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Statistical sampling library for use in virtualdataset libraries, based on apache commons math 4
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/**
 * 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.core;

import java.util.ArrayList;
import java.util.List;

import ch.qos.logback.core.helpers.CyclicBuffer;
import ch.qos.logback.core.spi.LogbackLock;
import ch.qos.logback.core.status.OnConsoleStatusListener;
import ch.qos.logback.core.status.Status;
import ch.qos.logback.core.status.StatusListener;
import ch.qos.logback.core.status.StatusManager;

public class BasicStatusManager implements StatusManager {

    public static final int MAX_HEADER_COUNT = 150;
    public static final int TAIL_SIZE = 150;

    int count = 0;

    // protected access was requested in http://jira.qos.ch/browse/LBCORE-36
    final protected List statusList = new ArrayList();
    final protected CyclicBuffer tailBuffer = new CyclicBuffer(TAIL_SIZE);
    final protected LogbackLock statusListLock = new LogbackLock();

    int level = Status.INFO;

    // protected access was requested in http://jira.qos.ch/browse/LBCORE-36
    final protected List statusListenerList = new ArrayList();
    final protected LogbackLock statusListenerListLock = new LogbackLock();

    // Note on synchronization
    // This class contains two separate locks statusListLock and
    // statusListenerListLock guarding respectively the statusList+tailBuffer and
    // statusListenerList fields. The locks are used internally
    // without cycles. They are exposed to derived classes which should be careful
    // not to create deadlock cycles.

    /**
     * Add a new status object.
     * 
     * @param newStatus
     *                the status message to add
     */
    public void add(Status newStatus) {
        // LBCORE-72: fire event before the count check
        fireStatusAddEvent(newStatus);

        count++;
        if (newStatus.getLevel() > level) {
            level = newStatus.getLevel();
        }

        synchronized (statusListLock) {
            if (statusList.size() < MAX_HEADER_COUNT) {
                statusList.add(newStatus);
            } else {
                tailBuffer.add(newStatus);
            }
        }

    }

    public List getCopyOfStatusList() {
        synchronized (statusListLock) {
            List tList = new ArrayList(statusList);
            tList.addAll(tailBuffer.asList());
            return tList;
        }
    }

    private void fireStatusAddEvent(Status status) {
        synchronized (statusListenerListLock) {
            for (StatusListener sl : statusListenerList) {
                sl.addStatusEvent(status);
            }
        }
    }

    public void clear() {
        synchronized (statusListLock) {
            count = 0;
            statusList.clear();
            tailBuffer.clear();
        }
    }

    public int getLevel() {
        return level;
    }

    public int getCount() {
        return count;
    }

    /**
     * This implementation does not allow duplicate installations of OnConsoleStatusListener
     * @param listener
     */
    public boolean add(StatusListener listener) {
        synchronized (statusListenerListLock) {
            if (listener instanceof OnConsoleStatusListener) {
                boolean alreadyPresent = checkForPresence(statusListenerList, listener.getClass());
                if (alreadyPresent)
                    return false;
            }
            statusListenerList.add(listener);
        }
        return true;
    }

    private boolean checkForPresence(List statusListenerList, Class aClass) {
        for (StatusListener e : statusListenerList) {
            if (e.getClass() == aClass)
                return true;
        }
        return false;
    }

    public void remove(StatusListener listener) {
        synchronized (statusListenerListLock) {
            statusListenerList.remove(listener);
        }
    }

    public List getCopyOfStatusListenerList() {
        synchronized (statusListenerListLock) {
            return new ArrayList(statusListenerList);
        }
    }

}