PriorityDataSource

@UnstableApi
public final class PriorityDataSource implements DataSource

A DataSource that can be used as part of a task registered with a .

Calls to open and read are allowed to proceed only if there are no higher priority tasks registered to the PriorityTaskManager. If there exists a higher priority task then PriorityTaskManager.PriorityTooLowException is thrown.

Instances of this class are intended to be used as parts of (possibly larger) tasks that are registered with the PriorityTaskManager, and hence do not register as tasks themselves.

Summary

Nested types
public final class PriorityDataSource.Factory implements DataSource.Factory

DataSource.Factory for PriorityDataSource instances.

Public constructors
PriorityDataSource(
    DataSource upstream,
    PriorityTaskManager priorityTaskManager,
    @C.Priority int priority
)

Public methods
void

Adds a TransferListener to listen to data transfers.
void

Closes the source.
Map<String, List<String>>

When the source is open, returns the response headers associated with the last open call.
@Nullable Uri

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 length)

Reads up to length bytes of data from the input.

Public constructors

PriorityDataSource

public PriorityDataSource(
    DataSource upstream,
    PriorityTaskManager priorityTaskManager,
    @C.Priority int priority
)
Parameters
DataSource upstream

The upstream DataSource.
PriorityTaskManager priorityTaskManager

The priority manager to which the task is registered.
@C.Priority int priority

The C.Priority of the task.

Public methods

addTransferListener

public void addTransferListener(TransferListener transferListener)

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

Parameters
TransferListener transferListener

A TransferListener.

close

public void close()

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

public Map<String, List<String>> getResponseHeaders()

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

public @Nullable Uri getUri()

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
@Nullable Uri

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

open

public long open(DataSpec dataSpec)

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:

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

public int read(byte[] buffer, int offset, int length)

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
byte[] buffer

A target array into which data should be written.
int offset

The offset into the target array at which to write.
int length

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.