Re: MD5 and RPG or...?

["David Morris" <David.Morris@xxxxxxxxxxxxx>]

Tom,

I use a simple Java program to do this. It works on large files. Here
is the source:

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * Generate an MD5 checksum and send it to STDOUT
 * @author David Morris
 */
public class CheckSum {
        public static void main(String[] args) {
                if (args.length != 1) {
                        System.err.println("Usage: java CheckSum
<filepath>");
                } else {
                        try {
                                System.out.println(Hex.encode(createMD5(new
File(args[0]))));
                        } catch (NoSuchAlgorithmException e) {
                                e.printStackTrace();
                        } catch (IOException e) {
                                e.printStackTrace();
                        }
                }
        }

        public static byte[] createMD5(final File file)
                throws NoSuchAlgorithmException, IOException {
                InputStream inputStream = new FileInputStream(file);
                MessageDigest md5 = MessageDigest.getInstance("MD5");
                final byte[] buf = new byte[8192];
                int bytes = 0;

                while ((bytes = inputStream.read(buf)) != -1) {
                        md5.update(buf, 0, bytes);
                }

                inputStream.close();
                return md5.digest();
        }

        static class Hex {

                /**
                 * Convert a byte array into a printable format
containing a
                 * String of hexadecimal digit characters (two per
byte).
                 * @param bytes Byte array representation
                 */
                public static String encode(byte bytes[]) {

                        StringBuffer sb = new StringBuffer(bytes.length
* 2);
                        for (int i = 0; i < bytes.length; i++) {
                                sb.append(convertDigit((int) (bytes[i]
>> 4)));
                                sb.append(convertDigit((int) (bytes[i] &
0x0f)));
                        }
                        return (sb.toString());
                }

                /**
                 * [Private] Convert the specified value (0 .. 15) to
the corresponding
                 * hexadecimal digit.
                 *
                 * @param value Value to be converted
                 */
                private static char convertDigit(int value) {

                        value &= 0x0f;
                        if (value >= 10)
                                return ((char) (value - 10 + 'a'));
                        else
                                return ((char) (value + '0'));
                }
        }
}

I use this script to run it:

#!/bin/sh                          
saveclasspath=$CLASSPATH           
export -s CLASSPATH=/java/somedirectory
java CheckSum $1                   
export -s CLASSPATH=$saveclasspath 

David Morris


>>> qsrvbas@xxxxxxxxxxxx 03/31/05 5:07 PM >>>
Some general background...

The archive has this item which seems to have never been responded to:

http://archive.midrange.com/midrange-l/200302/msg00838.html 

Also, Perl/php, Linux, various *nixes and who knows what else have
md5sum and other commands or utilities.

Under OS/400, we primarily have CIPHER or the _CIPHER  builtin.

But I'm unclear about CIPHER (and probably MD5 to boot). It seems that
the maximum string length would be 16MB since a pointer is input to the
function. Some process for handling a document (streamfile) >16MB would
seem to require a chaining from segment to segment or something like
that.

A google over AIX and MD5 left me with a sea of references that will
take a month to go through to see if PASE might help. QShell didn't have
anything that jumped out at me.

Is there any material on how to handle >16MB documents under OS/400?

Thanks in advance.

Tom Liotta