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 end of input has been reached or when the stream is explicitly closed. Not even a
028 * reference to the underlying stream is kept after it has been closed, so any allocated in-memory buffers can be freed even if the client application still
029 * keeps a reference to the proxy stream.
030 * <p>
031 * This class is typically used to release any resources related to an open stream as soon as possible even if the client application (by not explicitly closing
032 * the stream when no longer needed) or the underlying stream (by not releasing resources once the last byte has been read) do not do that.
033 * </p>
034 * <p>
035 * To build an instance, use {@link Builder}.
036 * </p>
037 *
038 * @since 1.4
039 * @see Builder
040 */
041public class AutoCloseInputStream extends ProxyInputStream {
042
043    // @formatter:off
044    /**
045     * Builds a new {@link AutoCloseInputStream} instance.
046     *
047     * <p>
048     * For example:
049     * </p>
050     * <pre>{@code
051     * AutoCloseInputStream s = AutoCloseInputStream.builder()
052     *   .setPath(path)
053     *   .get();}
054     * </pre>
055     * <pre>{@code
056     * AutoCloseInputStream s = AutoCloseInputStream.builder()
057     *   .setInputStream(inputStream)
058     *   .get();}
059     * </pre>
060     *
061     * @see #get()
062     * @since 2.13.0
063     */
064    // @formatter:on
065    public static class Builder extends AbstractStreamBuilder<AutoCloseInputStream, Builder> {
066
067        /**
068         * Builds a new {@link AutoCloseInputStream}.
069         * <p>
070         * You must set input that supports {@link #getInputStream()}, otherwise, this method throws an exception.
071         * </p>
072         * <p>
073         * This builder use the following aspects:
074         * </p>
075         * <ul>
076         * <li>{@link #getInputStream()}</li>
077         * </ul>
078         *
079         * @return a new instance.
080         * @throws IllegalStateException         if the {@code origin} is {@code null}.
081         * @throws UnsupportedOperationException if the origin cannot be converted to an {@link InputStream}.
082         * @throws IOException                   if an I/O error occurs.
083         * @see #getInputStream()
084         */
085        @SuppressWarnings("resource") // Caller closes
086        @Override
087        public AutoCloseInputStream get() throws IOException {
088            return new AutoCloseInputStream(getInputStream());
089        }
090
091    }
092
093    /**
094     * Constructs a new {@link Builder}.
095     *
096     * @return a new {@link Builder}.
097     * @since 2.12.0
098     */
099    public static Builder builder() {
100        return new Builder();
101    }
102
103    /**
104     * Constructs an automatically closing proxy for the given input stream.
105     *
106     * @param in underlying input stream
107     * @deprecated Use {@link #builder()}, {@link Builder}, and {@link Builder#get()}
108     */
109    @Deprecated
110    public AutoCloseInputStream(final InputStream in) {
111        super(in);
112    }
113
114    /**
115     * Automatically closes the stream if the end of stream was reached.
116     *
117     * @param n number of bytes read, or -1 if no more bytes are available
118     * @throws IOException if the stream could not be closed
119     * @since 2.0
120     */
121    @Override
122    protected void afterRead(final int n) throws IOException {
123        if (n == EOF) {
124            close();
125        }
126    }
127
128    /**
129     * Closes the underlying input stream and replaces the reference to it with a {@link ClosedInputStream} instance.
130     * <p>
131     * This method is automatically called by the read methods when the end of input has been reached.
132     * </p>
133     * <p>
134     * Note that it is safe to call this method any number of times. The original underlying input stream is closed and discarded only once when this method is
135     * first called.
136     * </p>
137     *
138     * @throws IOException if the underlying input stream can not be closed
139     */
140    @Override
141    public void close() throws IOException {
142        in.close();
143        in = ClosedInputStream.INSTANCE;
144    }
145
146    /**
147     * Ensures that the stream is closed before it gets garbage-collected. As mentioned in {@link #close()}, this is a no-op if the stream has already been
148     * closed.
149     *
150     * @throws Throwable if an error occurs
151     */
152    @Override
153    protected void finalize() throws Throwable {
154        close();
155        super.finalize();
156    }
157
158}