org.apache.directory.mavibot.btree

Class TupleCursor<K,V>

java.lang.Object

org.apache.directory.mavibot.btree.TupleCursor<K,V>

Type Parameters:

K - The type for the Key

V - The type for the stored value

Direct Known Subclasses:

EmptyTupleCursor

public class TupleCursor<K,V>
extends java.lang.Object

A Cursor is used to fetch elements in a BTree and is returned by the

See Also:

method. The cursor must be closed when the user is done with it.

Field Summary

Fields

Modifier and Type	Field and Description
private static int	AFTER_LAST A marker to tell that we are after the last element
private static int	BEFORE_FIRST A marker to tell that we are before the first element
protected int	depth The stack's depth
protected ParentPos<K,V>[]	stack The stack of pages from the root down to the leaf
protected ReadTransaction<K,V>	transaction The transaction used for this cursor

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	TupleCursor() Creates a new instance of Cursor.
	TupleCursor(ReadTransaction<K,V> transaction, ParentPos<K,V>[] stack, int depth) Creates a new instance of Cursor, starting on a page at a given position.

Method Summary

Modifier and Type	Method and Description
void	afterLast() Change the position in the current cursor to set it after the last key
void	beforeFirst() Change the position in the current cursor before the first key
void	close()
private ParentPos<K,V>	findNextParentPos() Find the leaf containing the following elements.
private ParentPos<K,V>	findPrevParentPos() Find the leaf containing the previous elements.
long	getCreationDate() Get the creation date
long	getRevision() Get the current revision
boolean	hasNext() Tells if the cursor can return a next element
boolean	hasNextKey() Tells if the cursor can return a next key
private boolean	hasNextParentPos() Tells if there is a next ParentPos
boolean	hasPrev() Tells if the cursor can return a previous element
boolean	hasPrevKey() Tells if the cursor can return a previous key
private boolean	hasPrevParentPos() Tells if there is a prev ParentPos
Tuple<K,V>	next() Find the next key/value
Tuple<K,V>	nextKey() Get the next non-duplicate key.
Tuple<K,V>	prev() Find the previous key/value
Tuple<K,V>	prevKey() Get the previous non-duplicate key.
java.lang.String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

BEFORE_FIRST

private static final int BEFORE_FIRST

A marker to tell that we are before the first element

See Also:

Constant Field Values

AFTER_LAST

private static final int AFTER_LAST

A marker to tell that we are after the last element

See Also:

Constant Field Values

stack

protected ParentPos<K,V>[] stack

The stack of pages from the root down to the leaf

depth

protected int depth

The stack's depth

transaction

protected ReadTransaction<K,V> transaction

The transaction used for this cursor

Constructor Detail

TupleCursor

protected TupleCursor()

Creates a new instance of Cursor.

TupleCursor

public TupleCursor(ReadTransaction<K,V> transaction,
                   ParentPos<K,V>[] stack,
                   int depth)

Creates a new instance of Cursor, starting on a page at a given position.

Parameters:

transaction - The transaction this operation is protected by

stack - The stack of parent's from root to this page

Method Detail

afterLast

public void afterLast()
               throws java.io.IOException

Change the position in the current cursor to set it after the last key

Throws:

java.io.IOException

beforeFirst

public void beforeFirst()
                 throws java.io.IOException

Change the position in the current cursor before the first key

Throws:

java.io.IOException

hasNext

public boolean hasNext()
                throws EndOfFileExceededException,
                       java.io.IOException

Tells if the cursor can return a next element

Returns:

true if there are some more elements

Throws:

java.io.IOException

EndOfFileExceededException

next

public Tuple<K,V> next()
                throws EndOfFileExceededException,
                       java.io.IOException

Find the next key/value

Returns:

A Tuple containing the found key and value

Throws:

java.io.IOException

EndOfFileExceededException

nextKey

public Tuple<K,V> nextKey()
                   throws EndOfFileExceededException,
                          java.io.IOException

Get the next non-duplicate key. If the BTree contains :

• <1,0>
• <1,1>
• <1,2>
• <2,0>
• <2,1>

and cursor is present at <1,1> then the returned tuple will be <2,0> (not <1,2>)

Returns:

A Tuple containing the found key and value

Throws:

EndOfFileExceededException

java.io.IOException

hasNextKey

public boolean hasNextKey()
                   throws EndOfFileExceededException,
                          java.io.IOException

Tells if the cursor can return a next key

Returns:

true if there are some more keys

Throws:

java.io.IOException

EndOfFileExceededException

hasPrev

public boolean hasPrev()
                throws EndOfFileExceededException,
                       java.io.IOException

Tells if the cursor can return a previous element

Returns:

true if there are some more elements

Throws:

java.io.IOException

EndOfFileExceededException

prev

public Tuple<K,V> prev()
                throws EndOfFileExceededException,
                       java.io.IOException

Find the previous key/value

Returns:

A Tuple containing the found key and value

Throws:

java.io.IOException

EndOfFileExceededException

prevKey

public Tuple<K,V> prevKey()
                   throws EndOfFileExceededException,
                          java.io.IOException

Get the previous non-duplicate key. If the BTree contains :

• <1,0>
• <1,1>
• <1,2>
• <2,0>
• <2,1>

and cursor is present at <2,1> then the returned tuple will be <1,0> (not <2,0>)

Returns:

A Tuple containing the found key and value

Throws:

EndOfFileExceededException

java.io.IOException

hasPrevKey

public boolean hasPrevKey()
                   throws EndOfFileExceededException,
                          java.io.IOException

Tells if the cursor can return a previous key

Returns:

true if there are some more keys

Throws:

java.io.IOException

EndOfFileExceededException

hasNextParentPos

private boolean hasNextParentPos()
                          throws EndOfFileExceededException,
                                 java.io.IOException

Tells if there is a next ParentPos

Returns:

the new ParentPos instance, or null if we have no following leaf

Throws:

java.io.IOException

EndOfFileExceededException

findNextParentPos

private ParentPos<K,V> findNextParentPos()
                                  throws EndOfFileExceededException,
                                         java.io.IOException

Find the leaf containing the following elements.

Returns:

the new ParentPos instance, or null if we have no following leaf

Throws:

java.io.IOException

EndOfFileExceededException

findPrevParentPos

private ParentPos<K,V> findPrevParentPos()
                                  throws EndOfFileExceededException,
                                         java.io.IOException

Find the leaf containing the previous elements.

Returns:

the new ParentPos instance, or null if we have no previous leaf

Throws:

java.io.IOException

EndOfFileExceededException

hasPrevParentPos

private boolean hasPrevParentPos()
                          throws EndOfFileExceededException,
                                 java.io.IOException

Tells if there is a prev ParentPos

Returns:

the new ParentPos instance, or null if we have no previous leaf

Throws:

java.io.IOException

EndOfFileExceededException

close

public void close()

getCreationDate

public long getCreationDate()

Get the creation date

Returns:

The creation date for this cursor

getRevision

public long getRevision()

Get the current revision

Returns:

The revision this cursor is based on

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object