Pak Files?

[M109uk]

I have written a pak editor that uses the same structure as Harry Hunt's, to compile the application you need delphi 7 and Jvcl component set, but the zip also contains the exe and a package.

The source code is a bit of a mess, i havnt really had much time to clear it yet. And their is still a few problems i need to sort out with in it!

The zip is 2.04mb : http://www.biocoders.org/kPak.zip

I hope it helps.

[xGTx]

Hey thanks alot.

[xGTx]

Why will this not work:

[pascal]Function IsAPack(FileNametring):Boolean;
Var Stream : TFileStream;
Signature : String[6];
Begin
Result := False; // Prove me wrong!
Stream := TFileStream.Create(FileName, fmOpenRead);
Stream.Position := Stream.Size-6;
Stream.ReadBuffer(Signature, 6);
Stream.Free;
If Signature = 'GTPACK' Then
Result := True;
End;[/pascal]

[xGTx]

The above gives out GTPAC

I dont know why.

And also, how do i know how many headers I have?

Currently i've come up with doing it like this... Im not sure how efficient it is:

[pascal]public
bob : Array of TPackageItem;
end;[/pascal]


[pascal]n := 1;
While n <> 0 do
begin
SetLength(Bob, High(Bob)+2);
Stream.ReadBuffer(Bob[High(Bob)],SizeOf(TPackageItem));
If (Stream.Size - Stream.Position) < SizeOf(TPackageItem) Then n := 0;
end;[/pascal]

[Harry Hunt]

a)
try
[pascal]
function IsAPack(FileName: string): Boolean;
var
Stream: TFileStream;
Signature: string[6];
begin
Result := False; // Prove me wrong!
Stream := TFileStream.Create(FileName, fmOpenRead);
Stream.Seek(SizeOf(Signature), soFromEnd);
Stream.ReadBuffer(Signature, SizeOf(Signature));
Stream.Free;
if Signature = 'GTPACK' then
Result := True;
end;
[/pascal]

b)
Your second question (how do you know how many headers you have) is answered by the image in my last post:
Your package file should have the following structure: the actual files followed by a file table follow by a footer. The footer can consist of only two values, the Signature and a value "FileCount" which tells you how many files there are in your package. You'd then do something like

[pascal]
PackageStream.Seek(SizeOf(Signature) + SizeOf(Int64) + (FileCount * SizeOf(TPackageItem)), soFromEnd);
for I := 1 to FileCount do
begin
Stream.Read(PackageItem, SizeOf(TPackageItem);
// Add the package item to a list
end;
[/pascal]

[xGTx]

I am not sure why, but when i do:

[pascal]Stream.Seek(SizeOf(Signature), soFromEnd);[/pascal]

The stream.position then becomes 125310 ... The file size is 125303

So it's obviously adding 7 wich is sizeof(signature) ... This shouldnt be happening right?

[Paulius]

This should be happening, soFromEnd does not reverse the direction ar anything, to seek back add a minus, Stream.Seek(-SizeOf(Signature), soFromEnd);

[Harry Hunt]

damn, I forgot the minus. Sorry 'bout that!

[xGTx]

Thanks paulius... and DAMN YOU Harry! Lol j/k! I was freaking out like my delphi was screwy or something... But yea, I started using a minus to see if it worked and it did... And anyway, I believe I have a pretty good understanding of filestreams in Delphi now, for wich I greatly thank you guys. I expect my packaging code to be finished by either tonight or tommarow. Thanks again!

Just curious... I tried:

[pascal]Var Signature tring[6]
Begin
Signature := 'GTPACK';
ShowMessage(IntToStr(SizeOf(Signature)));
End;[/pascal]
And it returns '4' ... Shouldnt it return 6? 1 byter per character?

[cairnswm]

It should return 7 one for each Character and a single byte storing the lengeth of the string.

Short Strings come from old Turbo Pascal days where the maximum length of a string was 255 characters. Each string was actually an array of characters with the zero index being a byte representing the length of the string. (This also allows you to do something like Password[1] to return the first character in the Password string)