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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  package org.apache.commons.io.input;
18  
19  import static org.apache.commons.io.IOUtils.EOF;
20  
21  import java.io.IOException;
22  import java.io.InputStream;
23  
24  import org.apache.commons.io.build.AbstractStreamBuilder;
25  
26  /**
27   * Proxy stream that closes and discards the underlying stream as soon as the
28   * end of input has been reached or when the stream is explicitly closed.
29   * Not even a reference to the underlying stream is kept after it has been
30   * closed, so any allocated in-memory buffers can be freed even if the
31   * client application still keeps a reference to the proxy stream.
32   * <p>
33   * This class is typically used to release any resources related to an open
34   * stream as soon as possible even if the client application (by not explicitly
35   * closing the stream when no longer needed) or the underlying stream (by not
36   * releasing resources once the last byte has been read) do not do that.
37   * </p>
38   *
39   * @since 1.4
40   */
41  public class AutoCloseInputStream extends ProxyInputStream {
42  
43      /**
44       * Builds a new {@link AutoCloseInputStream} instance.
45       * <p>
46       * For example:
47       * </p>
48       *
49       * <pre>{@code
50       * AutoCloseInputStream s = AutoCloseInputStream.builder()
51       *   .setPath(path)
52       *   .get();}
53       * </pre>
54       *
55       * <pre>{@code
56       * AutoCloseInputStream s = AutoCloseInputStream.builder()
57       *   .setInputStream(inputStream)
58       *   .get();}
59       * </pre>
60       *
61       * @since 2.13.0
62       */
63      public static class Builder extends AbstractStreamBuilder<AutoCloseInputStream, Builder> {
64  
65          /**
66           * Constructs a new instance.
67           * <p>
68           * This builder use the aspect InputStream.
69           * </p>
70           *
71           * @return a new instance.
72           * @throws IOException              if an I/O error occurs.
73           * @throws IllegalArgumentException if the buffer is not large enough to hold a complete character.
74           */
75          @SuppressWarnings("resource") // Caller closes
76          @Override
77          public AutoCloseInputStream get() throws IOException {
78              return new AutoCloseInputStream(getInputStream());
79          }
80  
81      }
82  
83      /**
84       * Constructs a new {@link Builder}.
85       *
86       * @return a new {@link Builder}.
87       * @since 2.12.0
88       */
89      public static Builder builder() {
90          return new Builder();
91      }
92  
93      /**
94       * Constructs an automatically closing proxy for the given input stream.
95       *
96       * @param in underlying input stream
97       * @deprecated Use {@link #builder()}, {@link Builder}, and {@link Builder#get()}
98       */
99      @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 }