org.apache.kahadb.page.Page Maven / Gradle / Ivy
/**
* 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.kahadb.page;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import org.apache.kahadb.util.ByteSequence;
import org.apache.kahadb.util.DataByteArrayInputStream;
import org.apache.kahadb.util.DataByteArrayOutputStream;
import org.apache.kahadb.util.Marshaller;
/**
* A Page within a file.
*
* @version $Revision: 713421 $
*/
public class Page {
public static final int PAGE_HEADER_SIZE = 21;
public static final byte PAGE_FREE_TYPE = 0;
public static final byte PAGE_PART_TYPE = 1;
public static final byte PAGE_END_TYPE = 2;
long pageId;
// The following fields are persisted
byte type = PAGE_FREE_TYPE;
long txId;
// A field reserved to hold checksums.. Not in use (yet)
int checksum;
// Points to the next page in the chunk stream
long next;
T data;
public Page() {
}
public Page(long pageId) {
this.pageId=pageId;
}
public void copy(Page other) {
this.pageId = other.pageId;
this.txId = other.txId;
this.type = other.type;
this.next = other.next;
this.data = other.data;
}
Page copy() {
Page rc = new Page();
rc.copy(this);
return rc;
}
void makeFree(long txId) {
this.type = Page.PAGE_FREE_TYPE;
this.txId = txId;
this.data = null;
this.next = 0;
}
public void makePagePart(long next, long txId) {
this.type = Page.PAGE_PART_TYPE;
this.next = next;
this.txId = txId;
}
public void makePageEnd(long size, long txId) {
this.type = Page.PAGE_END_TYPE;
this.next = size;
this.txId = txId;
}
void write(DataOutput os) throws IOException {
os.writeByte(type);
os.writeLong(txId);
os.writeLong(next);
os.writeInt(checksum);
}
void read(DataInput is) throws IOException {
type = is.readByte();
txId = is.readLong();
next = is.readLong();
checksum = is.readInt();
}
public long getPageId() {
return pageId;
}
public long getTxId() {
return txId;
}
public T get() {
return data;
}
public void set(T data) {
this.data = data;
}
public short getType() {
return type;
}
public long getNext() {
return next;
}
public String toString() {
return "[Page:" + getPageId()+", type: "+type+"]";
}
public int getChecksum() {
return checksum;
}
public void setChecksum(int checksum) {
this.checksum = checksum;
}
}