dirstoragefactory4.java

derby database source code.good for you.

/*

   Derby - Class org.apache.derby.impl.io.DirStorageFactory4

   Copyright 2004 The Apache Software Foundation or its licensors, as applicable.

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.

 */

package org.apache.derby.impl.io;

import org.apache.derby.io.StorageFile;
import org.apache.derby.iapi.services.info.JVMInfo;

import java.io.IOException;

/**
 * This class implements the WritableStorageFactory interface using features found in Java 1.4 but
 * not in earlier versions of Java.
 */
public class DirStorageFactory4 extends DirStorageFactory
{

	private static final boolean	rwsOK = JVMInfo.JDK_ID >= JVMInfo.J2SE_142;
    
    /**
     * Most of the initialization is done in the init method.
     */
    public DirStorageFactory4()
    {
        super();
    }

    /**
     * Construct a persistent StorageFile from a path name.
     *
     * @param path The path name of the file. Guaranteed not to be in the temporary file directory. If null
     *             then the database directory should be returned.
     *
     * @return A corresponding StorageFile object
     */
    StorageFile newPersistentFile( String path)
    {
        if( path == null)
            return new DirFile4( dataDirectory, rwsOK);
        return new DirFile4(dataDirectory, path, rwsOK);
    }

    /**
     * Construct a persistent StorageFile from a directory and path name.
     *
     * @param directory The path name of the directory. Guaranteed not to be in the temporary file directory.
     *                  Guaranteed not to be null
     * @param fileName The name of the file within the directory. Guaranteed not to be null.
     *
     * @return A corresponding StorageFile object
     */
    StorageFile newPersistentFile( String directoryName, String fileName)
    {
        return new DirFile4( separatedDataDirectory + directoryName, fileName, rwsOK);
    }

    /**
     * Construct a persistent StorageFile from a directory and path name.
     *
     * @param directory The path name of the directory. Guaranteed not to be to be null. Guaranteed to be
     *                  created by a call to one of the newPersistentFile methods.
     * @param fileName The name of the file within the directory. Guaranteed not to be null.
     *
     * @return A corresponding StorageFile object
     */
    StorageFile newPersistentFile( StorageFile directoryName, String fileName)
    {
        return new DirFile4( (DirFile) directoryName, fileName, rwsOK);
    }

	
    /**
     * This method tests whether the "rws" and "rwd" modes are implemented. If the "rws" method is supported
     * then the database engine will conclude that the write methods of "rws" mode StorageRandomAccessFiles are
     * slow but the sync method is fast and optimize accordingly.
     *
     * @return <b>true</b> if an StIRandomAccess file opened with "rws" or "rwd" modes immediately writes data to the
     *         underlying storage, <b>false</b> if not.
     */
    public boolean supportsRws()
    {
        return rwsOK;
    }
	

}