CODEWITHSUNDEEP
c++cobol
RyanA
RyanA

Reputation: 9

Data conversion from a .DAT file generated from COBOL

I am trying to get a value from a .DAT file generated by a COBOL program. But the problem is when I try to display the data to my c++ program. I get a weird value like for 15.25 i get 960000.

My question is: What's the preferred data type to import 

PIC  S9999V99  COMP-5  VALUE +0

and

PIC  S9(7)     COMP-5  VALUE +0

My c++ code to import bytes to long

BOOL Import( LONG &nVal, INT nNumChars, FILE *pFile )
{
   char strVal[10];

   for ( int n = 0; n < (nNumChars); n++ )
   {
      if ( fread( &strVal[n], 1, 1, pFile ) != 1 )
      {
         return FALSE;
      }
   }

   strVal[n] = NULL;

   nVal = atol(strVal);

   return TRUE;
}

Hex of the first record

30 31 34 38 35 37 42 E7    03 00 00 00 00 00 00 31
32 2F 34 32 20 20 31 30    30 30 30 20 20 20 20 20
20 20 20 20 20 20 20 20

Upvotes: 0

Views: 1146

Answers (4)

Dr. belisarius
Dr. belisarius

Reputation: 61056

This is the record you are trying to read: 

  0  1  4  8  5  7  B --    -- -- --  z e r o e s 1    2  / 4  2   b  b  1  0

 30 31 34 38 35 37 42 E7    03 00 00 00 00 00 00 31   32 2F 34 32 20 20 31 30 
 ///////////////////////////////////////////////////////////////////////////////    
  0  0  0  b  b  b  b  b     b  b  b  b  b  b  b  b  

 30 30 30 20 20 20 20 20    20 20 20 20 20 20 20 20

Where 

b means whitespace  

zeroes are binary zeros

-- is a BINARY NUMBER COMP-5 and reversed (000003E7) == 999

So, no trace of your 1525, but perhaps this may help you to identify the contents. Look at that "999"!

HTH!

Upvotes: 2

dan04
dan04

Reputation: 91217

PIC S9(7) COMP-5 VALUE +0

The COMP-5 means that the value is stored in binary. (You may need to swap bytes, depending on platform.) The S means the field is signed (probably two's complement). The 9(7) means the field must have room for values up to ±9999999, which requires 4 bytes (1 sign bit + 24 value bits + 7 padding bits). So the equivalent C data type is int32_t.

PIC S9999V99 COMP-5 VALUE +0

V is an implicit decimal place. Anything a COBOL program puts in it gets scaled by 100 behind the scenes (e.g., 15.25 gets stored as 001525, 16 gets stored as 001600, etc.). In C++, you'll have to do this scaling yourself.

I'd normally use double for the external data type, but two decimal places strongly suggests dollars and cents, for which you should use a decimal type if one is available.

30 31 34 38 35 37 42 E7    03 00 00 00 00 00 00 31
32 2F 34 32 20 20 31 30    30 30 30 20 20 20 20 20
20 20 20 20 20 20 20 20

This looks like the ASCII string 014857B�␃␀␀␀␀␀␀12/42 10000, which would suggest DISPLAY rather than COMP-5 numbers. Are you sure you're looking at the right part of the record?

Upvotes: 0

Bruce Martin
Bruce Martin

Reputation: 10553

As previously authors have stated, more inormation is needed; namely which Cobol Compiler; and the Cobol Copybook (or portion there of) would be useful.

But Reading in as a char array and using atol is probably wrong.

For most Cobol compilers (RM Cobol is different) you would

  • Read as byte array

  • Calculate from the byte array. For a 2 byte positive number you could

    long val = byte_array[0] * 256 + byte_array[1] /* Big Ending */ long val = byte_array[0] + byte_array[1] * 256 /* little Ending */

Note: the * 256 should be shift 8 bits but I do not rember the C shift operators

The V in Pic 99V99 is an assumed decimal place i.e. You will need to add the following calculation to the code

 double ret_val = long_val / 10      /* if  pic p(?)V9 */
 double ret_val = long_val / 100     /* if  pic p(?)V99 */
 double ret_val = long_val / 1000    /* if  pic p(?)V999 */
 double ret_val = long_val / 10000   /* if  pic p(?)V9990 */

to get the real Value.

Note: There are some editors that can display Cobol Data Files using a Cobol Copybook (Depends which version of Cobol though).

Upvotes: 0

EvilTeach
EvilTeach

Reputation: 28882

There really isn't enough information in your question to answer it.

The thing to do, is look at the program that generated the data file, and replicate the structures in there.

Upvotes: 0

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