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	/*
	* Copyright (c) 2000, 2020, 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
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	*/

	package java.util.logging;

	/**
	* {@code Handler} that buffers requests in a circular buffer in memory.
	* <p>
	* Normally this {@code Handler} simply stores incoming {@code LogRecords}
	* into its memory buffer and discards earlier records. This buffering
	* is very cheap and avoids formatting costs. On certain trigger
	* conditions, the {@code MemoryHandler} will push out its current buffer
	* contents to a target {@code Handler}, which will typically publish
	* them to the outside world.
	* <p>
	* There are three main models for triggering a push of the buffer:
	* <ul>
	* <li>
	* An incoming {@code LogRecord} has a type that is greater than
	* a pre-defined level, the {@code pushLevel}. </li>
	* <li>
	* An external class calls the {@code push} method explicitly. </li>
	* <li>
	* A subclass overrides the {@code log} method and scans each incoming
	* {@code LogRecord} and calls {@code push} if a record matches some
	* desired criteria. </li>
	* </ul>
	* <p>
	* <b>Configuration:</b>
	* By default each {@code MemoryHandler} is initialized using the following
	* {@code LogManager} configuration properties where {@code <handler-name>}
	* refers to the fully-qualified class name of the handler.
	* If properties are not defined
	* (or have invalid values) then the specified default values are used.
	* If no default value is defined then a RuntimeException is thrown.
	* <ul>
	* <li> <handler-name>.level
	* specifies the level for the {@code Handler}
	* (defaults to {@code Level.ALL}). </li>
	* <li> <handler-name>.filter
	* specifies the name of a {@code Filter} class to use
	* (defaults to no {@code Filter}). </li>
	* <li> <handler-name>.size
	* defines the buffer size (defaults to 1000). </li>
	* <li> <handler-name>.push
	* defines the {@code pushLevel} (defaults to {@code level.SEVERE}). </li>
	* <li> <handler-name>.target
	* specifies the name of the target {@code Handler } class.
	* (no default). </li>
	* </ul>
	* <p>
	* For example, the properties for {@code MemoryHandler} would be:
	* <ul>
	* <li> java.util.logging.MemoryHandler.level=INFO </li>
	* <li> java.util.logging.MemoryHandler.formatter=java.util.logging.SimpleFormatter </li>
	* </ul>
	* <p>
	* For a custom handler, e.g. com.foo.MyHandler, the properties would be:
	* <ul>
	* <li> com.foo.MyHandler.level=INFO </li>
	* <li> com.foo.MyHandler.formatter=java.util.logging.SimpleFormatter </li>
	* </ul>
	*
	* @since 1.4
	*/

	public class MemoryHandler extends Handler {
	private static final int DEFAULT_SIZE = 1000;
	private volatile Level pushLevel;
	private int size;
	private Handler target;
	private LogRecord buffer[];
	int start, count;

	/**
	* Create a {@code MemoryHandler} and configure it based on
	* {@code LogManager} configuration properties.
	*/
	public MemoryHandler() {
	// configure with specific defaults for MemoryHandler
	super(Level.ALL, new SimpleFormatter(), null);

	LogManager manager = LogManager.getLogManager();
	String cname = getClass().getName();
	pushLevel = manager.getLevelProperty(cname +".push", Level.SEVERE);
	size = manager.getIntProperty(cname + ".size", DEFAULT_SIZE);
	if (size <= 0) {
	size = DEFAULT_SIZE;
	}
	String targetName = manager.getProperty(cname+".target");
	if (targetName == null) {
	throw new RuntimeException("The handler " + cname
	+ " does not specify a target");
	}
	Class<?> clz;
	try {
	clz = ClassLoader.getSystemClassLoader().loadClass(targetName);
	@SuppressWarnings("deprecation")
	Object o = clz.newInstance();
	target = (Handler) o;
	} catch (ClassNotFoundException \| InstantiationException \| IllegalAccessException e) {
	throw new RuntimeException("MemoryHandler can't load handler target \"" + targetName + "\"" , e);
	}
	init();
	}

	// Initialize. Size is a count of LogRecords.
	private void init() {
	buffer = new LogRecord[size];
	start = 0;
	count = 0;
	}

	/**
	* Create a {@code MemoryHandler}.
	* <p>
	* The {@code MemoryHandler} is configured based on {@code LogManager}
	* properties (or their default values) except that the given {@code pushLevel}
	* argument and buffer size argument are used.
	*
	* @param target the Handler to which to publish output.
	* @param size the number of log records to buffer (must be greater than zero)
	* @param pushLevel message level to push on
	*
	* @throws IllegalArgumentException if {@code size is <= 0}
	*/
	public MemoryHandler(Handler target, int size, Level pushLevel) {
	// configure with specific defaults for MemoryHandler
	super(Level.ALL, new SimpleFormatter(), null);

	if (target == null \|\| pushLevel == null) {
	throw new NullPointerException();
	}
	if (size <= 0) {
	throw new IllegalArgumentException();
	}
	this.target = target;
	this.pushLevel = pushLevel;
	this.size = size;
	init();
	}

	/**
	* Store a {@code LogRecord} in an internal buffer.
	* <p>
	* If there is a {@code Filter}, its {@code isLoggable}
	* method is called to check if the given log record is loggable.
	* If not we return. Otherwise the given record is copied into
	* an internal circular buffer. Then the record's level property is
	* compared with the {@code pushLevel}. If the given level is
	* greater than or equal to the {@code pushLevel} then {@code push}
	* is called to write all buffered records to the target output
	* {@code Handler}.
	*
	* @param record description of the log event. A null record is
	* silently ignored and is not published
	*/
	@Override
	public synchronized void publish(LogRecord record) {
	if (!isLoggable(record)) {
	return;
	}
	int ix = (start+count)%buffer.length;
	buffer[ix] = record;
	if (count < buffer.length) {
	count++;
	} else {
	start++;
	start %= buffer.length;
	}
	if (record.getLevel().intValue() >= pushLevel.intValue()) {
	push();
	}
	}

	/**
	* Push any buffered output to the target {@code Handler}.
	* <p>
	* The buffer is then cleared.
	*/
	public synchronized void push() {
	for (int i = 0; i < count; i++) {
	int ix = (start+i)%buffer.length;
	LogRecord record = buffer[ix];
	target.publish(record);
	}
	// Empty the buffer.
	start = 0;
	count = 0;
	}

	/**
	* Causes a flush on the target {@code Handler}.
	* <p>
	* Note that the current contents of the {@code MemoryHandler}
	* buffer are <b>not</b> written out. That requires a "push".
	*/
	@Override
	public void flush() {
	target.flush();
	}

	/**
	* Close the {@code Handler} and free all associated resources.
	* This will also close the target {@code Handler}.
	*
	* @throws SecurityException if a security manager exists and if
	* the caller does not have {@code LoggingPermission("control")}.
	*/
	@Override
	public void close() throws SecurityException {
	target.close();
	setLevel(Level.OFF);
	}

	/**
	* Set the {@code pushLevel}. After a {@code LogRecord} is copied
	* into our internal buffer, if its level is greater than or equal to
	* the {@code pushLevel}, then {@code push} will be called.
	*
	* @param newLevel the new value of the {@code pushLevel}
	* @throws SecurityException if a security manager exists and if
	* the caller does not have {@code LoggingPermission("control")}.
	*/
	public synchronized void setPushLevel(Level newLevel) throws SecurityException {
	if (newLevel == null) {
	throw new NullPointerException();
	}
	checkPermission();
	pushLevel = newLevel;
	}

	/**
	* Get the {@code pushLevel}.
	*
	* @return the value of the {@code pushLevel}
	*/
	public Level getPushLevel() {
	return pushLevel;
	}

	/**
	* Check if this {@code Handler} would actually log a given
	* {@code LogRecord} into its internal buffer.
	* <p>
	* This method checks if the {@code LogRecord} has an appropriate level and
	* whether it satisfies any {@code Filter}. However it does <b>not</b>
	* check whether the {@code LogRecord} would result in a "push" of the
	* buffer contents. It will return false if the {@code LogRecord} is null.
	*
	* @param record a {@code LogRecord} (may be null).
	* @return true if the {@code LogRecord} would be logged.
	*
	*/
	@Override
	public boolean isLoggable(LogRecord record) {
	return super.isLoggable(record);
	}
	}

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