File conversion program...

Hi All, Hopefully one of you can help me, I think i've got to the stage where i've been staring at the code too long to miss an obvious problem..

I want to read in a binary file, look for all occurances of hex 0x00 and change those bytes to hex 0xFF.

My problem is, the resulting file is 'always' large than the original file.. It appears the last buffered read, is being written twice and I dont understand why.. my code is as follows..

Thanks in advance..

public static void main(String[] args) throws Exception{
             
        if (args.length == 0)
            System.out.println("Usage : java hexconv inFile outFile");
        else {
            String inFile = args[0];
            String outFile = args[1];
            char oldChar = (char)0x00;
            char newChar = (char)0xFF;                                         
            byte[] buffer = new byte[1024];
            FileInputStream in = new FileInputStream(inFile);
 
            OutputStreamWriter out = new OutputStreamWriter(
                    new FileOutputStream(outFile));
            
            String s = null;
            
            //... Loop as long as there are input lines.
            while (in.read(buffer) != -1) {                                              
                s = new String(buffer);
                s = s.replace(oldChar,newChar);                
                out.write(s);
            }
            
            out.close();    
            in.close();                                                                       
        }
    }

That int that in.readBuffer returns ... you test it for -1 to detect EOF. See if you don't need to keep it and use it in building the String.

And does char -> String -> char work out reliably for you? I rarely concern myself with the fact that String isn't just ASCII characters, but it isn't.
[ February 02, 2007: Message edited by: Stan James ]

Originally posted by Dave Brown:
Hi All, Hopefully one of you can help me, I think i've got to the stage where i've been staring at the code too long to miss an obvious problem..

I want to read in a binary file, look for all occurances of hex 0x00 and change those bytes to hex 0xFF.

My problem is, the resulting file is 'always' large than the original file.. It appears the last buffered read, is being written twice and I dont understand why.. my code is as follows..

Thanks in advance..

public static void main(String[] args) throws Exception{ if (args.length == 0) System.out.println("Usage : java hexconv inFile outFile"); else { String inFile = args[0]; String outFile = args[1]; char oldChar = (char)0x00; char newChar = (char)0xFF; byte[] buffer = new byte[1024]; FileInputStream in = new FileInputStream(inFile); OutputStreamWriter out = new OutputStreamWriter( new FileOutputStream(outFile)); String s = null; //... Loop as long as there are input lines. while (in.read(buffer) != -1) { s = new String(buffer); s = s.replace(oldChar,newChar); out.write(s); } out.close(); in.close(); } }

Hi
How about take in one byte at a time (byte[] buffer = new byte[1]

, compare read character with the old character, perform the change if there is a match. After your program ran, you may be able to see what's going on.
good luck.

I discovered that the line..

s = new String(buffer); would always return a string the length of the buffer... So on the last and final read, even though the number of bytes read was less than the buffer size.. the string was 1024 bytes.

So a quick check if the lengths differ, and a substring() call sorted that out.

Thanks for the replies..

Look through the String constructors. There's one that will save you the test and substring bits. I'm deliberately not quite giving the answer cause it's so much fun to go discover it.