/*

  * Copyright 2007, 2008 Ange Optimization ApS

  *

  * 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 eu.simuline.octave.util;

 import java.io.IOException;

 import java.io.Writer;

 import org.apache.commons.logging.Log;

 import org.apache.commons.logging.LogFactory;

 /**

  * Will protect a Writer from beeing closed by {@link #close()}, 

  * useful for protecting stdout and stderr from beeing closed. 

  * Trying to close via {@link #close()} results in loosing connection 

  * whereas {@link #reallyClose()} really closes the writer. 

  * 

  * @author Kim Hansen

  */

 public final class NoCloseWriter extends Writer {

     private static final Log LOG = LogFactory.getLog(NoCloseWriter.class);

     /**

      * A writer or <code>null</code>. 

      * The latter is the case if initialized with <code>null</code>, 

      * or if tried to close via {@link #close()}. 

      * In the latter case 

      * it is not even possible to close with {@link #reallyClose()}. 

      */

     private Writer writer;

     /**

      * Create a NoCloseWriter that will protect writer.

      * 

      * @param writer

      *    the writer to be protected from being closed by {@link #close()}.

      */

     public NoCloseWriter(final Writer writer) {

         this.writer = writer;

     }

     @Override

     public void write(final char[] cbuf, final int off, final int len) 

         throws IOException {

         if (this.writer == null) {

             return;

         }

         this.writer.write(cbuf, off, len);

     }

     @Override

     public void flush() throws IOException {

         if (this.writer == null) {

             return;

         }

         this.writer.flush();

     }

     /**

      * Flushes the writer and looses the connection to it. 

      * No close and also in future no close possible. 

      * 

      * @throws IOException

      *    from the underlying writer. 

      * @see #reallyClose()

      */

     @Override

     public void close() throws IOException {

         LOG.debug("ignoring close() on a writer");

         if (this.writer == null) {

             return;

         }

         this.writer.flush();

         this.writer = null;

     }

     /**

      * Really closes the underlying writer, with one exception ;-).

      * 

      * @throws IOException

      *    from the underlying writer.

      * @throws NullPointerException

      *    if the NoCloseWriter has been closed via {@link #close()}.

      */

     public void reallyClose() throws IOException {

         LOG.debug("reallyClose() a writer");

         this.writer.close();

     }

 }