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Java > Open Source Codes > org > archive > io > SeekInputStream


1 /* SeekInputStream
2 *
3 * Created on September 12, 2006
4 *
5 * Copyright (C) 2006 Internet Archive.
6 *
7 * This file is part of the Heritrix web crawler (crawler.archive.org).
8 *
9 * Heritrix is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU Lesser Public License as published by
11 * the Free Software Foundation; either version 2.1 of the License, or
12 * any later version.
13 *
14 * Heritrix is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 * GNU Lesser Public License for more details.
18 *
19 * You should have received a copy of the GNU Lesser Public License
20 * along with Heritrix; if not, write to the Free Software
21 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
22 */
23 package org.archive.io;
24
25
26 import it.unimi.dsi.fastutil.io.RepositionableStream;
27
28 import java.io.IOException JavaDoc;
29 import java.io.InputStream JavaDoc;
30
31
32 /**
33  * Base class for repositionable input streams.
34  *
35  * @author pjack
36  */
37 public abstract class SeekInputStream extends InputStream JavaDoc
38 implements RepositionableStream {
39
40
41     /**
42      * The marked file position. A value less than zero
43      * indicates that no mark has been set.
44      */
45     private long mark = -1;
46
47
48     /**
49      * Marks the current position of the stream. The limit parameter is
50      * ignored; the mark will remain valid until reset is called or the
51      * stream is closed.
52      *
53      * @param limit ignored
54      */
55     public void mark(int limit) {
56         try {
57             this.mark = position();
58         } catch (IOException JavaDoc e) {
59             mark = -1;
60         }
61     }
62
63
64     /**
65      * Resets this stream to its marked position.
66      *
67      * @throws IOException if there is no mark, or if an IO error occurs
68      */
69     public void reset() throws IOException JavaDoc {
70         if (mark < 0) {
71             throw new IOException JavaDoc("No mark.");
72         }
73         position(mark);
74     }
75
76
77     /**
78      * Returns true, since SeekInputStreams support mark/reset by default.
79      *
80      * @return true
81      */
82     public boolean markSupported() {
83         return true;
84     }
85 }
86
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