data/xulugridfile/BufferedRandomAccessFile.java

package appl.parallel.data.xulugridfile;

import java.io.IOException;
import java.io.RandomAccessFile;

/**
 * Copied from java world.
 * 
 * See http://www.javaworld.com/javaworld/javatips/jw-javatip26.html
 * 
 * @author Nick Zhang
 * 
 */
public class BufferedRandomAccessFile extends RandomAccessFile {

        byte buffer[];

        int buf_end = 0;

        int buf_pos = 0;

        long real_pos = 0;

        private int BUF_SIZE;

        public BufferedRandomAccessFile(String filename, String mode, int bufsize)
                        throws IOException {
                super(filename, mode);
                invalidate();
                BUF_SIZE = bufsize;
                buffer = new byte[BUF_SIZE];
        }

        public final int read() throws IOException {
                if (buf_pos >= buf_end) {
                        if (fillBuffer() < 0)
                                return -1;
                }
                if (buf_end == 0) {
                        return -1;
                } else {
                        return buffer[buf_pos++];
                }
        }

        private int fillBuffer() throws IOException {
                int n = super.read(buffer, 0, BUF_SIZE);
                if (n >= 0) {
                        real_pos += n;
                        buf_end = n;
                        buf_pos = 0;
                }
                return n;
        }

        private void invalidate() throws IOException {
                buf_end = 0;
                buf_pos = 0;
                real_pos = super.getFilePointer();
        }

        public int read(byte b[], int off, int len) throws IOException {
                int leftover = buf_end - buf_pos;
                if (len <= leftover) {
                        System.arraycopy(buffer, buf_pos, b, off, len);
                        buf_pos += len;
                        return len;
                }
                for (int i = 0; i < len; i++) {
                        int c = this.read();
                        if (c != -1)
                                b[off + i] = (byte) c;
                        else {
                                return i;
                        }
                }
                return len;
        }

        public long getFilePointer() throws IOException {
                long l = real_pos;
                return (l - buf_end + buf_pos);
        }

        public void seek(long pos) throws IOException {
                int n = (int) (real_pos - pos);
                if (n >= 0 && n <= buf_end) {
                        buf_pos = buf_end - n;
                } else {
                        super.seek(pos);
                        invalidate();
                }
        }

        /**
         * return a next line in String 
         */
        public final String getNextLine() throws IOException {
                String str = null;
                if (buf_end - buf_pos <= 0) {
                        if (fillBuffer() < 0) {
                                throw new IOException("error in filling buffer!");
                        }
                }
                int lineend = -1;
                for (int i = buf_pos; i < buf_end; i++) {
                        if (buffer[i] == '\n') {
                                lineend = i;
                                break;
                        }
                }
                if (lineend < 0) {
                        StringBuffer input = new StringBuffer(256);
                        int c;
                        while (((c = read()) != -1) && (c != '\n')) {
                                input.append((char) c);
                        }
                        if ((c == -1) && (input.length() == 0)) {
                                return null;
                        }
                        return input.toString();
                }
                if (lineend > 0 && buffer[lineend - 1] == '\r')
                        str = new String(buffer, 0, buf_pos, lineend - buf_pos - 1);
                else
                        str = new String(buffer, 0, buf_pos, lineend - buf_pos);
                buf_pos = lineend + 1;
                return str;
        }
}
1	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	}