| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, |
| * software distributed under the License is distributed on an |
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| * KIND, either express or implied. See the License for the |
| * specific language governing permissions and limitations |
| * under the License. |
| * |
| */ |
| package org.apache.directory.server.core.partition.impl.btree; |
| |
| |
| import java.util.HashMap; |
| import java.util.Map; |
| import java.util.NoSuchElementException; |
| |
| import javax.naming.NamingEnumeration; |
| import javax.naming.NamingException; |
| |
| |
| /** |
| * A prefetching NamingEnumeration over an underlying NamingEnumeration which |
| * determines if a element should be returned based on a Assertion. |
| * |
| * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a> |
| * @version $Rev$ |
| */ |
| public class IndexAssertionEnumeration implements NamingEnumeration<IndexRecord> |
| { |
| /** The prefetched candidate */ |
| private final IndexRecord prefetched = new IndexRecord(); |
| /** The returned candidate */ |
| private final IndexRecord candidate = new IndexRecord(); |
| /** The iteration cursor */ |
| private final NamingEnumeration<IndexRecord> underlying; |
| /** LUT used to avoid returning duplicates */ |
| private final Map<Object,Object> candidates; |
| /** */ |
| private final IndexAssertion assertion; |
| /** */ |
| private final boolean checkDups; |
| /** */ |
| private boolean hasMore = true; |
| |
| |
| // ------------------------------------------------------------------------ |
| // C O N S T R U C T O R S |
| // ------------------------------------------------------------------------ |
| |
| |
| public IndexAssertionEnumeration( NamingEnumeration<IndexRecord> underlying, IndexAssertion assertion ) |
| throws NamingException |
| { |
| this.underlying = underlying; |
| candidates = null; |
| this.assertion = assertion; |
| checkDups = false; |
| prefetch(); |
| } |
| |
| |
| public IndexAssertionEnumeration( NamingEnumeration<IndexRecord> underlying, IndexAssertion assertion, |
| boolean enableDupCheck ) throws NamingException |
| { |
| this.underlying = underlying; |
| candidates = new HashMap<Object,Object>(); |
| this.assertion = assertion; |
| checkDups = enableDupCheck; |
| prefetch(); |
| } |
| |
| |
| // ------------------------------------------------------------------------ |
| // Enumeration Method Implementations |
| // ------------------------------------------------------------------------ |
| |
| /** |
| * @see java.util.Enumeration#nextElement() |
| */ |
| public IndexRecord nextElement() |
| { |
| try |
| { |
| return next(); |
| } |
| catch ( NamingException e ) |
| { |
| throw new NoSuchElementException(); |
| } |
| } |
| |
| |
| /** |
| * @see java.util.Enumeration#hasMoreElements() |
| */ |
| public boolean hasMoreElements() |
| { |
| return hasMore; |
| } |
| |
| |
| // ------------------------------------------------------------------------ |
| // NamingEnumeration Method Implementations |
| // ------------------------------------------------------------------------ |
| |
| /** |
| * @see javax.naming.NamingEnumeration#next() |
| */ |
| public IndexRecord next() throws NamingException |
| { |
| candidate.copy( prefetched ); |
| prefetch(); |
| return candidate; |
| } |
| |
| |
| /** |
| * @see javax.naming.NamingEnumeration#hasMore() |
| */ |
| public boolean hasMore() |
| { |
| return hasMore; |
| } |
| |
| |
| /** |
| * @see javax.naming.NamingEnumeration#close() |
| */ |
| public void close() throws NamingException |
| { |
| hasMore = false; |
| underlying.close(); |
| } |
| |
| |
| // ------------------------------------------------------------------------ |
| // Private and Protected Methods |
| // ------------------------------------------------------------------------ |
| |
| private void prefetch() throws NamingException |
| { |
| IndexRecord rec = null; |
| |
| /* |
| * Scan underlying Cursor until we arrive at the next valid candidate |
| * if the cursor is exhuasted we clean up after completing the loop |
| */ |
| while ( underlying.hasMore() ) |
| { |
| rec = underlying.next(); |
| |
| // If value is valid then we set it as the next candidate to return |
| if ( assertion.assertCandidate( rec ) ) |
| { |
| if ( checkDups ) |
| { |
| boolean dup = candidates.containsKey( rec.getEntryId() ); |
| |
| if ( dup ) |
| { |
| /* |
| * Dup checking is on and candidate is a duplicate that |
| * has already been seen so we need to skip it. |
| */ |
| continue; |
| } |
| else |
| { |
| /* |
| * Dup checking is on and the candidate is not in the |
| * dup LUT so we need to set it as the next to return |
| * and add it to the LUT in case we encounter it another |
| * time. |
| */ |
| prefetched.copy( rec ); |
| candidates.put( rec.getEntryId(), rec.getEntryId() ); |
| return; |
| } |
| } |
| |
| prefetched.copy( rec ); |
| return; |
| } |
| } |
| |
| // At this pt the underlying Cursor has been exhausted so we close up |
| close(); |
| } |
| } |