/*
* Copyright 2004-2013 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.lealone.result;
import java.io.IOException;
import org.lealone.engine.SessionRemote;
import org.lealone.message.DbException;
import org.lealone.value.Transfer;
import org.lealone.value.Value;
public class ResultRemoteCursor extends ResultRemote {
//不能在这初始化为false，在super的构造函数中会调用fetchRows有可能把isEnd设为true了，
//如果初始化为false，相当于在调用完super(...)后再执行isEnd = false，这时前面的值就被覆盖了。
private boolean isEnd;
public ResultRemoteCursor(SessionRemote session, Transfer transfer, int id, int columnCount, int fetchSize)
throws IOException {
super(session, transfer, id, columnCount, -1, fetchSize);
}
@Override
public boolean next() {
if (isEnd && rowId - rowOffset >= result.size() - 1) {
currentRow = null;
return false;
}
rowId++;
if (!isEnd) {
remapIfOld();
if (rowId - rowOffset >= result.size()) {
fetchRows(true);
if (isEnd && result.size() == 0) {
currentRow = null;
return false;
}
}
}
currentRow = result.get(rowId - rowOffset);
return true;
}
@Override
public int getRowCount() {
return Integer.MAX_VALUE; //不能返回-1，JdbcResultSet那边会抛异常
}
@Override
protected void fetchRows(boolean sendFetch) {
synchronized (session) {
session.checkClosed();
try {
rowOffset += result.size();
result.clear();
if (sendFetch) {
sendFetch(fetchSize);
}
for (int r = 0; r < fetchSize; r++) {
boolean row = transfer.readBoolean();
if (!row) {
isEnd = true;
if (transfer.available() > 0) {
fetchRowsThrowException();
}
break;
}
int len = columns.length;
Value[] values = new Value[len];
for (int i = 0; i < len; i++) {
Value v = transfer.readValue();
values[i] = v;
}
result.add(values);
}
if (isEnd)
sendClose();
} catch (IOException e) {
throw DbException.convertIOException(e, null);
}
}
}
}