CODEWITHSUNDEEP
javacobolcomp-3
user7349775
user7349775

Reputation: 21

Decode encrypted cobol file with comp-3 and other data

I have a cobol file which is not in human-readable format: it has data(numbers) in comp-3 format, but also other strings and characters. I have the algorithm for converting the comp-3 format, but when I apply it to the array of bytes from the file, all the characters get converted and the output is not the right one. How could I decode the entire file correctly, taking into consideration both comp-3 data and normal data?

I will add some lines from the file below and also my algorithm for comp-3:

The file in Notepad++ looks like this(first lines):

AH4820øêæÉ* 200 DBAG DBAG 0
AED S EUR AED S KAS°ê¤ 2    ø TN Øê¤ ð §É! SN ê¤

The file in Notepad++ with the ASCII to HEX converted looks like this, even though this should not be right:

200F41483438323002C3B8C3AA01C3A6 01C3892A202020202020202020202020 20203230302044424147204442414720 30202020202020202020202020202020

   public static String unpackData(byte[] packedData) {
    String unpackedData = "";

    final int negativeSign = 13;
    for (int currentCharIndex = 0; currentCharIndex < packedData.length; currentCharIndex++) {
        byte firstDigit = (byte) ((packedData[currentCharIndex] >>> 4) & 0x0F);
        byte secondDigit = (byte) (packedData[currentCharIndex] & 0x0F);
        unpackedData += String.valueOf(firstDigit);
        if (currentCharIndex == (packedData.length - 1)) {
            if (secondDigit == negativeSign) {
                unpackedData = "-" + unpackedData;
            }
        } else {
            unpackedData += String.valueOf(secondDigit);
        }
    }
    return unpackedData;
}

Upvotes: -1

Views: 1529

Answers (2)

Bruce Martin
Bruce Martin

Reputation: 10543

Editing the File

Any hex editor that supports EBCDIC should be able to display the file in a readabhle. Wikipedia suggests HxD, VEdit, UltraEdit, WinHex are hex editor's that support Ebcdic.

Another alternative is the recordEditor It can display the file with/ without a Cobol Copybook

enter image description here

JRecord

JRecord lets you read/write Mainframe using a Cobol Copybook. You can generate basic Java~JRecord Code in the recordEditor

See How do you generate java~jrecord code for a Cobol copybook

Upvotes: 1

Simon Sobisch
Simon Sobisch

Reputation: 7287

...encrypted cobol file with comp-3 and other data ... not in human-readable format

Don't mix the two. An encrypted file could actually be human-readable (just not containing reasonable things) when the encryption happens by exchanging words. Not in human-readable format does not have anything to do with encryption (and I fail to see why this is tagged as spring).

Back to the original question:

How could I decode the entire file correctly, taking into consideration both comp-3 data and normal data?

You split the byte array into ranges "normal" (in your case I think you mean unpacked, very likely in a single-byte encoding) and "encoded" (packed) data.

Then convert the unpacked data to either String (effectively UTF-16) or to a numeric type and the packed data (did not checked if your comp-3 unpack is correct but looks fine at least not completely wrong [other then 13 may be not the only possible negative sign marker, but this depends on the data producing system]) to numeric types.

COBOL is record based, mostly fixed-length so the key to "decode the file" is to split the file into the records and fields (get the original COBOL record definition). In most cases you'd create a pojo with the same attributes as the COBOL definition and have a piece of code split the byte array into records and fields by positions, convert the pieces as needed and invoke your setters with the result. human-readable: an easy approach may be to generate the toString method...

Upvotes: 3

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