org.aksw.jena_sparql_api.io.binseach

Class PageNavigator

java.lang.Object

org.aksw.jena_sparql_api.io.binseach.PageNavigator

All Implemented Interfaces:

Closeable, AutoCloseable, Channel, ReadableByteChannel, Seekable

public class PageNavigator
extends Object
implements Seekable

An object for (predominantly relative) positioning over a sequence of fixed size pages

Author:

raven

Field Summary

Fields

Modifier and Type	Field and Description
protected int	absMaxIndexInPage
protected int	absMinIndexInPage
protected long	bufferForPage
protected int	displacement
protected int	index Index is relative to the the page's buffer.position()
protected int	maxIndex
protected long	maxPage
protected long	maxPos
protected int	minIndex
protected long	minPage
protected long	minPos
protected long	page Current page
protected ByteBuffer	pageBuffer
protected PageManager	pageManager
protected Reference<Page>	pageObj
protected int	pageSize
protected int	relMaxIndexInPage
protected int	relMinIndexInPage

Constructor Summary

Constructors

Constructor and Description
PageNavigator(PageManager pageManager)
PageNavigator(PageManager pageManager, long minPos, long maxPos)

Method Summary

Modifier and Type	Method and Description
boolean	canNextPos()
boolean	canPrevPos()
int	checkNext(int len, boolean changePos) Attempt to advance the position by the given number of bytes.
int	checkPrev(int len, boolean changePos)
PageNavigator	clone() Clone the state of the navigator, allowing independent positioning
void	close()
int	compareToPrefix(byte[] prefix) Compare the bytes at the current position to a given sequence of bytes If there are fewer bytes available in the seekable than provide for comparison, then only that many are compared.
byte	get() Get the byte at the current position Does not change the position Throws an exception if beyond end of data
ByteBuffer	getBufferForPage(long page) If a page with the given offset exists, the following fields are updated: - displacement - absMinIndexInPage - absMaxIndexInPage Note, that the relative caches are not updated
ByteBuffer	getBufferForPos(long pos)
int	getIndexForPos(long pos)
long	getMaxPos()
long	getMinPos()
long	getNextPosFor(byte delimiter) Returns the position of the next delimiter or the end of the stream
long	getPageForPos(long pos)
long	getPos() Optional operation.
long	getPrevPosFor(byte delimiter)
int	getRelMaxIndex(long page)
int	getRelMinIndex(long page)
boolean	isOpen()
boolean	isPosAfterEnd() The state of a seekable may be one unit beyond the end.
boolean	isPosBeforeStart() The state of a seekable may be one unit before the start.
PageNavigator	limitNext(long length) Limit the
PageNavigator	limitPrev(long length) Limit the
boolean	nextPos(int delta) Attempts to advance the position by delta bytes and returns true if this succeeded.
int	peekNextBytes(byte[] dst, int offset, int len) Reads bytes at the current position; does not advance pos
void	posToEnd() Optional operation.
boolean	posToNext(byte delimiter) Advances the position to the next matching delimiter or one byte past the end of the stream.
boolean	posToPrev(byte delimiter) Move the position to the previous delimiter if it exists, or one element past the end of data such that isPosBeforeStart() yields true.
void	posToStart() Optional operation.
boolean	prevPos(int delta) Attempt to step back the position by the given number of bytes.
int	read(ByteBuffer dst)
String	readLine()
static int	readRemaining(ByteBuffer dst, ByteBuffer src)
String	readString(int n)
void	setPos(long pos) Optional operation.
void	setPos(long page, int index)
void	updateRelCache(long page) Update relative min and max index for the given page, taking one byte before and after the selected range into account

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.aksw.jena_sparql_api.io.binseach.Seekable

binarySearch, cloneObject, compareArrays, deltaPos, get, posToNext, size

Field Detail

pageManager

protected PageManager pageManager

pageSize

protected int pageSize

page

protected long page

Current page

index

protected int index

Index is relative to the the page's buffer.position()

pageObj

protected Reference<Page> pageObj

pageBuffer

protected ByteBuffer pageBuffer

displacement

protected int displacement

bufferForPage

protected long bufferForPage

absMaxIndexInPage

protected int absMaxIndexInPage

absMinIndexInPage

protected int absMinIndexInPage

relMinIndexInPage

protected int relMinIndexInPage

relMaxIndexInPage

protected int relMaxIndexInPage

minPos

protected long minPos

minPage

protected long minPage

minIndex

protected int minIndex

maxPos

protected long maxPos

maxPage

protected long maxPage

maxIndex

protected int maxIndex

Constructor Detail

PageNavigator

public PageNavigator(PageManager pageManager)

PageNavigator

public PageNavigator(PageManager pageManager,
                     long minPos,
                     long maxPos)

Parameters:

pageManager -

minPos - inclusive

maxPos - exclusive

Method Detail

clone

public PageNavigator clone()

Clone the state of the navigator, allowing independent positioning

Specified by:

clone in interface Seekable

Overrides:

clone in class Object

limitNext

public PageNavigator limitNext(long length)

Limit the

Parameters:

length -

Returns:

limitPrev

public PageNavigator limitPrev(long length)

Limit the

Parameters:

length -

Returns:

getPos

public long getPos()

Description copied from interface: Seekable

Optional operation. Get the position in this seekable

Specified by:

getPos in interface Seekable

Returns:

isPosAfterEnd

public boolean isPosAfterEnd()

Description copied from interface: Seekable

The state of a seekable may be one unit beyond the end. In this state, if the seekable is non-empty, prevPos(1) must be a valid position

Specified by:

isPosAfterEnd in interface Seekable

Returns:

isPosBeforeStart

public boolean isPosBeforeStart()

Description copied from interface: Seekable

The state of a seekable may be one unit before the start. In this state, if the seekable is non-empty, nextPos(1) must be a valid position

Specified by:

isPosBeforeStart in interface Seekable

Returns:

getBufferForPage

public ByteBuffer getBufferForPage(long page)
                            throws IOException

If a page with the given offset exists, the following fields are updated: - displacement - absMinIndexInPage - absMaxIndexInPage Note, that the relative caches are not updated

Parameters:

page -

Returns:

Throws:

IOException

updateRelCache

public void updateRelCache(long page)

Update relative min and max index for the given page, taking one byte before and after the selected range into account

Parameters:

page -

getRelMaxIndex

public int getRelMaxIndex(long page)

getRelMinIndex

public int getRelMinIndex(long page)

getBufferForPos

public ByteBuffer getBufferForPos(long pos)
                           throws IOException

Throws:

IOException

getPageForPos

public long getPageForPos(long pos)

getIndexForPos

public int getIndexForPos(long pos)

posToStart

public void posToStart()

Description copied from interface: Seekable

Optional operation. Move one unit before the start of the seekable; raises an exception on infinite seekables

Specified by:

posToStart in interface Seekable

posToEnd

public void posToEnd()

Description copied from interface: Seekable

Optional operation. Move to one unit beyond the end of the seekable; raises an exception on infinite seekables

Specified by:

posToEnd in interface Seekable

setPos

public void setPos(long page,
                   int index)

setPos

public void setPos(long pos)

Description copied from interface: Seekable

Optional operation. Get the position in this seekable

Specified by:

setPos in interface Seekable

getMinPos

public long getMinPos()

getMaxPos

public long getMaxPos()

get

public byte get()
         throws IOException

Get the byte at the current position Does not change the position Throws an exception if beyond end of data

Specified by:

get in interface Seekable

Returns:

Throws:

IOException

canNextPos

public boolean canNextPos()

canPrevPos

public boolean canPrevPos()

checkNext

public int checkNext(int len,
                     boolean changePos)
              throws IOException

Description copied from interface: Seekable

Attempt to advance the position by the given number of bytes. Return the number of bytes by which the position was changed. Returning less bytes than requested implies that a end position was reached which cannot be passed. This method cannot pass beyond the end - i.e. isPosAfterEnd cannot change from false to true by calling this method.

Specified by:

checkNext in interface Seekable

Returns:

Throws:

IOException

checkPrev

public int checkPrev(int len,
                     boolean changePos)
              throws IOException

Specified by:

checkPrev in interface Seekable

Throws:

IOException

nextPos

public boolean nextPos(int delta)
                throws IOException

Attempts to advance the position by delta bytes and returns true if this succeeded. Position is unchanged if insufficient bytes are available Cannot advance beyond the last byte.

Specified by:

nextPos in interface Seekable

Returns:

Throws:

IOException

prevPos

public boolean prevPos(int delta)
                throws IOException

Description copied from interface: Seekable

Attempt to step back the position by the given number of bytes. Argument must not be negative.

Specified by:

prevPos in interface Seekable

Returns:

True if the position was changed by the *requested* amount of bytes. False means that the position was unchanged.

Throws:

IOException

posToNext

public boolean posToNext(byte delimiter)
                  throws IOException

Advances the position to the next matching delimiter or one byte past the end of the stream. Returns true if and only if the position was changed. Note, true does NOT mean that the byte at the new position matches delim. A match is implied if isPosAfterEnd() is false.

Specified by:

posToNext in interface Seekable

Parameters:

delimiter -

Returns:

Throws:

IOException

posToPrev

public boolean posToPrev(byte delimiter)
                  throws IOException

Description copied from interface: Seekable

Move the position to the previous delimiter if it exists, or one element past the end of data such that isPosBeforeStart() yields true. Position is unchanged if already at delimiter

Specified by:

posToPrev in interface Seekable

Returns:

true if the position was changed, false otherwise

Throws:

IOException

getNextPosFor

public long getNextPosFor(byte delimiter)
                   throws IOException

Returns the position of the next delimiter or the end of the stream

Parameters:

delimiter -

Returns:

Throws:

IOException

getPrevPosFor

public long getPrevPosFor(byte delimiter)
                   throws IOException

Throws:

IOException

compareToPrefix

public int compareToPrefix(byte[] prefix)
                    throws IOException

Description copied from interface: Seekable

Compare the bytes at the current position to a given sequence of bytes If there are fewer bytes available in the seekable than provide for comparison, then only that many are compared. This default implementation uses read(ByteBuffer). Other implementations may override this behavior to compare the given prefix directly against their internal data structures without the intermediate buffer copy due to read.

Specified by:

compareToPrefix in interface Seekable

Returns:

Throws:

IOException

peekNextBytes

public int peekNextBytes(byte[] dst,
                         int offset,
                         int len)
                  throws IOException

Reads bytes at the current position; does not advance pos

Specified by:

peekNextBytes in interface Seekable

Parameters:

n -

Returns:

Throws:

IOException

readLine

public String readLine()
                throws IOException

Throws:

IOException

readString

public String readString(int n)
                  throws IOException

Specified by:

readString in interface Seekable

Throws:

IOException

read

public int read(ByteBuffer dst)
         throws IOException

Specified by:

read in interface ReadableByteChannel

Specified by:

read in interface Seekable

Throws:

IOException

readRemaining

public static int readRemaining(ByteBuffer dst,
                                ByteBuffer src)

isOpen

public boolean isOpen()

Specified by:

isOpen in interface Channel

close

public void close()
           throws IOException

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Channel

Specified by:

close in interface Seekable

Throws:

IOException