Package org.apache.hadoop.hdfs.util

Class PersistentLongFile

java.lang.Object

org.apache.hadoop.hdfs.util.PersistentLongFile

@Private
public class PersistentLongFile
extends java.lang.Object

Class that represents a file on disk which persistently stores a single long value. The file is updated atomically and durably (i.e fsynced).

Constructor Summary

Constructors

Constructor	Description
PersistentLongFile(java.io.File file, long defaultVal)

Method Summary

Modifier and Type	Method	Description
long	get()
static long	readFile(java.io.File file, long defaultVal)
void	set(long newVal)
static void	writeFile(java.io.File file, long val)	Atomically write the given value to the given file, including fsyncing.

Methods inherited from class java.lang.Object

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

Constructor Detail

PersistentLongFile

public PersistentLongFile(java.io.File file,
                          long defaultVal)

Method Detail

get

public long get()
         throws java.io.IOException

Throws:

java.io.IOException

set

public void set(long newVal)
         throws java.io.IOException

Throws:

java.io.IOException

writeFile

public static void writeFile(java.io.File file,
                             long val)
                      throws java.io.IOException

Atomically write the given value to the given file, including fsyncing.

Parameters:

file - destination file

val - value to write

Throws:

java.io.IOException - if the file cannot be written

readFile

public static long readFile(java.io.File file,
                            long defaultVal)
                     throws java.io.IOException

Throws:

java.io.IOException