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/*******************************************************************************
* Copyright (c) 2010, 2012 Ericsson
*
* All rights reserved. This program and the accompanying materials are
* made available under the terms of the Eclipse Public License v1.0 which
* accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* Patrick Tasse - Initial API and implementation, based on article by Nick Zhang
* (http://www.javaworld.com/javatips/jw-javatip26.html)
******************************************************************************/
package org.eclipse.linuxtools.tmf.core.io;
import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.charset.Charset;
/**
* A class to mitigate the Java I/O inefficiency of RandomAccessFile.
*
* @version 1.0
* @author Patrick Tasse
*/
public class BufferedRandomAccessFile extends RandomAccessFile {
private static final int DEFAULT_BUF_SIZE = 8192;
private static final Charset CHARSET_UTF8 = Charset.forName("UTF-8"); //$NON-NLS-1$
final int BUF_SIZE;
byte buffer[];
int buf_end = 0;
int buf_pos = 0;
long real_pos = 0;
StringBuilder sb = new StringBuilder();
/**
* Constructor using the default buffer size
*
* @param name
* File path. This is passed as-is to the RandomeAccessFile's
* constructor.
* @param mode
* File open mode ("r", "rw", etc.). This is passed as-is to
* RandomAccessFile's constructor.
* @throws IOException
* If the file was not found or couldn't be opened with the
* request permissions
*/
public BufferedRandomAccessFile(String name, String mode) throws IOException {
this(name, mode, DEFAULT_BUF_SIZE);
}
/**
* Constructor using the default buffer size
*
* @param file
* File object. This is passed as-is to the RandomeAccessFile's
* constructor.
* @param mode
* File open mode ("r", "rw", etc.). This is passed as-is to
* RandomAccessFile's constructor.
* @throws IOException
* If the file was not found or couldn't be opened with the
* request permissions
*/
public BufferedRandomAccessFile(File file, String mode) throws IOException {
this(file, mode, DEFAULT_BUF_SIZE);
}
/**
* Standard constructor.
*
* @param name
* File path. This is passed as-is to the RandomeAccessFile's
* constructor.
* @param mode
* File open mode ("r", "rw", etc.). This is passed as-is to
* RandomAccessFile's constructor.
* @param bufsize
* Buffer size to use, in bytes
* @throws IOException
* If the file was not found or couldn't be opened with the
* request permissions
*/
public BufferedRandomAccessFile(String name, String mode, int bufsize) throws IOException {
super(name, mode);
invalidate();
BUF_SIZE = bufsize;
buffer = new byte[BUF_SIZE];
}
/**
* Standard constructor.
*
* @param file
* File object. This is passed as-is to the RandomeAccessFile's
* constructor.
* @param mode
* File open mode ("r", "rw", etc.). This is passed as-is to
* RandomAccessFile's constructor.
* @param bufsize
* Buffer size to use, in bytes
* @throws IOException
* If the file was not found or couldn't be opened with the
* request permissions
*/
public BufferedRandomAccessFile(File file, String mode, int bufsize) throws IOException {
super(file, mode);
invalidate();
BUF_SIZE = bufsize;
buffer = new byte[BUF_SIZE];
}
@Override
public final int read() throws IOException{
if (buf_pos >= buf_end) {
if (fillBuffer() < 0) {
return -1;
}
}
if (buf_end == 0) {
return -1;
}
return (buffer[buf_pos++] & 0xff);
}
@Override
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;
}
@Override
public long getFilePointer() throws IOException{
long l = real_pos;
return (l - buf_end + buf_pos);
}
@Override
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();
}
}
/**
* Read the next line from the buffer (ie, until the next '\n'). The bytes
* are interpreted as UTF-8 characters.
*
* @return The String that was read
* @throws IOException
* If we failed reading the file
*/
public final String getNextLine() throws IOException {
String str = null;
if (buf_end - buf_pos <= 0) {
if (fillBuffer() < 0) {
return null;
}
}
int lineend = -1;
for (int i = buf_pos; i < buf_end; i++) {
if (buffer[i] == '\n') {
lineend = i;
break;
}
}
if (lineend < 0) {
sb.delete(0, sb.length());
int c;
while (((c = read()) != -1) && (c != '\n')) {
sb.append((char) c);
}
if ((c == -1) && (sb.length() == 0)) {
return null;
}
if (sb.charAt(sb.length() - 1) == '\r') {
sb.deleteCharAt(sb.length() - 1);
}
return sb.toString();
}
if (lineend > 0 && buffer[lineend - 1] == '\r' && lineend > buf_pos) {
str = new String(buffer, buf_pos, lineend - buf_pos - 1, CHARSET_UTF8);
} else {
str = new String(buffer, buf_pos, lineend - buf_pos, CHARSET_UTF8);
}
buf_pos = lineend + 1;
return str;
}
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();
}
}
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