com.google.appengine.tools.mapreduce.inputs

Class ConcatenatingInputReader<I>

java.lang.Object

com.google.appengine.tools.mapreduce.InputReader<I>

com.google.appengine.tools.mapreduce.inputs.ConcatenatingInputReader<I>

Type Parameters:

I - type of values produced by this input

All Implemented Interfaces:

Serializable

public final class ConcatenatingInputReader<I>
extends InputReader<I>

Reads multiple inputs in sequence. The caller of the constructor is expected to provide an interface for getting the next underlying reader.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
ConcatenatingInputReader(List<? extends InputReader<I>> readers)

Method Summary

Methods

Modifier and Type	Method and Description
void	beginShard() Performs setup at the beginning of the shard.
void	beginSlice() Prepares the InputReader for reading, after possibly having gone through serialization and deserialization.
void	endShard() Called after endSlice if there will not be any subsequent calls to beginSlice or next.
void	endSlice() Prepares the InputReader for serialization.
long	estimateMemoryRequirement() Returns the estimated memory that will be used by this reader in bytes.
Double	getProgress() Returns the relative progress reading this input as a number from 0 to 1.
I	next() Returns the next input value, or throws NoSuchElementException when there is no more input data.

Methods inherited from class com.google.appengine.tools.mapreduce.InputReader

close, getContext, open, setContext

Methods inherited from class java.lang.Object

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

Constructor Detail

ConcatenatingInputReader

public ConcatenatingInputReader(List<? extends InputReader<I>> readers)

Method Detail

beginSlice

public void beginSlice()
                throws IOException

Description copied from class: InputReader

Prepares the InputReader for reading, after possibly having gone through serialization and deserialization.

Overrides:

beginSlice in class InputReader<I>

Throws:

IOException - in the event of failure

endSlice

public void endSlice()
              throws IOException

Description copied from class: InputReader

Prepares the InputReader for serialization.

Overrides:

endSlice in class InputReader<I>

Throws:

IOException - in the event of failure

next

public I next()
       throws IOException,
              NoSuchElementException

Description copied from class: InputReader

Returns the next input value, or throws NoSuchElementException when there is no more input data. This is done rather than providing a hasNext() function, to allow the implementation to deal with streams and remain serializable, even if the item being read is not.

Specified by:

next in class InputReader<I>

Throws:

IOException

NoSuchElementException

getProgress

public Double getProgress()

Description copied from class: InputReader

Returns the relative progress reading this input as a number from 0 to 1. Returns null if relative progress cannot be determined.

Overrides:

getProgress in class InputReader<I>

beginShard

public void beginShard()

Description copied from class: InputReader

Performs setup at the beginning of the shard. This method is invoked before the first call to InputReader.beginSlice(). It will not be invoked again unless the shard restarts. When a shard is restarted, this method is invoked and the input should be read from the beginning.

Overrides:

beginShard in class InputReader<I>

endShard

public void endShard()
              throws IOException

Description copied from class: InputReader

Called after endSlice if there will not be any subsequent calls to beginSlice or next. This may be used to teardown or finalize any state if required.

Overrides:

endShard in class InputReader<I>

Throws:

IOException - in the event of failure

estimateMemoryRequirement

public long estimateMemoryRequirement()

Description copied from class: InputReader

Returns the estimated memory that will be used by this reader in bytes. (This is normally just set to the size of the buffers used by the implementation)

Overrides:

estimateMemoryRequirement in class InputReader<I>