org.apache.hadoop.io

Class CompressedWritable

java.lang.Object

org.apache.hadoop.io.CompressedWritable

All Implemented Interfaces:

Writable

@InterfaceAudience.Public
 @InterfaceStability.Stable
public abstract class CompressedWritable
extends Object
implements Writable

A base-class for Writables which store themselves compressed and lazily inflate on field access. This is useful for large objects whose fields are not be altered during a map or reduce operation: leaving the field data compressed makes copying the instance from one file to another much faster.

Constructor Summary

Constructors

Constructor and Description
CompressedWritable()

Method Summary

Modifier and Type	Method and Description
protected void	ensureInflated() Must be called by all methods which access fields to ensure that the data has been uncompressed.
void	readFields(DataInput in) Deserialize the fields of this object from in.
protected abstract void	readFieldsCompressed(DataInput in) Subclasses implement this instead of readFields(DataInput).
void	write(DataOutput out) Serialize the fields of this object to out.
protected abstract void	writeCompressed(DataOutput out) Subclasses implement this instead of write(DataOutput).

Methods inherited from class java.lang.Object

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

Constructor Detail

CompressedWritable

public CompressedWritable()

Method Detail

readFields

public final void readFields(DataInput in)
                      throws IOException

Description copied from interface: Writable

Deserialize the fields of this object from in.

For efficiency, implementations should attempt to re-use storage in the existing object where possible.

Specified by:

readFields in interface Writable

Parameters:

in - DataInput to deseriablize this object from.

Throws:

IOException - any other problem for readFields.

ensureInflated

protected void ensureInflated()

Must be called by all methods which access fields to ensure that the data has been uncompressed.

readFieldsCompressed

protected abstract void readFieldsCompressed(DataInput in)
                                      throws IOException

Subclasses implement this instead of readFields(DataInput).

Parameters:

in - data input.

Throws:

IOException - raised on errors performing I/O.

write

public final void write(DataOutput out)
                 throws IOException

Description copied from interface: Writable

Serialize the fields of this object to out.

Specified by:

write in interface Writable

Parameters:

out - DataOuput to serialize this object into.

Throws:

IOException - any other problem for write.

writeCompressed

protected abstract void writeCompressed(DataOutput out)
                                 throws IOException

Subclasses implement this instead of write(DataOutput).

Parameters:

out - data output.

Throws:

IOException - raised on errors performing I/O.