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Java > Open Source Codes > org > archive > util > ms > PieceReader


1 /* PieceReader
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.util.ms;
24
25 import java.io.IOException JavaDoc;
26
27 import org.archive.io.Endian;
28 import org.archive.io.SeekInputStream;
29 import org.archive.io.SeekReader;
30
31
32 class PieceReader extends SeekReader {
33
34
35     private PieceTable table;
36     private SeekInputStream doc;
37     
38     private boolean unicode;
39     private int charPos;
40     private int limit;
41
42
43     public PieceReader(PieceTable table, SeekInputStream doc)
44     throws IOException JavaDoc {
45         this.table = table;
46         this.doc = doc;
47         charPos = 0;
48         limit = -1;
49     }
50
51
52     private void seekIfNecessary() throws IOException JavaDoc {
53         if (doc == null) {
54             throw new IOException JavaDoc("Stream closed.");
55         }
56         if (charPos >= table.getMaxCharPos()) {
57             return;
58         }
59         if (charPos < limit) {
60             return;
61         }
62         Piece piece = table.next();
63         unicode = piece.isUnicode();
64         limit = piece.getCharPosLimit();
65         doc.position(piece.getFilePos());
66     }
67
68
69     public int read() throws IOException JavaDoc {
70         seekIfNecessary();
71         if (doc == null) {
72             throw new IOException JavaDoc("Stream closed.");
73         }
74         if (charPos >= table.getMaxCharPos()) {
75             return -1;
76         }
77
78         int ch;
79         if (unicode) {
80             ch = Endian.littleChar(doc);
81         } else {
82             ch = Cp1252.decode(doc.read());
83         }
84         charPos++;
85         return ch;
86     }
87
88
89     public int read(char[] buf, int ofs, int len) throws IOException JavaDoc {
90         // FIXME: Think of a faster implementation that will work with
91 // both unicode and non-unicode.
92 seekIfNecessary();
93         if (doc == null) {
94             throw new IOException JavaDoc("Stream closed.");
95         }
96         if (charPos >= table.getMaxCharPos()) {
97             return 0;
98         }
99         for (int i = 0; i < len; i++) {
100             int ch = read();
101             if (ch < 0) {
102                 return i;
103             }
104             buf[ofs + i] = (char)ch;
105         }
106         return len;
107     }
108     
109     
110     public void close() throws IOException JavaDoc {
111         doc.close();
112         table = null;
113     }
114     
115     
116     public long position() throws IOException JavaDoc {
117         return charPos;
118     }
119     
120     
121     public void position(long p) throws IOException JavaDoc {
122         if (p > Integer.MAX_VALUE) {
123             throw new IOException JavaDoc("File too large.");
124         }
125         int charPos = (int)p;
126         Piece piece = table.pieceFor(charPos);
127         if (piece == null) {
128             throw new IOException JavaDoc("Illegal position: " + p);
129         }
130         unicode = piece.isUnicode();
131         limit = piece.getCharPosLimit();
132         
133         int ofs = charPos - piece.getCharPosStart();
134         this.charPos = charPos;
135         doc.position(piece.getFilePos() + ofs);
136     }
137 }
138
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