| /* |
| * 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.api.ldap.model.cursor; |
| |
| |
| import java.io.IOException; |
| import java.util.Collections; |
| import java.util.Comparator; |
| import java.util.List; |
| |
| import org.apache.directory.api.i18n.I18n; |
| import org.apache.directory.api.ldap.model.constants.Loggers; |
| import org.apache.directory.api.ldap.model.exception.LdapException; |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| |
| /** |
| * A simple implementation of a Cursor on a {@link List}. Optionally, the |
| * Cursor may be limited to a specific range within the list. |
| * |
| * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a> |
| * @param <E> The element on which this cursor will iterate |
| */ |
| public class ListCursor<E> extends AbstractCursor<E> |
| { |
| /** A dedicated log for cursors */ |
| private static final Logger LOG_CURSOR = LoggerFactory.getLogger( Loggers.CURSOR_LOG.getName() ); |
| |
| /** Speedup for logs */ |
| private static final boolean IS_DEBUG = LOG_CURSOR.isDebugEnabled(); |
| |
| /** The inner List */ |
| private final List<E> list; |
| |
| /** The associated comparator */ |
| private final Comparator<E> comparator; |
| |
| /** The starting position for the cursor in the list. It can be > 0 */ |
| private final int start; |
| |
| /** The ending position for the cursor in the list. It can be < List.size() */ |
| private final int end; |
| /** The current position in the list */ |
| |
| private int index = -1; |
| |
| |
| /** |
| * Creates a new ListCursor with lower (inclusive) and upper (exclusive) |
| * bounds. |
| * |
| * As with all Cursors, this ListCursor requires a successful return from |
| * advance operations (next() or previous()) to properly return values |
| * using the get() operation. |
| * |
| * @param comparator an optional comparator to use for ordering |
| * @param start the lower bound index |
| * @param list the list this ListCursor operates on |
| * @param end the upper bound index |
| */ |
| public ListCursor( Comparator<E> comparator, int start, List<E> list, int end ) |
| { |
| if ( list == null ) |
| { |
| list = Collections.emptyList(); |
| } |
| |
| if ( ( start < 0 ) || ( start > list.size() ) ) |
| { |
| throw new IllegalArgumentException( I18n.err( I18n.ERR_02005_START_INDEX_OUT_OF_RANGE, start ) ); |
| } |
| |
| if ( ( end < 0 ) || ( end > list.size() ) ) |
| { |
| throw new IllegalArgumentException( I18n.err( I18n.ERR_02006_END_INDEX_OUT_OF_RANGE, end ) ); |
| } |
| |
| // check list is not empty list since the empty list is the only situation |
| // where we allow for start to equal the end: in other cases it makes no sense |
| if ( !list.isEmpty() && ( start >= end ) ) |
| { |
| throw new IllegalArgumentException( I18n.err( I18n.ERR_02007_START_INDEX_ABOVE_END_INDEX, start, end ) ); |
| } |
| |
| if ( IS_DEBUG ) |
| { |
| LOG_CURSOR.debug( "Creating ListCursor {}", this ); |
| } |
| |
| this.comparator = comparator; |
| this.list = list; |
| this.start = start; |
| this.end = end; |
| } |
| |
| |
| /** |
| * Creates a new ListCursor with lower (inclusive) and upper (exclusive) |
| * bounds. |
| * |
| * As with all Cursors, this ListCursor requires a successful return from |
| * advance operations (next() or previous()) to properly return values |
| * using the get() operation. |
| * |
| * @param start the lower bound index |
| * @param list the list this ListCursor operates on |
| * @param end the upper bound index |
| */ |
| public ListCursor( int start, List<E> list, int end ) |
| { |
| this( null, start, list, end ); |
| } |
| |
| |
| /** |
| * Creates a new ListCursor with a specific upper (exclusive) bound: the |
| * lower (inclusive) bound defaults to 0. |
| * |
| * @param list the backing for this ListCursor |
| * @param end the upper bound index representing the position after the |
| * last element |
| */ |
| public ListCursor( List<E> list, int end ) |
| { |
| this( null, 0, list, end ); |
| } |
| |
| |
| /** |
| * Creates a new ListCursor with a specific upper (exclusive) bound: the |
| * lower (inclusive) bound defaults to 0. We also provide a comparator. |
| * |
| * @param comparator The comparator to use for the <E> elements |
| * @param list the backing for this ListCursor |
| * @param end the upper bound index representing the position after the |
| * last element |
| */ |
| public ListCursor( Comparator<E> comparator, List<E> list, int end ) |
| { |
| this( comparator, 0, list, end ); |
| } |
| |
| |
| /** |
| * Creates a new ListCursor with a lower (inclusive) bound: the upper |
| * (exclusive) bound is the size of the list. |
| * |
| * @param start the lower (inclusive) bound index: the position of the |
| * first entry |
| * @param list the backing for this ListCursor |
| */ |
| public ListCursor( int start, List<E> list ) |
| { |
| this( null, start, list, list.size() ); |
| } |
| |
| |
| /** |
| * Creates a new ListCursor with a lower (inclusive) bound: the upper |
| * (exclusive) bound is the size of the list. We also provide a comparator. |
| * |
| * @param comparator The comparator to use for the <E> elements |
| * @param start the lower (inclusive) bound index: the position of the |
| * first entry |
| * @param list the backing for this ListCursor |
| */ |
| public ListCursor( Comparator<E> comparator, int start, List<E> list ) |
| { |
| this( comparator, start, list, list.size() ); |
| } |
| |
| |
| /** |
| * Creates a new ListCursor without specific bounds: the bounds are |
| * acquired from the size of the list. |
| * |
| * @param list the backing for this ListCursor |
| */ |
| public ListCursor( List<E> list ) |
| { |
| this( null, 0, list, list.size() ); |
| } |
| |
| |
| /** |
| * Creates a new ListCursor without specific bounds: the bounds are |
| * acquired from the size of the list. We also provide a comparator. |
| * |
| * @param comparator The comparator to use for the <E> elements |
| * @param list the backing for this ListCursor |
| */ |
| public ListCursor( Comparator<E> comparator, List<E> list ) |
| { |
| this( comparator, 0, list, list.size() ); |
| } |
| |
| |
| /** |
| * Creates a new ListCursor without any elements. |
| */ |
| @SuppressWarnings("unchecked") |
| public ListCursor() |
| { |
| this( null, 0, Collections.EMPTY_LIST, 0 ); |
| } |
| |
| |
| /** |
| * Creates a new ListCursor without any elements. We also provide |
| * a comparator. |
| * |
| * @param comparator The comparator to use for the <E> elements |
| */ |
| @SuppressWarnings("unchecked") |
| public ListCursor( Comparator<E> comparator ) |
| { |
| this( comparator, 0, Collections.EMPTY_LIST, 0 ); |
| } |
| |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public boolean available() |
| { |
| return index >= 0 && index < end; |
| } |
| |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public void before( E element ) throws LdapException, CursorException |
| { |
| checkNotClosed( "before()" ); |
| |
| if ( comparator == null ) |
| { |
| throw new IllegalStateException(); |
| } |
| |
| // handle some special cases |
| if ( list.isEmpty() ) |
| { |
| return; |
| } |
| else if ( list.size() == 1 ) |
| { |
| if ( comparator.compare( element, list.get( 0 ) ) <= 0 ) |
| { |
| beforeFirst(); |
| } |
| else |
| { |
| afterLast(); |
| } |
| } |
| |
| throw new UnsupportedOperationException( I18n.err( I18n.ERR_02008_LIST_MAY_BE_SORTED ) ); |
| } |
| |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public void after( E element ) throws LdapException, CursorException |
| { |
| checkNotClosed( "after()" ); |
| |
| if ( comparator == null ) |
| { |
| throw new IllegalStateException(); |
| } |
| |
| // handle some special cases |
| if ( list.isEmpty() ) |
| { |
| return; |
| } |
| else if ( list.size() == 1 ) |
| { |
| if ( comparator.compare( element, list.get( 0 ) ) >= 0 ) |
| { |
| afterLast(); |
| } |
| else |
| { |
| beforeFirst(); |
| } |
| } |
| |
| throw new UnsupportedOperationException( I18n.err( I18n.ERR_02008_LIST_MAY_BE_SORTED ) ); |
| } |
| |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public void beforeFirst() throws LdapException, CursorException |
| { |
| checkNotClosed( "beforeFirst()" ); |
| this.index = -1; |
| } |
| |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public void afterLast() throws LdapException, CursorException |
| { |
| checkNotClosed( "afterLast()" ); |
| this.index = end; |
| } |
| |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public boolean first() throws LdapException, CursorException |
| { |
| checkNotClosed( "first()" ); |
| |
| if ( !list.isEmpty() ) |
| { |
| index = start; |
| |
| return true; |
| } |
| |
| return false; |
| } |
| |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public boolean last() throws LdapException, CursorException |
| { |
| checkNotClosed( "last()" ); |
| |
| if ( !list.isEmpty() ) |
| { |
| index = end - 1; |
| |
| return true; |
| } |
| |
| return false; |
| } |
| |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public boolean isFirst() |
| { |
| return !list.isEmpty() && index == start; |
| } |
| |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public boolean isLast() |
| { |
| return !list.isEmpty() && index == end - 1; |
| } |
| |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public boolean isAfterLast() |
| { |
| return index == end; |
| } |
| |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public boolean isBeforeFirst() |
| { |
| return index == -1; |
| } |
| |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public boolean previous() throws LdapException, CursorException |
| { |
| checkNotClosed( "previous()" ); |
| |
| // if parked at -1 we cannot go backwards |
| if ( index == -1 ) |
| { |
| return false; |
| } |
| |
| // if the index moved back is still greater than or eq to start then OK |
| if ( index - 1 >= start ) |
| { |
| index--; |
| |
| return true; |
| } |
| |
| // if the index currently less than or equal to start we need to park it at -1 and return false |
| if ( index <= start ) |
| { |
| index = -1; |
| |
| return false; |
| } |
| |
| if ( list.isEmpty() ) |
| { |
| index = -1; |
| } |
| |
| return false; |
| } |
| |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public boolean next() throws LdapException, CursorException |
| { |
| checkNotClosed( "next()" ); |
| |
| // if parked at -1 we advance to the start index and return true |
| if ( !list.isEmpty() && ( index == -1 ) ) |
| { |
| index = start; |
| |
| return true; |
| } |
| |
| // if the index plus one is less than the end then increment and return true |
| if ( !list.isEmpty() && ( index + 1 < end ) ) |
| { |
| index++; |
| |
| return true; |
| } |
| |
| // if the index plus one is equal to the end then increment and return false |
| if ( !list.isEmpty() && ( index + 1 == end ) ) |
| { |
| index++; |
| |
| return false; |
| } |
| |
| if ( list.isEmpty() ) |
| { |
| index = end; |
| } |
| |
| return false; |
| } |
| |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public E get() throws CursorException |
| { |
| checkNotClosed( "get()" ); |
| |
| if ( ( index < start ) || ( index >= end ) ) |
| { |
| throw new CursorException( I18n.err( I18n.ERR_02009_CURSOR_NOT_POSITIONED ) ); |
| } |
| |
| return list.get( index ); |
| } |
| |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public void close() throws IOException |
| { |
| if ( IS_DEBUG ) |
| { |
| LOG_CURSOR.debug( "Closing ListCursor {}", this ); |
| } |
| |
| super.close(); |
| } |
| |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public void close( Exception cause ) throws IOException |
| { |
| if ( IS_DEBUG ) |
| { |
| LOG_CURSOR.debug( "Closing ListCursor {}", this ); |
| } |
| |
| super.close( cause ); |
| } |
| } |