01: /* SeekInputStream
02: *
03: * Created on September 12, 2006
04: *
05: * Copyright (C) 2006 Internet Archive.
06: *
07: * This file is part of the Heritrix web crawler (crawler.archive.org).
08: *
09: * 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: import it.unimi.dsi.fastutil.io.RepositionableStream;
26:
27: import java.io.IOException;
28: import java.io.InputStream;
29:
30: /**
31: * Base class for repositionable input streams.
32: *
33: * @author pjack
34: */
35: public abstract class SeekInputStream extends InputStream implements
36: RepositionableStream {
37:
38: /**
39: * The marked file position. A value less than zero
40: * indicates that no mark has been set.
41: */
42: private long mark = -1;
43:
44: /**
45: * Marks the current position of the stream. The limit parameter is
46: * ignored; the mark will remain valid until reset is called or the
47: * stream is closed.
48: *
49: * @param limit ignored
50: */
51: public void mark(int limit) {
52: try {
53: this .mark = position();
54: } catch (IOException e) {
55: mark = -1;
56: }
57: }
58:
59: /**
60: * Resets this stream to its marked position.
61: *
62: * @throws IOException if there is no mark, or if an IO error occurs
63: */
64: public void reset() throws IOException {
65: if (mark < 0) {
66: throw new IOException("No mark.");
67: }
68: position(mark);
69: }
70:
71: /**
72: * Returns true, since SeekInputStreams support mark/reset by default.
73: *
74: * @return true
75: */
76: public boolean markSupported() {
77: return true;
78: }
79: }
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