| /* |
| * 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.cassandra.io.util; |
| |
| import java.nio.ByteBuffer; |
| import java.util.EnumMap; |
| |
| import io.netty.util.concurrent.FastThreadLocal; |
| |
| import org.apache.cassandra.io.compress.BufferType; |
| |
| /** |
| * Utility class that allow buffers to be reused by storing them in a thread local instance. |
| */ |
| public final class ThreadLocalByteBufferHolder |
| { |
| private static final EnumMap<BufferType, FastThreadLocal<ByteBuffer>> reusableBBHolder = new EnumMap<>(BufferType.class); |
| // Convenience variable holding a ref to the current resuableBB to avoid map lookups |
| private final FastThreadLocal<ByteBuffer> reusableBB; |
| |
| static |
| { |
| for (BufferType bbType : BufferType.values()) |
| { |
| reusableBBHolder.put(bbType, new FastThreadLocal<ByteBuffer>() |
| { |
| protected ByteBuffer initialValue() |
| { |
| return ByteBuffer.allocate(0); |
| } |
| }); |
| } |
| }; |
| |
| /** |
| * The type of buffer that will be returned |
| */ |
| private final BufferType bufferType; |
| |
| public ThreadLocalByteBufferHolder(BufferType bufferType) |
| { |
| this.bufferType = bufferType; |
| this.reusableBB = reusableBBHolder.get(bufferType); |
| } |
| |
| /** |
| * Returns the buffer for the current thread. |
| * |
| * <p>If the buffer for the current thread does not have a capacity large enough. A new buffer with the requested |
| * size will be instatiated an will replace the existing one.</p> |
| * |
| * @param size the buffer size |
| * @return the buffer for the current thread. |
| */ |
| public ByteBuffer getBuffer(int size) |
| { |
| ByteBuffer buffer = reusableBB.get(); |
| if (buffer.capacity() < size) |
| { |
| FileUtils.clean(buffer); |
| buffer = bufferType.allocate(size); |
| reusableBB.set(buffer); |
| } |
| buffer.clear().limit(size); |
| return buffer; |
| } |
| } |