/*
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* CDDL HEADER START
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*
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* The contents of this file are subject to the terms of the
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* Common Development and Distribution License, Version 1.0 only
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* (the "License"). You may not use this file except in compliance
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* with the License.
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*
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* You can obtain a copy of the license at legal-notices/CDDLv1_0.txt
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* or http://forgerock.org/license/CDDLv1.0.html.
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* See the License for the specific language governing permissions
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* and limitations under the License.
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*
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* When distributing Covered Code, include this CDDL HEADER in each
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* file and include the License file at legal-notices/CDDLv1_0.txt.
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* If applicable, add the following below this CDDL HEADER, with the
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* fields enclosed by brackets "[]" replaced with your own identifying
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* information:
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* Portions Copyright [yyyy] [name of copyright owner]
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*
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* CDDL HEADER END
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*
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*
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* Copyright 2013-2014 ForgeRock AS
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*/
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package org.opends.server.replication.server.changelog.je;
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import java.util.*;
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import java.util.Map.Entry;
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import org.opends.server.replication.common.CSN;
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import org.opends.server.replication.protocol.UpdateMsg;
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import org.opends.server.replication.server.changelog.api.ChangelogException;
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import org.opends.server.replication.server.changelog.api.DBCursor;
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import org.opends.server.util.StaticUtils;
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import com.forgerock.opendj.util.Pair;
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/**
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* {@link DBCursor} implementation that iterates across a Collection of
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* {@link DBCursor}s, advancing from the oldest to the newest change cross all
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* cursors.
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*
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* @param <T>
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* The type of data associated with each cursor
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* \@NotThreadSafe
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*/
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abstract class CompositeDBCursor<T> implements DBCursor<UpdateMsg>
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{
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private static final byte UNINITIALIZED = 0;
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private static final byte READY = 1;
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private static final byte CLOSED = 2;
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/**
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* The state of this cursor. One of {@link #UNINITIALIZED}, {@link #READY} or
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* {@link #CLOSED}
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*/
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private byte state = UNINITIALIZED;
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/**
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* These cursors are considered exhausted because they had no new changes the
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* last time {@link DBCursor#next()} was called on them. Exhausted cursors
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* might be recycled at some point when they start returning changes again.
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*/
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private final Map<DBCursor<UpdateMsg>, T> exhaustedCursors =
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new HashMap<DBCursor<UpdateMsg>, T>();
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/**
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* The cursors are sorted based on the current change of each cursor to
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* consider the next change across all available cursors.
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* <p>
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* New cursors for this Map must be created from the same thread that will
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* make use of them. When this rule is not obeyed, a JE exception will be
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* thrown about
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* "Non-transactional Cursors may not be used in multiple threads;".
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*/
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private final TreeMap<DBCursor<UpdateMsg>, T> cursors =
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new TreeMap<DBCursor<UpdateMsg>, T>(
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new Comparator<DBCursor<UpdateMsg>>()
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{
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@Override
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public int compare(DBCursor<UpdateMsg> o1, DBCursor<UpdateMsg> o2)
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{
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final CSN csn1 = o1.getRecord().getCSN();
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final CSN csn2 = o2.getRecord().getCSN();
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return CSN.compare(csn1, csn2);
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}
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});
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/** {@inheritDoc} */
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@Override
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public boolean next() throws ChangelogException
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{
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if (state == CLOSED)
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{
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return false;
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}
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// If previous state was ready, then we must advance the first cursor
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// (which UpdateMsg has been consumed).
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// To keep consistent the cursors' order in the SortedSet, it is necessary
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// to remove the first cursor, then add it again after moving it forward.
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final Entry<DBCursor<UpdateMsg>, T> cursorToAdvance =
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state != UNINITIALIZED ? cursors.pollFirstEntry() : null;
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state = READY;
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recycleExhaustedCursors();
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if (cursorToAdvance != null)
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{
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addCursor(cursorToAdvance.getKey(), cursorToAdvance.getValue());
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}
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incorporateNewCursors();
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return !cursors.isEmpty();
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}
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private void recycleExhaustedCursors() throws ChangelogException
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{
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if (!exhaustedCursors.isEmpty())
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{
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// try to recycle exhausted cursors in case the underlying replica DBs received new changes.
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final Map<DBCursor<UpdateMsg>, T> copy =
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new HashMap<DBCursor<UpdateMsg>, T>(exhaustedCursors);
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exhaustedCursors.clear();
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for (Entry<DBCursor<UpdateMsg>, T> entry : copy.entrySet())
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{
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addCursor(entry.getKey(), entry.getValue());
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}
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}
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}
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/**
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* Removes the cursor matching the provided data.
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*
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* @param dataToFind
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* the data for which the cursor must be found and removed
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*/
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protected void removeCursor(final T dataToFind)
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{
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removeCursor(this.cursors, dataToFind);
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removeCursor(this.exhaustedCursors, dataToFind);
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}
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private void removeCursor(Map<DBCursor<UpdateMsg>, T> cursors, T dataToFind)
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{
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for (Iterator<Entry<DBCursor<UpdateMsg>, T>> cursorIter =
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cursors.entrySet().iterator(); cursorIter.hasNext();)
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{
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final Entry<DBCursor<UpdateMsg>, T> entry = cursorIter.next();
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if (dataToFind.equals(entry.getValue()))
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{
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entry.getKey().close();
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cursorIter.remove();
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}
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}
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}
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/**
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* Adds a cursor to this composite cursor. It first calls
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* {@link DBCursor#next()} to verify whether it is exhausted or not.
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*
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* @param cursor
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* the cursor to add to this composite
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* @param data
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* the data associated to the provided cursor
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* @throws ChangelogException
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* if a database problem occurred
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*/
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protected void addCursor(final DBCursor<UpdateMsg> cursor, final T data) throws ChangelogException
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{
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if (cursor.next())
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{
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this.cursors.put(cursor, data);
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}
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else
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{
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this.exhaustedCursors.put(cursor, data);
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}
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}
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/** {@inheritDoc} */
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@Override
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public UpdateMsg getRecord()
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{
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// Cannot call incorporateNewCursors() here because
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// somebody might have already called DBCursor.getRecord() and read the record
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final Entry<DBCursor<UpdateMsg>, T> entry = cursors.firstEntry();
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if (entry != null)
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{
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return entry.getKey().getRecord();
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}
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return null;
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}
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/**
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* Called when implementors should incorporate new cursors into the current
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* composite DBCursor. Implementors should call
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* {@link #addCursor(DBCursor, Object)} to do so.
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*
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* @throws ChangelogException
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* if a database problem occurred
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*/
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protected abstract void incorporateNewCursors() throws ChangelogException;
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/**
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* Returns the data associated to the cursor that returned the current record.
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*
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* @return the data associated to the cursor that returned the current record.
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*/
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public T getData()
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{
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final Entry<DBCursor<UpdateMsg>, T> entry = cursors.firstEntry();
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if (entry != null)
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{
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return entry.getValue();
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}
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return null;
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}
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/**
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* Returns a snapshot of this cursor.
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*
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* @return a list of (Data, UpdateMsg) pairs representing the state of the
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* cursor. In each pair, the data or the update message may be
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* {@code null}, but at least one of them is non-null.
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*/
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public List<Pair<T, UpdateMsg>> getSnapshot()
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{
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final List<Pair<T, UpdateMsg>> snapshot = new ArrayList<Pair<T, UpdateMsg>>();
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for (Entry<DBCursor<UpdateMsg>, T> entry : cursors.entrySet())
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{
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final UpdateMsg updateMsg = entry.getKey().getRecord();
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final T data = entry.getValue();
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if (updateMsg != null || data != null)
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{
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snapshot.add(Pair.of(data, updateMsg));
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}
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}
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for (T data : exhaustedCursors.values())
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{
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if (data != null)
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{
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snapshot.add(Pair.of(data, (UpdateMsg) null));
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}
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}
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return snapshot;
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}
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/** {@inheritDoc} */
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@Override
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public void close()
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{
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state = CLOSED;
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StaticUtils.close(cursors.keySet());
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StaticUtils.close(exhaustedCursors.keySet());
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cursors.clear();
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exhaustedCursors.clear();
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}
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/** {@inheritDoc} */
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@Override
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public String toString()
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{
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return getClass().getSimpleName() + " openCursors=" + cursors
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+ " exhaustedCursors=" + exhaustedCursors;
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}
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}
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