I found the code for the demo app. Unfortunately its a
little more basic than I remember.
On the Delphi side I have TestLib.dpr with...
library TestLib;
uses
SysUtils,
Classes,
Windows;
{$R *.res}
function TestStringConverter(InputString :
PChar; OutputString : PChar; BufSize : Integer) : Integer;
stdcall;
var
Input : String;
Output : String;
OutputLength : Integer;
begin
Input := InputString;
// Do something with the input string
while Length(Output) < (BufSize -
Length(Input)) do
begin
Output := Output + Input;
end;
// Write to
output buffer
StrPCopy(OutputString, Output);
Result := Length(Output);
end;
exports
TestStringConverter name
'TestStringConverter';
begin
end.
From memory, the key was using PChar's and stdcall.
In .NET I had:
[DllImport("TestLib.dll")]
public static extern int TestStringConverter(string intput, StringBuilder buffer, int bufSize);
void Test()
{
StringBuilder buffer = new StringBuilder(20);
int result = TestStringConverter("Foo", buffer, buffer.Capacity);
string message = string.Format("Result = {0}\n\nBuffer:\n{1}", result, buffer.ToString());
MessageBox.Show(message);
}
In the production code we were passing a filename to the
Delphi function, which would read the contents of the file,
convert it (the bit we didn't have time to port to .NET) and
then pass the converted contents back to the .NET app as a
string. I think the first approach was to allocate the memory
in Delphi and then copy the data in .NET but then we had to
call another function in the Delphi library to cleanup (I
can't remember the specifics). This worked ok but in the end
I think we just used the above approach to allocate a buffer
in .NET and pass it to the Delphi function. We were dealing
with lots of small files so making the buffer large enough
wasn't an issue, although we did have to check the return
value to see if the buffer was too small (if so then make a
bigger one and try again).
I hope this helps. Ping me off list if you'd like the full
code for the demo app (not much more than what I've pasted
above). Maybe some of the guys I used to work with might be
willing to take a look at the code and offer some insight.
Cheers.
On Wed, Dec 15, 2010 at 7:30 PM, Peter
Maddin
<[email protected]>
wrote:
I would very much
appreciate a copy of your demo if you can locate it.
Thanks for the offer.
I was going to write up a limited dummy dll for proof of
concept.
If that did not work, try COM.
I have a text "Delphi COM Programming" by Eric Harmon
buts its pretty ancient (but then so is the Delphi code
I am looking at)
I have not had much exposure to COM. My only endeavour
has been to write one using C# for use by Access VBA.
That was a very simple hash function for passwords. It
worked ok but I don't think they have ever used it.
On 15/12/2010 5:03 PM, Matt Siebert wrote:
Hi Peter,
I found myself in a similar situation a while
ago (wanting to pass strings between a Delphi DLL
and .NET).
There was something slightly tricky about
strings but it wasn't too bad. I think I did
something with allocating memory which may be
similar to your need to store the xml in memory on
the Delphi side.
Unfortunately I can't remember the details
right now and I've since changed jobs. I remember
making a demo app in my spare time as a proof of
concept before implementing it at work. I'll have
a look for the demo app tonight and let you know.
Cheers,
Matt.
On Wed, Dec 15, 2010 at
4:00 PM, Peter Maddin
<[email protected]>
wrote:
I have
some cipher units written for Delphi 7.
These are fairly complex (at least for
me). They contain methods (sorry functions
and procedures) for the elliptic curve
asymmetric cipher, The Rijndael symmetric
cipher and the SHA-1 hash.
The system that uses these is using file
downloads and uploads using Delphi 7
Isapi dlls.
The system while working, is suffering
congestion problems especially with
uploads.
What I would like to use is WCF web
services to handle data downloads and
create local server files from parameters
sent to the WCF web service on the server
rather than perform uploads (the file
contents is very small).
Writing the WCF should not be too much of
a challenge but I need to use the delphi
code to handle decryption/encryption.
I thought of writing a Win32 dll for the
encryption logic called from C# WinForms
(or maybe WPF) application.
Has anyone done this sort of thing before?
I understand that value types are ok to
exchange but reference types are a pain,
this includes strings.
I have googled and there is a fair bit out
there. Most of this is dealing with the
pain of trying do it.
I only need to exchange ints, bools and
strings. Nothing too fancy.
Has anyone some sample code they would be
willing to share?
Also I would like be able call a method in
the dll to store information in memory to
be used by other method calls. This
information is stored in an xml file and I
would rather it be read and processed once
rather than repeat this each time I need
to use a method. In other words in using
delphi dll, will it preserve state between
method calls?
If I can't get the dll to work I will fall
back on the crypographic support in the
framework but this basically triples the
effort required and data encrypted by the
current system will not be compatible with
the framework cryptographic routines.
Any help very much appreciated.
