com.google.android.exoplayer2.upstream.cache

Class CacheDataSource

java.lang.Object

com.google.android.exoplayer2.upstream.cache.CacheDataSource

All Implemented Interfaces:

DataSource

public final class CacheDataSource
extends java.lang.Object
implements DataSource

A DataSource that reads and writes a Cache. Requests are fulfilled from the cache when possible. When data is not cached it is requested from an upstream DataSource and written into the cache.

By default requests whose length can not be resolved are not cached. This is to prevent caching of progressive live streams, which should usually not be cached. Caching of this kind of requests can be enabled per request with DataSpec.FLAG_ALLOW_CACHING_UNKNOWN_LENGTH.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	CacheDataSource.CacheIgnoredReason Reasons the cache may be ignored.
static interface	CacheDataSource.EventListener Listener of CacheDataSource events.
static interface	CacheDataSource.Flags Flags controlling the cache's behavior.

Nested classes/interfaces inherited from interface com.google.android.exoplayer2.upstream.DataSource

DataSource.Factory

Field Summary

Fields

Modifier and Type	Field and Description
static int	CACHE_IGNORED_REASON_ERROR Cache ignored due to a cache related error.
static int	CACHE_IGNORED_REASON_UNSET_LENGTH Cache ignored due to a request with an unset length.
static long	DEFAULT_MAX_CACHE_FILE_SIZE Default maximum single cache file size.
static int	FLAG_BLOCK_ON_CACHE A flag indicating whether we will block reads if the cache key is locked.
static int	FLAG_IGNORE_CACHE_FOR_UNSET_LENGTH_REQUESTS A flag indicating that the cache should be bypassed for requests whose lengths are unset.
static int	FLAG_IGNORE_CACHE_ON_ERROR A flag indicating whether the cache is bypassed following any cache related error.

Constructor Summary

Constructors

Constructor and Description
CacheDataSource(Cache cache, DataSource upstream) Constructs an instance with default DataSource and DataSink instances for reading and writing the cache.
CacheDataSource(Cache cache, DataSource upstream, DataSource cacheReadDataSource, DataSink cacheWriteDataSink, int flags, CacheDataSource.EventListener eventListener) Constructs an instance with arbitrary DataSource and DataSink instances for reading and writing the cache.
CacheDataSource(Cache cache, DataSource upstream, int flags) Constructs an instance with default DataSource and DataSink instances for reading and writing the cache.
CacheDataSource(Cache cache, DataSource upstream, int flags, long maxCacheFileSize) Constructs an instance with default DataSource and DataSink instances for reading and writing the cache.

Method Summary

Modifier and Type	Method and Description
void	close() Closes the source.
android.net.Uri	getUri() When the source is open, returns the Uri from which data is being read.
long	open(DataSpec dataSpec) Opens the source to read the specified data.
int	read(byte[] buffer, int offset, int readLength) Reads up to length bytes of data and stores them into buffer, starting at index offset.

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_MAX_CACHE_FILE_SIZE

public static final long DEFAULT_MAX_CACHE_FILE_SIZE

Default maximum single cache file size.

See Also:

CacheDataSource(Cache, DataSource, int), CacheDataSource(Cache, DataSource, int, long), Constant Field Values

FLAG_BLOCK_ON_CACHE

public static final int FLAG_BLOCK_ON_CACHE

A flag indicating whether we will block reads if the cache key is locked. If unset then data is read from upstream if the cache key is locked, regardless of whether the data is cached.

See Also:

Constant Field Values

FLAG_IGNORE_CACHE_ON_ERROR

public static final int FLAG_IGNORE_CACHE_ON_ERROR

A flag indicating whether the cache is bypassed following any cache related error. If set then cache related exceptions may be thrown for one cycle of open, read and close calls. Subsequent cycles of these calls will then bypass the cache.

See Also:

Constant Field Values

FLAG_IGNORE_CACHE_FOR_UNSET_LENGTH_REQUESTS

public static final int FLAG_IGNORE_CACHE_FOR_UNSET_LENGTH_REQUESTS

A flag indicating that the cache should be bypassed for requests whose lengths are unset. This flag is provided for legacy reasons only.

See Also:

Constant Field Values

CACHE_IGNORED_REASON_ERROR

public static final int CACHE_IGNORED_REASON_ERROR

Cache ignored due to a cache related error.

See Also:

Constant Field Values

CACHE_IGNORED_REASON_UNSET_LENGTH

public static final int CACHE_IGNORED_REASON_UNSET_LENGTH

Cache ignored due to a request with an unset length.

See Also:

Constant Field Values

Constructor Detail

CacheDataSource

public CacheDataSource(Cache cache,
                       DataSource upstream)

Constructs an instance with default DataSource and DataSink instances for reading and writing the cache.

Parameters:

cache - The cache.

upstream - A DataSource for reading data not in the cache.

CacheDataSource

public CacheDataSource(Cache cache,
                       DataSource upstream,
                       int flags)

Constructs an instance with default DataSource and DataSink instances for reading and writing the cache.

Parameters:

cache - The cache.

upstream - A DataSource for reading data not in the cache.

flags - A combination of FLAG_BLOCK_ON_CACHE, FLAG_IGNORE_CACHE_ON_ERROR and FLAG_IGNORE_CACHE_FOR_UNSET_LENGTH_REQUESTS, or 0.

CacheDataSource

public CacheDataSource(Cache cache,
                       DataSource upstream,
                       int flags,
                       long maxCacheFileSize)

Constructs an instance with default DataSource and DataSink instances for reading and writing the cache. The sink is configured to fragment data such that no single cache file is greater than maxCacheFileSize bytes.

Parameters:

cache - The cache.

upstream - A DataSource for reading data not in the cache.

flags - A combination of FLAG_BLOCK_ON_CACHE, FLAG_IGNORE_CACHE_ON_ERROR and FLAG_IGNORE_CACHE_FOR_UNSET_LENGTH_REQUESTS, or 0.

maxCacheFileSize - The maximum size of a cache file, in bytes. If the cached data size exceeds this value, then the data will be fragmented into multiple cache files. The finer-grained this is the finer-grained the eviction policy can be.

CacheDataSource

public CacheDataSource(Cache cache,
                       DataSource upstream,
                       DataSource cacheReadDataSource,
                       DataSink cacheWriteDataSink,
                       int flags,
                       @Nullable
                       CacheDataSource.EventListener eventListener)

Constructs an instance with arbitrary DataSource and DataSink instances for reading and writing the cache. One use of this constructor is to allow data to be transformed before it is written to disk.

Parameters:

cache - The cache.

upstream - A DataSource for reading data not in the cache.

cacheReadDataSource - A DataSource for reading data from the cache.

cacheWriteDataSink - A DataSink for writing data to the cache. If null, cache is accessed read-only.

flags - A combination of FLAG_BLOCK_ON_CACHE, FLAG_IGNORE_CACHE_ON_ERROR and FLAG_IGNORE_CACHE_FOR_UNSET_LENGTH_REQUESTS, or 0.

eventListener - An optional CacheDataSource.EventListener to receive events.

Method Detail

open

public long open(DataSpec dataSpec)
          throws java.io.IOException

Description copied from interface: DataSource

Opens the source to read the specified data.

Note: If an IOException is thrown, callers must still call DataSource.close() to ensure that any partial effects of the invocation are cleaned up.

Specified by:

open in interface DataSource

Parameters:

dataSpec - Defines the data to be read.

Returns:

The number of bytes that can be read from the opened source. For unbounded requests (i.e. requests where DataSpec.length equals C.LENGTH_UNSET) this value is the resolved length of the request, or C.LENGTH_UNSET if the length is still unresolved. For all other requests, the value returned will be equal to the request's DataSpec.length.

Throws:

java.io.IOException - If an error occurs opening the source. DataSourceException can be thrown or used as a cause of the thrown exception to specify the reason of the error.

read

public int read(byte[] buffer,
                int offset,
                int readLength)
         throws java.io.IOException

Description copied from interface: DataSource

Reads up to length bytes of data and stores them into buffer, starting at index offset.

If length is zero then 0 is returned. Otherwise, if no data is available because the end of the opened range has been reached, then C.RESULT_END_OF_INPUT is returned. Otherwise, the call will block until at least one byte of data has been read and the number of bytes read is returned.

Specified by:

read in interface DataSource

Parameters:

buffer - The buffer into which the read data should be stored.

offset - The start offset into buffer at which data should be written.

readLength - The maximum number of bytes to read.

Returns:

The number of bytes read, or C.RESULT_END_OF_INPUT if no data is available because the end of the opened range has been reached.

Throws:

java.io.IOException - If an error occurs reading from the source.

getUri

public android.net.Uri getUri()

Description copied from interface: DataSource

When the source is open, returns the Uri from which data is being read. The returned Uri will be identical to the one passed DataSource.open(DataSpec) in the DataSpec unless redirection has occurred. If redirection has occurred, the Uri after redirection is returned.

Specified by:

getUri in interface DataSource

Returns:

The Uri from which data is being read, or null if the source is not open.

close

public void close()
           throws java.io.IOException

Description copied from interface: DataSource

Closes the source.

Note: This method must be called even if the corresponding call to DataSource.open(DataSpec) threw an IOException. See DataSource.open(DataSpec) for more details.

Specified by:

close in interface DataSource

Throws:

java.io.IOException - If an error occurs closing the source.