CacheDataSource

Artifact: androidx.media3:media3-datasource

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---

Kotlin |Java

@UnstableApi
class CacheDataSource : 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.

Summary

Nested types
@Documented @Retention(value = RetentionPolicy.SOURCE) @Target(value = ) @IntDef(value = ) annotation CacheDataSource.CacheIgnoredReason Reasons the cache may be ignored.
interface CacheDataSource.EventListener Listener of CacheDataSource events.
class CacheDataSource.Factory : DataSource.Factory DataSource.Factory for CacheDataSource instances.
@Documented @Retention(value = RetentionPolicy.SOURCE) @Target(value = TYPE_USE) @IntDef(flag = true, value = ) annotation CacheDataSource.Flags Flags controlling the CacheDataSource's behavior.

Constants
const Int	CACHE_IGNORED_REASON_ERROR = 0 Cache ignored due to a cache related error.
const Int	CACHE_IGNORED_REASON_UNSET_LENGTH = 1 Cache ignored due to a request with an unset length.
const Int	FLAG_BLOCK_ON_CACHE = 1 A flag indicating whether we will block reads if the cache key is locked.
const Int	FLAG_IGNORE_CACHE_FOR_UNSET_LENGTH_REQUESTS = 4 A flag indicating that the cache should be bypassed for requests whose lengths are unset.
const Int	FLAG_IGNORE_CACHE_ON_ERROR = 2 A flag indicating whether the cache is bypassed following any cache related error.

Public constructors
CacheDataSource(cache: Cache!, upstreamDataSource: DataSource?) Constructs an instance with default DataSource and DataSink instances for reading and writing the cache.
CacheDataSource(     cache: Cache!,     upstreamDataSource: DataSource?,     @CacheDataSource.Flags flags: Int ) Constructs an instance with default DataSource and DataSink instances for reading and writing the cache.
CacheDataSource(     cache: Cache!,     upstreamDataSource: DataSource?,     cacheReadDataSource: DataSource!,     cacheWriteDataSink: DataSink?,     @CacheDataSource.Flags flags: Int,     eventListener: CacheDataSource.EventListener? ) Constructs an instance with arbitrary DataSource and DataSink instances for reading and writing the cache.
CacheDataSource(     cache: Cache!,     upstreamDataSource: DataSource?,     cacheReadDataSource: DataSource!,     cacheWriteDataSink: DataSink?,     @CacheDataSource.Flags flags: Int,     eventListener: CacheDataSource.EventListener?,     cacheKeyFactory: CacheKeyFactory? ) Constructs an instance with arbitrary DataSource and DataSink instances for reading and writing the cache.

Public functions
Unit	addTransferListener(transferListener: TransferListener!) Adds a TransferListener to listen to data transfers.
Unit	close() Closes the source.
(Mutable)Map<String!, (Mutable)List<String!>!>!	getResponseHeaders() When the source is open, returns the response headers associated with the last open call.
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(buffer: ByteArray!, offset: Int, length: Int) Reads up to length bytes of data from the input.

Public properties
Cache!	cache
CacheKeyFactory!	cacheKeyFactory

Constants

CACHE_IGNORED_REASON_ERROR

const val CACHE_IGNORED_REASON_ERROR = 0: Int

Cache ignored due to a cache related error.

CACHE_IGNORED_REASON_UNSET_LENGTH

const val CACHE_IGNORED_REASON_UNSET_LENGTH = 1: Int

Cache ignored due to a request with an unset length.

FLAG_BLOCK_ON_CACHE

const val FLAG_BLOCK_ON_CACHE = 1: Int

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.

FLAG_IGNORE_CACHE_FOR_UNSET_LENGTH_REQUESTS

const val FLAG_IGNORE_CACHE_FOR_UNSET_LENGTH_REQUESTS = 4: Int

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

FLAG_IGNORE_CACHE_ON_ERROR

const val FLAG_IGNORE_CACHE_ON_ERROR = 2: Int

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.

Public constructors

CacheDataSource

CacheDataSource(cache: Cache!, upstreamDataSource: DataSource?)

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

Parameters
cache: Cache!	The cache.
upstreamDataSource: DataSource?	A DataSource for reading data not in the cache. If null, reading will fail if a cache miss occurs.

CacheDataSource

CacheDataSource(
    cache: Cache!,
    upstreamDataSource: DataSource?,
    @CacheDataSource.Flags flags: Int
)

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

Parameters
cache: Cache!	The cache.
upstreamDataSource: DataSource?	A DataSource for reading data not in the cache. If null, reading will fail if a cache miss occurs.
@CacheDataSource.Flags flags: Int	A combination of FLAG_BLOCK_ON_CACHE, FLAG_IGNORE_CACHE_ON_ERROR and FLAG_IGNORE_CACHE_FOR_UNSET_LENGTH_REQUESTS, or 0.

CacheDataSource

CacheDataSource(
    cache: Cache!,
    upstreamDataSource: DataSource?,
    cacheReadDataSource: DataSource!,
    cacheWriteDataSink: DataSink?,
    @CacheDataSource.Flags flags: Int,
    eventListener: CacheDataSource.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: Cache!	The cache.
upstreamDataSource: DataSource?	A DataSource for reading data not in the cache. If null, reading will fail if a cache miss occurs.
cacheReadDataSource: DataSource!	A DataSource for reading data from the cache.
cacheWriteDataSink: DataSink?	A DataSink for writing data to the cache. If null, cache is accessed read-only.
@CacheDataSource.Flags flags: Int	A combination of FLAG_BLOCK_ON_CACHE, FLAG_IGNORE_CACHE_ON_ERROR and FLAG_IGNORE_CACHE_FOR_UNSET_LENGTH_REQUESTS, or 0.
eventListener: CacheDataSource.EventListener?	An optional EventListener to receive events.

CacheDataSource

CacheDataSource(
    cache: Cache!,
    upstreamDataSource: DataSource?,
    cacheReadDataSource: DataSource!,
    cacheWriteDataSink: DataSink?,
    @CacheDataSource.Flags flags: Int,
    eventListener: CacheDataSource.EventListener?,
    cacheKeyFactory: CacheKeyFactory?
)

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: Cache!	The cache.
upstreamDataSource: DataSource?	A DataSource for reading data not in the cache. If null, reading will fail if a cache miss occurs.
cacheReadDataSource: DataSource!	A DataSource for reading data from the cache.
cacheWriteDataSink: DataSink?	A DataSink for writing data to the cache. If null, cache is accessed read-only.
@CacheDataSource.Flags flags: Int	A combination of FLAG_BLOCK_ON_CACHE, FLAG_IGNORE_CACHE_ON_ERROR and FLAG_IGNORE_CACHE_FOR_UNSET_LENGTH_REQUESTS, or 0.
eventListener: CacheDataSource.EventListener?	An optional EventListener to receive events.
cacheKeyFactory: CacheKeyFactory?	An optional factory for cache keys.

Public functions

addTransferListener

fun addTransferListener(transferListener: TransferListener!): Unit

Adds a TransferListener to listen to data transfers. This method is not thread-safe.

Parameters
transferListener: TransferListener!	A TransferListener.

close

fun close(): Unit

Closes the source. This method must be called even if the corresponding call to open threw an IOException.

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

getResponseHeaders

fun getResponseHeaders(): (Mutable)Map<String!, (Mutable)List<String!>!>!

When the source is open, returns the response headers associated with the last open call. Otherwise, returns an empty map.

Key look-up in the returned map is case-insensitive.

getUri

fun getUri(): Uri?

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

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

open

fun open(dataSpec: DataSpec!): Long

Opens the source to read the specified data. If an IOException is thrown, callers must still call close to ensure that any partial effects of the invocation are cleaned up.

The following edge case behaviors apply:

• If the requested position is within the resource, but the requested length extends beyond the end of the resource, then open will succeed and data from the requested position to the end of the resource will be made available through read.
• If the requested position is equal to the length of the resource, then open will succeed, and read will immediately return RESULT_END_OF_INPUT.
• If the requested position is greater than the length of the resource, then open will throw an IOException for which isCausedByPositionOutOfRange will be true.

Parameters
dataSpec: DataSpec!	Defines the data to be read.

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

fun read(buffer: ByteArray!, offset: Int, length: Int): Int

Reads up to length bytes of data from the input.

If readLength is zero then 0 is returned. Otherwise, if no data is available because the end of the opened range has been reached, then 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.

Parameters
buffer: ByteArray!	A target array into which data should be written.
offset: Int	The offset into the target array at which to write.
length: Int	The maximum number of bytes to read from the input.

Returns
Int	The number of bytes read, or RESULT_END_OF_INPUT if the input has ended. This may be less than length because the end of the input (or available data) was reached, the method was interrupted, or the operation was aborted early for another reason.

Throws
java.io.IOException	If an error occurs reading from the input.

Public properties

cache

val cache: Cache!

cacheKeyFactory

val cacheKeyFactory: CacheKeyFactory!