C# wrapper and Callbacks
- by fergs
I'm in the process of writing a C# wrapper for Dallmeier Common API light (Camera & Surviellance systems) and I've never written a wrapper before, but I have used the Canon EDSDK C# wrapper. So I'm using the Canon wrapper as a guide to writing the Dallmeier wrapper.
I'm currently having issues with wrapping a callback. In the API manual it has the following:
dlm_connect
int(unsigned long uLWindowHandle,
const char * strIP,
const char* strUser1,
const char* strPwd1,
const char* strUser2,
const char* strPwd2,
void (*callback)(void *pParameters, void *pResult, void *pInput),
void * pInput)
Arguments
- ulWindowhandle - handle of the window that is passed to the ViewerSDK to display video and messages there
- strUser1/2 - names of the users to log in. If only single user login is used strUser2 is
- NULL
- strPwd1/2 - passwords of both users. If strUser2 is NULL strPwd2 is ignored.
Return
This function creates a SessionHandle that has to be passed
Callback
pParameters will be structured:
- unsigned long ulFunctionID
- unsigned long ulSocketHandle, //handle to socket of the established connection
- unsigned long ulWindowHandle,
- int SessionHandle, //session handle of the session created
- const char * strIP,
- const char* strUser1,
- const char* strPwd1,
- const char* strUser2,
- const char * strPWD2
pResult is a pointer to an integer, representing the result of the operation. Zero on success.
Negative values are error codes.
So from what I've read on the Net and Stack Overflow - C# uses delegates for the purpose of callbacks. So I create a my Callback function :
public delegate uint DallmeierCallback(DallPparameters pParameters, IntPtr pResult, IntPtr pInput);
I create the connection function
[DllImport("davidapidis.dll")]
public extern static int dlm_connect(ulong ulWindowHandle, string strIP, string strUser1, string strPwd1, string strUser2, string strPwd2, DallmeierCallback inDallmeierFunc
And (I think) the DallPParameters as a struct :
[StructLayout(LayoutKind.Sequential)]
public struct DallPParameters
{
public ulong ulfunctionID;
public ulong ulsocketHandle;
public ulong ulWindowHandle;
...
}
All of this is in my wrapper class.
Am I heading in the right direction or is this completely wrong?
