LPSTR Strings in DLL

[CactusCat]

I have a VC++ DLL function that should be called from VB. The function Encrypts a string (It's more complex than the one shown). This following code, however, returns the exact same string, can anyone see whats wrong?

From VB, the function is called like this
a$="Test String"
EncryptString(a$)

DLL Function
void _stdcall EncryptString(LPSTR data) {
for (int i=0; i<strlen(data); ++i) {
data[i]^=5;
}
}

[HairyDave]

Because the data is not passed 'By reference'. VB automatically passes vars by ref, but C/C++ does it by value.

void _stdcall EncryptString(LPSTR &data) {...}

This should work fine. The '&' tells C++ that the variable will be passed by reference and therefore any local manipulation is done on the actual string - and not some stack variable.

In C this has to be done by dereferencing the variable:

void _stdcall EncryptString(LPSTR *data)
{
  for(int i=0; i < strlen(data); ++i)
  {
    *data[i]^=5;
  }
}

Nasty eh?

HD

[CactusCat]

I doesn't seem to make any difference... I'll try to describe it better:
The function declaration in VB looks like this

Private Declare Sub EncryptString Lib "Encryptor.dll" (ByVal Data As String)

I have tried both ByVal and ByRef for this.

This is how I call the DLL Function

a$="Test String"
EncryptString(a$)
MsgBox a$

The result is a message box reading "Test String"

The DLL Function looks like this
void _stdcall EncryptString(LPSTR data) {
long dataLen=strlen(data);
for (long i=0; i<dataLen; ++i) {
data[i]^=5;
}
}

When I use "LPSTR &data" I get an error when using the strlen function, an access violation.

I realise the encryption is bad, but it's only a test encryptor.
Someone please help!

[CactusCat]

Oh, wait... It does work! Sorry, my fault... Thank muchly hairy dude

[HairyDave]

No Probs buddy.

HD

[CornedBee]

Just had a deja vu...