Hi there,

I need a solution for a packed record containing 4-byte 32-bit integers and cardinals, and other byte 8 bit and word 16 bit sized variables to overlay over a stream.

Example:
*type*
* TMyBinaryHeader = packed record*
* Sender : Cardinal;*

* Target : Cardinal;*

* Reference : Integer; *

* Flags : Word;*
* CheckByte : Byte;*
* end;*

So on 32 bit systems, SizeOf(TMyBinaryHeader) will report 15 bytes. How do I accomplish this on 64 bit platform and avoiding "myprotocollib.pas(x,y) Error: Typecast has different size (4 -> 8) in assignment" without having to port to ugly byte copy operations.

Thanks.

DJ Coertzen schrieb am Mi., 27. März 2019,
18:27:

Would you show the code at/around the error location, please? I suspect that it isn't the record that's the problem, but how you use it.

Regards,
Sven

Perhaps use size explicit types such as uint32 and int32?

Pointer arithmetic:
*for Indx := 0 to SizeOf(TTCPPackageHeader) - 1 do Dec(Byte(Pointer(Cardinal(@x) + Indx)^), ARollCount);*

I discovered UInt32 in the meanwhile . Thanks. I replied on the wrong response about pointer arithmetic

On Wed, Mar 27, 2019 at 7:47 PM Sven Barth via fpc-devel <

Pointer arithmetic:
*for Indx := 0 to SizeOf(TTCPPackageHeader) - 1 do Dec(Byte(Pointer(Cardinal(@x) + Indx)^), ARollCount);*

the error has nothing to do with your record,
its that part:
Pointer(Cardinal(@x) + Indx)^)

The problem is that Cardinale is an unsigned 32-bit integer, while on 64-bit, you will need UINT64,

You should use PtrUInt type that is an unsigned type that always have the size of an address instead of cardinal here!

Pierre

I think the official unsigned 32-bit integer type in Pascal is "LongWord". As others have said, be aware that pointers are 64-bit under x64... that's kind of why it's called x64!  If you absolutely must have a packed record with 32-bit types, I recommend changing Sender and Target to indices that are added to a base address.
Similar to what Pierre said, change your Pointer code to something like this:
for Indx := 0 to SizeOf(TTCPPackageHeader) - 1 do
Dec(Byte(Pointer(PtrUInt(@x) + Indx)^), ARollCount);

So similarly with your record, instead of directly derefencing Sender and Target - since I assume your record type must stay fixed at 15 bytes - have something akin to "Pointer(PtrUInt(@BaseAddr) + Sender)".

The first rule, first and foremost... don't assume the Pointer is a fixed size.  Hope all of this helps.

Gareth aka. Kit
P.S. I would recommend adding a "Filler" or "Reserved" byte at the end of your record type to make it 16 bytes long - such a size is more efficient when it's part of an array in memory.

On Wed 27/03/19 21:11 , Pierre Muller sent:

_______________________________________________ fpc-devel maillist  -  http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel

[2]">http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel

Pointer arithmetic: *for Indx := 0 to SizeOf(TTCPPackageHeader) - 1 do

Dec(Byte(Pointer(Cardinal(@x) + Indx)^), ARollCount);* the error has nothing to do with your record,
its that part:
Pointer(Cardinal(@x) + Indx)^)

The problem is that Cardinale is an unsigned 32-bit integer, while on 64-bit, you will need UINT64,

You should use PtrUInt type that is an unsigned type that always have the size of an address instead of cardinal here!

Pierre

Heh, much better - thank you!

On Thu 28/03/19 14:31 , "Karoly Balogh (Charlie/SGR)" sent:
Hi,

Dec(Byte(Pointer(PtrUInt(@x) + Indx)^), ARollCount);

How about Dec(PByte(@x)[Indx], ARollCount); instead? That doesn't look like an angry C programmer tried to convert some abomination to Pascal, and works on all pointer sizes.

(Unless it also has to compile with say, Delphi.)

Charlie

Hi,

How about Dec(PByte(@x)[Indx], ARollCount); instead? That doesn't look like an angry C programmer tried to convert some abomination to Pascal, and works on all pointer sizes.

(Unless it also has to compile with say, Delphi.)

Charlie

Op 2019-03-28 om 15:31 schreef Karoly Balogh (Charlie/SGR):

(Unless it also has to compile with say, Delphi.)

Everybody has {$pointermath on} is the include file included in every unit nowadays. Or at least I hope :-)