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Java > Open Source Codes > com > quadcap > io > RandomAccessFileInputStream


1 package com.quadcap.io;
2
3 /* Copyright 1997 - 2003 Quadcap Software. All rights reserved.
4  *
5  * This software is distributed under the Quadcap Free Software License.
6  * This software may be used or modified for any purpose, personal or
7  * commercial. Open Source redistributions are permitted. Commercial
8  * redistribution of larger works derived from, or works which bundle
9  * this software requires a "Commercial Redistribution License"; see
10  * http://www.quadcap.com/purchase.
11  *
12  * Redistributions qualify as "Open Source" under one of the following terms:
13  *
14  * Redistributions are made at no charge beyond the reasonable cost of
15  * materials and delivery.
16  *
17  * Redistributions are accompanied by a copy of the Source Code or by an
18  * irrevocable offer to provide a copy of the Source Code for up to three
19  * years at the cost of materials and delivery. Such redistributions
20  * must allow further use, modification, and redistribution of the Source
21  * Code under substantially the same terms as this license.
22  *
23  * Redistributions of source code must retain the copyright notices as they
24  * appear in each source code file, these license terms, and the
25  * disclaimer/limitation of liability set forth as paragraph 6 below.
26  *
27  * Redistributions in binary form must reproduce this Copyright Notice,
28  * these license terms, and the disclaimer/limitation of liability set
29  * forth as paragraph 6 below, in the documentation and/or other materials
30  * provided with the distribution.
31  *
32  * The Software is provided on an "AS IS" basis. No warranty is
33  * provided that the Software is free of defects, or fit for a
34  * particular purpose.
35  *
36  * Limitation of Liability. Quadcap Software shall not be liable
37  * for any damages suffered by the Licensee or any third party resulting
38  * from use of the Software.
39  */
40
41 import java.io.InputStream JavaDoc;
42 import java.io.IOException JavaDoc;
43 import java.io.RandomAccessFile JavaDoc;
44
45 import com.quadcap.util.Debug;
46
47 /**
48  * This class implements an input stream filter which keeps track of how
49  * many bytes have been read.
50  *
51  * @author Stan Bailes
52  */
53 public class RandomAccessFileInputStream extends InputStream JavaDoc {
54     long mark = -1;
55     RandomAccessFile JavaDoc ra;
56
57     /**
58      * Construct a new RandomAccessFileInputStream rearang from the
59      * specified file.
60      *
61      * @param ra the file
62      */
63     public RandomAccessFileInputStream(RandomAccessFile JavaDoc ra) {
64     this.ra = ra;
65     }
66
67     /**
68      * Read the next byte from this input stream.
69      *
70      * @exception IOException if an I/O error occurs.
71      */
72     public int read() throws IOException JavaDoc {
73 // Debug.println(0, "read[" + ra.getFilePointer() + "] (" + 1 + ")");
74 return ra.read();
75     }
76
77     /**
78      * Read a block of bytes from this input stream.
79      *
80      * @exception IOException if an I/O error occcurs.
81      */
82     public int read(byte[] buf, int offset, int count) throws IOException JavaDoc {
83 // Debug.println(0, "read[" + ra.getFilePointer() + "] (" + count + ")");
84 return ra.read(buf, offset, count);
85     }
86
87     /**
88      * Read a block of bytes from this input stream.
89      *
90      * @exception IOException if an I/O error occcurs.
91      */
92     public int read(byte[] buf) throws IOException JavaDoc {
93 // Debug.println(0, "read[" + ra.getFilePointer() + "] (" +
94 // buf.length + ")");
95 return ra.read(buf);
96     }
97
98     /**
99      * Return the number of bytes that can be read without blocking.
100      */
101     public int available() throws IOException JavaDoc {
102     return (int)(ra.length() - ra.getFilePointer());
103     }
104
105     /**
106      * Close the stream.
107      */
108     public void close() throws IOException JavaDoc {
109     ra.close();
110     }
111
112     /**
113      * Skip ahead in the stream.
114      */
115     public long skip(long n) throws IOException JavaDoc {
116     ra.seek(ra.getFilePointer() + n);
117     return n;
118     }
119
120     /**
121      * Mark the current position in the input stream.
122      */
123     public void mark(int readLimit) {
124     try {
125         this.mark = ra.getFilePointer();
126     } catch (IOException JavaDoc e) {
127         Debug.print(e);
128         throw new RuntimeException JavaDoc(e.toString());
129     }
130     }
131
132     /**
133      * Return to the previously marked position in the input stream.
134      */
135     public void reset() throws IOException JavaDoc {
136     if (mark < 0) throw new IOException JavaDoc("no mark");
137     ra.seek(mark);
138     }
139
140     /**
141      * Return true if mark/reset supported (they are.)
142      */
143     public boolean markSupported() {
144     return true;
145     }
146 }
147
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