SCViewer/com.minres.scviewer.databas.../src/org/apache/jdbm/StorageMemory.java

97 lines
2.4 KiB
Java
Raw Normal View History

package org.apache.jdbm;
import java.io.*;
import java.nio.ByteBuffer;
/**
* Storage which keeps all data in memory.
* Data are lost after storage is closed.
*/
class StorageMemory implements Storage {
private LongHashMap<byte[]> pages = new LongHashMap<byte[]>();
private boolean transactionsDisabled;
StorageMemory(boolean transactionsDisabled){
this.transactionsDisabled = transactionsDisabled;
}
public ByteBuffer read(long pageNumber) throws IOException {
byte[] data = pages.get(pageNumber);
if (data == null) {
//out of bounds, so just return empty data
return ByteBuffer.wrap(PageFile.CLEAN_DATA).asReadOnlyBuffer();
}else{
ByteBuffer b = ByteBuffer.wrap(data);
if(!transactionsDisabled)
return b.asReadOnlyBuffer();
else
return b;
}
}
public void write(long pageNumber, ByteBuffer data) throws IOException {
if (data.capacity() != PAGE_SIZE) throw new IllegalArgumentException();
byte[] b = pages.get(pageNumber);
if(transactionsDisabled && data.hasArray() && data.array() == b){
//already putted directly into array
return;
}
if(b == null)
b = new byte[PAGE_SIZE];
data.position(0);
data.get(b,0, PAGE_SIZE);
pages.put(pageNumber,b);
}
public void sync() throws IOException {
}
public void forceClose() throws IOException {
pages = null;
}
private ByteArrayOutputStream transLog;
public DataInputStream readTransactionLog() {
if (transLog == null)
return null;
DataInputStream ret = new DataInputStream(
new ByteArrayInputStream(transLog.toByteArray()));
//read stream header
try {
ret.readShort();
} catch (IOException e) {
throw new IOError(e);
}
return ret;
}
public void deleteTransactionLog() {
transLog = null;
}
public DataOutputStream openTransactionLog() throws IOException {
if (transLog == null)
transLog = new ByteArrayOutputStream();
return new DataOutputStream(transLog);
}
public void deleteAllFiles() throws IOException {
}
public boolean isReadonly() {
return false;
}
}