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The MongoDB Asynchronous Driver
/*
* Copyright 2015 MongoDB, Inc.
*
* 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 com.mongodb.async.client.gridfs;
import com.mongodb.MongoGridFSException;
import com.mongodb.async.AsyncBatchCursor;
import com.mongodb.async.SingleResultCallback;
import com.mongodb.async.client.MongoCollection;
import com.mongodb.client.gridfs.model.GridFSFile;
import com.mongodb.diagnostics.logging.Logger;
import com.mongodb.diagnostics.logging.Loggers;
import org.bson.Document;
import org.bson.types.Binary;
import java.nio.ByteBuffer;
import java.util.List;
import java.util.concurrent.ConcurrentLinkedQueue;
import static com.mongodb.assertions.Assertions.isTrueArgument;
import static com.mongodb.assertions.Assertions.notNull;
import static com.mongodb.internal.async.ErrorHandlingResultCallback.errorHandlingCallback;
import static java.lang.String.format;
final class GridFSDownloadStreamImpl implements GridFSDownloadStream {
private static final Logger LOGGER = Loggers.getLogger("client.gridfs");
private final GridFSFindIterable fileInfoIterable;
private final MongoCollection chunksCollection;
private final ConcurrentLinkedQueue resultsQueue = new ConcurrentLinkedQueue();
private final Object closeAndReadingLock = new Object();
/* protected by `closeAndReadingLock` */
private boolean reading;
private boolean closed;
/* protected by `closeAndReadingLock` */
private GridFSFile fileInfo;
private int numberOfChunks;
private AsyncBatchCursor cursor;
private int batchSize;
private int chunkIndex;
private int bufferOffset;
private long currentPosition;
private byte[] buffer = null;
GridFSDownloadStreamImpl(final GridFSFindIterable fileInfoIterable, final MongoCollection chunksCollection) {
this.fileInfoIterable = notNull("file information", fileInfoIterable);
this.chunksCollection = notNull("chunks collection", chunksCollection);
}
@Override
public void getGridFSFile(final SingleResultCallback callback) {
notNull("callback", callback);
final SingleResultCallback errHandlingCallback = errorHandlingCallback(callback, LOGGER);
if (hasFileInfo()) {
errHandlingCallback.onResult(fileInfo, null);
return;
}
if (!tryGetReadingLock(errHandlingCallback)) {
return;
}
fileInfoIterable.first(new SingleResultCallback() {
@Override
public void onResult(final GridFSFile result, final Throwable t) {
releaseReadingLock();
if (t != null) {
errHandlingCallback.onResult(null, t);
} else if (result == null) {
errHandlingCallback.onResult(null, new MongoGridFSException("File not found"));
} else {
fileInfo = result;
numberOfChunks = (int) Math.ceil((double) fileInfo.getLength() / fileInfo.getChunkSize());
errHandlingCallback.onResult(result, null);
}
}
});
}
@Override
public GridFSDownloadStream batchSize(final int batchSize) {
isTrueArgument("batchSize cannot be negative", batchSize >= 0);
this.batchSize = batchSize;
discardCursor();
return this;
}
@Override
public void read(final ByteBuffer dst, final SingleResultCallback callback) {
notNull("dst", dst);
notNull("callback", callback);
final SingleResultCallback errHandlingCallback = errorHandlingCallback(callback, LOGGER);
if (!hasFileInfo()) {
getGridFSFile(new SingleResultCallback() {
@Override
public void onResult(final GridFSFile result, final Throwable t) {
if (t != null) {
errHandlingCallback.onResult(null, t);
} else {
read(dst, errHandlingCallback);
}
}
});
return;
}
if (!tryGetReadingLock(errHandlingCallback)) {
return;
} else if (currentPosition == fileInfo.getLength()) {
releaseReadingLock();
errHandlingCallback.onResult(-1, null);
return;
}
checkAndFetchResults(0, dst, new SingleResultCallback() {
@Override
public void onResult(final Integer result, final Throwable t) {
releaseReadingLock();
errHandlingCallback.onResult(result, t);
}
});
}
private void checkAndFetchResults(final int amountRead, final ByteBuffer dst, final SingleResultCallback callback) {
if (currentPosition == fileInfo.getLength() || dst.remaining() == 0) {
callback.onResult(amountRead, null);
} else if (hasResultsToProcess()) {
processResults(amountRead, dst, callback);
} else if (cursor == null) {
chunksCollection.find(new Document("files_id", fileInfo.getId())
.append("n", new Document("$gte", chunkIndex)))
.batchSize(batchSize).sort(new Document("n", 1))
.batchCursor(new SingleResultCallback>() {
@Override
public void onResult(final AsyncBatchCursor result, final Throwable t) {
if (t != null) {
callback.onResult(null, t);
} else {
cursor = result;
checkAndFetchResults(amountRead, dst, callback);
}
}
});
} else {
cursor.next(new SingleResultCallback>() {
@Override
public void onResult(final List result, final Throwable t) {
if (t != null) {
callback.onResult(null, t);
} else if (result == null || result.isEmpty()) {
callback.onResult(null, chunkNotFound(chunkIndex));
} else {
resultsQueue.addAll(result);
if (batchSize == 1) {
discardCursor();
}
processResults(amountRead, dst, callback);
}
}
});
}
}
private void processResults(final int previousAmountRead, final ByteBuffer dst, final SingleResultCallback callback) {
try {
int amountRead = previousAmountRead;
int amountToCopy = dst.remaining();
while (currentPosition < fileInfo.getLength() && amountToCopy > 0) {
if (getBufferFromResultsQueue()) {
buffer = getBufferFromChunk(resultsQueue.poll(), chunkIndex);
bufferOffset = 0;
chunkIndex += 1;
}
if (amountToCopy > buffer.length - bufferOffset) {
amountToCopy = buffer.length - bufferOffset;
}
if (amountToCopy > 0) {
dst.put(buffer, bufferOffset, amountToCopy);
bufferOffset += amountToCopy;
currentPosition += amountToCopy;
amountRead += amountToCopy;
amountToCopy = dst.remaining();
}
}
checkAndFetchResults(amountRead, dst, callback);
} catch (MongoGridFSException e) {
callback.onResult(null, e);
}
}
@Override
public void close(final SingleResultCallback callback) {
notNull("callback", callback);
SingleResultCallback errHandlingCallback = errorHandlingCallback(callback, LOGGER);
if (checkClosed()) {
errHandlingCallback.onResult(null, null);
} else if (!getReadingLock()) {
callbackIsReadingException(callback);
} else {
synchronized (closeAndReadingLock) {
if (!closed) {
closed = true;
}
}
discardCursor();
errHandlingCallback.onResult(null, null);
}
}
private boolean hasFileInfo() {
boolean hasInfo = false;
synchronized (closeAndReadingLock) {
hasInfo = fileInfo != null;
}
return hasInfo;
}
private MongoGridFSException chunkNotFound(final int chunkIndex) {
return new MongoGridFSException(format("Could not find file chunk for files_id: %s at chunk index %s.", fileInfo.getId(),
chunkIndex));
}
private byte[] getBufferFromChunk(final Document chunk, final int expectedChunkIndex) {
if (chunk == null || chunk.getInteger("n") != expectedChunkIndex) {
throw chunkNotFound(expectedChunkIndex);
} else if (!(chunk.get("data") instanceof Binary)) {
throw new MongoGridFSException("Unexpected data format for the chunk");
}
byte[] data = chunk.get("data", Binary.class).getData();
long expectedDataLength =
expectedChunkIndex + 1 == numberOfChunks
? fileInfo.getLength() - (expectedChunkIndex * (long) fileInfo.getChunkSize())
: fileInfo.getChunkSize();
if (data.length != expectedDataLength) {
throw new MongoGridFSException(format("Chunk size data length is not the expected size. "
+ "The size was %s for file_id: %s chunk index %s it should be %s bytes.", data.length, fileInfo.getId(),
expectedChunkIndex, expectedDataLength));
}
return data;
}
private boolean getBufferFromResultsQueue() {
return !resultsQueue.isEmpty() && (buffer == null || bufferOffset == buffer.length);
}
private boolean hasResultsToProcess() {
return !resultsQueue.isEmpty() || (buffer != null && bufferOffset < buffer.length);
}
private boolean tryGetReadingLock(final SingleResultCallback callback) {
if (checkClosed()) {
callbackClosedException(callback);
return false;
} else if (!getReadingLock()) {
callbackIsReadingException(callback);
return false;
} else {
return true;
}
}
private boolean checkClosed() {
synchronized (closeAndReadingLock) {
return closed;
}
}
private boolean getReadingLock() {
boolean gotLock = false;
synchronized (closeAndReadingLock) {
if (!reading) {
reading = true;
gotLock = true;
}
}
return gotLock;
}
private void releaseReadingLock() {
synchronized (closeAndReadingLock) {
reading = false;
}
}
private void discardCursor() {
synchronized (closeAndReadingLock) {
if (cursor != null) {
cursor.close();
cursor = null;
}
}
}
private void callbackClosedException(final SingleResultCallback callback) {
callback.onResult(null, new MongoGridFSException("The AsyncInputStream has been closed"));
}
private void callbackIsReadingException(final SingleResultCallback callback) {
callback.onResult(null, new MongoGridFSException("The AsyncInputStream does not support concurrent reading."));
}
}
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