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
024import org.apache.commons.io.build.AbstractStreamBuilder;
025
026/**
027 * Proxy stream that closes and discards the underlying stream as soon as the
028 * end of input has been reached or when the stream is explicitly closed.
029 * Not even a reference to the underlying stream is kept after it has been
030 * closed, so any allocated in-memory buffers can be freed even if the
031 * client application still keeps a reference to the proxy stream.
032 * <p>
033 * This class is typically used to release any resources related to an open
034 * stream as soon as possible even if the client application (by not explicitly
035 * closing the stream when no longer needed) or the underlying stream (by not
036 * releasing resources once the last byte has been read) do not do that.
037 * </p>
038 *
039 * @since 1.4
040 */
041public class AutoCloseInputStream extends ProxyInputStream {
042
043    /**
044     * Builds a new {@link AutoCloseInputStream} instance.
045     * <p>
046     * For example:
047     * </p>
048     *
049     * <pre>{@code
050     * AutoCloseInputStream s = AutoCloseInputStream.builder()
051     *   .setPath(path)
052     *   .get();}
053     * </pre>
054     *
055     * <pre>{@code
056     * AutoCloseInputStream s = AutoCloseInputStream.builder()
057     *   .setInputStream(inputStream)
058     *   .get();}
059     * </pre>
060     *
061     * @since 2.13.0
062     */
063    public static class Builder extends AbstractStreamBuilder<AutoCloseInputStream, Builder> {
064
065        /**
066         * Constructs a new instance.
067         * <p>
068         * This builder use the aspect InputStream.
069         * </p>
070         *
071         * @return a new instance.
072         * @throws IOException              if an I/O error occurs.
073         * @throws IllegalArgumentException if the buffer is not large enough to hold a complete character.
074         */
075        @SuppressWarnings("resource") // Caller closes
076        @Override
077        public AutoCloseInputStream get() throws IOException {
078            return new AutoCloseInputStream(getInputStream());
079        }
080
081    }
082
083    /**
084     * Constructs a new {@link Builder}.
085     *
086     * @return a new {@link Builder}.
087     * @since 2.12.0
088     */
089    public static Builder builder() {
090        return new Builder();
091    }
092
093    /**
094     * Constructs an automatically closing proxy for the given input stream.
095     *
096     * @param in underlying input stream
097     * @deprecated Use {@link #builder()}, {@link Builder}, and {@link Builder#get()}
098     */
099    @Deprecated
100    public AutoCloseInputStream(final InputStream in) {
101        super(in);
102    }
103
104    /**
105     * Automatically closes the stream if the end of stream was reached.
106     *
107     * @param n number of bytes read, or -1 if no more bytes are available
108     * @throws IOException if the stream could not be closed
109     * @since 2.0
110     */
111    @Override
112    protected void afterRead(final int n) throws IOException {
113        if (n == EOF) {
114            close();
115        }
116    }
117
118    /**
119     * Closes the underlying input stream and replaces the reference to it
120     * with a {@link ClosedInputStream} instance.
121     * <p>
122     * This method is automatically called by the read methods when the end
123     * of input has been reached.
124     * <p>
125     * Note that it is safe to call this method any number of times. The original
126     * underlying input stream is closed and discarded only once when this
127     * method is first called.
128     *
129     * @throws IOException if the underlying input stream can not be closed
130     */
131    @Override
132    public void close() throws IOException {
133        in.close();
134        in = ClosedInputStream.INSTANCE;
135    }
136
137    /**
138     * Ensures that the stream is closed before it gets garbage-collected.
139     * As mentioned in {@link #close()}, this is a no-op if the stream has
140     * already been closed.
141     * @throws Throwable if an error occurs
142     */
143    @Override
144    protected void finalize() throws Throwable {
145        close();
146        super.finalize();
147    }
148
149}