org.archive.io
Class DiskByteQueue

java.lang.Object
  org.archive.io.DiskByteQueue

All Implemented Interfaces:

java.io.Serializable

public class DiskByteQueue
extends java.lang.Object
implements java.io.Serializable

FIFO byte queue, using disk space as needed. TODO: add maximum size? Flips between two backing files: as soon as reading head reaches end of one, and is about to start at the front of the other, the writing tail flips to a new file. The current write-target file (tail) has a file extension ".qout", the current read file (head) has a file extension ".qin".

Author:

Gordon Mohr

See Also:

Serialized Form

Nested Class Summary

class	DiskByteQueue.FlipFileInputStream An input stream that supports the DiskBackedByteQueue, by always reading from the current inFile, and triggering a "flip" when one inFile is exhausted.
(package private) class	DiskByteQueue.FlipFileOutputStream An output stream that supports the DiskBackedByteQueue, by always appending to the current outFile.

Field Summary

(package private) java.lang.String	backingFilenamePrefix
(package private) DiskByteQueue.FlipFileInputStream	headStream
(package private) java.io.File	inFile
(package private) java.io.File	outFile
(package private) long	rememberedPosition
(package private) DiskByteQueue.FlipFileOutputStream	tailStream
(package private) java.io.File	tempDir

Constructor Summary

DiskByteQueue(java.io.File tempDir, java.lang.String backingFilenamePrefix, boolean reuse)
Create a new BiskBackedByteQueue in the given directory with given filename prefix

Method Summary

void	close()
void	connect()
void	discard() frees all streams/files associated with this object
void	disconnect()
(package private) void	flip() flip the current outFile to the inFile role, make new outFile
java.io.InputStream	getHeadStream()
java.io.InputStream	getReadAllInputStream() Returns an input stream that covers the entire queue.
java.io.OutputStream	getTailStream()

Methods inherited from class java.lang.Object

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

Field Detail

tempDir

java.io.File tempDir

backingFilenamePrefix

java.lang.String backingFilenamePrefix

inFile

java.io.File inFile

outFile

java.io.File outFile

headStream

transient DiskByteQueue.FlipFileInputStream headStream

rememberedPosition

long rememberedPosition

tailStream

transient DiskByteQueue.FlipFileOutputStream tailStream

Constructor Detail

DiskByteQueue

public DiskByteQueue(java.io.File tempDir,
                     java.lang.String backingFilenamePrefix,
                     boolean reuse)

Create a new BiskBackedByteQueue in the given directory with given filename prefix

Parameters:

tempDir -

backingFilenamePrefix -

reuse - whether to reuse any prexisting backing files

Method Detail

getHeadStream

public java.io.InputStream getHeadStream()
                                  throws java.io.IOException

Returns:

The stream to read from this byte queue

Throws:

java.io.IOException

getTailStream

public java.io.OutputStream getTailStream()
                                   throws java.io.FileNotFoundException

Returns:

The stream to write to this byte queue

Throws:

java.io.FileNotFoundException

flip

void flip()
    throws java.io.IOException

flip the current outFile to the inFile role, make new outFile

Throws:

java.io.IOException

getReadAllInputStream

public java.io.InputStream getReadAllInputStream()
                                          throws java.io.IOException

Returns an input stream that covers the entire queue. It only allows read access. Reading from it will not affect the queue in any way. It is not safe to add or remove items to the queue while using this stream.

Returns:

an input stream that covers the entire queue

Throws:

java.io.IOException

close

public void close()
           throws java.io.IOException

Throws:

java.io.IOException

discard

public void discard()
             throws java.io.IOException

frees all streams/files associated with this object

Throws:

java.io.IOException

disconnect

public void disconnect()
                throws java.io.IOException

Throws:

java.io.IOException

connect

public void connect()
             throws java.io.IOException

Throws:

java.io.IOException