After I received comments from ispak on Flickr I made a few fixes.

ispak pointed out that it was a bad idea reading one byte at the time, also I had a gay ass try/catch that didn’t catch any exception :p

So now I read 16 byte chunks, and I also take care of the file ending. The previous version used to print the file ending with a bunch of null bytes. Now it stops reading at the end, and formats the output accordingly.

Here’s the new source:

//HexViewer.java
import java.io.*;

public final class HexViewer {
    public final static void printFile(String filePath) {
        try {
            File f = new File(filePath);
            BufferedInputStream bis =
                new BufferedInputStream(new FileInputStream(f));

            byte[] chunk = null;
            int readStatus = 0;
            while (true) {
                chunk = new byte[16];
                readStatus = bis.read(chunk, 0, 16);
                char[] line = new char[16];

                if (readStatus == -1)
                    break;

                for (byte i=0; i < readStatus; i++) {
                    int readByte = (chunk[i] < 0) ? (-1 * (int) chunk[i]) : chunk[i];
                    String paddingZero = (readByte < 16) ? "0" : "";
                    System.out.print(paddingZero + Integer.toHexString(readByte).toUpperCase() + " ");
                    line[i] = (readByte >= 33 && readByte <= 126) ? (char) readByte : '.';
                }

                //We add some padding to print the text line right below the one above.
                String padding = new String();
                if (readStatus < 16) {
                    for (byte i=0; i < 16-readStatus; i++) {
                        padding += "   ";
                    }
                }

                System.out.println(padding + new String(line));
            }
        } catch (Exception e1) { e1.printStackTrace(); }
    }

    public final static void main(String[] args) {
        if (args.length == 0)
            return;

        printFile(args[0]);
    }
}

And see how it now handles file endings when the file size is not a multiple of 16 :p

This entry was posted on Monday, April 20th, 2009 at 5:13 am and is filed under Code, Linux. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.