src/main/include/log4cxx/helpers/cyclicbuffer.h

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef _LOG4CXX_HELPERS_CYCLICBUFFER_H
#define _LOG4CXX_HELPERS_CYCLICBUFFER_H

#include <log4cxx/spi/loggingevent.h>

namespace log4cxx
{
namespace helpers
{
/**
CyclicBuffer is used by other appenders to hold instances of
{@link log4cxx::spi::LoggingEvent LoggingEvent} for immediate
or deferred display.
<p>This buffer gives read access to any element in the buffer not
just the first or last element.
*/
class LOG4CXX_EXPORT CyclicBuffer
{
        log4cxx::spi::LoggingEventList ea;
        int first;
        int last;
        int numElems;
        int maxSize;

    public:
        /**
        Instantiate a new CyclicBuffer of at most <code>maxSize</code>
        events.
        The <code>maxSize</code> argument must a positive integer.
        @param maxSize The maximum number of elements in the buffer.
        @throws IllegalArgumentException if <code>maxSize</code>
        is negative.
        */
        CyclicBuffer(int maxSize);
        ~CyclicBuffer();

        /**
        Add an <code>event</code> as the last event in the buffer.
        */
        void add(const spi::LoggingEventPtr& event);

        /**
        Get the <i>i</i>th oldest event 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.
        */
        spi::LoggingEventPtr get(int i);

        int getMaxSize() const
        {
            return maxSize;
        }

        /**
        Get the oldest (first) element in the buffer. The oldest element
        is removed from the buffer.
        */
        spi::LoggingEventPtr get();

        /**
        Get the number of elements in the buffer. This number is
        guaranteed to be in the range 0 to <code>maxSize</code>
        (inclusive).
        */
        int length() const
        {
            return numElems;
        }

        /**
        Resize the cyclic buffer to <code>newSize</code>.
        @throws IllegalArgumentException if <code>newSize</code> is negative.
        */
        void resize(int newSize);
}; // class CyclicBuffer
}  //namespace helpers
} //namespace log4cxx

#endif //_LOG4CXX_HELPERS_CYCLICBUFFER_H