/*

 * Copyright (c) 2001, 2011, 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.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package sun.nio.cs;

import java.nio.charset.*;

/**

 * Utility class for caching per-thread decoders and encoders.

 */

public class ThreadLocalCoders {

    private static final int CACHE_SIZE = 3;

    private abstract static class Cache {

        // Thread-local reference to array of cached objects, in LRU order

        private ThreadLocal<Object[]> cache = new ThreadLocal<>();

        private final int size;

        Cache(int size) {

            this.size = size;

        }

        abstract Object create(Object name);

        private void moveToFront(Object[] oa, int i) {

            Object ob = oa[i];

            for (int j = i; j > 0; j--)

                oa[j] = oa[j - 1];

            oa[0] = ob;

        }

        abstract boolean hasName(Object ob, Object name);

        Object forName(Object name) {

            Object[] oa = cache.get();

            if (oa == null) {

                oa = new Object[size];

                cache.set(oa);

            } else {

                for (int i = 0; i < oa.length; i++) {

                    Object ob = oa[i];

                    if (ob == null)

                        continue;

                    if (hasName(ob, name)) {

                        if (i > 0)

                            moveToFront(oa, i);

                        return ob;

                    }

                }

            }

            // Create a new object

            Object ob = create(name);

            oa[oa.length - 1] = ob;

            moveToFront(oa, oa.length - 1);

            return ob;

        }

    }

    private static Cache decoderCache = new Cache(CACHE_SIZE) {

            boolean hasName(Object ob, Object name) {

                if (name instanceof String)

                    return (((CharsetDecoder)ob).charset().name().equals(name));

                if (name instanceof Charset)

                    return ((CharsetDecoder)ob).charset().equals(name);

                return false;

            }

            Object create(Object name) {

                if (name instanceof String)

                    return Charset.forName((String)name).newDecoder();

                if (name instanceof Charset)

                    return ((Charset)name).newDecoder();

                assert false;

                return null;

            }

        };

    public static CharsetDecoder decoderFor(Object name) {

        CharsetDecoder cd = (CharsetDecoder)decoderCache.forName(name);

        cd.reset();

        return cd;

    }

    private static Cache encoderCache = new Cache(CACHE_SIZE) {

            boolean hasName(Object ob, Object name) {

                if (name instanceof String)

                    return (((CharsetEncoder)ob).charset().name().equals(name));

                if (name instanceof Charset)

                    return ((CharsetEncoder)ob).charset().equals(name);

                return false;

            }

            Object create(Object name) {

                if (name instanceof String)

                    return Charset.forName((String)name).newEncoder();

                if (name instanceof Charset)

                    return ((Charset)name).newEncoder();

                assert false;

                return null;

            }

        };

    public static CharsetEncoder encoderFor(Object name) {

        CharsetEncoder ce = (CharsetEncoder)encoderCache.forName(name);

        ce.reset();

        return ce;

    }

}