/*

 * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

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package jdk.internal.net.http.common;

import java.nio.ByteBuffer;

import java.util.concurrent.ConcurrentLinkedQueue;

import java.util.function.Supplier;

/**

 *  This interface allows to recycle buffers used for SSL decryption.

 *  Buffers that are used for reading SSL encrypted data are typically

 *  very short lived, as it is necessary to aggregate their content

 *  before calling SSLEngine::unwrap.

 *  Because both reading and copying happen in the SelectorManager

 *  thread, then it makes it possible to pool these buffers and

 *  recycle them for the next socket read, instead of simply

 *  letting them be GC'ed. That also makes it possible to use

 *  direct byte buffers, and avoid another layer of copying by

 *  the SocketChannel implementation.

 *

 *  The HttpClientImpl has an implementation of this interface

 *  that allows to reuse the same 3 direct buffers for reading

 *  off SSL encrypted data from the socket.

 *  The BufferSupplier::get method is called by SocketTube

 *  (see SocketTube.SSLDirectBufferSource) and BufferSupplier::recycle

 *  is called by SSLFlowDelegate.Reader.

 **/

public interface BufferSupplier extends Supplier<ByteBuffer> {

    /**

     * Returns a buffer to read encrypted data off the socket.

     * @return a buffer to read encrypted data off the socket.

     */

    ByteBuffer get();

    /**

     * Returns a buffer to the pool.

     *

     * @param buffer This must be a buffer previously obtained

     *               by calling BufferSupplier::get. The caller must

     *               not touch the buffer after returning it to

     *               the pool.

     */

    void recycle(ByteBuffer buffer);

}