Reading from binary file and converting certain info to string

Question

I have to read data from a binary file like S/W version,vendor etc. i have to show the output in a textarea.After reading the configurations the usre can send the selected file through a serial port. I have written some code here:

InputStream is=null;
    try {
        File urt=filebrowser.getSelectedFile();
        is = new FileInputStream(urt);
        DataInputStream in = new DataInputStream(is);
        long l=urt.length();

        char[] bytes= new char[(int)l];
         int o=bytes.length;
         errlabel.setText(String.valueOf(o));
         String content;
        int offset;
   BufferedReader br = new BufferedReader(new InputStreamReader(in));
         int numRead;
        try {

         br.read(bytes, 0, 46);
         while ((content = br.readLine()) != null)   {
StringBuilder sb=new StringBuilder(content);

jTextArea1.setText(sb.toString());
errlabel.setText(""+sb.length());


}





        } catch (IOException ex) {
            Logger.getLogger(MyBoxUpdator.class.getName()).log(Level.SEVERE, null, ex);
        }


    } catch (FileNotFoundException ex) {
        Logger.getLogger(MyBoxUpdator.class.getName()).log(Level.SEVERE, null, ex);
    } finally {
        try {
            is.close();
        } catch (IOException ex) {
            Logger.getLogger(MyBoxUpdator.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

And The Output

EE��6**UT�h��}�(:�萢Ê�*:�茢���_��(RQ��N���S��h����rMQ��(_Q����9mTT��\�nE�PtP�!E�UtBߌz��z���������

What may be wrong?

@martijno is right. You don't need an intermediate DataInputStream. Its purpose is reading atomic data (as integer, String, Date, etc). It seems you only need FileInputStream (read bytes from file) +InputStreamReader (read chars from bytes). — helios
– helios, Commented Aug 20, 2012 at 10:03
The only thing you could use is a BufferedInputStream (instead of DataInputStream). It provides the same InputStream but it reads big chunks of data and buffer it, to avoid asking 4 bytes each time a lot of times. I mean: it optimizes reading while you use it normally. — helios
– helios, Commented Aug 20, 2012 at 10:05

helios · Accepted Answer · 2012-08-20 08:25:15Z

2

You are converting bytes into chars

So you must tell what encoding to use. If you don't indicate one the InputStreamReader (it is: reader that reads chars from an input stream of bytes) will use a default. I'm sure the default is not what you need.

Try this:

new InputStreamReader(in, "UTF-8"); // or whatever encoding you need

As a general rule: always indicate encoding when dealing with char to bytes conversion and viceversa! :)

Edit

Of course, I'm assuming your file has TEXT encoded into it. If it's binary as @alfasin said... well... it's normal to see garbage. You should read bytes and write chars representing them (as an hex representation of each byte, by example).

answered Aug 20, 2012 at 8:25

helios

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3 Comments

lazyprogrammer Over a year ago

thanks for helping...random access file also proved helpful...just sharing

helios Over a year ago

Great. Anyway RAF doesn't provide a way to indicate encoding, right? If I remember well, it's ISO-8859-1 hardcoded (Western).

lazyprogrammer Over a year ago

can you help me with this link

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