01: /* SeekReader
02: *
03: * Created on September 18, 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 java.io.IOException;
26: import java.io.Reader;
27:
28: import it.unimi.dsi.fastutil.io.RepositionableStream;
29:
30: /**
31: * Base class for repositionable readers.
32: *
33: * @author pjack
34: */
35: public abstract class SeekReader extends Reader 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: @Override
52: public void mark(int limit) {
53: try {
54: this .mark = position();
55: } catch (IOException e) {
56: mark = -1;
57: }
58: }
59:
60: /**
61: * Resets this stream to its marked position.
62: *
63: * @throws IOException if there is no mark, or if an IO error occurs
64: */
65: @Override
66: public void reset() throws IOException {
67: if (mark < 0) {
68: throw new IOException("No mark.");
69: }
70: position(mark);
71: }
72:
73: /**
74: * Returns true, since SeekInputStreams support mark/reset by default.
75: *
76: * @return true
77: */
78: @Override
79: public boolean markSupported() {
80: return true;
81: }
82: }
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