Package org.apache.hadoop.io

Class DataOutputBuffer

java.lang.Object

java.io.OutputStream

java.io.FilterOutputStream

java.io.DataOutputStream

org.apache.hadoop.io.DataOutputBuffer

All Implemented Interfaces:

java.io.Closeable, java.io.DataOutput, java.io.Flushable, java.lang.AutoCloseable

@LimitedPrivate({"HDFS","MapReduce"})
@Unstable
public class DataOutputBuffer
extends java.io.DataOutputStream

A reusable DataOutput implementation that writes to an in-memory buffer.

This saves memory over creating a new DataOutputStream and ByteArrayOutputStream each time data is written.

Typical usage is something like the following:

 DataOutputBuffer buffer = new DataOutputBuffer();
 while (... loop condition ...) {
   buffer.reset();
   ... write buffer using DataOutput methods ...
   byte[] data = buffer.getData();
   int dataLength = buffer.getLength();
   ... write data to its ultimate destination ...
 }
 

Field Summary

Fields inherited from class java.io.DataOutputStream

written

Fields inherited from class java.io.FilterOutputStream

out

Constructor Summary

Constructors

Constructor	Description
DataOutputBuffer()	Constructs a new empty buffer.
DataOutputBuffer(int size)

Method Summary

Modifier and Type	Method	Description
byte[]	getData()	Returns the current contents of the buffer.
int	getLength()	Returns the length of the valid data currently in the buffer.
DataOutputBuffer	reset()	Resets the buffer to empty.
void	write(java.io.DataInput in, int length)	Writes bytes from a DataInput directly into the buffer.
void	writeInt(int v, int offset)	Overwrite an integer into the internal buffer.
void	writeTo(java.io.OutputStream out)	Write to a file stream.

Methods inherited from class java.io.DataOutputStream

flush, size, write, write, writeBoolean, writeByte, writeBytes, writeChar, writeChars, writeDouble, writeFloat, writeInt, writeLong, writeShort, writeUTF

Methods inherited from class java.io.FilterOutputStream

close, write

Methods inherited from class java.io.OutputStream

nullOutputStream

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.io.DataOutput

write

Constructor Detail

DataOutputBuffer

public DataOutputBuffer()

Constructs a new empty buffer.

DataOutputBuffer

public DataOutputBuffer(int size)

Method Detail

getData

public byte[] getData()

Returns the current contents of the buffer. Data is only valid to getLength().

Returns:

data byte.

getLength

public int getLength()

Returns the length of the valid data currently in the buffer.

Returns:

length.

reset

public DataOutputBuffer reset()

Resets the buffer to empty.

Returns:

DataOutputBuffer.

write

public void write(java.io.DataInput in,
                  int length)
           throws java.io.IOException

Writes bytes from a DataInput directly into the buffer.

Parameters:

in - data input.

length - length.

Throws:

java.io.IOException - raised on errors performing I/O.

writeTo

public void writeTo(java.io.OutputStream out)
             throws java.io.IOException

Write to a file stream.

Parameters:

out - OutputStream.

Throws:

java.io.IOException - raised on errors performing I/O.

writeInt

public void writeInt(int v,
                     int offset)
              throws java.io.IOException

Overwrite an integer into the internal buffer. Note that this call can only be used to overwrite existing data in the buffer, i.e., buffer#count cannot be increased, and DataOutputStream#written cannot be increased.

Parameters:

v - v.

offset - offset.

Throws:

java.io.IOException - raised on errors performing I/O.