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+/*
+ * 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