TableView.java :  » Database-DBMS » smallsql » smallsql » database » Java Open Source

/* =============================================================
 * SmallSQL : a free Java DBMS library for the Java(tm) platform
 * =============================================================
 *
 * (C) Copyright 2004-2007, by Volker Berlin.
 *
 * Project Info:  http://www.smallsql.de/
 *
 * 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 the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, 
 * USA.  
 *
 * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 
 * in the United States and other countries.]
 *
 * ---------------
 * TableView.java
 * ---------------
 * Author: Volker Berlin
 * 
 * Created on 05.06.2004
 */
package smallsql.database;

import java.io.*;
import java.sql.*;
import smallsql.database.language.Language;


/**
 * @author Volker Berlin
 */
abstract class TableView {

  static final int MAGIC_TABLE = 'S' << 24 | 'Q' << 16 | 'L' << 8 | 'T';
  static final int MAGIC_VIEW  = 'S' << 24 | 'Q' << 16 | 'L' << 8 | 'V';
  static final int TABLE_VIEW_VERSION = 2;
  static final int TABLE_VIEW_OLD_VERSION = 1;
  
  final String name;
  final Columns columns;

  /** 
   * Mark the last change on the structure of the Table or View.
   * If this value change then PreparedStatements need to recompile.
   */
  private long timestamp = System.currentTimeMillis();
  
  static final int LOCK_NONE   = 0; // read on READ_COMMITED and READ_UNCOMMITED
  static final int LOCK_INSERT = 1; // prevent only LOCK_TAB
  static final int LOCK_READ   = 2; // occur on read and prevent a write of data, it can occur more as one LOCK_READ per page
  static final int LOCK_WRITE  = 3; // occur on write and prevent every other access to the data, it is only one LOCK_WRITE per page possible
  static final int LOCK_TAB    = 4; // lock the total table


  TableView(String name, Columns columns){
    this.name = name;
    this.columns = columns;
  }
  
  /**
   * Load a Table or View object. 
   */
  static TableView load(SSConnection con, Database database, String name) throws SQLException{
    RandomAccessFile raFile = null;
    try{
      String fileName = Utils.createTableViewFileName( database, name );
      File file = new File( fileName );
      if(!file.exists())
        throw SmallSQLException.create(Language.TABLE_OR_VIEW_MISSING, name);
      raFile = Utils.openRaFile( file );
      int magic   = raFile.readInt();
      int version = raFile.readInt();
      switch(magic){
        case MAGIC_TABLE:
        case MAGIC_VIEW:
            break;
        default:
          throw SmallSQLException.create(Language.TABLE_OR_VIEW_FILE_INVALID, fileName);
      }
      if(version > TABLE_VIEW_VERSION)
        throw SmallSQLException.create(Language.FILE_TOONEW, new Object[] { new Integer(version), fileName });
      if(version < TABLE_VIEW_OLD_VERSION)
        throw SmallSQLException.create(Language.FILE_TOOOLD, new Object[] { new Integer(version), fileName });
      if(magic == MAGIC_TABLE)
        return new Table( database, con, name, raFile, raFile.getFilePointer(), version);
        return new View ( con, name, raFile, raFile.getFilePointer());
    }catch(Throwable e){
      if(raFile != null)
        try{
          raFile.close();
        }catch(Exception e2){
          DriverManager.println(e2.toString());
        }
      throw SmallSQLException.createFromException(e);
    }
  }
  
  
  File getFile(Database database) throws Exception{
    return new File( Utils.createTableViewFileName( database, name ) );
  }
  

  RandomAccessFile createFile(Database database) throws Exception{
    File file = getFile( database );
    boolean ok = file.createNewFile();
    if(!ok) throw SmallSQLException.create(Language.TABLE_EXISTENT, name);
    RandomAccessFile raFile = Utils.openRaFile( file );
    writeMagic(raFile);
    return raFile;
  }
  
  abstract void writeMagic(RandomAccessFile raFile) throws Exception;

  
  String getName(){
    return name;
  }
    

  long getTimestamp(){
    return timestamp;
  }
  

  /**
   * Returns the index of a column name. The first column has the index 0.
   */
  final int findColumnIdx(String columnName){
    // FIXME switch to a tree search on performance reason
    for(int i=0; i<columns.size(); i++){
      if( columns.get(i).getName().equalsIgnoreCase(columnName) ) return i;
    }
    return -1;
  }


  /**
   * Returns the Column of a column name.
   */
  final Column findColumn(String columnName){
    for(int i=0; i<columns.size(); i++){
      Column column = columns.get(i);
      if( column.getName().equalsIgnoreCase(columnName) ) return column;
    }
    return null;
  }


  
  /**
   * Close it and free all resources.
   */
  void close() throws Exception{/* in this abstract class is nothing to free */}

}