core/src/main/java/org/apache/james/mime4j/util/ByteArrayOutputStreamRecycler.java

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 * 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   *
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package org.apache.james.mime4j.util;

import java.util.concurrent.ConcurrentLinkedQueue;

import org.apache.commons.io.output.ByteArrayOutputStream;
import org.apache.commons.io.output.UnsynchronizedByteArrayOutputStream;

public class ByteArrayOutputStreamRecycler {
    public static class Wrapper {
        private final ByteArrayOutputStreamRecycler recycler;
        private final UnsynchronizedByteArrayOutputStream value;

        public Wrapper(ByteArrayOutputStreamRecycler recycler, UnsynchronizedByteArrayOutputStream value) {
            this.recycler = recycler;
            this.value = value;
        }

        public void release() {
            recycler.release(value);
        }

        public UnsynchronizedByteArrayOutputStream getValue() {
            return value;
        }
    }

    protected final ConcurrentLinkedQueue<UnsynchronizedByteArrayOutputStream> buffers;

    public ByteArrayOutputStreamRecycler() {
        buffers = new ConcurrentLinkedQueue<>();
    }

    public Wrapper allocOutputStream() {
        UnsynchronizedByteArrayOutputStream result = buffers.poll();
        if (result == null) {
            result = new UnsynchronizedByteArrayOutputStream();
        }
        return new Wrapper(this, result);
    }

    private void release(UnsynchronizedByteArrayOutputStream value) {
        if (value != null && BufferRecycler.ENABLED) {
            value.reset();
            buffers.offer(value);
        }
    }
}