- /*
- * Copyright 2001-2004 The Apache Software Foundation.
- *
- * 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.commons.io.output;
-
- import java.io.IOException;
- import java.io.OutputStream;
-
-
- /**
- * An output stream which triggers an event when a specified number of bytes of
- * data have been written to it. The event can be used, for example, to throw
- * an exception if a maximum has been reached, or to switch the underlying
- * stream type when the threshold is exceeded.
- * <p>
- * This class overrides all <code>OutputStream</code> methods. However, these
- * overrides ultimately call the corresponding methods in the underlying output
- * stream implementation.
- * <p>
- * NOTE: This implementation may trigger the event <em>before</em> the threshold
- * is actually reached, since it triggers when a pending write operation would
- * cause the threshold to be exceeded.
- *
- * @author <a href="mailto:martinc@apache.org">Martin Cooper</a>
- *
- * @version $Id: ThresholdingOutputStream.java,v 1.2 2004/02/23 04:40:29 bayard Exp $
- */
- public abstract class ThresholdingOutputStream
- extends OutputStream
- {
-
- // ----------------------------------------------------------- Data members
-
-
- /**
- * The threshold at which the event will be triggered.
- */
- private int threshold;
-
-
- /**
- * The number of bytes written to the output stream.
- */
- private long written;
-
-
- /**
- * Whether or not the configured threshold has been exceeded.
- */
- private boolean thresholdExceeded;
-
-
- // ----------------------------------------------------------- Constructors
-
-
- /**
- * Constructs an instance of this class which will trigger an event at the
- * specified threshold.
- *
- * @param threshold The number of bytes at which to trigger an event.
- */
- public ThresholdingOutputStream(int threshold)
- {
- this.threshold = threshold;
- }
-
-
- // --------------------------------------------------- OutputStream methods
-
-
- /**
- * Writes the specified byte to this output stream.
- *
- * @param b The byte to be written.
- *
- * @exception IOException if an error occurs.
- */
- public void write(int b) throws IOException
- {
- checkThreshold(1);
- getStream().write(b);
- written++;
- }
-
-
- /**
- * Writes <code>b.length</code> bytes from the specified byte array to this
- * output stream.
- *
- * @param b The array of bytes to be written.
- *
- * @exception IOException if an error occurs.
- */
- public void write(byte b[]) throws IOException
- {
- checkThreshold(b.length);
- getStream().write(b);
- written += b.length;
- }
-
-
- /**
- * Writes <code>len</code> bytes from the specified byte array starting at
- * offset <code>off</code> to this output stream.
- *
- * @param b The byte array from which the data will be written.
- * @param off The start offset in the byte array.
- * @param len The number of bytes to write.
- *
- * @exception IOException if an error occurs.
- */
- public void write(byte b[], int off, int len) throws IOException
- {
- checkThreshold(len);
- getStream().write(b, off, len);
- written += len;
- }
-
-
- /**
- * Flushes this output stream and forces any buffered output bytes to be
- * written out.
- *
- * @exception IOException if an error occurs.
- */
- public void flush() throws IOException
- {
- getStream().flush();
- }
-
-
- /**
- * Closes this output stream and releases any system resources associated
- * with this stream.
- *
- * @exception IOException if an error occurs.
- */
- public void close() throws IOException
- {
- try
- {
- flush();
- }
- catch (IOException ignored)
- {
- // ignore
- }
- getStream().close();
- }
-
-
- // --------------------------------------------------------- Public methods
-
-
- /**
- * Returns the threshold, in bytes, at which an event will be triggered.
- *
- * @return The threshold point, in bytes.
- */
- public int getThreshold()
- {
- return threshold;
- }
-
-
- /**
- * Returns the number of bytes that have been written to this output stream.
- *
- * @return The number of bytes written.
- */
- public long getByteCount()
- {
- return written;
- }
-
-
- /**
- * Determines whether or not the configured threshold has been exceeded for
- * this output stream.
- *
- * @return <code>true</code> if the threshold has been reached;
- * <code>false</code> otherwise.
- */
- public boolean isThresholdExceeded()
- {
- return (written > threshold);
- }
-
-
- // ------------------------------------------------------ Protected methods
-
-
- /**
- * Checks to see if writing the specified number of bytes would cause the
- * configured threshold to be exceeded. If so, triggers an event to allow
- * a concrete implementation to take action on this.
- *
- * @param count The number of bytes about to be written to the underlying
- * output stream.
- *
- * @exception IOException if an error occurs.
- */
- protected void checkThreshold(int count) throws IOException
- {
- if (!thresholdExceeded && (written + count > threshold))
- {
- thresholdReached();
- thresholdExceeded = true;
- }
- }
-
-
- // ------------------------------------------------------- Abstract methods
-
-
- /**
- * Returns the underlying output stream, to which the corresponding
- * <code>OutputStream</code> methods in this class will ultimately delegate.
- *
- * @return The underlying output stream.
- *
- * @exception IOException if an error occurs.
- */
- protected abstract OutputStream getStream() throws IOException;
-
-
- /**
- * Indicates that the configured threshold has been reached, and that a
- * subclass should take whatever action necessary on this event. This may
- * include changing the underlying output stream.
- *
- * @exception IOException if an error occurs.
- */
- protected abstract void thresholdReached() throws IOException;
- }