/**
 *  Hexdump.java
 *
 *  Dumps a binary file to a ascii, in hexadecimal.
 *  Copyright (c) 1999-2003 W.Finlay McWalter and the Free Software Foundation
 *  Licence: version 2 of the GNU General Public Licence
 * 
 */
import java.io.*;

public class Hexdump {
    private static final int BYTES_PER_LINE = 16;
    private static final int PADDING = 4;

    /**
     *   returns a char corresponding to the hex digit of the
     *   supplied integer.
     */
    private static char charFromHexDigit(int digit){
	if((digit >= 0) && (digit <=9))
	    return (char)(digit + '0');
	else
	    return (char)(digit -10 + 'a');
    }
    
    /**
     *  hexdumps the contents of a given open input file to stdout
     */    
    private static void dumpFile(FileInputStream in){
	try {
	    byte[]       inBuf = new byte[BYTES_PER_LINE]; 
	    int          count;
	    StringBuffer line = new StringBuffer();

	    while((count = in.read(inBuf)) >0){
		line.setLength(0);

		// print hexbytes
		for(int x=0; x<count; x++){

		    int i = (inBuf[x]>=0)?inBuf[x]:(256+inBuf[x]);

		    line.append(charFromHexDigit(i/16));
		    line.append(charFromHexDigit(i%16));
		    line.append(' ');			       		  		    		}

		// print padding between hexbytes and ascii
		for(int x=0; x < PADDING + ((BYTES_PER_LINE-count)*3); x++){
		    line.append(' ');
		}
		      		
		// print ascii
		for(int x=0; x<count; x++){
		    char v = (char)inBuf[x];
		    if((v >= ' ') && (v < (char)0x7f)){
			line.append(v);
		    }
		    else {
			line.append('.');
		    }
		}
		
		System.out.println(line);
	    }
	}
	catch (IOException e){
	    System.out.println("error reading file");
	}
    }
    
    public static final void main (String [] args){
	if(args.length == 1){
	    try {
		FileInputStream inStream = new FileInputStream(args[0]);
		dumpFile(inStream);
		inStream.close();
	    }
	    catch (FileNotFoundException e){
		System.out.println("File \"" + args[0] + "\" not found");
	    }
	    catch (IOException e){
		System.out.println("error closing file");
	    }
	}
	else {
	    System.out.println("usage:\n  java Hexdump <filename>\n");
	}
    }
}