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Moving from byteint array to record

Fri, 12 Jun 2009 14:59:06 -0700

Sorry have not dealt in Pascal in quite some time
so any help appreciated.

Here is my scenerio:

bulkrec = record
job : LongInt;
relation : packed array [1..8] of char;
reclen : LongInt;
bulk : array [1.. 1000] of ByteInt;

pbulkrec = ^bulkrec;

and then I have another record like:

custfile = record
custnum : ShortNat;
group : ShortNat;
name : packed array [1..20] of char;
flag1 : boolean;
flag2 : boolean;
flag3 : boolean;
flag4 : boolean;
end;

pcustfile = ^custfile;

Problem then is that the bulkrec.bulk field actually
holds the custfile data and I want to move it from that
array into custfile record... i.e.

custnum is a 2 byte field so the concatenation of
bulk[1] and bulk[2] holds its value.

group also is a 2 byte field so the concatenation of
bulk[3] and bulk[4] holds its value.

name is 20 byte field and thus
bulk[5] thru bulk[24] hold its value.

flags1-4 hold 1 byte a piece
bulk[25] to bulk[28] respectively.

How do I make this assignment from the bulkrec.bulk
variable to the custfile record???

Any help appreciated.

Re: Moving from byteint array to record

Fri, 12 Jun 2009 17:24:29 -0700

What is a ByteInt? What is a ShortNat?

Neither of these terms is part of modern Pascal.

I'm guessing that

Type
   ByteInt = 0 .. 255 ;  { i.e., type Byte }
   ShortNat = -128 .. 127 ;

By the way the word packed is obsolete.

Re: Moving from byteint array to record

Fri, 12 Jun 2009 17:57:16 -0700

Not using modern Pascal.

ShortNat
Format of type shortnat
Total size in bytes: 2
Type is packed
range (type:integer) from 0 to 32767

Format of type byteint
Total size in bytes: 1
Type is packed
range (type:integer) from -128 to 127

Re: Moving from byteint array to record

Fri, 12 Jun 2009 20:49:10 -0700

: bulkrec = record
:   job          : LongInt;    
:   relation     : packed array [1..8] of char;
:   reclen       : LongInt;
:   bulk : array [1.. 1000] of ByteInt;
: 
: pbulkrec = ^bulkrec;

:
:
: and then I have another record like:
:

: custfile = record
:    custnum  : ShortNat;
:      group  : ShortNat;
:       name  : packed array [1..20] of char;
:       flag1 : boolean;
:       flag2 : boolean;
:       flag3 : boolean;
:       flag4 : boolean;
: end;
: 
: pcustfile = ^custfile;

:
:
: Problem then is that the bulkrec.bulk field actually
: holds the custfile data and I want to move it from that
: array into custfile record... i.e.
:
: custnum is a 2 byte field so the concatenation of
: bulk[1] and bulk[2] holds its value.
:
: group also is a 2 byte field so the concatenation of
: bulk[3] and bulk[4] holds its value.
:
: name is 20 byte field and thus
: bulk[5] thru bulk[24] hold its value.
:
: flags1-4 hold 1 byte a piece
: bulk[25] to bulk[28] respectively.
:
: How do I make this assignment from the bulkrec.bulk
: variable to the custfile record???
:
: Any help appreciated.
:
:

The first problem I see is your declarations

   pbulkrec  : ^bulkrec;
   pcustfile : ^custfile;

where you declare pbulkrec and pcustfile as pointers. The "problem" is that having to reference and de-reference the adds to the complexity and gets in the way of addressing the other issues. I have not idea why you declare these as pointers instead of variables, but I'm going to address your other issues in terms of this declaration:

   pbulkrec  : bulkrec;
   pcustfile : custfile;

If you really need these to be pointers I'll leave it to you to make that adjustment.

: custnum is a 2 byte field so the concatenation of
: bulk[1] and bulk[2] holds its value.

I'm assuming that the definition of BulkRec is being forced upon you by some existing software or data. If so then the method of "concatenation" is ambiguous and we have to guess how the original programmer did it. The simplest would be

   with pbulkrec do
      with pcustfile do
         CustNum := 128*Bulk[1] + Bulk[2] ;

This assumes that Bulk[1] is the most significant byte, but it could be that Bulk[2] is the MSB.

However, Bulk is signed and CustNum is unsigned. I think this is more likely:

   with pbulkrec do
      with pcustfile do
         CustNum := (256*(Bulk[1] + 128) MOD 32768) + (Bulk[2] + 128 ;

Adding 128 to each Bulk element shifts it into positive territory, and the MOD operator keeps CustNum in range. Of course this assumes that the original programmer took this same approach.

: name is 20 byte field and thus
: bulk[5] thru bulk[24] hold its value.

   for i := 1 to 20 do
      name[i] := bulk[i + 4] ;  { there may be problems with pack and unpack }

: flags1-4 hold 1 byte a piece
: bulk[25] to bulk[28] respectively.

   flag1 := (bulk[25] = 0) ; { assume zero means FALSE }
   flag2 := (bulk[26] = 0) ; { any else means TRUE }
   flag3 := (bulk[27] = 0) ;
   flag4 := (bulk[28] = 0) ;

What do Bulk[29] .. Bulk[1000] hold ?

What implementation of Pascal are you using? What kind of computer and operating system?

Re: Moving from byteint array to record

Sat, 13 Jun 2009 07:00:10 -0700

I appreciate your reply...

However, I am not really looking for help in deciphering how to cast the byte(ints) into the individual fields but was really wondering whether there was some Pascal capability to overlay (or point to) the same data but from the viewpoint of differently defined stuctures and have them correctly "cast" automatically. I may be asking for a ability that does not exist. But simplistically I am looking for:

custfile:=bulkfile.bulk[1..28];

As to your final question...in my example what is held in bytes 29-1000 is superfluous to the problem but can be understood if one rationalizes that bulkfile can hold the data in the same way for various other file structures. Thus I could have an address record that is 130 bytes long and when stored in the bulk file it would take up the first 130 bytes of bulkfile.bulk. Note one of the fields of the bulkfile record is "reclen" which would of course hold a 28 in my original example thus allowing the programmer to know how many significant bytes the bulkfile.bulk field held.

Thanks again...

Re: Moving from byteint array to record

Sat, 13 Jun 2009 08:42:59 -0700

: I
: may be asking for a ability that does not exist. But simplistically
: I am looking for:
:
:
: custfile:=bulkfile.bulk[1..28];
:
:
I'm fairly certain that such a thing does not exist in classical Pascals such as described by Jensen and Wirth.

I think you might be able to do something like this in Turbo Pascal or FreePascal. I'd have to give it some thought as to exactly how.

Re: Moving from byteint array to record

Sat, 13 Jun 2009 12:46:03 -0700

How about Move();

Just copy all the data from the ByteArray to the start address of the custfile. This should fill in all the data.

 Move(bulkfile.bulk, custfile, 28);