org.apache.druid.frame.channel

Interface ReadableFrameChannel

All Superinterfaces:

AutoCloseable, Closeable

All Known Implementing Classes:

ComposingReadableFrameChannel, ReadableByteChunksFrameChannel, ReadableConcatFrameChannel, ReadableFileFrameChannel, ReadableInputStreamFrameChannel, ReadableNilFrameChannel

public interface ReadableFrameChannel
extends Closeable

Interface for reading a sequence of frames. Supports nonblocking reads through the canRead() and readabilityFuture() methods. May be implemented using an in-memory queue, disk file, stream, etc. Channels implementing this interface are used by a single reader; they do not support concurrent reads.

Method Summary

Modifier and Type	Method and Description
boolean	canRead() Returns whether this channel has a frame or error condition currently available.
void	close() Releases any resources associated with this readable channel.
boolean	isFinished() Returns whether this channel is finished.
Frame	read() Returns the next available frame from this channel.
com.google.common.util.concurrent.ListenableFuture<?>	readabilityFuture() Returns a future that will resolve when either isFinished() or canRead() would return true.

Method Detail

isFinished

boolean isFinished()

Returns whether this channel is finished. Finished channels will not generate any further frames or errors. Generally, once you discover that a channel is finished, you should call close() and then discard it. Note that it is possible for a channel to be unfinished and also have no available frames or errors. This happens when it is not in a ready-for-reading state. See readabilityFuture() for details.

canRead

boolean canRead()

Returns whether this channel has a frame or error condition currently available. If this method returns true, then you can call read() to retrieve the frame or error. Note that it is possible for a channel to be unfinished and also have no available frames or errors. This happens when it is not in a ready-for-reading state. See readabilityFuture() for details.

read

Frame read()

Returns the next available frame from this channel. Before calling this method, you should check canRead() to ensure there is a frame or error available.

Throws:

NoSuchElementException - if there is no frame currently available

readabilityFuture

com.google.common.util.concurrent.ListenableFuture<?> readabilityFuture()

Returns a future that will resolve when either isFinished() or canRead() would return true. The future will never resolve to an exception. If something exceptional has happened, the exception can be retrieved from read().

close

void close()

Releases any resources associated with this readable channel. After calling this, you should not call any other methods on the channel.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable