/**
* JDBM LICENSE v1.00
*
* Redistribution and use of this software and associated documentation
* ("Software"), with or without modification, are permitted provided
* that the following conditions are met:
*
* 1. Redistributions of source code must retain copyright
* statements and notices. Redistributions must also contain a
* copy of this document.
*
* 2. Redistributions in binary form must reproduce the
* above copyright notice, this list of conditions and the
* following disclaimer in the documentation and/or other
* materials provided with the distribution.
*
* 3. The name "JDBM" must not be used to endorse or promote
* products derived from this Software without prior written
* permission of Cees de Groot. For written permission,
* please contact cg@cdegroot.com.
*
* 4. Products derived from this Software may not be called "JDBM"
* nor may "JDBM" appear in their names without prior written
* permission of Cees de Groot.
*
* 5. Due credit should be given to the JDBM Project
* (http://jdbm.sourceforge.net/).
*
* THIS SOFTWARE IS PROVIDED BY THE JDBM PROJECT AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
* NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
* FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
* CEES DE GROOT OR ANY CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Copyright 2001 (C) Alex Boisvert. All Rights Reserved.
* Contributions are Copyright (C) 2001 by their associated contributors.
*
*/
package jdbm.btree;
import jdbm.helper.Serializer;
import jdbm.helper.Tuple;
import jdbm.helper.TupleBrowser;
import java.io.IOException;
import java.io.ByteArrayOutputStream;
import java.io.ByteArrayInputStream;
import java.io.ObjectInput;
import java.io.ObjectOutput;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import org.apache.directory.server.i18n.I18n;
/**
* Page of a Btree.
* <p>
* The page contains a number of key-value pairs. Keys are ordered to allow
* dichotomic search.
* <p>
* If the page is a leaf page, the keys and values are user-defined and
* represent entries inserted by the user.
* <p>
* If the page is non-leaf, each key represents the greatest key in the
* underlying BPages and the values are recids pointing to the children BPages.
* The only exception is the rightmost BPage, which is considered to have an
* "infinite" key value, meaning that any insert will be to the left of this
* pseudo-key
*
* @author <a href="mailto:boisvert@intalio.com">Alex Boisvert</a>
* @version $Id: BPage.java,v 1.6 2003/09/21 15:46:59 boisvert Exp $
*/
public final class BPage
implements Serializer
{
private static final boolean DEBUG = false;
/**
* Version id for serialization.
*/
final static long serialVersionUID = 1L;
/**
* Parent B+Tree.
*/
transient BTree _btree;
/**
* This BPage's record ID in the PageManager.
*/
protected transient long _recid;
/**
* Flag indicating if this is a leaf BPage.
*/
protected boolean _isLeaf;
/**
* Keys of children nodes
*/
protected Object[] _keys;
/**
* Values associated with keys. (Only valid if leaf BPage)
*/
protected Object[] _values;
/**
* Children pages (recids) associated with keys. (Only valid if non-leaf BPage)
*/
protected long[] _children;
/**
* Index of first used item at the page
*/
protected int _first;
/**
* Previous leaf BPage (only if this BPage is a leaf)
*/
protected long _previous;
/**
* Next leaf BPage (only if this BPage is a leaf)
*/
protected long _next;
/**
* No-argument constructor used by serialization.
*/
public BPage()
{
// empty
}
/**
* Root page overflow constructor
*/
BPage( BTree btree, BPage root, BPage overflow )
throws IOException
{
_btree = btree;
_isLeaf = false;
_first = _btree._pageSize-2;
_keys = new Object[ _btree._pageSize ];
_keys[ _btree._pageSize-2 ] = overflow.getLargestKey();
_keys[ _btree._pageSize-1 ] = root.getLargestKey();
_children = new long[ _btree._pageSize ];
_children[ _btree._pageSize-2 ] = overflow._recid;
_children[ _btree._pageSize-1 ] = root._recid;
_recid = _btree._recman.insert( this, this );
}
/**
* Root page (first insert) constructor.
*/
BPage( BTree btree, Object key, Object value )
throws IOException
{
_btree = btree;
_isLeaf = true;
_first = btree._pageSize-2;
_keys = new Object[ _btree._pageSize ];
_keys[ _btree._pageSize-2 ] = key;
_keys[ _btree._pageSize-1 ] = null; // I am the root BPage for now
_values = new Object[ _btree._pageSize ];
_values[ _btree._pageSize-2 ] = value;
_values[ _btree._pageSize-1 ] = null; // I am the root BPage for now
_recid = _btree._recman.insert( this, this );
}
/**
* Overflow page constructor. Creates an empty BPage.
*/
BPage( BTree btree, boolean isLeaf )
throws IOException
{
_btree = btree;
_isLeaf = isLeaf;
// page will initially be half-full
_first = _btree._pageSize/2;
_keys = new Object[ _btree._pageSize ];
if ( isLeaf ) {
_values = new Object[ _btree._pageSize ];
} else {
_children = new long[ _btree._pageSize ];
}
_recid = _btree._recman.insert( this, this );
}
/**
* Get largest key under this BPage. Null is considered to be the
* greatest possible key.
*/
Object getLargestKey()
{
return _keys[ _btree._pageSize-1 ];
}
/**
* Return true if BPage is empty.
*/
boolean isEmpty()
{
if ( _isLeaf ) {
return ( _first == _values.length-1 );
} else {
return ( _first == _children.length-1 );
}
}
/**
* Return true if BPage is full.
*/
boolean isFull() {
return ( _first == 0 );
}
/**
* Find the object associated with the given key.
*
* @param height Height of the current BPage (zero is leaf page)
* @param key The key
* @return TupleBrowser positionned just before the given key, or before
* next greater key if key isn't found.
*/
TupleBrowser find( int height, Object key )
throws IOException
{
int index = findChildren( key );
/*
if ( DEBUG ) {
System.out.println( "BPage.find() current: " + this
+ " height: " + height);
}
*/
height -= 1;
if ( height == 0 ) {
// leaf BPage
return new Browser( this, index );
} else {
// non-leaf BPage
BPage child = childBPage( index );
return child.find( height, key );
}
}
/**
* Find first entry and return a browser positioned before it.
*
* @return TupleBrowser positionned just before the first entry.
*/
TupleBrowser findFirst()
throws IOException
{
if ( _isLeaf ) {
return new Browser( this, _first );
} else {
BPage child = childBPage( _first );
return child.findFirst();
}
}
/**
* Insert the given key and value.
* <p>
* Since the Btree does not support duplicate entries, the caller must
* specify whether to replace the existing value.
*
* @param height Height of the current BPage (zero is leaf page)
* @param key Insert key
* @param value Insert value
* @param replace Set to true to replace the existing value, if one exists.
* @return Insertion result containing existing value OR a BPage if the key
* was inserted and provoked a BPage overflow.
*/
InsertResult insert( int height, Object key, Object value, boolean replace )
throws IOException
{
InsertResult result;
long overflow;
int index = findChildren( key );
height -= 1;
if ( height == 0 ) {
result = new InsertResult();
// inserting on a leaf BPage
overflow = -1;
if ( DEBUG ) {
System.out.println( "Bpage.insert() Insert on leaf Bpage key=" + key
+ " value=" + value + " index="+index);
}
if ( compare( key, _keys[ index ] ) == 0 ) {
// key already exists
if ( DEBUG ) {
System.out.println( "Bpage.insert() Key already exists." ) ;
}
result._existing = _values[ index ];
if ( replace ) {
_values [ index ] = value;
_btree._recman.update( _recid, this, this );
}
// return the existing key
return result;
}
} else {
// non-leaf BPage
BPage child = childBPage( index );
result = child.insert( height, key, value, replace );
if ( result._existing != null ) {
// return existing key, if any.
return result;
}
if ( result._overflow == null ) {
// no overflow means we're done with insertion
return result;
}
// there was an overflow, we need to insert the overflow page
// on this BPage
if ( DEBUG ) {
System.out.println( "BPage.insert() Overflow page: " + result._overflow._recid );
}
key = result._overflow.getLargestKey();
overflow = result._overflow._recid;
// update child's largest key
_keys[ index ] = child.getLargestKey();
// clean result so we can reuse it
result._overflow = null;
}
// if we get here, we need to insert a new entry on the BPage
// before _children[ index ]
if ( !isFull() ) {
if ( height == 0 ) {
insertEntry( this, index-1, key, value );
} else {
insertChild( this, index-1, key, overflow );
}
_btree._recman.update( _recid, this, this );
return result;
}
// page is full, we must divide the page
int half = _btree._pageSize >> 1;
BPage newPage = new BPage( _btree, _isLeaf );
if ( index < half ) {
// move lower-half of entries to overflow BPage,
// including new entry
if ( DEBUG ) {
System.out.println( "Bpage.insert() move lower-half of entries to overflow BPage, including new entry." ) ;
}
if ( height == 0 ) {
copyEntries( this, 0, newPage, half, index );
setEntry( newPage, half+index, key, value );
copyEntries( this, index, newPage, half+index+1, half-index-1 );
} else {
copyChildren( this, 0, newPage, half, index );
setChild( newPage, half+index, key, overflow );
copyChildren( this, index, newPage, half+index+1, half-index-1 );
}
} else {
// move lower-half of entries to overflow BPage,
// new entry stays on this BPage
if ( DEBUG ) {
System.out.println( "Bpage.insert() move lower-half of entries to overflow BPage. New entry stays" ) ;
}
if ( height == 0 ) {
copyEntries( this, 0, newPage, half, half );
copyEntries( this, half, this, half-1, index-half );
setEntry( this, index-1, key, value );
} else {
copyChildren( this, 0, newPage, half, half );
copyChildren( this, half, this, half-1, index-half );
setChild( this, index-1, key, overflow );
}
}
_first = half-1;
// nullify lower half of entries
for ( int i=0; i<_first; i++ ) {
if ( height == 0 ) {
setEntry( this, i, null, null );
} else {
setChild( this, i, null, -1 );
}
}
if ( _isLeaf ) {
// link newly created BPage
newPage._previous = _previous;
newPage._next = _recid;
if ( _previous != 0 ) {
BPage previous = loadBPage( _previous );
previous._next = newPage._recid;
_btree._recman.update( _previous, previous, this );
}
_previous = newPage._recid;
}
_btree._recman.update( _recid, this, this );
_btree._recman.update( newPage._recid, newPage, this );
result._overflow = newPage;
return result;
}
/**
* Remove the entry associated with the given key.
*
* @param height Height of the current BPage (zero is leaf page)
* @param key Removal key
* @return Remove result object
*/
RemoveResult remove( int height, Object key )
throws IOException
{
RemoveResult result;
int half = _btree._pageSize / 2;
int index = findChildren( key );
height -= 1;
if ( height == 0 ) {
// remove leaf entry
if ( compare( _keys[ index ], key ) != 0 ) {
throw new IllegalArgumentException( I18n.err( I18n.ERR_514, key ) );
}
result = new RemoveResult();
result._value = _values[ index ];
removeEntry( this, index );
// update this BPage
_btree._recman.update( _recid, this, this );
} else {
// recurse into Btree to remove entry on a children page
BPage child = childBPage( index );
result = child.remove( height, key );
// update children
_keys[ index ] = child.getLargestKey();
_btree._recman.update( _recid, this, this );
if ( result._underflow ) {
// underflow occured
if ( child._first != half+1 ) {
throw new IllegalStateException( I18n.err( I18n.ERR_513, "1" ) );
}
if ( index < _children.length-1 ) {
// exists greater brother page
BPage brother = childBPage( index+1 );
int bfirst = brother._first;
if ( bfirst < half ) {
// steal entries from "brother" page
int steal = ( half - bfirst + 1 ) / 2;
brother._first += steal;
child._first -= steal;
if ( child._isLeaf ) {
copyEntries( child, half+1, child, half+1-steal, half-1 );
copyEntries( brother, bfirst, child, 2*half-steal, steal );
} else {
copyChildren( child, half+1, child, half+1-steal, half-1 );
copyChildren( brother, bfirst, child, 2*half-steal, steal );
}
for ( int i=bfirst; i<bfirst+steal; i++ ) {
if ( brother._isLeaf ) {
setEntry( brother, i, null, null );
} else {
setChild( brother, i, null, -1 );
}
}
// update child's largest key
_keys[ index ] = child.getLargestKey();
// no change in previous/next BPage
// update BPages
_btree._recman.update( _recid, this, this );
_btree._recman.update( brother._recid, brother, this );
_btree._recman.update( child._recid, child, this );
} else {
// move all entries from page "child" to "brother"
if ( brother._first != half ) {
throw new IllegalStateException( I18n.err( I18n.ERR_513, "2" ) );
}
brother._first = 1;
if ( child._isLeaf ) {
copyEntries( child, half+1, brother, 1, half-1 );
} else {
copyChildren( child, half+1, brother, 1, half-1 );
}
_btree._recman.update( brother._recid, brother, this );
// remove "child" from current BPage
if ( _isLeaf ) {
copyEntries( this, _first, this, _first+1, index-_first );
setEntry( this, _first, null, null );
} else {
copyChildren( this, _first, this, _first+1, index-_first );
setChild( this, _first, null, -1 );
}
_first += 1;
_btree._recman.update( _recid, this, this );
// re-link previous and next BPages
if ( child._previous != 0 ) {
BPage prev = loadBPage( child._previous );
prev._next = child._next;
_btree._recman.update( prev._recid, prev, this );
}
if ( child._next != 0 ) {
BPage next = loadBPage( child._next );
next._previous = child._previous;
_btree._recman.update( next._recid, next, this );
}
// delete "child" BPage
_btree._recman.delete( child._recid );
}
} else {
// page "brother" is before "child"
BPage brother = childBPage( index-1 );
int bfirst = brother._first;
if ( bfirst < half ) {
// steal entries from "brother" page
int steal = ( half - bfirst + 1 ) / 2;
brother._first += steal;
child._first -= steal;
if ( child._isLeaf ) {
copyEntries( brother, 2*half-steal, child,
half+1-steal, steal );
copyEntries( brother, bfirst, brother,
bfirst+steal, 2*half-bfirst-steal );
} else {
copyChildren( brother, 2*half-steal, child,
half+1-steal, steal );
copyChildren( brother, bfirst, brother,
bfirst+steal, 2*half-bfirst-steal );
}
for ( int i=bfirst; i<bfirst+steal; i++ ) {
if ( brother._isLeaf ) {
setEntry( brother, i, null, null );
} else {
setChild( brother, i, null, -1 );
}
}
// update brother's largest key
_keys[ index-1 ] = brother.getLargestKey();
// no change in previous/next BPage
// update BPages
_btree._recman.update( _recid, this, this );
_btree._recman.update( brother._recid, brother, this );
_btree._recman.update( child._recid, child, this );
} else {
// move all entries from page "brother" to "child"
if ( brother._first != half ) {
throw new IllegalStateException( I18n.err( I18n.ERR_513, "3" ) );
}
child._first = 1;
if ( child._isLeaf ) {
copyEntries( brother, half, child, 1, half );
} else {
copyChildren( brother, half, child, 1, half );
}
_btree._recman.update( child._recid, child, this );
// remove "brother" from current BPage
if ( _isLeaf ) {
copyEntries( this, _first, this, _first+1, index-1-_first );
setEntry( this, _first, null, null );
} else {
copyChildren( this, _first, this, _first+1, index-1-_first );
setChild( this, _first, null, -1 );
}
_first += 1;
_btree._recman.update( _recid, this, this );
// re-link previous and next BPages
if ( brother._previous != 0 ) {
BPage prev = loadBPage( brother._previous );
prev._next = brother._next;
_btree._recman.update( prev._recid, prev, this );
}
if ( brother._next != 0 ) {
BPage next = loadBPage( brother._next );
next._previous = brother._previous;
_btree._recman.update( next._recid, next, this );
}
// delete "brother" BPage
_btree._recman.delete( brother._recid );
}
}
}
}
// underflow if page is more than half-empty
result._underflow = _first > half;
return result;
}
/**
* Find the first children node with a key equal or greater than the given
* key.
*
* @return index of first children with equal or greater key.
*/
private int findChildren( Object key )
{
int left = _first;
int right = _btree._pageSize-1;
// binary search
while ( left < right ) {
int middle = ( left + right ) / 2;
if ( compare( _keys[ middle ], key ) < 0 ) {
left = middle+1;
} else {
right = middle;
}
}
return right;
}
/**
* Insert entry at given position.
*/
private static void insertEntry( BPage page, int index,
Object key, Object value )
{
Object[] keys = page._keys;
Object[] values = page._values;
int start = page._first;
int count = index-page._first+1;
// shift entries to the left
System.arraycopy( keys, start, keys, start-1, count );
System.arraycopy( values, start, values, start-1, count );
page._first -= 1;
keys[ index ] = key;
values[ index ] = value;
}
/**
* Insert child at given position.
*/
private static void insertChild( BPage page, int index,
Object key, long child )
{
Object[] keys = page._keys;
long[] children = page._children;
int start = page._first;
int count = index-page._first+1;
// shift entries to the left
System.arraycopy( keys, start, keys, start-1, count );
System.arraycopy( children, start, children, start-1, count );
page._first -= 1;
keys[ index ] = key;
children[ index ] = child;
}
/**
* Remove entry at given position.
*/
private static void removeEntry( BPage page, int index )
{
Object[] keys = page._keys;
Object[] values = page._values;
int start = page._first;
int count = index-page._first;
System.arraycopy( keys, start, keys, start+1, count );
keys[ start ] = null;
System.arraycopy( values, start, values, start+1, count );
values[ start ] = null;
page._first++;
}
/**
* Remove child at given position.
*/
/*
private static void removeChild( BPage page, int index )
{
Object[] keys = page._keys;
long[] children = page._children;
int start = page._first;
int count = index-page._first;
System.arraycopy( keys, start, keys, start+1, count );
keys[ start ] = null;
System.arraycopy( children, start, children, start+1, count );
children[ start ] = (long) -1;
page._first++;
}
*/
/**
* Set the entry at the given index.
*/
private static void setEntry( BPage page, int index, Object key, Object value )
{
page._keys[ index ] = key;
page._values[ index ] = value;
}
/**
* Set the child BPage recid at the given index.
*/
private static void setChild( BPage page, int index, Object key, long recid )
{
page._keys[ index ] = key;
page._children[ index ] = recid;
}
/**
* Copy entries between two BPages
*/
private static void copyEntries( BPage source, int indexSource,
BPage dest, int indexDest, int count )
{
System.arraycopy( source._keys, indexSource, dest._keys, indexDest, count);
System.arraycopy( source._values, indexSource, dest._values, indexDest, count);
}
/**
* Copy child BPage recids between two BPages
*/
private static void copyChildren( BPage source, int indexSource,
BPage dest, int indexDest, int count )
{
System.arraycopy( source._keys, indexSource, dest._keys, indexDest, count);
System.arraycopy( source._children, indexSource, dest._children, indexDest, count);
}
/**
* Return the child BPage at given index.
*/
BPage childBPage( int index )
throws IOException
{
return loadBPage( _children[ index ] );
}
/**
* Load the BPage at the given recid.
*/
private BPage loadBPage( long recid )
throws IOException
{
BPage child = (BPage) _btree._recman.fetch( recid, this );
child._recid = recid;
child._btree = _btree;
return child;
}
private final int compare( Object value1, Object value2 )
{
if ( value1 == null ) {
return 1;
}
if ( value2 == null ) {
return -1;
}
return _btree._comparator.compare( value1, value2 );
}
static byte[] readByteArray( ObjectInput in )
throws IOException
{
int len = in.readInt();
if ( len < 0 ) {
return null;
}
byte[] buf = new byte[ len ];
in.readFully( buf );
return buf;
}
static void writeByteArray( ObjectOutput out, byte[] buf )
throws IOException
{
if ( buf == null ) {
out.writeInt( -1 );
} else {
out.writeInt( buf.length );
out.write( buf );
}
}
/**
* Dump the structure of the tree on the screen. This is used for debugging
* purposes only.
*/
private void dump( int height )
{
String prefix = "";
for ( int i=0; i<height; i++ ) {
prefix += " ";
}
System.out.println( prefix + "-------------------------------------- BPage recid=" + _recid);
System.out.println( prefix + "first=" + _first );
for ( int i=0; i< _btree._pageSize; i++ ) {
if ( _isLeaf ) {
System.out.println( prefix + "BPage [" + i + "] " + _keys[ i ] + " " + _values[ i ] );
} else {
System.out.println( prefix + "BPage [" + i + "] " + _keys[ i ] + " " + _children[ i ] );
}
}
System.out.println( prefix + "--------------------------------------" );
}
/**
* Recursively dump the state of the BTree on screen. This is used for
* debugging purposes only.
*/
void dumpRecursive( int height, int level )
throws IOException
{
height -= 1;
level += 1;
if ( height > 0 ) {
for ( int i=_first; i<_btree._pageSize; i++ ) {
if ( _keys[ i ] == null ) break;
BPage child = childBPage( i );
child.dump( level );
child.dumpRecursive( height, level );
}
}
}
/**
* Assert the ordering of the keys on the BPage. This is used for testing
* purposes only.
*/
private void assertConsistency()
{
for ( int i=_first; i<_btree._pageSize-1; i++ ) {
if ( compare( (byte[]) _keys[ i ], (byte[]) _keys[ i+1 ] ) >= 0 ) {
dump( 0 );
throw new Error( I18n.err( I18n.ERR_515 ) );
}
}
}
/**
* Recursively assert the ordering of the BPage entries on this page
* and sub-pages. This is used for testing purposes only.
*/
void assertConsistencyRecursive( int height )
throws IOException
{
assertConsistency();
if ( --height > 0 ) {
for ( int i=_first; i<_btree._pageSize; i++ ) {
if ( _keys[ i ] == null ) break;
BPage child = childBPage( i );
if ( compare( (byte[]) _keys[ i ], child.getLargestKey() ) != 0 ) {
dump( 0 );
child.dump( 0 );
throw new Error( I18n.err( I18n.ERR_516 ) );
}
child.assertConsistencyRecursive( height );
}
}
}
/**
* Deserialize the content of an object from a byte array.
*
* @param serialized Byte array representation of the object
* @return deserialized object
*
*/
public Object deserialize( byte[] serialized )
throws IOException
{
ByteArrayInputStream bais;
ObjectInputStream ois;
BPage bpage;
bpage = new BPage();
bais = new ByteArrayInputStream( serialized );
ois = new ObjectInputStream( bais );
bpage._isLeaf = ois.readBoolean();
if ( bpage._isLeaf ) {
bpage._previous = ois.readLong();
bpage._next = ois.readLong();
}
bpage._first = ois.readInt();
bpage._keys = new Object[ _btree._pageSize ];
try {
for ( int i=bpage._first; i<_btree._pageSize; i++ ) {
if ( _btree._keySerializer == null ) {
bpage._keys[ i ] = ois.readObject();
} else {
serialized = readByteArray( ois );
if ( serialized != null ) {
bpage._keys[ i ] = _btree._keySerializer.deserialize( serialized );
}
}
}
} catch ( ClassNotFoundException except ) {
throw new IOException( except.getLocalizedMessage() );
}
if ( bpage._isLeaf ) {
bpage._values = new Object[ _btree._pageSize ];
try {
for ( int i=bpage._first; i<_btree._pageSize; i++ ) {
if ( _btree._valueSerializer == null ) {
bpage._values[ i ] = ois.readObject();
} else {
serialized = readByteArray( ois );
if ( serialized != null ) {
bpage._values[ i ] = _btree._valueSerializer.deserialize( serialized );
}
}
}
} catch ( ClassNotFoundException except ) {
throw new IOException( except.getLocalizedMessage() );
}
} else {
bpage._children = new long[ _btree._pageSize ];
for ( int i=bpage._first; i<_btree._pageSize; i++ ) {
bpage._children[ i ] = ois.readLong();
}
}
ois.close();
bais.close();
return bpage;
}
/**
* Serialize the content of an object into a byte array.
*
* @param obj Object to serialize
* @return a byte array representing the object's state
*
*/
public byte[] serialize( Object obj )
throws IOException
{
byte[] serialized;
ByteArrayOutputStream baos;
ObjectOutputStream oos;
BPage bpage;
byte[] data;
// note: It is assumed that BPage instance doing the serialization is the parent
// of the BPage object being serialized.
bpage = (BPage) obj;
baos = new ByteArrayOutputStream();
oos = new ObjectOutputStream( baos );
oos.writeBoolean( bpage._isLeaf );
if ( bpage._isLeaf ) {
oos.writeLong( bpage._previous );
oos.writeLong( bpage._next );
}
oos.writeInt( bpage._first );
for ( int i=bpage._first; i<_btree._pageSize; i++ ) {
if ( _btree._keySerializer == null ) {
oos.writeObject( bpage._keys[ i ] );
} else {
if ( bpage._keys[ i ] != null ) {
serialized = _btree._keySerializer.serialize( bpage._keys[ i ] );
writeByteArray( oos, serialized );
} else {
writeByteArray( oos, null );
}
}
}
if ( bpage._isLeaf ) {
for ( int i=bpage._first; i<_btree._pageSize; i++ ) {
if ( _btree._valueSerializer == null ) {
oos.writeObject( bpage._values[ i ] );
} else {
if ( bpage._values[ i ] != null ) {
serialized = _btree._valueSerializer.serialize( bpage._values[ i ] );
writeByteArray( oos, serialized );
} else {
writeByteArray( oos, null );
}
}
}
} else {
for ( int i=bpage._first; i<_btree._pageSize; i++ ) {
oos.writeLong( bpage._children[ i ] );
}
}
oos.flush();
data = baos.toByteArray();
oos.close();
baos.close();
return data;
}
/** STATIC INNER CLASS
* Result from insert() method call
*/
static class InsertResult {
/**
* Overflow page.
*/
BPage _overflow;
/**
* Existing value for the insertion key.
*/
Object _existing;
}
/** STATIC INNER CLASS
* Result from remove() method call
*/
static class RemoveResult {
/**
* Set to true if underlying pages underflowed
*/
boolean _underflow;
/**
* Removed entry value
*/
Object _value;
}
/** PRIVATE INNER CLASS
* Browser to traverse leaf BPages.
*/
static class Browser
extends TupleBrowser
{
/**
* Current page.
*/
private BPage _page;
/**
* Current index in the page. The index positionned on the next
* tuple to return.
*/
private int _index;
/**
* Create a browser.
*
* @param page Current page
* @param index Position of the next tuple to return.
*/
Browser( BPage page, int index )
{
_page = page;
_index = index;
}
public boolean getNext( Tuple tuple )
throws IOException
{
if ( _index < _page._btree._pageSize ) {
if ( _page._keys[ _index ] == null ) {
// reached end of the tree.
return false;
}
} else if ( _page._next != 0 ) {
// move to next page
_page = _page.loadBPage( _page._next );
_index = _page._first;
}
tuple.setKey( _page._keys[ _index ] );
tuple.setValue( _page._values[ _index ] );
_index++;
return true;
}
public boolean getPrevious( Tuple tuple )
throws IOException
{
if ( _index == _page._first ) {
if ( _page._previous != 0 ) {
_page = _page.loadBPage( _page._previous );
_index = _page._btree._pageSize;
} else {
// reached beginning of the tree
return false;
}
}
_index--;
tuple.setKey( _page._keys[ _index ] );
tuple.setValue( _page._values[ _index ] );
return true;
}
}
}