/*
* Copyright 2016 The Simple File Server Authors
*
* 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 org.sfs.filesystem.volume;
import com.google.common.collect.Lists;
import org.sfs.SfsVertx;
import org.sfs.filesystem.ChecksummedPositional;
import rx.Observable;
import rx.Producer;
import rx.Subscriber;
import java.util.List;
import java.util.concurrent.atomic.AtomicLong;
import static com.google.common.base.Preconditions.checkState;
import static java.lang.Long.MAX_VALUE;
import static org.sfs.block.RangeLock.lockedObservable;
import static org.sfs.filesystem.volume.IndexBlockReader.LockType.NONE;
import static org.sfs.filesystem.volume.IndexBlockReader.LockType.READ;
import static org.sfs.filesystem.volume.IndexBlockReader.LockType.WRITE;
import static org.sfs.protobuf.XVolume.XIndexBlock;
import static rx.Observable.create;
import static rx.internal.operators.BackpressureUtils.getAndAddRequest;
public class IndexBlockReader {
public enum LockType {
READ,
WRITE,
NONE
}
private final SfsVertx vertx;
private long position = 0;
private final long lastBlockPosition;
private final int batchSize;
private final int readSize;
private IndexFile blockFile;
private LockType lockType = NONE;
private long lockWaitTimeout = -1;
private boolean hasNext = true;
public IndexBlockReader(SfsVertx vertx, IndexFile blockFile, int blockSize, int batchSize, long lastBlockPosition) {
this.vertx = vertx;
this.blockFile = blockFile;
this.batchSize = batchSize;
this.readSize = blockSize * batchSize;
this.lastBlockPosition = lastBlockPosition;
}
public IndexBlockReader enableLocking(LockType lockType, long lockWaitTimeout) {
this.lockType = lockType;
this.lockWaitTimeout = lockWaitTimeout;
return this;
}
public Observable<Iterable<ChecksummedPositional<XIndexBlock>>> toObservable() {
return create(new OnSubscribeFromBlockReader<>(this));
}
protected boolean hasNext() {
return hasNext;
}
protected Observable<? extends List<ChecksummedPositional<XIndexBlock>>> next() {
if (READ.equals(lockType) || WRITE.equals(lockType)) {
checkState(lockWaitTimeout > 0, "Invalid LockWaitTimeout value %s", lockWaitTimeout);
return lockedObservable(vertx,
() -> {
if (WRITE.equals(lockType)) {
return blockFile.tryWriteLock(position, readSize);
} else if (READ.equals(lockType)) {
return blockFile.tryReadLock(position, readSize);
} else {
throw new IllegalStateException("Unsupported Locked Type " + lockType);
}
},
() -> blockFile.getBlocks(vertx, position, batchSize)
.map(Lists::newArrayList)
.doOnNext(checksummedPositionals -> hasNext = !checksummedPositionals.isEmpty())
.doOnNext(checksummedPositionals -> position = position + readSize),
lockWaitTimeout);
} else {
return blockFile.getBlocks(vertx, position, batchSize)
.map(Lists::newArrayList)
.doOnNext(checksummedPositionals -> hasNext = !checksummedPositionals.isEmpty())
.doOnNext(checksummedPositionals -> position = position + readSize);
}
}
protected static class OnSubscribeFromBlockReader<T extends Iterable<ChecksummedPositional<XIndexBlock>>> implements Observable.OnSubscribe<T> {
final IndexBlockReader blockReader;
public OnSubscribeFromBlockReader(IndexBlockReader iterable) {
if (iterable == null) {
throw new NullPointerException("iterable must not be null");
}
this.blockReader = iterable;
}
@Override
public void call(Subscriber<? super T> o) {
if (!blockReader.hasNext() && !o.isUnsubscribed()) {
o.onCompleted();
} else {
o.setProducer(new BlockReaderProducer<>(o, blockReader));
}
}
private static final class BlockReaderProducer<T extends Iterable<ChecksummedPositional<XIndexBlock>>> extends AtomicLong implements Producer {
/** */
private static final long serialVersionUID = -1L;
private final Subscriber<? super T> o;
private final IndexBlockReader blockReader;
BlockReaderProducer(Subscriber<? super T> o, IndexBlockReader blockReader) {
this.o = o;
this.blockReader = blockReader;
}
@Override
public void request(long n) {
if (get() == MAX_VALUE) {
// already started with fast-path
return;
}
if (n == MAX_VALUE && compareAndSet(0, MAX_VALUE)) {
fastpath();
} else if (n > 0 && getAndAddRequest(this, n) == 0L) {
slowpath(n, 0);
}
}
void slowpath(long n, long numberEmitted) {
if (o.isUnsubscribed()) {
// don't recurse
} else if (numberEmitted < n) {
if (blockReader.hasNext()) {
blockReader.next()
.subscribe(new Subscriber<Iterable<ChecksummedPositional<XIndexBlock>>>() {
@Override
public void onCompleted() {
o.onCompleted();
}
@Override
public void onError(Throwable e) {
o.onError(e);
}
@Override
public void onNext(Iterable<ChecksummedPositional<XIndexBlock>> checksummedPositionals) {
o.onNext((T) checksummedPositionals);
blockReader.vertx.runOnContext(event -> slowpath(n, numberEmitted + 1));
}
});
} else {
if (!o.isUnsubscribed()) {
o.onCompleted();
}
}
} else if (numberEmitted >= n) {
if (!o.isUnsubscribed()) {
o.onCompleted();
}
}
}
void fastpath() {
// fast-path without backpressure
final Subscriber<? super T> o = this.o;
final IndexBlockReader it = this.blockReader;
if (o.isUnsubscribed()) {
return;
} else if (it.hasNext()) {
it.next().subscribe(
new Subscriber<Iterable<ChecksummedPositional<XIndexBlock>>>() {
@Override
public void onCompleted() {
o.onCompleted();
}
@Override
public void onError(Throwable e) {
o.onError(e);
}
@Override
public void onNext(Iterable<ChecksummedPositional<XIndexBlock>> checksummedPositionals) {
o.onNext((T) checksummedPositionals);
blockReader.vertx.runOnContext(event -> fastpath());
}
});
} else if (!o.isUnsubscribed()) {
o.onCompleted();
return;
} else {
// is unsubscribed
return;
}
}
}
}
}