/*
* ============================================================================
* The Apache Software License, Version 1.1
* ============================================================================
*
* Copyright (C) 1999 The Apache Software Foundation. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modifica-
* tion, are permitted provided that the following conditions are met: 1.
* Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer. 2. Redistributions in
* binary form must reproduce the above copyright notice, this list of
* conditions and the following disclaimer in the documentation and/or other
* materials provided with the distribution. 3. The end-user documentation
* included with the redistribution, if any, must include the following
* acknowledgment: "This product includes software developed by the Apache
* Software Foundation (http://www.apache.org/)." Alternately, this
* acknowledgment may appear in the software itself, if and wherever such
* third-party acknowledgments normally appear. 4. The names "log4j" and
* "Apache Software Foundation" must not be used to endorse or promote products
* derived from this software without prior written permission. For written
* permission, please contact apache@apache.org. 5. Products derived from this
* software may not be called "Apache", nor may "Apache" appear in their name,
* without prior written permission of the Apache Software Foundation.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
* FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* APACHE SOFTWARE FOUNDATION OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLU-
* DING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
* ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* This software consists of voluntary contributions made by many individuals
* on behalf of the Apache Software Foundation. For more information on the
* Apache Software Foundation, please see <http://www.apache.org/> .
*
*/
package smtphandler;
import java.util.logging.LogRecord;
/**
*
* CyclicBuffer is used by other handlers to hold {@link LogRecord} objects for
* immediate or differed display.
*
* <p>
* This buffer gives read access to any element in the buffer not just the
* first or last element.
*
* @author Ceki Gülcü
* @author Sean C. Sullivan
*
*/
public class CyclicBuffer
{
private LogRecord[] records;
private int first;
private int last;
private int numElems;
private int maxSize;
/**
* Instantiate a new CyclicBuffer of at most <code>maxSize</code>
* records.
*
* The <code>maxSize</code> argument must a positive integer.
*
* @param maxSize
* The maximum number of elements in the buffer.
*/
public CyclicBuffer(int maxSize) throws IllegalArgumentException
{
if (maxSize < 1)
{
throw new IllegalArgumentException(
"The maxSize argument ("
+ maxSize
+ ") is not a positive integer.");
}
this.maxSize = maxSize;
records = new LogRecord[maxSize];
first = 0;
last = 0;
numElems = 0;
}
/**
* Add a <code>record</code> as the last record in the buffer.
*
* @param record must be non-null
*
*/
public void add(LogRecord record)
{
records[last] = record;
if (++last == maxSize)
last = 0;
if (numElems < maxSize)
numElems++;
else if (++first == maxSize)
first = 0;
}
/**
* Get the <i>i</i> th oldest record currently in the buffer. If <em>i</em>
* is outside the range 0 to the number of elements currently in the
* buffer, then <code>null</code> is returned.
*
* @return may return null
*
*/
public LogRecord get(int i)
{
if (i < 0 || i >= numElems)
return null;
return records[(first + i) % maxSize];
}
public int getMaxSize()
{
return maxSize;
}
/**
* Get the oldest (first) element in the buffer. The oldest element is
* removed from the buffer.
*
* @return may return null
*
*/
public LogRecord get()
{
LogRecord r = null;
if (numElems > 0)
{
numElems--;
r = records[first];
records[first] = null;
if (++first == maxSize)
first = 0;
}
return r;
}
/**
* Get the number of elements in the buffer. This number is guaranteed to
* be in the range 0 to <code>maxSize</code> (inclusive).
*/
public int length()
{
return numElems;
}
/**
* Resize the cyclic buffer to <code>newSize</code>.
*
* @throws IllegalArgumentException
* if <code>newSize</code> is negative.
*/
public void resize(int newSize)
{
if (newSize < 0)
{
throw new IllegalArgumentException(
"Negative array size [" + newSize + "] not allowed.");
}
if (newSize == numElems)
{
return; // nothing to do
}
LogRecord[] temp = new LogRecord[newSize];
int loopLen = newSize < numElems ? newSize : numElems;
for (int i = 0; i < loopLen; i++)
{
temp[i] = records[first];
records[first] = null;
if (++first == numElems)
first = 0;
}
records = temp;
first = 0;
numElems = loopLen;
maxSize = newSize;
if (loopLen == newSize)
{
last = 0;
}
else
{
last = loopLen;
}
}
public String toString()
{
StringBuffer sb = new StringBuffer();
sb.append("length=" + length());
return sb.toString();
}
}