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JDBC driver for MariaDB and MySQL
There is a newer version: 3.4.1
/*
 *
 * MariaDB Client for Java
 *
 * Copyright (c) 2012-2014 Monty Program Ab.
 * Copyright (c) 2015-2020 MariaDB Corporation Ab.
 *
 * This library is free software; you can redistribute it and/or modify it under
 * the terms of the GNU Lesser General Public License as published by the Free
 * Software Foundation; either version 2.1 of the License, or (at your option)
 * any later version.
 *
 * This library 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 Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License along
 * with this library; if not, write to Monty Program Ab [email protected].
 *
 * This particular MariaDB Client for Java file is work
 * derived from a Drizzle-JDBC. Drizzle-JDBC file which is covered by subject to
 * the following copyright and notice provisions:
 *
 * Copyright (c) 2009-2011, Marcus Eriksson
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 * Redistributions of source code must retain the above copyright notice, this list
 * of conditions and the following disclaimer.
 *
 * 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.
 *
 * Neither the name of the driver nor the names of its contributors may not be
 * used to endorse or promote products derived from this software without specific
 * prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS  AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS 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 COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 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.
 *
 */

package org.mariadb.jdbc.internal.io;

import java.time.Instant;
import java.time.format.DateTimeFormatter;
import java.util.Collection;
import java.util.ConcurrentModificationException;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.concurrent.atomic.AtomicLong;
import org.mariadb.jdbc.internal.util.Utils;

public class LruTraceCache extends LinkedHashMap {

  private AtomicLong increment = new AtomicLong();

  public LruTraceCache() {
    super(16, 1.0f, false);
  }

  /**
   * Add value to map.
   *
   * @param value value to add
   * @return added value
   */
  public TraceObject put(TraceObject value) {
    String key =
        increment.incrementAndGet() + "- " + DateTimeFormatter.ISO_INSTANT.format(Instant.now());
    return put(key, value);
  }

  @Override
  protected boolean removeEldestEntry(Map.Entry eldest) {
    return size() > 10;
  }

  /**
   * Value of trace cache in a readable format.
   *
   * @return trace cache value
   */
  public synchronized String printStack() {
    StringBuilder sb = new StringBuilder();
    boolean finished = false;
    while (!finished) {
      try {
        @SuppressWarnings("unchecked")
        Map.Entry[] arr =
            entrySet().toArray((Map.Entry[]) new Map.Entry[0]);
        for (Map.Entry entry : arr) {
          TraceObject traceObj = entry.getValue();
          if (traceObj.getBuf() != null) {
            String key = entry.getKey();
            String indicator = "";

            switch (traceObj.getIndicatorFlag()) {
              case TraceObject.COMPRESSED_PROTOCOL_NOT_COMPRESSED_PACKET:
                indicator = " (compressed protocol - packet not compressed)";
                break;
              case TraceObject.COMPRESSED_PROTOCOL_COMPRESSED_PACKET:
                indicator = " (compressed protocol - packet compressed)";
                break;
              default:
                break;
            }
            sb.append("\nthread:").append(traceObj.getThreadId());
            if (traceObj.isSend()) {
              sb.append(" send at -exchange:");
            } else {
              sb.append(" read at -exchange:");
            }

            sb.append(key).append(indicator).append(Utils.hexdump(traceObj.getBuf()));
          }
        }
        finished = true;
      } catch (ConcurrentModificationException cc) {
        // eat
      }
    }

    this.clear();
    return sb.toString();
  }

  /** Permit to clear array's of array, to help garbage. */
  public synchronized void clearMemory() {
    try {
      Collection traceObjects = values();
      for (TraceObject traceObject : traceObjects) {
        traceObject.remove();
      }
    } catch (ConcurrentModificationException c) {
      // eat
    }
    this.clear();
  }
}