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A full SQL database system with JDBC driver that can be embedded in a Java application or operate as a stand-alone server with clients connecting via TCP/IP.
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/**
 * com.mckoi.database.V1FileStoreSystem  04 Feb 2003
 *
 * Mckoi SQL Database ( http://www.mckoi.com/database )
 * Copyright (C) 2000, 2001, 2002  Diehl and Associates, Inc.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * Version 2 as published by the Free Software Foundation.
 *
 * This program 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 General Public License Version 2 for more details.
 *
 * You should have received a copy of the GNU General Public License
 * Version 2 along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 * Change Log:
 * 
 * 
 */

package com.mckoi.database;

import com.mckoi.store.*;
import com.mckoi.debug.Lvl;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;

/**
 * An implementation of StoreSystem that manages persistant data through the
 * native file system.  Each store is represented by a ScatteringFileStore
 * object against the current path.  This implementation is compatible with
 * versions of the database from 0.94 onwards.
 *
 * @author Tobias Downer
 */

class V1FileStoreSystem implements StoreSystem {

  /**
   * The name of the file extention of the file lock on this conglomerate.
   */
  private static final String FLOCK_EXT = ".lock";
  
  /**
   * The TransactionSystem that contains the various configuration options for
   * the database.
   */
  private TransactionSystem system;

  /**
   * The path in the filesystem where the data files are located.
   */
  private File path;

  /**
   * True if the stores are read-only.
   */
  private boolean read_only;

  /**
   * The lock file.
   */
  private FileOutputStream lock_file;
  
  /**
   * Constructor.
   */
  public V1FileStoreSystem(TransactionSystem system, File path,
                           boolean read_only) {
    this.system = system;
    this.path = path;
    this.read_only = read_only;
    // If the database path doesn't exist, create it now,
    if (!read_only && !path.exists()) {
      path.mkdirs();
    }
  }

  /**
   * Creates the JournalledFileStore object for this table.
   */
  private JournalledFileStore createFileStore(String file_name)
                                                           throws IOException {
    LoggingBufferManager buffer_manager = system.getBufferManager();
    return new JournalledFileStore(file_name, buffer_manager, read_only);
  }

  // ---------- Implemented from StoreSystem ----------
  
  public boolean storeExists(String name) {
    try {
      JournalledFileStore store = createFileStore(name);
      return store.exists();
    }
    catch (IOException e) {
      system.Debug().writeException(e);
      throw new RuntimeException("IO Error: " + e.getMessage());
    }
  }

  public Store createStore(String name) {
    LoggingBufferManager buffer_manager = system.getBufferManager();
    if (read_only) {
      throw new RuntimeException(
                        "Can not create store because system is read-only.");
    }
    try {
      buffer_manager.lockForWrite();
      
      JournalledFileStore store = createFileStore(name);
      if (!store.exists()) {
        store.open();
        return store;
      }
      else {
        throw new RuntimeException("Can not create - store with name " + name +
                                   " already exists.");
      }
    }
    catch (IOException e) {
      system.Debug().writeException(e);
      throw new RuntimeException("IO Error: " + e.getMessage());
    }
    catch (InterruptedException e) {
      throw new Error("Interrupted: " + e.getMessage());
    }
    finally {
      buffer_manager.unlockForWrite();
    }
    
  }

  public Store openStore(String name) {
    LoggingBufferManager buffer_manager = system.getBufferManager();
    try {
      buffer_manager.lockForWrite();
      
      JournalledFileStore store = createFileStore(name);
      if (store.exists()) {
        store.open();
        return store;
      }
      else {
        throw new RuntimeException("Can not open - store with name " + name +
                                   " does not exist.");
      }
    }
    catch (IOException e) {
      system.Debug().writeException(e);
      throw new RuntimeException("IO Error: " + e.getMessage());
    }
    catch (InterruptedException e) {
      throw new Error("Interrupted: " + e.getMessage());
    }
    finally {
      buffer_manager.unlockForWrite();
    }
    
  }

  public boolean closeStore(Store store) {
    LoggingBufferManager buffer_manager = system.getBufferManager();
    try {
      buffer_manager.lockForWrite();

      ((JournalledFileStore) store).close();
      return true;
    }
    catch (IOException e) {
      system.Debug().writeException(e);
      throw new RuntimeException("IO Error: " + e.getMessage());
    }
    catch (InterruptedException e) {
      throw new Error("Interrupted: " + e.getMessage());
    }
    finally {
      buffer_manager.unlockForWrite();
    }
    
  }

  public boolean deleteStore(Store store) {
    LoggingBufferManager buffer_manager = system.getBufferManager();
    try {
      buffer_manager.lockForWrite();

      return ((JournalledFileStore) store).delete();
    }
    catch (IOException e) {
      system.Debug().writeException(e);
      throw new RuntimeException("IO Error: " + e.getMessage());
    }
    catch (InterruptedException e) {
      throw new Error("Interrupted: " + e.getMessage());
    }
    finally {
      buffer_manager.unlockForWrite();
    }
    
  }

  public void setCheckPoint() {
    try {
      LoggingBufferManager buffer_manager = system.getBufferManager();
      buffer_manager.setCheckPoint(false);
    }
    catch (IOException e) {
      system.Debug().writeException(e);
      throw new RuntimeException("IO Error: " + e.getMessage());
    }
    catch (InterruptedException e) {
      system.Debug().writeException(e);
      throw new RuntimeException("Interrupted Error: " + e.getMessage());
    }
  }
  
  public void lock(String name) throws IOException {
    File flock_fn = new File(path, name + FLOCK_EXT);
    if (flock_fn.exists()) {
      // Okay, the file lock exists.  This means either an extremely bad
      // crash or there is another database locked on the files.  If we can
      // delete the lock then we can go on.
      system.Debug().write(Lvl.WARNING, this,
                           "File lock file exists: " + flock_fn);
      boolean deleted = false;
      deleted = flock_fn.delete();
      if (!deleted) {
        // If we couldn't delete, then most likely database being used.
        System.err.println("\n" +
            "I couldn't delete the file lock for Database '" + name + "'.\n" +
            "This most likely means the database is open and being used by\n" +
            "another process.\n" +
            "The lock file is: " + flock_fn + "\n\n");
        throw new IOException("Couldn't delete conglomerate file lock.");
      }
    }
//#IFDEF(NO_1.1)
    // Atomically create the file,
    flock_fn.createNewFile();
    // Set it to delete on normal exit of the JVM.
    flock_fn.deleteOnExit();
//#ENDIF
    // Open up a stream and lock it in the OS
    lock_file = new FileOutputStream(flock_fn);
  }

  public void unlock(String name) throws IOException {
    // Close and delete the lock file.
    if (lock_file != null) {
      lock_file.close();
    }
    // Try and delete it
    File flock_fn = new File(path, name + FLOCK_EXT);
    flock_fn.delete();
  }
  
}