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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.flink.runtime.state.gemini.engine.rm;

import org.apache.flink.runtime.state.gemini.engine.exceptions.GeminiRuntimeException;

import java.nio.ByteBuffer;

/**
 * GByteBuffer.
 */
public class GPooledByteBuffer extends AbstractGByteBufferReference {
	private final ByteBuffer byteBuffer;
	private volatile Chunk chunk;
	private final int offset;
	private final int len;
	private GPooledByteBufferFreeWrapper freeWrapper = null;

	public GPooledByteBuffer(Chunk chunk, int offset, int len, Allocator allocator) {
		super(allocator);
		this.chunk = chunk;
		ByteBuffer duplicateByteBuffer = chunk.getMemory().duplicate();
		duplicateByteBuffer.limit(offset + len);
		duplicateByteBuffer.position(offset);
		byteBuffer = duplicateByteBuffer.slice();
		this.offset = offset;
		this.len = len;
		retain();
	}

	@Override
	public int capacity() {
		return this.byteBuffer.capacity();
	}

	@Override
	public ByteBuffer getByteBuffer() {
		return this.byteBuffer;
	}

	@Override
	public void doFree() throws GeminiRuntimeException {
		getCleaner().clean();
	}

	@Override
	public boolean isFreed() {
		return getCleaner().cleaned();
	}

	static class GPooledByteBufferFreeWrapper implements FinalizableCleaner {
		private volatile Chunk chunk;
		private Allocator allocator;
		private final int offset;
		private final int len;
		private volatile boolean freed;

		public GPooledByteBufferFreeWrapper(Chunk chunk, int offset, int len,  Allocator allocator) {
			this.chunk = chunk;
			this.offset = offset;
			this.len = len;
			this.allocator = allocator;
			this.freed = false;
		}

		@Override
		public void clean() {
			if (chunk == null) {
				//It can't happen.
				return;
			}
			this.freed = true;
			synchronized (this) {
				if (chunk != null) {
					chunk.free(offset, len);
					chunk = null;
					allocator.statSize(-len);
				}
			}
		}

		@Override
		public boolean cleaned() {
			return freed;
		}

		@Override
		public void cleanedByLeakDetector() {}
	}

	@Override
	public FinalizableCleaner getCleaner() {
		if (freeWrapper == null) {
			freeWrapper = new GPooledByteBufferFreeWrapper(chunk, offset, len, allocator);
		}
		return freeWrapper;
	}

	@Override
	public boolean isPooled() {
		return true;
	}
}