🚀 go-pugleaf

Lapo Guidi wrote:

That error message means that the compiler was expecting to assign a
value into something and the something you gave it isn't something that
can be assigned to.

>  T4x4LongWordRecord Hash;
>  AnsiString Hex;
>  TIdHashMessageDigest5 *MD5=new TIdHashMessageDigest5();
>  Hash=MD5->HashValue("testmessage");

I haven't used Indy but looking at the online docs it appears that
HashValue() returns an array of 32 bit values. That means you're trying
to assign to an array which is not allowed in C++ eg;

typedef DWORD array[ 4 ] Tbaddy;

Tbaddy someFunction();

Tbaddy array=someFunction(); 
// An array cannot be assigned to hence is not a valid Left Hand Side 
//   of an expression

Then again why call it 'T4x4LongWord/Record/' if it is an array?

Presumably there is some C++ specific workaround implemented - what
does the C++ specific documentation say for HashValue() and
T4x4LongWord?
-- 
Andrue Cope [TeamB]
[Bicester, Uk]
http://info.borland.com/newsgroups/guide.html

> Presumably there is some C++ specific workaround implemented - what
> does the C++ specific documentation say for HashValue() and
> T4x4LongWord?

Thanks for the fast reply.
Unfortunately I'm not able to find C++ specific documentation.
I found many people asking for a C++ example, but I can see just Delphi 
examples.
Anyway, I'll try to find another MD5 library.

Thank you very much

Lapo 

Lapo Guidi wrote:

> Thanks for the fast reply.
> Unfortunately I'm not able to find C++ specific documentation.
> I found many people asking for a C++ example, but I can see just
> Delphi examples.  Anyway, I'll try to find another MD5 library.

Well you can use Goto declaration to find out how T4x4LongWordRecord is
declared. That might give an indication of how they get around it.

-- 
Andrue Cope [TeamB]
[Bicester, Uk]
http://info.borland.com/newsgroups/guide.html

> Well you can use Goto declaration to find out how T4x4LongWordRecord is
> declared. That might give an indication of how they get around it.

This is the T4x4LongWordRecord declaration:
T4x4LongWordRecord = array [0..3] of LongWord;

"Lapo Guidi" <lapoguidi@inwind.it> wrote in message
news:44a15dd2@newsgroups.borland.com...

> This is the T4x4LongWordRecord declaration:
> T4x4LongWordRecord = array [0..3] of LongWord;

In C++, it comes out as the following:

    typedef unsigned T4x4LongWordRecord[4];

The declaration for T4x4x4LongWordRecord in C++ comes out as follows:

    typedef unsigned T4x4x4LongWordRecord[4][4];

Functions in C++ can't return array values.  However, if you look at the
declaration for HashValue() itself in C++, it does not return an array at
all:

    unsigned __fastcall HashValue(const AnsiString ASrc);

What you can try doing is to add a Delphi .pas file to your C++ project, and
have that file call HashValue() and return the array in a manner that C++
can handle.  For example (untested):

    --- HashValueUnit.pas ---

    unit HashValueUnit;

    uses
        IdHashMessageDigest5;

    interface

    procedure MD5HashValue(MD5: TIdHashMessageDigest5; const S: String; var
Hash: PLongWord);

    implementation

    procedure MD5HashValue(MD5: TIdHashMessageDigest5; const S: String;
Hash: PLongWord);
    var
        Tmp: T4x4LongWordRecord;
    begin
        Tmp := MD5.HashValue(S);
        Move(Tmp[0], Hash, SizeOf(LongWord)*4);
    end;

    end.


    --- MyForm.cpp ---

    #include "HashValueUnit.hpp"

    {
        //...
        TIdHashMessageDigest5 *MD5 = new TIdHashMessageDigest5;

        T4x4LongWordRecord Hash;
        MD5HashValue(MD5, "testmessage", Hash);

        AnsiString Hex = MD5->AsHex(__classid(TIdHashMessageDigest5), Hash);
        //...
    }


Gambit