How to Access ConnectServer Method in XA_Session.dll using COM in Go?

Accessing Windows DLLs Using COM in Go

Your goal is to leverage a Windows DLL (XA_Session.dll) within your Go program, particularly accessing its ConnectServer method. However, you faced challenges due to a compilation error indicating that proc.ConnectServer is undefined.

The issue stems from the incorrect method invocation. To call a syscall.LazyProc, you need to utilize its Call function, rather than directly referencing its fields. COM functions, like DllGetClassObject, require specific parameter values.

In your specific case, DllGetClassObject expects three parameters: a CLSID, IID, and a pointer to the COM object. These parameters should be passed to proc.Call as uintptrs. Here's an improved version of your code:

<code class="go">package main

import (
    "syscall"
    "fmt"
)

var (
    xaSession      = syscall.NewLazyDLL("XA_Session.dll")
    getClassObject = xaSession.NewProc("DllGetClassObject")
)

func main() {
    // TODO: Set these variables to the appropriate values
    var rclsid, riid, ppv uintptr
    ret, _, _ := getClassObject.Call(rclsid, riid, ppv)
    // Check ret for errors (assuming it's an HRESULT)

    // Assuming ppv now points to your XA_Session object, you can
    // create wrapper types to access its methods:

    type XASession struct {
        vtbl *xaSessionVtbl
    }

    type xaSessionVtbl struct {
        // Every COM object starts with these three
        QueryInterface uintptr
        AddRef         uintptr
        Release        uintptr

        // Additional methods of this COM object
        ConnectServer    uintptr
        DisconnectServer uintptr
    }

    xasession := NewXASession(ppv)

    if b := xasession.ConnectServer(20001); b == 1 {
        fmt.Println("Success")
    } else {
        fmt.Println("Fail")
    }
}</code>

Note that you need to correctly set the CLSID and IID values, which are typically provided in the accompanying C header file for the DLL. You also need to implement wrapper functions for the additional COM methods you wish to access, which requires understanding their exact signatures and order.

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