/[xulu]/branches/1.8-gt2-2.6/src/appl/parallel/data/xulugridfile/BufferedRandomAccessFile.java
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Annotation of /branches/1.8-gt2-2.6/src/appl/parallel/data/xulugridfile/BufferedRandomAccessFile.java

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Revision 2 - (hide annotations)
Wed Feb 25 11:54:01 2009 UTC (15 years, 9 months ago) by mojays
Original Path: trunk/src/appl/parallel/data/xulugridfile/BufferedRandomAccessFile.java
File size: 2765 byte(s)
First Commit, corresponds to Revision 1008 of Wikisquare-SVN 
1 mojays 2 package appl.parallel.data.xulugridfile;
2    
3     import java.io.IOException;
4     import java.io.RandomAccessFile;
5    
6     /**
7     * Copied from java world.
8     *
9     * See http://www.javaworld.com/javaworld/javatips/jw-javatip26.html
10     *
11     * @author Nick Zhang
12     *
13     */
14     public class BufferedRandomAccessFile extends RandomAccessFile {
15    
16     byte buffer[];
17    
18     int buf_end = 0;
19    
20     int buf_pos = 0;
21    
22     long real_pos = 0;
23    
24     private int BUF_SIZE;
25    
26     public BufferedRandomAccessFile(String filename, String mode, int bufsize)
27     throws IOException {
28     super(filename, mode);
29     invalidate();
30     BUF_SIZE = bufsize;
31     buffer = new byte[BUF_SIZE];
32     }
33    
34     public final int read() throws IOException {
35     if (buf_pos >= buf_end) {
36     if (fillBuffer() < 0)
37     return -1;
38     }
39     if (buf_end == 0) {
40     return -1;
41     } else {
42     return buffer[buf_pos++];
43     }
44     }
45    
46     private int fillBuffer() throws IOException {
47     int n = super.read(buffer, 0, BUF_SIZE);
48     if (n >= 0) {
49     real_pos += n;
50     buf_end = n;
51     buf_pos = 0;
52     }
53     return n;
54     }
55    
56     private void invalidate() throws IOException {
57     buf_end = 0;
58     buf_pos = 0;
59     real_pos = super.getFilePointer();
60     }
61    
62     public int read(byte b[], int off, int len) throws IOException {
63     int leftover = buf_end - buf_pos;
64     if (len <= leftover) {
65     System.arraycopy(buffer, buf_pos, b, off, len);
66     buf_pos += len;
67     return len;
68     }
69     for (int i = 0; i < len; i++) {
70     int c = this.read();
71     if (c != -1)
72     b[off + i] = (byte) c;
73     else {
74     return i;
75     }
76     }
77     return len;
78     }
79    
80     public long getFilePointer() throws IOException {
81     long l = real_pos;
82     return (l - buf_end + buf_pos);
83     }
84    
85     public void seek(long pos) throws IOException {
86     int n = (int) (real_pos - pos);
87     if (n >= 0 && n <= buf_end) {
88     buf_pos = buf_end - n;
89     } else {
90     super.seek(pos);
91     invalidate();
92     }
93     }
94    
95     /**
96     * return a next line in String
97     */
98     public final String getNextLine() throws IOException {
99     String str = null;
100     if (buf_end - buf_pos <= 0) {
101     if (fillBuffer() < 0) {
102     throw new IOException("error in filling buffer!");
103     }
104     }
105     int lineend = -1;
106     for (int i = buf_pos; i < buf_end; i++) {
107     if (buffer[i] == '\n') {
108     lineend = i;
109     break;
110     }
111     }
112     if (lineend < 0) {
113     StringBuffer input = new StringBuffer(256);
114     int c;
115     while (((c = read()) != -1) && (c != '\n')) {
116     input.append((char) c);
117     }
118     if ((c == -1) && (input.length() == 0)) {
119     return null;
120     }
121     return input.toString();
122     }
123     if (lineend > 0 && buffer[lineend - 1] == '\r')
124     str = new String(buffer, 0, buf_pos, lineend - buf_pos - 1);
125     else
126     str = new String(buffer, 0, buf_pos, lineend - buf_pos);
127     buf_pos = lineend + 1;
128     return str;
129     }
130     }

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