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BoundedBufferedReader.java
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BoundedBufferedReader.java
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/**
* The BoundedBufferedReader class
*
* A BufferedReader that prevents DoS attacks by providing bounds for line length and number of lines
*
* Copyright (c) 2011 - Sean Malone
*
* The BoundedBufferedReader is published by Sean Malone under the BSD license. You should read and accept the
* LICENSE before you use, modify, and/or redistribute this software.
*
* @author Sean Malone <sean@seantmalone.com>
* @version 1.1
*/
import java.io.*;
class BoundedBufferedReader extends BufferedReader
{
private static final int DEFAULT_MAX_LINES = 1024; //Max lines per file
private static final int DEFAULT_MAX_LINE_LENGTH = 1024; //Max bytes per line
private int readerMaxLines;
private int readerMaxLineLen;
private int currentLine = 1;
public BoundedBufferedReader(FileReader reader, int maxLines, int maxLineLen)
{
super(reader);
if ((maxLines<=0) || (maxLineLen<=0)) throw new IllegalArgumentException("BoundedBufferedReader - maxLines and maxLineLen must be greater than 0");
readerMaxLines = maxLines;
readerMaxLineLen = maxLineLen;
}
public BoundedBufferedReader(FileReader reader)
{
super(reader);
readerMaxLines = DEFAULT_MAX_LINES;
readerMaxLineLen = DEFAULT_MAX_LINE_LENGTH;
}
public String readLine() throws IOException
{
//Check readerMaxLines limit
if (currentLine > readerMaxLines) throw new IOException("BoundedBufferedReader - Line read limit has been reached.");
currentLine++;
int currentPos=0;
char[] data=new char[readerMaxLineLen];
final int CR = 13;
final int LF = 10;
int currentCharVal=super.read();
//Read characters and add them to the data buffer until we hit the end of a line or the end of the file.
while( (currentCharVal!=CR) && (currentCharVal!=LF) && (currentCharVal>=0))
{
data[currentPos++]=(char) currentCharVal;
//Check readerMaxLineLen limit
if (currentPos<readerMaxLineLen)
currentCharVal = super.read();
else
break;
}
if (currentCharVal<0)
{
//End of file
if (currentPos>0)
//Return last line
return(new String(data,0,currentPos));
else
return null;
}
else
{
//Remove newline characters from the buffer
if(currentCharVal==CR)
{
//Check for LF and remove from buffer
super.mark(1);
if (super.read() != LF)
super.reset();
}
else if(currentCharVal!=LF)
{
//readerMaxLineLen has been hit, but we still need to remove newline characters.
super.mark(1);
int nextCharVal = super.read();
if (nextCharVal==CR)
{
super.mark(1);
if (super.read() != LF)
super.reset();
}
else if (nextCharVal!=LF)
super.reset();
}
return(new String(data,0,currentPos));
}
}
}