001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.io.input;
018
019import static org.apache.commons.io.IOUtils.EOF;
020
021import java.io.IOException;
022import java.io.InputStream;
023
024/**
025 * Proxy stream that closes and discards the underlying stream as soon as the
026 * end of input has been reached or when the stream is explicitly closed.
027 * Not even a reference to the underlying stream is kept after it has been
028 * closed, so any allocated in-memory buffers can be freed even if the
029 * client application still keeps a reference to the proxy stream.
030 * <p>
031 * This class is typically used to release any resources related to an open
032 * stream as soon as possible even if the client application (by not explicitly
033 * closing the stream when no longer needed) or the underlying stream (by not
034 * releasing resources once the last byte has been read) do not do that.
035 *
036 * @since 1.4
037 */
038public class AutoCloseInputStream extends ProxyInputStream {
039
040    /**
041     * Creates an automatically closing proxy for the given input stream.
042     *
043     * @param in underlying input stream
044     */
045    public AutoCloseInputStream(final InputStream in) {
046        super(in);
047    }
048
049    /**
050     * Closes the underlying input stream and replaces the reference to it
051     * with a {@link ClosedInputStream} instance.
052     * <p>
053     * This method is automatically called by the read methods when the end
054     * of input has been reached.
055     * <p>
056     * Note that it is safe to call this method any number of times. The original
057     * underlying input stream is closed and discarded only once when this
058     * method is first called.
059     *
060     * @throws IOException if the underlying input stream can not be closed
061     */
062    @Override
063    public void close() throws IOException {
064        in.close();
065        in = ClosedInputStream.CLOSED_INPUT_STREAM;
066    }
067
068    /**
069     * Automatically closes the stream if the end of stream was reached.
070     *
071     * @param n number of bytes read, or -1 if no more bytes are available
072     * @throws IOException if the stream could not be closed
073     * @since 2.0
074     */
075    @Override
076    protected void afterRead(final int n) throws IOException {
077        if (n == EOF) {
078            close();
079        }
080    }
081
082    /**
083     * Ensures that the stream is closed before it gets garbage-collected.
084     * As mentioned in {@link #close()}, this is a no-op if the stream has
085     * already been closed.
086     * @throws Throwable if an error occurs
087     */
088    @Override
089    protected void finalize() throws Throwable {
090        close();
091        super.finalize();
092    }
093
094}