How can I compute the 8-bit CRC sum check within an Net Express/VC COBOL program? - Micro Focus Community

GOYO · ‎2021-01-04

Hello,
I need to calculate the CRC code to a 36 position alphanumeric field, applying the crc8 algorithm. Is there any example in COBOL for NetExpress or VC?
I have tried, from several examples in C#, to generate a cobol program, using the C# to MF COBOL converter from https://cs2cobol.microfocuscloud.com/, but the sources that generate give problems.

GOYO · ‎2021-01-04

Attached examples of C# programs used

Chris Glazier · ‎2021-01-05

Neither one of these example programs is a C# program.
crc8.zip contains a native C program source and prcrc8.txt is a Java program.

On what platform do you require this routine?
How are you compiling, to native code or to managed code?

GOYO · ‎2021-01-05

Hello,

In my case, I prefer the routine in native code.

I searched the RM-Cobol forum and found a sample file crc32.zip.

Thank you.

Chris Glazier · ‎2021-01-07

I wasn't sure if your last reply here meant that you already had a solution to your question but the following is a translation to COBOL of the C program you attached. I don't know much about CRC so cannot guarantee the validity of the program functionality but here is the conversion anyway.

Calling Program:

       identification division.
       program-id. mainprog.
       data division.
       working-storage section.
       01 input-str pic x(10) value "ABCDEFGHIJ".
	   01 num-bytes binary-long value 10.
	   01 crc       binary-char unsigned value zeroes.
       procedure division.

           call "crc8" using input-str num-bytes crc
           display crc
           goback.

CRC subprogram:

      $set sourceformat"variable"
       identification division.
       program-id. crc-8.
       data division.
       working-storage section.
	   78 CRC-START-8 value 0.
       01 sht75-crc-table binary-char unsigned occurs 256
          values  0, 49, 98, 83, 196, 245, 166, 151, 185, 136, 219, 234, 125, 76,  31,  46,
	             67,  114, 33,  16,  135, 182, 229, 212, 250, 203, 152, 169, 62,  15,  92,  109,
	            134, 183, 228, 213, 66,  115, 32,  17,  63,  14,  93,  108, 251, 202, 153, 168,
	            197, 244, 167, 150, 1,   48,  99,  82,  124, 77,  30,  47,  184, 137, 218, 235,
	             61,  12,  95,  110, 249, 200, 155, 170, 132, 181, 230, 215, 64,  113, 34,  19,
	            126, 79,  28,  45,  186, 139, 216, 233, 199, 246, 165, 148, 3,   50,  97,  80,
	            187, 138, 217, 232, 127, 78,  29,  44,  2,   51,  96,  81,  198, 247, 164, 149,
	            248, 201, 154, 171, 60,  13,  94,  111, 65,  112, 35,  18,  133, 180, 231, 214,
	            122, 75,  24,  41,  190, 143, 220, 237, 195, 242, 161, 144, 7,   54,  101, 84,
	             57,  8,   91,  106, 253, 204, 159, 174, 128, 177, 226, 211, 68,  117, 38,  23,
	            252, 205, 158, 175, 56,  9,   90,  107, 69,  116, 39,  22,  129, 176, 227, 210,
	            191, 142, 221, 236, 123, 74,  25,  40,  6,   55,  100, 85,  194, 243, 160, 145,
	             71,  118, 37,  20,  131, 178, 225, 208, 254, 207, 156, 173, 58,  11,  88,  105,
	              4,   53,  102, 87,  192, 241, 162, 147, 189, 140, 223, 238, 121, 72,  27,  42,
	            193, 240, 163, 146, 5,   52,  103, 86,  120, 73,  26,  43,  188, 141, 222, 239,
	            130, 179, 224, 209, 70,  119, 36,  21,  59,  10,  89,  104, 255, 206, 157, 172.
	   	   
	   01 char-pos       binary-long value 0.
	   01 input-str-hold pic x.
	   01 input-str-b    binary-char unsigned redefines input-str-hold.
	   linkage section.
	   01 input-str pic x.  *>  this will actually be num-bytes in length
	   01 num-bytes binary-long.
	   01 crc       binary-char unsigned. *> This will be the return value
       procedure division using input-str num-bytes crc.

		   move CRC-START-8 to crc
		   perform varying char-pos from 1 by 1 until char-pos > num-bytes
			   move input-str(char-pos:1) to input-str-hold
               compute crc = sht75-crc-table(input-str-b b-xor crc)
           end-perform
           goback.

GOYO · ‎2021-01-08

Hello,

In principle, yes, thank you very much.
I have had to adapt the source program a bit, to which I attach, to try it with different strings. And I see that the value of crc-8 is always the same, I do not know if the program is correct.

For example:

*01 input-str pic x(36) value
* "TBAI-00000006Y-251019-btFpwP8dcLGAF-". .
*01 num-bytes binary-long value 36.
*01 crc binary-char unsigned value zeroes.

ccrc8. CALL "crc8" USING input-str num-bytes crc.

Can you confirm me if it is correct?

Chris Glazier · ‎2021-01-08

I tested your version of the program and it worked fine. If I change the input string value then the return value will be a different value. What values do you see being returned?

I tested under Visual COBOL 6.0.

GOYO · ‎2021-01-08

Hello,

In my case, varying the characters of the 36 position string, the result is always the same: crc = 544.

I have tried it with VC 60 and with NetExpress, and crc = 544.

On the other hand, debugging the program crc8.cbl, in VC 6.0, I find it complicated, examine and monitor the crc field, while in NetExpress, it seems simpler, passing the mouse over the field, it does it by default, and pressing the right button, you have the option to change, monitor it.

How should I configure the editor in VCVS2019, so that it behaves in a similar way to NE?

Reading the help in
https://www.microfocus.com/documentation/visual-cobol/vc60/VS2019/GUID-C4313D85-8CD0-47AE-9154-E09DCE81FA0D.html
Pressing Shift+F9 , Examine data item' on VC60, shows nothing.

Translated with www.DeepL.com/Translator (free version)

Chris Glazier · ‎2021-01-08

Visual COBOL should allow you to hover the mouse over the data item and it should display in a popup. You can edit the value in place. You can also right click on a data item and select Watch to place it in a watch list.

Something appears to be wrong with your project.

Can you please zip up the solution/project folder and attach it to this post or email it to chris.glazier@microfocus.com?

Thanks