returned by getFile(java.lang.String) is still referenced.

The cache keys are restricted to a subset of ASCII: letters, digits and dashes. Usually a MD5 or SHA1 hash is used.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected static class	LRUFileCache.LRUFileCacheEntry In-memory entry for a cached file.

Field Summary

Fields

Modifier and Type	Field and Description
protected Map<String,LRUFileCache.LRUFileCacheEntry>	cache Cached files.
protected long	cacheSize Size of the cached files.
protected File	dir
protected Map<String,File>	files Referenced files on the filesystem.
protected LinkedList<String>	lru Most recently used entries from the cache are first.
protected long	maxSize
static Pattern	SIMPLE_ASCII Allowed key pattern, used as file path.

Constructor Summary

Constructors

Constructor and Description
LRUFileCache(File dir, long maxSize) Constructs a cache in the given directory with the given maximum size (in bytes).

Method Summary

Modifier and Type	Method and Description
protected void	add(String key, LRUFileCache.LRUFileCacheEntry entry)
protected void	checkKey(String key)
void	clear() Clears the cache.
protected void	ensureCapacity(long size)
File	getFile(String key) Gets a file from the cache.
int	getNumberOfItems() Gets the number of items in the cache.
long	getSize() Gets the size of the cache, in bytes.
File	getTempFile() Creates a temporary file.
File	putFile(String key, File file) Puts a file in the cache.
File	putFile(String key, InputStream in) Puts a file in the cache.
protected File	putFileInCache(String key, File file) Puts a file that's already in the correct filesystem location in the internal cache datastructures.
protected void	recordAccess(String key)
protected void	remove(String key)

Methods inherited from class java.lang.Object

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

Field Detail

SIMPLE_ASCII

public static final Pattern SIMPLE_ASCII

Allowed key pattern, used as file path.

dir

protected final File dir

maxSize

protected final long maxSize

cache

protected final Map<String,LRUFileCache.LRUFileCacheEntry> cache

Cached files.

files

protected final Map<String,File> files

Referenced files on the filesystem. Contains all the cached files, plus all those that have been marked for deletion but haven't been deleted yet. Because of the latter, this is a weak value map.

cacheSize

protected long cacheSize

Size of the cached files.

lru

protected final LinkedList<String> lru

Most recently used entries from the cache are first.

Constructor Detail

LRUFileCache

public LRUFileCache(File dir,
                    long maxSize)

Constructs a cache in the given directory with the given maximum size (in bytes).

Parameters:

dir - the directory to use to store cached files

maxSize - the maximum size of the cache (in bytes)

Method Detail

getSize

public long getSize()

Description copied from interface: FileCache

Gets the size of the cache, in bytes.

Specified by:

getSize in interface FileCache

getNumberOfItems

public int getNumberOfItems()

Description copied from interface: FileCache

Gets the number of items in the cache.

Specified by:

getNumberOfItems in interface FileCache

getTempFile

public File getTempFile()
                 throws IOException

Description copied from interface: FileCache

Creates a temporary file.

Specified by:

getTempFile in interface FileCache

Throws:

IOException

putFile

public File putFile(String key,
                    InputStream in)
             throws IOException

Puts a file in the cache.

The key is used as a file name in the directory cache.

Specified by:

putFile in interface FileCache

Parameters:

key - the cache key

in - the input stream to cache (closed afterwards)

Returns:

the cached file

Throws:

IOException

putFile

public File putFile(String key,
                    File file)
             throws IllegalArgumentException,
                    IOException

Puts a file in the cache.

The file must have been created through FileCache.getTempFile(). The file is "given" to this method, who will delete it or rename it.

The key is used as a file name in the directory cache.

Specified by:

putFile in interface FileCache

Parameters:

key - the cache key

file - the file to cache

Returns:

the cached file

Throws:

IllegalArgumentException - if the key is illegal

IOException

putFileInCache

protected File putFileInCache(String key,
                              File file)

Puts a file that's already in the correct filesystem location in the internal cache datastructures.

checkKey

protected void checkKey(String key)
                 throws IllegalArgumentException

Throws:

IllegalArgumentException

getFile

public File getFile(String key)

Description copied from interface: FileCache

Gets a file from the cache.

A returned file will never be deleted from the filesystem while the returned file object is still referenced, although it may be purged from the cache.

Specified by:

getFile in interface FileCache

Parameters:

key - the cache key

Returns:

the cached file, or null if absent

clear

public void clear()

Description copied from interface: FileCache

Clears the cache.

Files will not be deleted from the filesystm while the returned file objects are still referenced.

Specified by:

clear in interface FileCache

recordAccess

protected void recordAccess(String key)

add

protected void add(String key,
                   LRUFileCache.LRUFileCacheEntry entry)

remove

protected void remove(String key)

ensureCapacity

protected void ensureCapacity(long size)