org.apache.flink.runtime.io.disk.iomanager

Interface BlockChannelReader<T>

All Superinterfaces:

FileIOChannel

All Known Implementing Classes:

AsynchronousBlockReader, CompressedBlockChannelReader

public interface BlockChannelReader<T>
extends FileIOChannel

A reader that reads data in blocks from a file channel. The reader reads the blocks into a MemorySegment. To support asynchronous implementations, the read method does not immediately return the full memory segment, but rather adds it to a blocking queue of finished read operations.

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.flink.runtime.io.disk.iomanager.FileIOChannel

FileIOChannel.Enumerator, FileIOChannel.ID

Method Summary

Modifier and Type	Method and Description
T	getNextReturnedBlock() Gets the next memory segment that has been filled with data by the reader.
LinkedBlockingQueue<T>	getReturnQueue() Gets the queue in which the full memory segments are queued after the read is complete.
void	readBlock(T segment) Issues a read request, which will fill the given segment with the next block in the underlying file channel.
void	seekToPosition(long position)

Methods inherited from interface org.apache.flink.runtime.io.disk.iomanager.FileIOChannel

close, closeAndDelete, deleteChannel, getChannelID, getNioFileChannel, getSize, isClosed

Method Detail

readBlock

void readBlock(T segment)
        throws IOException

Issues a read request, which will fill the given segment with the next block in the underlying file channel. Once the read request is fulfilled, the segment will be added to this reader's return queue.

Parameters:

segment - The segment to read the block into.

Throws:

IOException - Thrown, when the reader encounters an I/O error.

seekToPosition

void seekToPosition(long position)
             throws IOException

Throws:

IOException

getNextReturnedBlock

T getNextReturnedBlock()
                throws IOException

Gets the next memory segment that has been filled with data by the reader. This method blocks until such a segment is available, or until an error occurs in the reader, or the reader is closed.

WARNING: If this method is invoked without any segment ever returning (for example, because the readBlock(T) method has not been invoked appropriately), the method may block forever.

Returns:

The next memory segment from the reader's return queue.

Throws:

IOException - Thrown, if an I/O error occurs in the reader while waiting for the request to return.

getReturnQueue

LinkedBlockingQueue<T> getReturnQueue()

Gets the queue in which the full memory segments are queued after the read is complete.

Returns:

The queue with the full memory segments.