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- /*
- Copyright (c) 2013 James Ahlborn
-
- Licensed 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 com.healthmarketscience.jackcess.impl;
-
- import java.io.IOException;
-
- import com.healthmarketscience.jackcess.impl.TableImpl.RowState;
-
-
- /**
- * Simple un-indexed cursor.
- *
- * @author James Ahlborn
- */
- public class TableScanCursor extends CursorImpl
- {
- /** first position for the TableScanCursor */
- private static final ScanPosition FIRST_SCAN_POSITION =
- new ScanPosition(RowIdImpl.FIRST_ROW_ID);
- /** last position for the TableScanCursor */
- private static final ScanPosition LAST_SCAN_POSITION =
- new ScanPosition(RowIdImpl.LAST_ROW_ID);
-
-
- /** ScanDirHandler for forward traversal */
- private final ScanDirHandler _forwardDirHandler =
- new ForwardScanDirHandler();
- /** ScanDirHandler for backward traversal */
- private final ScanDirHandler _reverseDirHandler =
- new ReverseScanDirHandler();
- /** Cursor over the pages that this table owns */
- private final UsageMap.PageCursor _ownedPagesCursor;
-
- public TableScanCursor(TableImpl table) {
- super(new IdImpl(table, null), table,
- FIRST_SCAN_POSITION, LAST_SCAN_POSITION);
- _ownedPagesCursor = table.getOwnedPagesCursor();
- }
-
- @Override
- protected ScanDirHandler getDirHandler(boolean moveForward) {
- return (moveForward ? _forwardDirHandler : _reverseDirHandler);
- }
-
- @Override
- protected boolean isUpToDate() {
- return(super.isUpToDate() && _ownedPagesCursor.isUpToDate());
- }
-
- @Override
- protected void reset(boolean moveForward) {
- _ownedPagesCursor.reset(moveForward);
- super.reset(moveForward);
- }
-
- @Override
- protected void restorePositionImpl(PositionImpl curPos, PositionImpl prevPos)
- throws IOException
- {
- if(!(curPos instanceof ScanPosition) ||
- !(prevPos instanceof ScanPosition)) {
- throw new IllegalArgumentException(
- "Restored positions must be scan positions");
- }
- _ownedPagesCursor.restorePosition(curPos.getRowId().getPageNumber(),
- prevPos.getRowId().getPageNumber());
- super.restorePositionImpl(curPos, prevPos);
- }
-
- @Override
- protected PositionImpl getRowPosition(RowIdImpl rowId) throws IOException
- {
- return new ScanPosition(rowId);
- }
-
- @Override
- protected PositionImpl findAnotherPosition(
- RowState rowState, PositionImpl curPos, boolean moveForward)
- throws IOException
- {
- ScanDirHandler handler = getDirHandler(moveForward);
-
- // figure out how many rows are left on this page so we can find the
- // next row
- RowIdImpl curRowId = curPos.getRowId();
- TableImpl.positionAtRowHeader(rowState, curRowId);
- int currentRowNumber = curRowId.getRowNumber();
-
- // loop until we find the next valid row or run out of pages
- while(true) {
-
- currentRowNumber = handler.getAnotherRowNumber(currentRowNumber);
- curRowId = new RowIdImpl(curRowId.getPageNumber(), currentRowNumber);
- TableImpl.positionAtRowHeader(rowState, curRowId);
-
- if(!rowState.isValid()) {
-
- // load next page
- curRowId = new RowIdImpl(handler.getAnotherPageNumber(),
- RowIdImpl.INVALID_ROW_NUMBER);
- TableImpl.positionAtRowHeader(rowState, curRowId);
-
- if(!rowState.isHeaderPageNumberValid()) {
- //No more owned pages. No more rows.
- return handler.getEndPosition();
- }
-
- // update row count and initial row number
- currentRowNumber = handler.getInitialRowNumber(
- rowState.getRowsOnHeaderPage());
-
- } else if(!rowState.isDeleted()) {
-
- // we found a valid, non-deleted row, return it
- return new ScanPosition(curRowId);
- }
-
- }
- }
-
- /**
- * Handles moving the table scan cursor in a given direction. Separates
- * cursor logic from value storage.
- */
- private abstract class ScanDirHandler extends DirHandler {
- public abstract int getAnotherRowNumber(int curRowNumber);
- public abstract int getAnotherPageNumber();
- public abstract int getInitialRowNumber(int rowsOnPage);
- }
-
- /**
- * Handles moving the table scan cursor forward.
- */
- private final class ForwardScanDirHandler extends ScanDirHandler {
- @Override
- public PositionImpl getBeginningPosition() {
- return getFirstPosition();
- }
- @Override
- public PositionImpl getEndPosition() {
- return getLastPosition();
- }
- @Override
- public int getAnotherRowNumber(int curRowNumber) {
- return curRowNumber + 1;
- }
- @Override
- public int getAnotherPageNumber() {
- return _ownedPagesCursor.getNextPage();
- }
- @Override
- public int getInitialRowNumber(int rowsOnPage) {
- return -1;
- }
- }
-
- /**
- * Handles moving the table scan cursor backward.
- */
- private final class ReverseScanDirHandler extends ScanDirHandler {
- @Override
- public PositionImpl getBeginningPosition() {
- return getLastPosition();
- }
- @Override
- public PositionImpl getEndPosition() {
- return getFirstPosition();
- }
- @Override
- public int getAnotherRowNumber(int curRowNumber) {
- return curRowNumber - 1;
- }
- @Override
- public int getAnotherPageNumber() {
- return _ownedPagesCursor.getPreviousPage();
- }
- @Override
- public int getInitialRowNumber(int rowsOnPage) {
- return rowsOnPage;
- }
- }
-
- /**
- * Value object which maintains the current position of a TableScanCursor.
- */
- private static final class ScanPosition extends PositionImpl
- {
- private final RowIdImpl _rowId;
-
- private ScanPosition(RowIdImpl rowId) {
- _rowId = rowId;
- }
-
- @Override
- public RowIdImpl getRowId() {
- return _rowId;
- }
-
- @Override
- protected boolean equalsImpl(Object o) {
- return getRowId().equals(((ScanPosition)o).getRowId());
- }
-
- @Override
- public String toString() {
- return "RowId = " + getRowId();
- }
- }
- }
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