jetbrains.exodus.io.SharedMappedByteBuffer Maven / Gradle / Ivy
/**
* Copyright 2010 - 2022 JetBrains s.r.o.
*
* 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
*
* https://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 jetbrains.exodus.io;
import jetbrains.exodus.util.SafeByteBufferCleaner;
import jetbrains.exodus.util.SharedRandomAccessFile;
import org.jetbrains.annotations.NotNull;
import java.io.Closeable;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.util.concurrent.atomic.AtomicInteger;
final class SharedMappedByteBuffer implements Closeable {
@NotNull
private final ByteBuffer buffer;
private final AtomicInteger clients;
SharedMappedByteBuffer(@NotNull final SharedRandomAccessFile file) throws IOException {
buffer = file.getChannel().map(FileChannel.MapMode.READ_ONLY, 0L, file.length());
clients = new AtomicInteger();
}
void employ() {
clients.incrementAndGet();
}
@NotNull
ByteBuffer getBuffer() {
return buffer.slice();
}
@Override
public void close() {
if (clients.decrementAndGet() < 0) {
SafeByteBufferCleaner.clean(buffer);
}
}
}