com.android.volley.toolbox

Class DiskBasedCache

java.lang.Object

com.android.volley.toolbox.DiskBasedCache

All Implemented Interfaces:

Cache

public class DiskBasedCache
extends java.lang.Object
implements Cache

Cache implementation that caches files directly onto the hard disk in the specified directory. The default disk usage size is 5MB, but is configurable.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
(package private) static class	DiskBasedCache.CacheHeader Handles holding onto the cache headers for an entry.
private static class	DiskBasedCache.CountingInputStream

Nested classes/interfaces inherited from interface com.android.volley.Cache

Cache.Entry

Field Summary

Fields

Modifier and Type	Field and Description
private static int	CACHE_MAGIC Magic number for current version of cache file format.
private static int	DEFAULT_DISK_USAGE_BYTES Default maximum disk usage in bytes.
private static float	HYSTERESIS_FACTOR High water mark percentage for the cache
private java.util.Map<java.lang.String,DiskBasedCache.CacheHeader>	mEntries Map of the Key, CacheHeader pairs
private int	mMaxCacheSizeInBytes The maximum size of the cache in bytes.
private java.io.File	mRootDirectory The root directory to use for the cache.
private long	mTotalSize Total amount of space currently used by the cache in bytes.

Constructor Summary

Constructors

Constructor and Description
DiskBasedCache(java.io.File rootDirectory) Constructs an instance of the DiskBasedCache at the specified directory using the default maximum cache size of 5MB.
DiskBasedCache(java.io.File rootDirectory, int maxCacheSizeInBytes) Constructs an instance of the DiskBasedCache at the specified directory.

Method Summary

Modifier and Type	Method and Description
void	clear() Clears the cache.
Cache.Entry	get(java.lang.String key) Returns the cache entry with the specified key if it exists, null otherwise.
java.io.File	getFileForKey(java.lang.String key) Returns a file object for the given cache key.
private java.lang.String	getFilenameForKey(java.lang.String key) Creates a pseudo-unique filename for the specified cache key.
void	initialize() Initializes the DiskBasedCache by scanning for all files currently in the specified root directory.
void	invalidate(java.lang.String key, boolean fullExpire) Invalidates an entry in the cache.
private void	pruneIfNeeded(int neededSpace) Prunes the cache to fit the amount of bytes specified.
void	put(java.lang.String key, Cache.Entry entry) Puts the entry with the specified key into the cache.
private void	putEntry(java.lang.String key, DiskBasedCache.CacheHeader entry) Puts the entry with the specified key into the cache.
private static int	read(java.io.InputStream is) Simple wrapper around InputStream.read() that throws EOFException instead of returning -1.
(package private) static int	readInt(java.io.InputStream is)
(package private) static long	readLong(java.io.InputStream is)
(package private) static java.lang.String	readString(java.io.InputStream is)
(package private) static java.util.Map<java.lang.String,java.lang.String>	readStringStringMap(java.io.InputStream is)
void	remove(java.lang.String key) Removes the specified key from the cache if it exists.
private void	removeEntry(java.lang.String key) Removes the entry identified by 'key' from the cache.
private static byte[]	streamToBytes(java.io.InputStream in, int length) Reads the contents of an InputStream into a byte[].
(package private) static void	writeInt(java.io.OutputStream os, int n)
(package private) static void	writeLong(java.io.OutputStream os, long n)
(package private) static void	writeString(java.io.OutputStream os, java.lang.String s)
(package private) static void	writeStringStringMap(java.util.Map<java.lang.String,java.lang.String> map, java.io.OutputStream os)

Methods inherited from class java.lang.Object

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

Field Detail

mEntries

private final java.util.Map<java.lang.String,DiskBasedCache.CacheHeader> mEntries

Map of the Key, CacheHeader pairs

mTotalSize

private long mTotalSize

Total amount of space currently used by the cache in bytes.

mRootDirectory

private final java.io.File mRootDirectory

The root directory to use for the cache.

mMaxCacheSizeInBytes

private final int mMaxCacheSizeInBytes

The maximum size of the cache in bytes.

DEFAULT_DISK_USAGE_BYTES

private static final int DEFAULT_DISK_USAGE_BYTES

Default maximum disk usage in bytes.

See Also:

Constant Field Values

HYSTERESIS_FACTOR

private static final float HYSTERESIS_FACTOR

High water mark percentage for the cache

See Also:

Constant Field Values

CACHE_MAGIC

private static final int CACHE_MAGIC

Magic number for current version of cache file format.

See Also:

Constant Field Values

Constructor Detail

DiskBasedCache

public DiskBasedCache(java.io.File rootDirectory,
                      int maxCacheSizeInBytes)

Constructs an instance of the DiskBasedCache at the specified directory.

Parameters:

rootDirectory - The root directory of the cache.

maxCacheSizeInBytes - The maximum size of the cache in bytes.

DiskBasedCache

public DiskBasedCache(java.io.File rootDirectory)

Constructs an instance of the DiskBasedCache at the specified directory using the default maximum cache size of 5MB.

Parameters:

rootDirectory - The root directory of the cache.

Method Detail

clear

public void clear()

Clears the cache. Deletes all cached files from disk.

Specified by:

clear in interface Cache

get

public Cache.Entry get(java.lang.String key)

Returns the cache entry with the specified key if it exists, null otherwise.

Specified by:

get in interface Cache

Parameters:

key - Cache key

Returns:

An Cache.Entry or null in the event of a cache miss

initialize

public void initialize()

Initializes the DiskBasedCache by scanning for all files currently in the specified root directory. Creates the root directory if necessary.

Specified by:

initialize in interface Cache

invalidate

public void invalidate(java.lang.String key,
                       boolean fullExpire)

Invalidates an entry in the cache.

Specified by:

invalidate in interface Cache

Parameters:

key - Cache key

fullExpire - True to fully expire the entry, false to soft expire

put

public void put(java.lang.String key,
                Cache.Entry entry)

Puts the entry with the specified key into the cache.

Specified by:

put in interface Cache

Parameters:

key - Cache key

entry - Data to store and metadata for cache coherency, TTL, etc.

remove

public void remove(java.lang.String key)

Removes the specified key from the cache if it exists.

Specified by:

remove in interface Cache

Parameters:

key - Cache key

getFilenameForKey

private java.lang.String getFilenameForKey(java.lang.String key)

Creates a pseudo-unique filename for the specified cache key.

Parameters:

key - The key to generate a file name for.

Returns:

A pseudo-unique filename.

getFileForKey

public java.io.File getFileForKey(java.lang.String key)

Returns a file object for the given cache key.

pruneIfNeeded

private void pruneIfNeeded(int neededSpace)

Prunes the cache to fit the amount of bytes specified.

Parameters:

neededSpace - The amount of bytes we are trying to fit into the cache.

putEntry

private void putEntry(java.lang.String key,
                      DiskBasedCache.CacheHeader entry)

Puts the entry with the specified key into the cache.

Parameters:

key - The key to identify the entry by.

entry - The entry to cache.

removeEntry

private void removeEntry(java.lang.String key)

Removes the entry identified by 'key' from the cache.

streamToBytes

private static byte[] streamToBytes(java.io.InputStream in,
                                    int length)
                             throws java.io.IOException

Reads the contents of an InputStream into a byte[].

Throws:

java.io.IOException

read

private static int read(java.io.InputStream is)
                 throws java.io.IOException

Simple wrapper around InputStream.read() that throws EOFException instead of returning -1.

Throws:

java.io.IOException

writeInt

static void writeInt(java.io.OutputStream os,
                     int n)
              throws java.io.IOException

Throws:

java.io.IOException

readInt

static int readInt(java.io.InputStream is)
            throws java.io.IOException

Throws:

java.io.IOException

writeLong

static void writeLong(java.io.OutputStream os,
                      long n)
               throws java.io.IOException

Throws:

java.io.IOException

readLong

static long readLong(java.io.InputStream is)
              throws java.io.IOException

Throws:

java.io.IOException

writeString

static void writeString(java.io.OutputStream os,
                        java.lang.String s)
                 throws java.io.IOException

Throws:

java.io.IOException

readString

static java.lang.String readString(java.io.InputStream is)
                            throws java.io.IOException

Throws:

java.io.IOException

writeStringStringMap

static void writeStringStringMap(java.util.Map<java.lang.String,java.lang.String> map,
                                 java.io.OutputStream os)
                          throws java.io.IOException

Throws:

java.io.IOException

readStringStringMap

static java.util.Map<java.lang.String,java.lang.String> readStringStringMap(java.io.InputStream is)
                                                                     throws java.io.IOException

Throws:

java.io.IOException