StoredIterator.java

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 2000-2005
 *      Sleepycat Software.  All rights reserved.
 *
 * $Id: StoredIterator.java,v 12.1 2005/01/31 19:27:32 mark Exp $
 */

package com.sleepycat.collections;

import java.util.Iterator;
import java.util.ListIterator;
import java.util.NoSuchElementException;

import com.sleepycat.db.DatabaseException;
import com.sleepycat.db.OperationStatus;

public class StoredIterator implements ListIterator, Cloneable {

    public static void close(Iterator i) {

        if (i instanceof StoredIterator) {
            ((StoredIterator) i).close();
        }
    }

    private static final int MOVE_NEXT = 1;
    private static final int MOVE_PREV = 2;
    private static final int MOVE_FIRST = 3;

    private boolean lockForWrite;
    private StoredCollection coll;
    private DataCursor cursor;
    private int toNext;
    private int toPrevious;
    private int toCurrent;
    private boolean writeAllowed;
    private boolean setAndRemoveAllowed;
    private Object currentData;
    private final boolean recNumAccess;

    StoredIterator(StoredCollection coll, boolean writeAllowed,
                   DataCursor joinCursor) {
        try {
            this.coll = coll;
            this.writeAllowed = writeAllowed;
            if (joinCursor == null)
                this.cursor = new DataCursor(coll.view, writeAllowed);
            else
                this.cursor = joinCursor;
            this.recNumAccess = cursor.hasRecNumAccess();
            reset();
        } catch (Exception e) {
            try {
                /* Ensure that the cursor is closed.  [#10516] */
                close();
            } catch (Exception ignored) {}
            throw StoredContainer.convertException(e);
        }
    }

    protected Object clone() {

        try {
            StoredIterator o = (StoredIterator) super.clone();
            o.cursor = cursor.cloneCursor();
            return o;
        } catch (Exception e) {
            throw StoredContainer.convertException(e);
        }
    }

    public final boolean isReadModifyWrite() {

        return lockForWrite;
    }

    public void setReadModifyWrite(boolean lockForWrite) {

        this.lockForWrite = lockForWrite;
    }

    // --- begin Iterator/ListIterator methods ---

    public boolean hasNext() {

        if (cursor == null) {
            return false;
        }
        try {
            if (toNext != 0) {
                OperationStatus status = move(toNext);
                if (status == OperationStatus.SUCCESS) {
                    toNext = 0;
                    toPrevious = MOVE_PREV;
                    toCurrent = MOVE_PREV;
                }
            }
            return (toNext == 0);
        }
        catch (Exception e) {
            throw StoredContainer.convertException(e);
        }
    }

    public boolean hasPrevious() {

        if (cursor == null) {
            return false;
        }
        try {
            if (toPrevious != 0) {
                OperationStatus status = move(toPrevious);
                if (status == OperationStatus.SUCCESS) {
                    toPrevious = 0;
                    toNext = MOVE_NEXT;
                    toCurrent = MOVE_NEXT;
                }
            }
            return (toPrevious == 0);
        } catch (Exception e) {
            throw StoredContainer.convertException(e);
        }
    }

    public Object next() {

        try {
            if (toNext != 0) {
                OperationStatus status = move(toNext);
                if (status == OperationStatus.SUCCESS) {
                    toNext = 0;
                }
            }
            if (toNext == 0) {
                currentData = coll.makeIteratorData(this, cursor);
                toNext = MOVE_NEXT;
                toPrevious = 0;
                toCurrent = 0;
                setAndRemoveAllowed = true;
                return currentData;
            }
            // else throw NoSuchElementException below
        } catch (Exception e) {
            throw StoredContainer.convertException(e);
        }
        throw new NoSuchElementException();
    }

    public Object previous() {

        try {
            if (toPrevious != 0) {
                OperationStatus status = move(toPrevious);
                if (status == OperationStatus.SUCCESS) {
                    toPrevious = 0;
                }
            }
            if (toPrevious == 0) {
                currentData = coll.makeIteratorData(this, cursor);
                toPrevious = MOVE_PREV;
                toNext = 0;
                toCurrent = 0;
                setAndRemoveAllowed = true;
                return currentData;
            }
            // else throw NoSuchElementException below
        } catch (Exception e) {
            throw StoredContainer.convertException(e);
        }
        throw new NoSuchElementException();
    }

    public int nextIndex() {

        if (!recNumAccess) {
            throw new UnsupportedOperationException(
                "Record number access not supported");
        }
        try {
            return hasNext() ? (cursor.getCurrentRecordNumber() -
                                coll.getIndexOffset())
                             : Integer.MAX_VALUE;
        } catch (Exception e) {
            throw StoredContainer.convertException(e);
        }
    }

    public int previousIndex() {

        if (!recNumAccess) {
            throw new UnsupportedOperationException(
                "Record number access not supported");
        }
        try {
            return hasPrevious() ? (cursor.getCurrentRecordNumber() -
                                    coll.getIndexOffset())
                                 : -1;
        } catch (Exception e) {
            throw StoredContainer.convertException(e);
        }
    }

    public void set(Object value) {

        if (!coll.hasValues()) throw new UnsupportedOperationException();
        if (!setAndRemoveAllowed) throw new IllegalStateException();
        try {
            moveToCurrent();
            cursor.putCurrent(value);
        } catch (Exception e) {
            throw StoredContainer.convertException(e);
        }
    }

    public void remove() {

        if (!setAndRemoveAllowed) throw new IllegalStateException();
        try {
            moveToCurrent();
            cursor.delete();
            setAndRemoveAllowed = false;
        } catch (Exception e) {
            throw StoredContainer.convertException(e);
        }
    }

    public void add(Object value) {

        coll.checkIterAddAllowed();
        try {
            OperationStatus status = OperationStatus.SUCCESS;
            if (toNext != 0 && toPrevious != 0) { // database is empty
                if (coll.view.keysRenumbered) { // recno-renumber database
                    /*
                     * Close cursor during append and then reopen to support
                     * CDB restriction that append may not be called with a
                     * cursor open; note the append will still fail if the
                     * application has another cursor open.
                     */
                    close();
                    status = coll.view.append(value, null, null);
                    cursor = new DataCursor(coll.view, writeAllowed);
                    reset();
                    next(); // move past new record
                } else { // hash/btree with duplicates
                    throw new IllegalStateException(
                        "Collection is empty, cannot add() duplicate");
                }
            } else { // database is not empty
                boolean putBefore = false;
                if (coll.view.keysRenumbered) { // recno-renumber database
                    moveToCurrent();
                    if (hasNext()) {
                        status = cursor.putBefore(value);
                        putBefore = true;
                    } else {
                        status = cursor.putAfter(value);
                    }
                } else { // hash/btree with duplicates
                    if (coll.areDuplicatesOrdered()) {
                        status = cursor.putNoDupData(null, value, null, true);
                    } else if (toNext == 0) {
                        status = cursor.putBefore(value);
                        putBefore = true;
                    } else {
                        status = cursor.putAfter(value);
                    }
                }
                if (putBefore) {
                    toPrevious = 0;
                    toNext = MOVE_NEXT;
                }
            }
            if (status == OperationStatus.KEYEXIST) {
                throw new IllegalArgumentException("Duplicate value");
            } else if (status != OperationStatus.SUCCESS) {
                throw new IllegalArgumentException("Could not insert: " +
                                                    status);
            }
            setAndRemoveAllowed = false;
        } catch (Exception e) {
            throw StoredContainer.convertException(e);
        }
    }

    // --- end Iterator/ListIterator methods ---

    private void reset() {

        toNext = MOVE_FIRST;
        toPrevious = MOVE_PREV;
        toCurrent = 0;
        currentData = null;
        /* 
         * Initialize cursor at beginning to avoid "initial previous == last"
         * behavior when cursor is uninitialized.
         *
         * FindBugs whines about us ignoring the return value from hasNext().
         */
        hasNext();
    }

    public int count() {

        if (!setAndRemoveAllowed) throw new IllegalStateException();
        try {
            moveToCurrent();
            return cursor.count();
        } catch (Exception e) {
            throw StoredContainer.convertException(e);
        }
    }

    public void close() {

        if (cursor != null) {
            coll.closeCursor(cursor);
            cursor = null;
        }
    }

    public final StoredCollection getCollection() {

        return coll;
    }

    final boolean isCurrentData(Object currentData) {

        return (this.currentData == currentData);
    }

    final boolean moveToIndex(int index) {

        try {
            OperationStatus status =
                cursor.getSearchKey(new Integer(index), null, lockForWrite);
            setAndRemoveAllowed = (status == OperationStatus.SUCCESS);
            return setAndRemoveAllowed;
        } catch (Exception e) {
            throw StoredContainer.convertException(e);
        }
    }

    private void moveToCurrent()
        throws DatabaseException {

        if (toCurrent != 0) {
            move(toCurrent);
            toCurrent = 0;
        }
    }

    private OperationStatus move(int direction)
        throws DatabaseException {

        switch (direction) {
            case MOVE_NEXT:
                if (coll.iterateDuplicates()) {
                    return cursor.getNext(lockForWrite);
                } else {
                    return cursor.getNextNoDup(lockForWrite);
                }
            case MOVE_PREV:
                if (coll.iterateDuplicates()) {
                    return cursor.getPrev(lockForWrite);
                } else {
                    return cursor.getPrevNoDup(lockForWrite);
                }
            case MOVE_FIRST:
                return cursor.getFirst(lockForWrite);
            default:
                throw new IllegalArgumentException(String.valueOf(direction));
        }
    }
}

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