1/****************************************************************
2 * Licensed to the Apache Software Foundation (ASF) under one   *
3 * or more contributor license agreements.  See the NOTICE file *
4 * distributed with this work for additional information        *
5 * regarding copyright ownership.  The ASF licenses this file   *
6 * to you under the Apache License, Version 2.0 (the            *
7 * "License"); you may not use this file except in compliance   *
8 * with the License.  You may obtain a copy of the License at   *
9 *                                                              *
10 *   http://www.apache.org/licenses/LICENSE-2.0                 *
11 *                                                              *
12 * Unless required by applicable law or agreed to in writing,   *
13 * software distributed under the License is distributed on an  *
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY       *
15 * KIND, either express or implied.  See the License for the    *
16 * specific language governing permissions and limitations      *
17 * under the License.                                           *
18 ****************************************************************/
19
20package org.apache.james.mime4j;
21
22import java.io.InputStream;
23import java.io.IOException;
24
25/**
26 * InputStream that shields its underlying input stream from
27 * being closed.
28 *
29 *
30 * @version $Id: CloseShieldInputStream.java,v 1.2 2004/10/02 12:41:10 ntherning Exp $
31 */
32public class CloseShieldInputStream extends InputStream {
33
34    /**
35     * Underlying InputStream
36     */
37    private InputStream is;
38
39    public CloseShieldInputStream(InputStream is) {
40        this.is = is;
41    }
42
43    public InputStream getUnderlyingStream() {
44        return is;
45    }
46
47    /**
48     * @see java.io.InputStream#read()
49     */
50    public int read() throws IOException {
51        checkIfClosed();
52        return is.read();
53    }
54
55    /**
56     * @see java.io.InputStream#available()
57     */
58    public int available() throws IOException {
59        checkIfClosed();
60        return is.available();
61    }
62
63
64    /**
65     * Set the underlying InputStream to null
66     */
67    public void close() throws IOException {
68        is = null;
69    }
70
71    /**
72     * @see java.io.FilterInputStream#reset()
73     */
74    public synchronized void reset() throws IOException {
75        checkIfClosed();
76        is.reset();
77    }
78
79    /**
80     * @see java.io.FilterInputStream#markSupported()
81     */
82    public boolean markSupported() {
83        if (is == null)
84            return false;
85        return is.markSupported();
86    }
87
88    /**
89     * @see java.io.FilterInputStream#mark(int)
90     */
91    public synchronized void mark(int readlimit) {
92        if (is != null)
93            is.mark(readlimit);
94    }
95
96    /**
97     * @see java.io.FilterInputStream#skip(long)
98     */
99    public long skip(long n) throws IOException {
100        checkIfClosed();
101        return is.skip(n);
102    }
103
104    /**
105     * @see java.io.FilterInputStream#read(byte[])
106     */
107    public int read(byte b[]) throws IOException {
108        checkIfClosed();
109        return is.read(b);
110    }
111
112    /**
113     * @see java.io.FilterInputStream#read(byte[], int, int)
114     */
115    public int read(byte b[], int off, int len) throws IOException {
116        checkIfClosed();
117        return is.read(b, off, len);
118    }
119
120    /**
121     * Check if the underlying InputStream is null. If so throw an Exception
122     *
123     * @throws IOException if the underlying InputStream is null
124     */
125    private void checkIfClosed() throws IOException {
126        if (is == null)
127            throw new IOException("Stream is closed");
128    }
129}
130