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A reactive Java web server.
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/*
 * Copyright (c) 1998-2015 Caucho Technology -- all rights reserved
 *
 * This file is part of Baratine(TM)(TM)
 *
 * Each copy or derived work must preserve the copyright notice and this
 * notice unmodified.
 *
 * Baratine is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * Baratine 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, or any warranty
 * of NON-INFRINGEMENT.  See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Baratine; if not, write to the
 *
 *   Free Software Foundation, Inc.
 *   59 Temple Place, Suite 330
 *   Boston, MA 02111-1307  USA
 *
 * @author Scott Ferguson
 */

package com.caucho.v5.vfs;

import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import com.caucho.v5.loader.EnvironmentLocal;

/**
 * The top-level filesystem schemes are collected into a single map.
 *
 * The default scheme has a number of standard filesystems, file:, mailto:,
 * jndi:, http:.
 *
 * 
Applications can add schemes in the configuration file.  When first
 * accessed, the SchemeMap will look in the Registry to match the scheme.
 * If the new scheme exists, it will instantiate a single root instance and
 * use that for the remainder of the application.
 * 
 * <caucho.com>
 *  <vfs scheme="foo" class-name="test.vfs.FooPath"/>
 * </caucho.com>
 * 
 */
public class SchemeMap {
  // Constant null scheme map for protected filesystems.
  private static SchemeMap _nullSchemeMap;

  private final EnvironmentLocal> _schemeMap
    = new EnvironmentLocal<>();

  /**
   * Create an empty SchemeMap.
   */
  public SchemeMap()
  {
    _schemeMap.set(new ConcurrentHashMap(), null);
  }

  /**
   * Create an empty SchemeMap.
   */
  private SchemeMap(Map map)
  {
    getUpdateMap().putAll(map);
  }

  /**
   * The null scheme map is useful for protected filesystems as used
   * in createRoot().  That way, no dangerous code can get access to
   * files using, for example, the file: scheme.
   */
  static SchemeMap getNullSchemeMap()
  {
    synchronized (SchemeMap.class) {
      if (_nullSchemeMap == null) {
        _nullSchemeMap = new SchemeMap();
      }
      
      return _nullSchemeMap;
    }
  }

  /**
   * Gets the scheme from the schemeMap.
   */
  public PathImpl get(String scheme)
  {
    ConcurrentHashMap map = getMap();
    
    SchemeRoot root = map.get(scheme);

    if (root == null) {
      PathImpl rootPath = createLazyScheme(scheme);
      
      if (rootPath != null) {
        map.putIfAbsent(scheme, new SchemeRoot(rootPath));
        root = map.get(scheme);
      }
    }
    
    PathImpl path = null;
    
    if (root != null) {
      path = root.getRoot();
    }
    
    if (path != null) {
      return path;
    }
    else {
      return new NotFoundPath(this, scheme + ":");
    }
  }
  
  protected PathImpl createLazyScheme(String file)
  {
    return null;
  }
  
  public SchemeRoot getSchemeRoot(String scheme)
  {
    return getMap().get(scheme);
  }

  /**
   * Puts a new value in the schemeMap.
   */
  public PathImpl put(String scheme, PathImpl path)
  {
    SchemeRoot oldRoot = getUpdateMap().put(scheme, new SchemeRoot(path));
    
    return oldRoot != null ? oldRoot.getRoot() : null;
  }

  /**
   * Puts a new value in the schemeMap.
   */
  public SchemeRoot put(String scheme, SchemeRoot root)
  {
    return getUpdateMap().put(scheme, root);
  }

  public SchemeMap copy()
  {
    return new SchemeMap(getMap());
  }

  /**
   * Removes value from the schemeMap.
   */
  public PathImpl remove(String scheme)
  {
    SchemeRoot oldRoot = getUpdateMap().remove(scheme);
    
    return oldRoot != null ? oldRoot.getRoot() : null;
  }
  
  private ConcurrentHashMap getMap()
  {
    ConcurrentHashMap map = _schemeMap.get();
    
    return map;
  }
  
  private ConcurrentHashMap getUpdateMap()
  {
    ConcurrentHashMap map = _schemeMap.getLevel();
    
    if (map == null) {
      ConcurrentHashMap oldMap = getMap();
      
      if (oldMap != null)
        map = new ConcurrentHashMap(oldMap);
      else
        map = new ConcurrentHashMap();
      
      _schemeMap.set(map);
    }
    
    return map;
  }
}