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/*
* Copyright 2004-2010 H2 Group. Multiple-Licensed under the H2 License,
* Version 1.0, and under the Eclipse Public License, Version 1.0
* (http://h2database.com/html/license.html).
* Initial Developer: H2 Group
*/
package org.h2.store;
import java.io.IOException;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.zip.CRC32;
import org.h2.command.CommandInterface;
import org.h2.command.ddl.CreateTableData;
import org.h2.constant.ErrorCode;
import org.h2.constant.SysProperties;
import org.h2.engine.Constants;
import org.h2.engine.Database;
import org.h2.engine.Session;
import org.h2.index.Cursor;
import org.h2.index.Index;
import org.h2.index.IndexType;
import org.h2.index.MultiVersionIndex;
import org.h2.index.PageBtreeIndex;
import org.h2.index.PageBtreeLeaf;
import org.h2.index.PageBtreeNode;
import org.h2.index.PageDataIndex;
import org.h2.index.PageDataLeaf;
import org.h2.index.PageDataNode;
import org.h2.index.PageDataOverflow;
import org.h2.index.PageDelegateIndex;
import org.h2.index.PageIndex;
import org.h2.message.DbException;
import org.h2.message.Trace;
import org.h2.result.Row;
import org.h2.schema.Schema;
import org.h2.table.Column;
import org.h2.table.IndexColumn;
import org.h2.table.RegularTable;
import org.h2.table.Table;
import org.h2.util.BitField;
import org.h2.util.Cache;
import org.h2.util.CacheLRU;
import org.h2.util.CacheObject;
import org.h2.util.CacheWriter;
import org.h2.util.IOUtils;
import org.h2.util.IntArray;
import org.h2.util.IntIntHashMap;
import org.h2.util.New;
import org.h2.util.StatementBuilder;
import org.h2.util.StringUtils;
import org.h2.value.CompareMode;
import org.h2.value.Value;
import org.h2.value.ValueInt;
import org.h2.value.ValueString;
/**
* This class represents a file that is organized as a number of pages. Page 0
* contains a static file header, and pages 1 and 2 both contain the variable
* file header (page 2 is a copy of page 1 and is only read if the checksum of
* page 1 is invalid). The format of page 0 is:
*
*
0-47: file header (3 time "-- H2 0.5/B -- \n")
*
48-51: page size in bytes (512 - 32768, must be a power of 2)
*
52: write version (read-only if larger than 1)
*
53: read version (opening fails if larger than 1)
*
* The format of page 1 and 2 is:
*
*
CRC32 of the remaining data: int (0-3)
*
write counter (incremented on each write): long (4-11)
*
log trunk key: int (12-15)
*
log trunk page (0 for none): int (16-19)
*
log data page (0 for none): int (20-23)
*
* Page 3 contains the first free list page.
* Page 4 contains the meta table root page.
*/
public class PageStore implements CacheWriter {
// TODO test running out of disk space (using a special file system)
// TODO unused pages should be freed once in a while
// TODO node row counts are incorrect (it's not splitting row counts)
// TODO after opening the database, delay writing until required
// TODO optimization: try to avoid allocating a byte array per page
// TODO optimization: check if calling Data.getValueLen slows things down
// TODO order pages so that searching for a key only seeks forward
// TODO optimization: update: only log the key and changed values
// TODO index creation: use less space (ordered, split at insertion point)
// TODO detect circles in linked lists
// (input stream, free list, extend pages...)
// at runtime and recovery
// TODO remove trace or use isDebugEnabled
// TODO recover tool: support syntax to delete a row with a key
// TODO don't store default values (store a special value)
// TODO check for file size (exception if not exact size expected)
// TODO online backup using bsdiff
/**
* The smallest possible page size.
*/
public static final int PAGE_SIZE_MIN = 64;
/**
* The biggest possible page size.
*/
public static final int PAGE_SIZE_MAX = 32768;
/**
* This log mode means the transaction log is not used.
*/
public static final int LOG_MODE_OFF = 0;
/**
* This log mode means the transaction log is used and FileDescriptor.sync()
* is called for each checkpoint. This is the default level.
*/
public static final int LOG_MODE_SYNC = 2;
private static final int PAGE_ID_FREE_LIST_ROOT = 3;
private static final int PAGE_ID_META_ROOT = 4;
private static final int MIN_PAGE_COUNT = 6;
private static final int INCREMENT_KB = 1024;
private static final int INCREMENT_PERCENT_MIN = 20;
private static final int READ_VERSION = 3;
private static final int WRITE_VERSION = 3;
private static final int META_TYPE_DATA_INDEX = 0;
private static final int META_TYPE_BTREE_INDEX = 1;
private static final int META_TABLE_ID = -1;
private static final int COMPACT_BLOCK_SIZE = 1536;
private Database database;
private final Trace trace;
private String fileName;
private FileStore file;
private String accessMode;
private int pageSize = SysProperties.PAGE_SIZE;
private int pageSizeShift;
private long writeCountBase, writeCount, readCount;
private int logKey, logFirstTrunkPage, logFirstDataPage;
private Cache cache;
private int freeListPagesPerList;
private boolean recoveryRunning;
/**
* The file size in bytes.
*/
private long fileLength;
/**
* Number of pages (including free pages).
*/
private int pageCount;
private PageLog log;
private Schema metaSchema;
private RegularTable metaTable;
private PageDataIndex metaIndex;
private IntIntHashMap metaRootPageId = new IntIntHashMap();
private HashMap metaObjects = New.hashMap();
private HashMap tempObjects;
/**
* The map of reserved pages, to ensure index head pages
* are not used for regular data during recovery. The key is the page id,
* and the value the latest transaction position where this page is used.
*/
private HashMap reservedPages;
private boolean isNew;
private long maxLogSize = Constants.DEFAULT_MAX_LOG_SIZE;
private Session systemSession;
private BitField freed = new BitField();
private ArrayList freeLists = New.arrayList();
private boolean recordPageReads;
private ArrayList recordedPagesList;
private IntIntHashMap recordedPagesIndex;
/**
* The change count is something like a "micro-transaction-id".
* It is used to ensure that changed pages are not written to the file
* before the the current operation is not finished. This is only a problem
* when using a very small cache size. The value starts at 1 so that
* pages with change count 0 can be evicted from the cache.
*/
private int changeCount = 1;
private Data emptyPage;
private long logSizeBase;
private HashMap statistics;
private int logMode = LOG_MODE_SYNC;
private boolean lockFile;
/**
* Create a new page store object.
*
* @param database the database
* @param fileName the file name
* @param accessMode the access mode
* @param cacheSizeDefault the default cache size
*/
public PageStore(Database database, String fileName, String accessMode, int cacheSizeDefault) {
this.fileName = fileName;
this.accessMode = accessMode;
this.database = database;
trace = database.getTrace(Trace.PAGE_STORE);
// if (fileName.endsWith("X.h2.db"))
// trace.setLevel(TraceSystem.DEBUG);
String cacheType = database.getCacheType();
this.cache = CacheLRU.getCache(this, cacheType, cacheSizeDefault);
systemSession = new Session(database, null, 0);
}
/**
* Start collecting statistics.
*/
public void statisticsStart() {
statistics = New.hashMap();
}
/**
* Stop collecting statistics.
*
* @return the statistics
*/
public HashMap statisticsEnd() {
HashMap result = statistics;
statistics = null;
return result;
}
private void statisticsIncrement(String key) {
if (statistics != null) {
Integer old = statistics.get(key);
statistics.put(key, old == null ? 1 : old + 1);
}
}
/**
* Copy the next page to the output stream.
*
* @param pageId the page to copy
* @param out the output stream
* @return the new position, or -1 if there is no more data to copy
*/
public int copyDirect(int pageId, OutputStream out) throws IOException {
synchronized (database) {
byte[] buffer = new byte[pageSize];
if (pageId >= pageCount) {
return -1;
}
file.seek((long) pageId << pageSizeShift);
file.readFullyDirect(buffer, 0, pageSize);
readCount++;
out.write(buffer, 0, pageSize);
return pageId + 1;
}
}
/**
* Open the file and read the header.
*/
public void open() {
try {
metaRootPageId.put(META_TABLE_ID, PAGE_ID_META_ROOT);
if (IOUtils.exists(fileName)) {
long length = IOUtils.length(fileName);
if (length < MIN_PAGE_COUNT * PAGE_SIZE_MIN) {
if (database.isReadOnly()) {
throw DbException.get(ErrorCode.FILE_CORRUPTED_1, fileName + " length: " + length);
}
// the database was not fully created
openNew();
} else {
openExisting();
}
} else {
openNew();
}
} catch (DbException e) {
close();
throw e;
}
}
private void openNew() {
setPageSize(pageSize);
freeListPagesPerList = PageFreeList.getPagesAddressed(pageSize);
file = database.openFile(fileName, accessMode, false);
lockFile();
recoveryRunning = true;
writeStaticHeader();
writeVariableHeader();
log = new PageLog(this);
increaseFileSize(MIN_PAGE_COUNT);
openMetaIndex();
logFirstTrunkPage = allocatePage();
log.openForWriting(logFirstTrunkPage, false);
isNew = true;
recoveryRunning = false;
increaseFileSize();
}
private void lockFile() {
if (lockFile) {
if (!file.tryLock()) {
throw DbException.get(ErrorCode.DATABASE_ALREADY_OPEN_1, fileName);
}
}
}
private void openExisting() {
try {
file = database.openFile(fileName, accessMode, true);
} catch (DbException e) {
// in Windows, you can't open a locked file
// (in other operating systems, you can)
if (e.getErrorCode() == ErrorCode.IO_EXCEPTION_2) {
throw DbException.get(ErrorCode.DATABASE_ALREADY_OPEN_1, e, fileName);
}
throw e;
}
lockFile();
readStaticHeader();
freeListPagesPerList = PageFreeList.getPagesAddressed(pageSize);
fileLength = file.length();
pageCount = (int) (fileLength / pageSize);
if (pageCount < MIN_PAGE_COUNT) {
if (database.isReadOnly()) {
throw DbException.get(ErrorCode.FILE_CORRUPTED_1, fileName + " pageCount: " + pageCount);
}
file.releaseLock();
file.close();
IOUtils.delete(fileName);
openNew();
return;
}
readVariableHeader();
log = new PageLog(this);
log.openForReading(logKey, logFirstTrunkPage, logFirstDataPage);
boolean old = database.isMultiVersion();
// temporarily disabling multi-version concurrency, because
// the multi-version index sometimes compares rows
// and the LOB storage is not yet available.
database.setMultiVersion(false);
recover();
database.setMultiVersion(old);
if (!database.isReadOnly()) {
recoveryRunning = true;
log.free();
logFirstTrunkPage = allocatePage();
log.openForWriting(logFirstTrunkPage, false);
recoveryRunning = false;
freed.set(0, pageCount, true);
checkpoint();
removeOldTempIndexes();
}
}
private void removeOldTempIndexes() {
if (tempObjects != null) {
metaObjects.putAll(tempObjects);
for (PageIndex index: tempObjects.values()) {
if (index.getTable().isTemporary()) {
index.truncate(systemSession);
index.remove(systemSession);
}
}
systemSession.commit(true);
tempObjects = null;
}
metaObjects.clear();
metaObjects.put(-1, metaIndex);
}
private void writeIndexRowCounts() {
for (PageIndex index: metaObjects.values()) {
index.writeRowCount();
}
}
private void writeBack() {
ArrayList list = cache.getAllChanged();
Collections.sort(list);
for (int i = 0, size = list.size(); i < size; i++) {
writeBack(list.get(i));
}
}
/**
* Flush all pending changes to disk, and switch the new transaction log.
*/
public void checkpoint() {
trace.debug("checkpoint");
if (log == null || database.isReadOnly()) {
// the file was never fully opened
return;
}
synchronized (database) {
database.checkPowerOff();
writeIndexRowCounts();
log.checkpoint();
writeBack();
int firstUncommittedSection = getFirstUncommittedSection();
log.removeUntil(firstUncommittedSection);
// write back the free list
writeBack();
// ensure the free list is backed up again
log.checkpoint();
if (trace.isDebugEnabled()) {
trace.debug("writeFree");
}
byte[] test = new byte[16];
byte[] empty = new byte[pageSize];
for (int i = PAGE_ID_FREE_LIST_ROOT; i < pageCount; i++) {
if (isUsed(i)) {
freed.clear(i);
} else if (!freed.get(i)) {
if (trace.isDebugEnabled()) {
trace.debug("free " + i);
}
file.seek((long) i << pageSizeShift);
file.readFully(test, 0, 16);
if (test[0] != 0) {
file.seek((long) i << pageSizeShift);
file.write(empty, 0, pageSize);
writeCount++;
}
freed.set(i);
}
}
}
}
/**
* Shrink the file so there are no empty pages at the end.
*
* @param compactMode 0 if no compacting should happen, otherwise
* TransactionCommand.SHUTDOWN_COMPACT or TransactionCommand.SHUTDOWN_DEFRAG
*/
public void compact(int compactMode) {
if (!SysProperties.PAGE_STORE_TRIM) {
return;
}
// find the last used page
int lastUsed = -1;
for (int i = getFreeListId(pageCount); i >= 0; i--) {
lastUsed = getFreeList(i).getLastUsed();
if (lastUsed != -1) {
break;
}
}
// open a new log at the very end
// (to be truncated later)
writeBack();
log.free();
recoveryRunning = true;
try {
logFirstTrunkPage = lastUsed + 1;
allocatePage(logFirstTrunkPage);
log.openForWriting(logFirstTrunkPage, true);
// ensure the free list is backed up again
log.checkpoint();
} finally {
recoveryRunning = false;
}
long start = System.currentTimeMillis();
boolean isCompactFully = compactMode == CommandInterface.SHUTDOWN_COMPACT;
boolean isDefrag = compactMode == CommandInterface.SHUTDOWN_DEFRAG;
if (SysProperties.defragAlways) {
isCompactFully = isDefrag = true;
}
int maxCompactTime = SysProperties.MAX_COMPACT_TIME;
int maxMove = SysProperties.MAX_COMPACT_COUNT;
if (isCompactFully || isDefrag) {
maxCompactTime = Integer.MAX_VALUE;
maxMove = Integer.MAX_VALUE;
}
int blockSize = isCompactFully ? COMPACT_BLOCK_SIZE : 1;
int firstFree = MIN_PAGE_COUNT;
for (int x = lastUsed, j = 0; x > MIN_PAGE_COUNT && j < maxMove; x -= blockSize) {
for (int full = x - blockSize + 1; full <= x; full++) {
if (full > MIN_PAGE_COUNT && isUsed(full)) {
synchronized (database) {
firstFree = getFirstFree(firstFree);
if (firstFree == -1 || firstFree >= full) {
j = maxMove;
break;
}
if (compact(full, firstFree)) {
j++;
long now = System.currentTimeMillis();
if (now > start + maxCompactTime) {
j = maxMove;
break;
}
}
}
}
}
}
if (isDefrag) {
writeBack();
cache.clear();
ArrayList
tables = database.getAllTablesAndViews(false);
recordedPagesList = New.arrayList();
recordedPagesIndex = new IntIntHashMap();
recordPageReads = true;
Session s = database.getSystemSession();
for (Table table : tables) {
if (!table.isTemporary() && table.getTableType().equals(Table.TABLE)) {
Index scanIndex = table.getScanIndex(s);
Cursor cursor = scanIndex.find(s, null, null);
while (cursor.next()) {
cursor.get();
}
for (Index index : table.getIndexes()) {
if (index != scanIndex) {
cursor = index.find(s, null, null);
while (cursor.next()) {
// the data is already read
}
}
}
}
}
recordPageReads = false;
int target = MIN_PAGE_COUNT - 1;
int temp = 0;
for (int i = 0, size = recordedPagesList.size(); i < size; i++) {
writeBack();
int source = recordedPagesList.get(i);
Page pageSource = getPage(source);
if (!pageSource.canMove()) {
continue;
}
while (true) {
Page pageTarget = getPage(++target);
if (pageTarget == null || pageTarget.canMove()) {
break;
}
}
if (target == source) {
continue;
}
temp = getFirstFree(temp);
if (temp == -1) {
DbException.throwInternalError("no free page for defrag");
}
cache.clear();
swap(source, target, temp);
int index = recordedPagesIndex.get(target);
if (index != IntIntHashMap.NOT_FOUND) {
recordedPagesList.set(index, source);
recordedPagesIndex.put(source, index);
}
recordedPagesList.set(i, target);
recordedPagesIndex.put(target, i);
}
recordedPagesList = null;
recordedPagesIndex = null;
}
// TODO can most likely be simplified
checkpoint();
log.checkpoint();
writeIndexRowCounts();
log.checkpoint();
writeBack();
commit(systemSession);
writeBack();
log.checkpoint();
log.free();
// truncate the log
recoveryRunning = true;
try {
setLogFirstPage(0, 0, 0);
} finally {
recoveryRunning = false;
}
writeBack();
for (int i = getFreeListId(pageCount); i >= 0; i--) {
lastUsed = getFreeList(i).getLastUsed();
if (lastUsed != -1) {
break;
}
}
int newPageCount = lastUsed + 1;
if (newPageCount < pageCount) {
freed.set(newPageCount, pageCount, false);
}
pageCount = newPageCount;
// the easiest way to remove superfluous entries
freeLists.clear();
trace.debug("pageCount:" + pageCount);
long newLength = (long) pageCount << pageSizeShift;
if (file.length() != newLength) {
file.setLength(newLength);
writeCount++;
}
}
private int getFirstFree(int start) {
int free = -1;
for (int id = getFreeListId(start); start < pageCount; id++) {
free = getFreeList(id).getFirstFree(start);
if (free != -1) {
break;
}
}
return free;
}
private void swap(int a, int b, int free) {
if (a < MIN_PAGE_COUNT || b < MIN_PAGE_COUNT) {
System.out.println(isUsed(a) + " " + isUsed(b));
DbException.throwInternalError("can't swap " + a + " and " + b);
}
Page f = (Page) cache.get(free);
if (f != null) {
DbException.throwInternalError("not free: " + f);
}
trace.debug("swap " + a + " and " + b + " via " + free);
Page pageA = null;
if (isUsed(a)) {
pageA = getPage(a);
if (pageA != null) {
pageA.moveTo(systemSession, free);
}
free(a);
}
if (free != b) {
if (isUsed(b)) {
Page pageB = getPage(b);
if (pageB != null) {
pageB.moveTo(systemSession, a);
}
free(b);
}
if (pageA != null) {
f = getPage(free);
if (f != null) {
f.moveTo(systemSession, b);
}
free(free);
}
}
}
private boolean compact(int full, int free) {
if (full < MIN_PAGE_COUNT || free == -1 || free >= full || !isUsed(full)) {
return false;
}
Page f = (Page) cache.get(free);
if (f != null) {
DbException.throwInternalError("not free: " + f);
}
Page p = getPage(full);
if (p != null) {
trace.debug("move " + p.getPos() + " to " + free);
try {
p.moveTo(systemSession, free);
} finally {
changeCount++;
}
} else {
freePage(full);
}
return true;
}
/**
* Read a page from the store.
*
* @param pageId the page id
* @return the page
*/
public Page getPage(int pageId) {
synchronized (database) {
Page p = (Page) cache.get(pageId);
if (p != null) {
return p;
}
Data data = createData();
readPage(pageId, data);
int type = data.readByte();
if (type == Page.TYPE_EMPTY) {
return null;
}
data.readShortInt();
data.readInt();
if (!checksumTest(data.getBytes(), pageId, pageSize)) {
throw DbException.get(ErrorCode.FILE_CORRUPTED_1, "wrong checksum");
}
switch (type & ~Page.FLAG_LAST) {
case Page.TYPE_FREE_LIST:
p = PageFreeList.read(this, data, pageId);
break;
case Page.TYPE_DATA_LEAF: {
int indexId = data.readVarInt();
PageIndex idx = metaObjects.get(indexId);
if (idx == null) {
throw DbException.get(ErrorCode.FILE_CORRUPTED_1, "index not found " + indexId);
}
if (!(idx instanceof PageDataIndex)) {
throw DbException.get(ErrorCode.FILE_CORRUPTED_1, "not a data index " + indexId + " " + idx);
}
PageDataIndex index = (PageDataIndex) idx;
if (statistics != null) {
statisticsIncrement(index.getTable().getName() + "." + index.getName() + " read");
}
p = PageDataLeaf.read(index, data, pageId);
break;
}
case Page.TYPE_DATA_NODE: {
int indexId = data.readVarInt();
PageIndex idx = metaObjects.get(indexId);
if (idx == null) {
throw DbException.get(ErrorCode.FILE_CORRUPTED_1, "index not found " + indexId);
}
if (!(idx instanceof PageDataIndex)) {
throw DbException.get(ErrorCode.FILE_CORRUPTED_1, "not a data index " + indexId + " " + idx);
}
PageDataIndex index = (PageDataIndex) idx;
if (statistics != null) {
statisticsIncrement(index.getTable().getName() + "." + index.getName() + " read");
}
p = PageDataNode.read(index, data, pageId);
break;
}
case Page.TYPE_DATA_OVERFLOW: {
p = PageDataOverflow.read(this, data, pageId);
if (statistics != null) {
statisticsIncrement("overflow read");
}
break;
}
case Page.TYPE_BTREE_LEAF: {
int indexId = data.readVarInt();
PageIndex idx = metaObjects.get(indexId);
if (idx == null) {
throw DbException.get(ErrorCode.FILE_CORRUPTED_1, "index not found " + indexId);
}
if (!(idx instanceof PageBtreeIndex)) {
throw DbException.get(ErrorCode.FILE_CORRUPTED_1, "not a btree index " + indexId + " " + idx);
}
PageBtreeIndex index = (PageBtreeIndex) idx;
if (statistics != null) {
statisticsIncrement(index.getTable().getName() + "." + index.getName() + " read");
}
p = PageBtreeLeaf.read(index, data, pageId);
break;
}
case Page.TYPE_BTREE_NODE: {
int indexId = data.readVarInt();
PageIndex idx = metaObjects.get(indexId);
if (idx == null) {
throw DbException.get(ErrorCode.FILE_CORRUPTED_1, "index not found " + indexId);
}
if (!(idx instanceof PageBtreeIndex)) {
throw DbException.get(ErrorCode.FILE_CORRUPTED_1, "not a btree index " + indexId + " " + idx);
}
PageBtreeIndex index = (PageBtreeIndex) idx;
if (statistics != null) {
statisticsIncrement(index.getTable().getName() + "." + index.getName() + " read");
}
p = PageBtreeNode.read(index, data, pageId);
break;
}
case Page.TYPE_STREAM_TRUNK:
p = PageStreamTrunk.read(this, data, pageId);
break;
case Page.TYPE_STREAM_DATA:
p = PageStreamData.read(this, data, pageId);
break;
default:
throw DbException.get(ErrorCode.FILE_CORRUPTED_1, "page=" + pageId + " type=" + type);
}
cache.put(p);
return p;
}
}
private int getFirstUncommittedSection() {
trace.debug("getFirstUncommittedSection");
Session[] sessions = database.getSessions(true);
int firstUncommittedSection = log.getLogSectionId();
for (Session session : sessions) {
int firstUncommitted = session.getFirstUncommittedLog();
if (firstUncommitted != Session.LOG_WRITTEN) {
if (firstUncommitted < firstUncommittedSection) {
firstUncommittedSection = firstUncommitted;
}
}
}
return firstUncommittedSection;
}
private void readStaticHeader() {
file.seek(FileStore.HEADER_LENGTH);
Data page = Data.create(database, new byte[PAGE_SIZE_MIN - FileStore.HEADER_LENGTH]);
file.readFully(page.getBytes(), 0, PAGE_SIZE_MIN - FileStore.HEADER_LENGTH);
readCount++;
setPageSize(page.readInt());
int writeVersion = page.readByte();
int readVersion = page.readByte();
if (readVersion > READ_VERSION) {
throw DbException.get(ErrorCode.FILE_VERSION_ERROR_1, fileName);
}
if (writeVersion > WRITE_VERSION) {
close();
database.setReadOnly(true);
accessMode = "r";
file = database.openFile(fileName, accessMode, true);
}
}
private void readVariableHeader() {
Data page = createData();
for (int i = 1;; i++) {
if (i == 3) {
throw DbException.get(ErrorCode.FILE_CORRUPTED_1, fileName);
}
page.reset();
readPage(i, page);
CRC32 crc = new CRC32();
crc.update(page.getBytes(), 4, pageSize - 4);
int expected = (int) crc.getValue();
int got = page.readInt();
if (expected == got) {
writeCountBase = page.readLong();
logKey = page.readInt();
logFirstTrunkPage = page.readInt();
logFirstDataPage = page.readInt();
break;
}
}
}
/**
* Set the page size. The size must be a power of two. This method must be
* called before opening.
*
* @param size the page size
*/
public void setPageSize(int size) {
if (size < PAGE_SIZE_MIN || size > PAGE_SIZE_MAX) {
throw DbException.get(ErrorCode.FILE_CORRUPTED_1, fileName + " pageSize: " + size);
}
boolean good = false;
int shift = 0;
for (int i = 1; i <= size;) {
if (size == i) {
good = true;
break;
}
shift++;
i += i;
}
if (!good) {
throw DbException.get(ErrorCode.FILE_CORRUPTED_1, fileName);
}
pageSize = size;
emptyPage = createData();
pageSizeShift = shift;
}
private void writeStaticHeader() {
Data page = Data.create(database, new byte[pageSize - FileStore.HEADER_LENGTH]);
page.writeInt(pageSize);
page.writeByte((byte) WRITE_VERSION);
page.writeByte((byte) READ_VERSION);
file.seek(FileStore.HEADER_LENGTH);
file.write(page.getBytes(), 0, pageSize - FileStore.HEADER_LENGTH);
writeCount++;
}
/**
* Set the trunk page and data page id of the log.
*
* @param logKey the log key of the trunk page
* @param trunkPageId the trunk page id
* @param dataPageId the data page id
*/
void setLogFirstPage(int logKey, int trunkPageId, int dataPageId) {
if (trace.isDebugEnabled()) {
trace.debug("setLogFirstPage key: " + logKey + " trunk: " + trunkPageId + " data: " + dataPageId);
}
this.logKey = logKey;
this.logFirstTrunkPage = trunkPageId;
this.logFirstDataPage = dataPageId;
writeVariableHeader();
}
private void writeVariableHeader() {
trace.debug("writeVariableHeader");
if (logMode == LOG_MODE_SYNC) {
file.sync();
}
Data page = createData();
page.writeInt(0);
page.writeLong(getWriteCountTotal());
page.writeInt(logKey);
page.writeInt(logFirstTrunkPage);
page.writeInt(logFirstDataPage);
CRC32 crc = new CRC32();
crc.update(page.getBytes(), 4, pageSize - 4);
page.setInt(0, (int) crc.getValue());
file.seek(pageSize);
file.write(page.getBytes(), 0, pageSize);
file.seek(pageSize + pageSize);
file.write(page.getBytes(), 0, pageSize);
// don't increment the write counter, because it was just written
}
/**
* Close the file without further writing.
*/
public void close() {
trace.debug("close");
synchronized (database) {
if (log != null) {
log.close();
log = null;
}
if (file != null) {
try {
file.releaseLock();
file.close();
} finally {
file = null;
}
}
}
}
public void flushLog() {
if (file != null) {
synchronized (database) {
log.flush();
}
}
}
/**
* Flush the transaction log and sync the file.
*/
public void sync() {
if (file != null) {
synchronized (database) {
log.flush();
file.sync();
}
}
}
public Trace getTrace() {
return trace;
}
public void writeBack(CacheObject obj) {
Page record = (Page) obj;
if (trace.isDebugEnabled()) {
trace.debug("writeBack " + record);
}
synchronized (database) {
record.write();
record.setChanged(false);
}
}
/**
* Write an undo log entry if required.
*
* @param page the page
* @param old the old data (if known) or null
*/
public void logUndo(Page page, Data old) {
if (logMode == LOG_MODE_OFF) {
return;
}
synchronized (database) {
checkOpen();
database.checkWritingAllowed();
if (!recoveryRunning) {
int pos = page.getPos();
if (!log.getUndo(pos)) {
if (old == null) {
old = readPage(pos);
}
log.addUndo(pos, old);
}
}
}
}
/**
* Update a page.
*
* @param page the page
*/
public void update(Page page) {
synchronized (database) {
if (trace.isDebugEnabled()) {
if (!page.isChanged()) {
trace.debug("updateRecord " + page.toString());
}
}
checkOpen();
database.checkWritingAllowed();
page.setChanged(true);
int pos = page.getPos();
if (SysProperties.CHECK && !recoveryRunning) {
// ensure the undo entry is already written
if (logMode != LOG_MODE_OFF) {
log.addUndo(pos, null);
}
}
allocatePage(pos);
cache.update(pos, page);
}
}
private int getFreeListId(int pageId) {
return (pageId - PAGE_ID_FREE_LIST_ROOT) / freeListPagesPerList;
}
private PageFreeList getFreeListForPage(int pageId) {
return getFreeList(getFreeListId(pageId));
}
private PageFreeList getFreeList(int i) {
PageFreeList list = null;
if (i < freeLists.size()) {
list = freeLists.get(i);
if (list != null) {
return list;
}
}
synchronized (database) {
int p = PAGE_ID_FREE_LIST_ROOT + i * freeListPagesPerList;
while (p >= pageCount) {
increaseFileSize();
}
if (p < pageCount) {
list = (PageFreeList) getPage(p);
}
if (list == null) {
list = PageFreeList.create(this, p);
cache.put(list);
}
while (freeLists.size() <= i) {
freeLists.add(null);
}
freeLists.set(i, list);
return list;
}
}
private void freePage(int pageId) {
PageFreeList list = getFreeListForPage(pageId);
list.free(pageId);
}
/**
* Set the bit of an already allocated page.
*
* @param pageId the page to allocate
*/
void allocatePage(int pageId) {
PageFreeList list = getFreeListForPage(pageId);
list.allocate(pageId);
}
private boolean isUsed(int pageId) {
return getFreeListForPage(pageId).isUsed(pageId);
}
/**
* Allocate a number of pages.
*
* @param list the list where to add the allocated pages
* @param pagesToAllocate the number of pages to allocate
* @param exclude the exclude list
* @param after all allocated pages are higher than this page
*/
void allocatePages(IntArray list, int pagesToAllocate, BitField exclude, int after) {
list.ensureCapacity(list.size() + pagesToAllocate);
for (int i = 0; i < pagesToAllocate; i++) {
int page = allocatePage(exclude, after);
after = page;
list.add(page);
}
}
/**
* Allocate a page.
*
* @return the page id
*/
public int allocatePage() {
int pos = allocatePage(null, 0);
if (!recoveryRunning) {
if (logMode != LOG_MODE_OFF) {
log.addUndo(pos, emptyPage);
}
}
return pos;
}
private int allocatePage(BitField exclude, int first) {
int page;
synchronized (database) {
// TODO could remember the first possible free list page
for (int i = 0;; i++) {
PageFreeList list = getFreeList(i);
page = list.allocate(exclude, first);
if (page >= 0) {
break;
}
}
while (page >= pageCount) {
increaseFileSize();
}
if (trace.isDebugEnabled()) {
// trace.debug("allocatePage " + pos);
}
return page;
}
}
private void increaseFileSize() {
int increment = INCREMENT_KB * 1024 / pageSize;
int percent = pageCount * INCREMENT_PERCENT_MIN / 100;
if (increment < percent) {
increment = (1 + (percent / increment)) * increment;
}
increaseFileSize(increment);
}
private void increaseFileSize(int increment) {
for (int i = pageCount; i < pageCount + increment; i++) {
freed.set(i);
}
pageCount += increment;
long newLength = (long) pageCount << pageSizeShift;
file.setLength(newLength);
writeCount++;
fileLength = newLength;
}
/**
* Add a page to the free list. The undo log entry must have been written.
*
* @param pageId the page id
*/
public void free(int pageId) {
free(pageId, true);
}
/**
* Add a page to the free list.
*
* @param pageId the page id
* @param undo if the undo record must have been written
*/
void free(int pageId, boolean undo) {
if (trace.isDebugEnabled()) {
// trace.debug("free " + pageId + " " + undo);
}
synchronized (database) {
cache.remove(pageId);
if (SysProperties.CHECK && !recoveryRunning && undo) {
// ensure the undo entry is already written
if (logMode != LOG_MODE_OFF) {
log.addUndo(pageId, null);
}
}
freePage(pageId);
if (recoveryRunning) {
writePage(pageId, createData());
if (reservedPages != null && reservedPages.containsKey(pageId)) {
// re-allocate the page if it is used later on again
int latestPos = reservedPages.get(pageId);
if (latestPos > log.getLogPos()) {
allocatePage(pageId);
}
}
}
}
}
/**
* Add a page to the free list. The page is not used, therefore doesn't need
* to be overwritten.
*
* @param pageId the page id
*/
void freeUnused(int pageId) {
if (trace.isDebugEnabled()) {
trace.debug("freeUnused " + pageId);
}
synchronized (database) {
cache.remove(pageId);
freePage(pageId);
freed.set(pageId);
}
}
/**
* Create a data object.
*
* @return the data page.
*/
public Data createData() {
return Data.create(database, new byte[pageSize]);
}
/**
* Read a page.
*
* @param pos the page id
* @return the page
*/
public Data readPage(int pos) {
Data page = createData();
readPage(pos, page);
return page;
}
/**
* Read a page.
*
* @param pos the page id
* @param page the page
*/
void readPage(int pos, Data page) {
if (recordPageReads) {
if (pos >= MIN_PAGE_COUNT && recordedPagesIndex.get(pos) == IntIntHashMap.NOT_FOUND) {
recordedPagesIndex.put(pos, recordedPagesList.size());
recordedPagesList.add(pos);
}
}
synchronized (database) {
if (pos < 0 || pos >= pageCount) {
throw DbException.get(ErrorCode.FILE_CORRUPTED_1, pos + " of " + pageCount);
}
file.seek((long) pos << pageSizeShift);
file.readFully(page.getBytes(), 0, pageSize);
readCount++;
}
}
/**
* Get the page size.
*
* @return the page size
*/
public int getPageSize() {
return pageSize;
}
/**
* Get the number of pages (including free pages).
*
* @return the page count
*/
public int getPageCount() {
return pageCount;
}
/**
* Write a page.
*
* @param pageId the page id
* @param data the data
*/
public void writePage(int pageId, Data data) {
if (pageId <= 0) {
DbException.throwInternalError("write to page " + pageId);
}
byte[] bytes = data.getBytes();
if (SysProperties.CHECK) {
boolean shouldBeFreeList = (pageId - PAGE_ID_FREE_LIST_ROOT) % freeListPagesPerList == 0;
boolean isFreeList = bytes[0] == Page.TYPE_FREE_LIST;
if (bytes[0] != 0 && shouldBeFreeList != isFreeList) {
throw DbException.throwInternalError();
}
}
checksumSet(bytes, pageId);
synchronized (database) {
file.seek((long) pageId << pageSizeShift);
file.write(bytes, 0, pageSize);
writeCount++;
}
}
/**
* Remove a page from the cache.
*
* @param pageId the page id
*/
public void removeRecord(int pageId) {
synchronized (database) {
cache.remove(pageId);
}
}
Database getDatabase() {
return database;
}
/**
* Run recovery.
*/
private void recover() {
trace.debug("log recover");
recoveryRunning = true;
log.recover(PageLog.RECOVERY_STAGE_UNDO);
if (reservedPages != null) {
for (int r : reservedPages.keySet()) {
if (trace.isDebugEnabled()) {
trace.debug("reserve " + r);
}
allocatePage(r);
}
}
log.recover(PageLog.RECOVERY_STAGE_ALLOCATE);
openMetaIndex();
readMetaData();
log.recover(PageLog.RECOVERY_STAGE_REDO);
boolean setReadOnly = false;
if (!database.isReadOnly()) {
if (log.getInDoubtTransactions().size() == 0) {
log.recoverEnd();
int firstUncommittedSection = getFirstUncommittedSection();
log.removeUntil(firstUncommittedSection);
} else {
setReadOnly = true;
}
}
PageDataIndex systemTable = (PageDataIndex) metaObjects.get(0);
isNew = systemTable == null;
for (PageIndex index : metaObjects.values()) {
if (index.getTable().isTemporary()) {
// temporary indexes are removed after opening
if (tempObjects == null) {
tempObjects = New.hashMap();
}
tempObjects.put(index.getId(), index);
} else {
index.close(systemSession);
}
}
allocatePage(PAGE_ID_META_ROOT);
writeIndexRowCounts();
recoveryRunning = false;
reservedPages = null;
writeBack();
// clear the cache because it contains pages with closed indexes
cache.clear();
freeLists.clear();
metaObjects.clear();
metaObjects.put(-1, metaIndex);
if (setReadOnly) {
database.setReadOnly(true);
}
trace.debug("log recover done");
}
/**
* A record is added to a table, or removed from a table.
*
* @param session the session
* @param tableId the table id
* @param row the row to add
* @param add true if the row is added, false if it is removed
*/
public void logAddOrRemoveRow(Session session, int tableId, Row row, boolean add) {
if (logMode != LOG_MODE_OFF) {
if (!recoveryRunning) {
synchronized (database) {
log.logAddOrRemoveRow(session, tableId, row, add);
}
}
}
}
/**
* Mark a committed transaction.
*
* @param session the session
*/
public void commit(Session session) {
synchronized (database) {
checkOpen();
log.commit(session.getId());
if (log.getSize() - logSizeBase > maxLogSize) {
checkpoint();
logSizeBase = log.getSize();
}
}
}
/**
* Prepare a transaction.
*
* @param session the session
* @param transaction the name of the transaction
*/
public void prepareCommit(Session session, String transaction) {
synchronized (database) {
log.prepareCommit(session, transaction);
}
}
/**
* Check whether this is a new database.
*
* @return true if it is
*/
public boolean isNew() {
return isNew;
}
/**
* Reserve the page if this is a index root page entry.
*
* @param logPos the redo log position
* @param tableId the table id
* @param row the row
*/
void allocateIfIndexRoot(int logPos, int tableId, Row row) {
if (tableId == META_TABLE_ID) {
int rootPageId = row.getValue(3).getInt();
if (reservedPages == null) {
reservedPages = New.hashMap();
}
reservedPages.put(rootPageId, logPos);
}
}
/**
* Redo a delete in a table.
*
* @param logPos the redo log position
* @param tableId the object id of the table
* @param key the key of the row to delete
*/
void redoDelete(int logPos, int tableId, long key) {
Index index = metaObjects.get(tableId);
PageDataIndex scan = (PageDataIndex) index;
Row row = scan.getRowWithKey(key);
redo(logPos, tableId, row, false);
}
/**
* Redo a change in a table.
*
* @param logPos the redo log position
* @param tableId the object id of the table
* @param row the row
* @param add true if the record is added, false if deleted
*/
void redo(int logPos, int tableId, Row row, boolean add) {
if (tableId == META_TABLE_ID) {
if (add) {
addMeta(row, systemSession, true);
} else {
removeMeta(logPos, row);
}
}
Index index = metaObjects.get(tableId);
if (index == null) {
throw DbException.throwInternalError("Table not found: " + tableId + " " + row + " " + add);
}
Table table = index.getTable();
if (add) {
table.addRow(systemSession, row);
} else {
table.removeRow(systemSession, row);
}
}
/**
* Redo a truncate.
*
* @param tableId the object id of the table
*/
void redoTruncate(int tableId) {
Index index = metaObjects.get(tableId);
Table table = index.getTable();
table.truncate(systemSession);
}
private void openMetaIndex() {
CreateTableData data = new CreateTableData();
ArrayList cols = data.columns;
cols.add(new Column("ID", Value.INT));
cols.add(new Column("TYPE", Value.INT));
cols.add(new Column("PARENT", Value.INT));
cols.add(new Column("HEAD", Value.INT));
cols.add(new Column("OPTIONS", Value.STRING));
cols.add(new Column("COLUMNS", Value.STRING));
metaSchema = new Schema(database, 0, "", null, true);
data.schema = metaSchema;
data.tableName = "PAGE_INDEX";
data.id = META_TABLE_ID;
data.temporary = false;
data.persistData = true;
data.persistIndexes = true;
data.create = false;
data.session = systemSession;
metaTable = new RegularTable(data);
metaIndex = (PageDataIndex) metaTable.getScanIndex(
systemSession);
metaObjects.clear();
metaObjects.put(-1, metaIndex);
}
private void readMetaData() {
Cursor cursor = metaIndex.find(systemSession, null, null);
// first, create all tables
while (cursor.next()) {
Row row = cursor.get();
int type = row.getValue(1).getInt();
if (type == META_TYPE_DATA_INDEX) {
addMeta(row, systemSession, false);
}
}
// now create all secondary indexes
// otherwise the table might not be created yet
cursor = metaIndex.find(systemSession, null, null);
while (cursor.next()) {
Row row = cursor.get();
int type = row.getValue(1).getInt();
if (type != META_TYPE_DATA_INDEX) {
addMeta(row, systemSession, false);
}
}
}
private void removeMeta(int logPos, Row row) {
int id = row.getValue(0).getInt();
PageIndex index = metaObjects.get(id);
index.getTable().removeIndex(index);
if (index instanceof PageBtreeIndex || index instanceof PageDelegateIndex) {
if (index.isTemporary()) {
systemSession.removeLocalTempTableIndex(index);
} else {
index.getSchema().remove(index);
}
}
index.remove(systemSession);
metaObjects.remove(id);
}
private void addMeta(Row row, Session session, boolean redo) {
int id = row.getValue(0).getInt();
int type = row.getValue(1).getInt();
int parent = row.getValue(2).getInt();
int rootPageId = row.getValue(3).getInt();
String options = row.getValue(4).getString();
String columnList = row.getValue(5).getString();
String[] columns = StringUtils.arraySplit(columnList, ',', false);
String[] ops = StringUtils.arraySplit(options, ',', false);
Index meta;
if (trace.isDebugEnabled()) {
trace.debug("addMeta id=" + id + " type=" + type + " root=" + rootPageId + " parent=" + parent + " columns=" + columnList);
}
if (redo && rootPageId != 0) {
// ensure the page is empty, but not used by regular data
writePage(rootPageId, createData());
allocatePage(rootPageId);
}
metaRootPageId.put(id, rootPageId);
if (type == META_TYPE_DATA_INDEX) {
CreateTableData data = new CreateTableData();
if (SysProperties.CHECK) {
if (columns == null) {
throw DbException.throwInternalError(row.toString());
}
}
for (int i = 0, len = columns.length; i < len; i++) {
Column col = new Column("C" + i, Value.INT);
data.columns.add(col);
}
data.schema = metaSchema;
data.tableName = "T" + id;
data.id = id;
data.temporary = ops[2].equals("temp");
data.persistData = true;
data.persistIndexes = true;
data.create = false;
data.session = session;
RegularTable table = new RegularTable(data);
CompareMode mode = CompareMode.getInstance(ops[0], Integer.parseInt(ops[1]));
table.setCompareMode(mode);
meta = table.getScanIndex(session);
} else {
Index p = metaObjects.get(parent);
if (p == null) {
throw DbException.get(ErrorCode.FILE_CORRUPTED_1, "Table not found:" + parent + " for " + row + " meta:" + metaObjects);
}
RegularTable table = (RegularTable) p.getTable();
Column[] tableCols = table.getColumns();
int len = columns.length;
IndexColumn[] cols = new IndexColumn[len];
for (int i = 0; i < len; i++) {
String c = columns[i];
IndexColumn ic = new IndexColumn();
int idx = c.indexOf('/');
if (idx >= 0) {
String s = c.substring(idx + 1);
ic.sortType = Integer.parseInt(s);
c = c.substring(0, idx);
}
Column column = tableCols[Integer.parseInt(c)];
ic.column = column;
cols[i] = ic;
}
IndexType indexType;
if (ops[3].equals("d")) {
indexType = IndexType.createPrimaryKey(true, false);
Column[] tableColumns = table.getColumns();
for (IndexColumn indexColumn : cols) {
tableColumns[indexColumn.column.getColumnId()].setNullable(false);
}
} else {
indexType = IndexType.createNonUnique(true);
}
meta = table.addIndex(session, "I" + id, id, cols, indexType, false, null);
}
PageIndex index;
if (meta instanceof MultiVersionIndex) {
index = (PageIndex) ((MultiVersionIndex) meta).getBaseIndex();
} else {
index = (PageIndex) meta;
}
metaObjects.put(id, index);
}
/**
* Add an index to the in-memory index map.
*
* @param index the index
*/
public void addIndex(PageIndex index) {
metaObjects.put(index.getId(), index);
}
/**
* Add the meta data of an index.
*
* @param index the index to add
* @param session the session
*/
public void addMeta(PageIndex index, Session session) {
int type = index instanceof PageDataIndex ? META_TYPE_DATA_INDEX : META_TYPE_BTREE_INDEX;
IndexColumn[] columns = index.getIndexColumns();
StatementBuilder buff = new StatementBuilder();
for (IndexColumn col : columns) {
buff.appendExceptFirst(",");
int id = col.column.getColumnId();
buff.append(id);
int sortType = col.sortType;
if (sortType != 0) {
buff.append('/');
buff.append(sortType);
}
}
String columnList = buff.toString();
Table table = index.getTable();
CompareMode mode = table.getCompareMode();
String options = mode.getName()+ "," + mode.getStrength() + ",";
if (table.isTemporary()) {
options += "temp";
}
options += ",";
if (index instanceof PageDelegateIndex) {
options += "d";
}
Row row = metaTable.getTemplateRow();
row.setValue(0, ValueInt.get(index.getId()));
row.setValue(1, ValueInt.get(type));
row.setValue(2, ValueInt.get(table.getId()));
row.setValue(3, ValueInt.get(index.getRootPageId()));
row.setValue(4, ValueString.get(options));
row.setValue(5, ValueString.get(columnList));
row.setKey(index.getId() + 1);
metaIndex.add(session, row);
}
/**
* Remove the meta data of an index.
*
* @param index the index to remove
* @param session the session
*/
public void removeMeta(Index index, Session session) {
if (!recoveryRunning) {
removeMetaIndex(index, session);
metaObjects.remove(index.getId());
}
}
private void removeMetaIndex(Index index, Session session) {
int key = index.getId() + 1;
Row row = metaIndex.getRow(session, key);
if (row.getKey() != key) {
throw DbException.get(ErrorCode.FILE_CORRUPTED_1, "key: " + key + " index: " + index + " table: " + index.getTable() + " row: " + row);
}
metaIndex.remove(session, row);
}
/**
* Set the maximum transaction log size in megabytes.
*
* @param maxSize the new maximum log size
*/
public void setMaxLogSize(long maxSize) {
this.maxLogSize = maxSize;
}
/**
* Commit or rollback a prepared transaction after opening a database with
* in-doubt transactions.
*
* @param sessionId the session id
* @param pageId the page where the transaction was prepared
* @param commit if the transaction should be committed
*/
public void setInDoubtTransactionState(int sessionId, int pageId, boolean commit) {
boolean old = database.isReadOnly();
try {
database.setReadOnly(false);
log.setInDoubtTransactionState(sessionId, pageId, commit);
} finally {
database.setReadOnly(old);
}
}
/**
* Get the list of in-doubt transaction.
*
* @return the list
*/
public ArrayList getInDoubtTransactions() {
return log.getInDoubtTransactions();
}
/**
* Check whether the recovery process is currently running.
*
* @return true if it is
*/
public boolean isRecoveryRunning() {
return this.recoveryRunning;
}
private void checkOpen() {
if (file == null) {
throw DbException.get(ErrorCode.DATABASE_IS_CLOSED);
}
}
/**
* Get the file write count since the database was created.
*
* @return the write count
*/
public long getWriteCountTotal() {
return writeCount + writeCountBase;
}
/**
* Get the file write count since the database was opened.
*
* @return the write count
*/
public long getWriteCount() {
return writeCount;
}
/**
* Get the file read count since the database was opened.
*
* @return the read count
*/
public long getReadCount() {
return readCount;
}
/**
* A table is truncated.
*
* @param session the session
* @param tableId the table id
*/
public void logTruncate(Session session, int tableId) {
synchronized (database) {
if (!recoveryRunning) {
log.logTruncate(session, tableId);
}
}
}
/**
* Get the root page of an index.
*
* @param indexId the index id
* @return the root page
*/
public int getRootPageId(int indexId) {
return metaRootPageId.get(indexId);
}
public Cache getCache() {
return cache;
}
private void checksumSet(byte[] d, int pageId) {
int ps = pageSize;
int type = d[0];
if (type == Page.TYPE_EMPTY) {
return;
}
int s1 = 255 + (type & 255), s2 = 255 + s1;
s2 += s1 += d[6] & 255;
s2 += s1 += d[(ps >> 1) - 1] & 255;
s2 += s1 += d[ps >> 1] & 255;
s2 += s1 += d[ps - 2] & 255;
s2 += s1 += d[ps - 1] & 255;
d[1] = (byte) (((s1 & 255) + (s1 >> 8)) ^ pageId);
d[2] = (byte) (((s2 & 255) + (s2 >> 8)) ^ (pageId >> 8));
}
/**
* Check if the stored checksum is correct
* @param d the data
* @param pageId the page id
* @param pageSize the page size
* @return true if it is correct
*/
public static boolean checksumTest(byte[] d, int pageId, int pageSize) {
int ps = pageSize;
int s1 = 255 + (d[0] & 255), s2 = 255 + s1;
s2 += s1 += d[6] & 255;
s2 += s1 += d[(ps >> 1) - 1] & 255;
s2 += s1 += d[ps >> 1] & 255;
s2 += s1 += d[ps - 2] & 255;
s2 += s1 += d[ps - 1] & 255;
if (d[1] != (byte) (((s1 & 255) + (s1 >> 8)) ^ pageId)
|| d[2] != (byte) (((s2 & 255) + (s2 >> 8)) ^ (pageId >> 8))) {
return false;
}
return true;
}
/**
* Increment the change count. To be done after the operation has finished.
*/
public void incrementChangeCount() {
changeCount++;
}
/**
* Get the current change count. The first value is 1
*
* @return the change count
*/
public int getChangeCount() {
return changeCount;
}
public void setLogMode(int logMode) {
this.logMode = logMode;
}
public int getLogMode() {
return logMode;
}
public void setLockFile(boolean lockFile) {
this.lockFile = lockFile;
}
}
