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   *  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
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   *
   *    https://www.apache.org/licenses/LICENSE-2.0
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  package org.apache.cayenne.template;
  
  import java.io.ByteArrayInputStream;
  import java.util.concurrent.ArrayBlockingQueue;
  
  import org.apache.cayenne.template.parser.SQLTemplateParser;
  
  /**
   * @since 4.1
   */
  class TemplateParserPool {
  
      final static int INITIAL_POOL_SIZE = 4;
      final static int MAX_POOL_SIZE = 20;
  
      private ArrayBlockingQueue<SQLTemplateParser> parsers = new ArrayBlockingQueue<>(MAX_POOL_SIZE);
  
      TemplateParserPool() {
          for(int i=0; i<INITIAL_POOL_SIZE; i++) {
              parsers.offer(createNewParser());
          }
      }
  
      SQLTemplateParser get() {
          SQLTemplateParser parser = parsers.poll();
          if(parser == null) {
              parser = createNewParser();
          }
          return parser;
      }
  
      void put(SQLTemplateParser parser) {
          parser.ReInit(new ByteArrayInputStream("\n".getBytes()));
          parsers.offer(parser);
      }
  
      SQLTemplateParser createNewParser() {
          return new SQLTemplateParser(new ByteArrayInputStream("\n".getBytes()));
      }
  
  }
  