Logback: the reliable, generic, fast and flexible logging framework.
Copyright (C) 1999-2015, QOS.ch. All rights reserved.
This program and the accompanying materials are dual-licensed under
either the terms of the Eclipse Public License v1.0 as published by
the Eclipse Foundation
  or (per the licensee's choosing)
under the terms of the GNU Lesser General Public License version 2.1
as published by the Free Software Foundation.
/**
 * Logback: the reliable, generic, fast and flexible logging framework.
 * Copyright (C) 1999-2015, QOS.ch. All rights reserved.
 *
 * This program and the accompanying materials are dual-licensed under
 * either the terms of the Eclipse Public License v1.0 as published by
 * the Eclipse Foundation
 *
 *   or (per the licensee's choosing)
 *
 * under the terms of the GNU Lesser General Public License version 2.1
 * as published by the Free Software Foundation.
 */
package ch.qos.logback.classic.turbo;

import java.util.LinkedHashMap;
import java.util.Map;

Clients of this class should only use the getMessageCountAndThenIncrement method. Other methods inherited via LinkedHashMap are not thread safe. /**
 * Clients of this class should only use the  {@link #getMessageCountAndThenIncrement} method. Other methods inherited
 * via LinkedHashMap are not thread safe.
 */
class LRUMessageCache extends LinkedHashMap<String, Integer> {

    private static final long serialVersionUID = 1L;
    final int cacheSize;

    LRUMessageCache(int cacheSize) {
        super((int) (cacheSize * (4.0f / 3)), 0.75f, true);
        if (cacheSize < 1) {
            throw new IllegalArgumentException("Cache size cannot be smaller than 1");
        }
        this.cacheSize = cacheSize;
    }

    int getMessageCountAndThenIncrement(String msg) {
        // don't insert null elements
        if (msg == null) {
            return 0;
        }

        Integer i;
        // LinkedHashMap is not LinkedHashMap. See also LBCLASSIC-255
        synchronized (this) {
            i = super.get(msg);
            if (i == null) {
                i = 0;
            } else {
                i = i + 1;
            }
            super.put(msg, i);
        }
        return i;
    }

    // called indirectly by get() or put() which are already supposed to be
    // called from within a synchronized block
    protected boolean removeEldestEntry(Map.Entry eldest) {
        return (size() > cacheSize);
    }

    @Override
    synchronized public void clear() {
        super.clear();
    }
}