C#•3y ago

❔ Importing functions by RVA instead of Name

right now, I have a function imported from a cpp library which I pass in a function name and params, and it gives me back a pointer to that function. And currently, I just cast it to a unmanaged function pointer and it works fine. Does anyone here know if there is a way to simplify this process by using a custom attribute? example: instead of

delegate* unmanaged[Cdecl]<int,int,void> DoThing = (delegate* unmanaged[Cdecl]<int,int,void>)ResolveFunc("DoThing(int, int)");

delegate* unmanaged[Cdecl]<int,int,void> DoThing = (delegate* unmanaged[Cdecl]<int,int,void>)ResolveFunc("DoThing(int, int)");

just

[Resolvable("DoThing(int, int)")]
public static extern void DoThing(int pA, int pB);

[Resolvable("DoThing(int, int)")]
public static extern void DoThing(int pA, int pB);

or similar. How can I go about making ResolvableAttribute?

16 Replies

Kouhai•3y ago

Get the attribute and call ResolveFunc with the value of ResolvableAttribute

GlatrixOP•3y ago

right, but where? is there a way to override invoke in the attribute class?

Kouhai•3y ago

I'm not sure what do you mean override invoke, you can do it with reflection.

GlatrixOP•3y ago

what will reflection even do for me in this case? I'm working with function pointers, and I need to make an attribute which shortens the process thats all if I have

[Resolvable("DoThing(int, int)")]
public static extern void DoThing(int pA, int pB);

[Resolvable("DoThing(int, int)")]
public static extern void DoThing(int pA, int pB);

and I call it, it should make sure it has the pointer by calling ResolveFunc with the value ive passed in, and then call it with the args pA and pB instead of

var DoThing = (delegate* unmanaged[Cdecl]<int,int,void>)ResolveFunc("DoThing(int, int)");

var DoThing = (delegate* unmanaged[Cdecl]<int,int,void>)ResolveFunc("DoThing(int, int)");

I want to put the

ResolveFunc("DoThing(int, int)");

ResolveFunc("DoThing(int, int)");

functionality inside the attribute somehow, and get rid of the annoyingly long cast if possible

Kouhai•3y ago

What's the return type of ResolveFunc?

GlatrixOP•3y ago

IntPtr which is the address of the function in memory when I cast it as a func pointer it works, im just looking to simplify the process

Kouhai•3y ago

A very simple example

class Test
{
    [Resolvable("DoThing(int, int)")]
    public static extern void DoThing(int pA, int pB);
    public static void Init()
    {
        foreach (var field in typeof(Test).GetFields(BindingFlags.Public | BindingFlags.Static))
        {
            var resolvable = field.GetCustomAttribute<ResolvableAttribute>();
            if(resolvable != null)
            {
                var methodPtr = ResolveFunc(resolvable.Name);
                try
                {
                    if (methodPtr != IntPtr.Zero)
                        field.SetValue(null, Marshal.GetDelegateForFunctionPointer(methodPtr, field.FieldType));
                }
                catch (Exception ex)
                {
                    Console.WriteLine(ex.Message);
                }
            }
        }
    }
}

class Test
{
    [Resolvable("DoThing(int, int)")]
    public static extern void DoThing(int pA, int pB);
    public static void Init()
    {
        foreach (var field in typeof(Test).GetFields(BindingFlags.Public | BindingFlags.Static))
        {
            var resolvable = field.GetCustomAttribute<ResolvableAttribute>();
            if(resolvable != null)
            {
                var methodPtr = ResolveFunc(resolvable.Name);
                try
                {
                    if (methodPtr != IntPtr.Zero)
                        field.SetValue(null, Marshal.GetDelegateForFunctionPointer(methodPtr, field.FieldType));
                }
                catch (Exception ex)
                {
                    Console.WriteLine(ex.Message);
                }
            }
        }
    }
}

Init would initialize all fields that has the attribute Resolvable

internal class ResolvableAttribute : Attribute
{
    public string Name { get; }

    public ResolvableAttribute(string name)
    {
        this.Name = name;
    }
}

internal class ResolvableAttribute : Attribute
{
    public string Name { get; }

    public ResolvableAttribute(string name)
    {
        this.Name = name;
    }
}

GlatrixOP•3y ago

would public static extern void DoThing(int pA, int pB); be considered a field?

Kouhai•3y ago

Yup, it's a field

GlatrixOP•3y ago

oh I didnt know that interesting and it can be set to a delegate?

Kouhai•3y ago

oops sorry, I messed u, you need to define the delegate

GlatrixOP•3y ago

is the delegate not already defined here somehow?

    [Resolvable("DoThing(int, int)")]
    public static extern void DoThing(int pA, int pB);

    [Resolvable("DoThing(int, int)")]
    public static extern void DoThing(int pA, int pB);

like void DoThing(int pA, int pB);

Kouhai•3y ago

or field with an action I messed up, that won't work with GetField Lemme send the correct code This

public delegate void DoThingDelegate(int pA, int pB);
[Resolvable("DoThing(int, int)")]
public static DoThingDelegate? DoThing;

public delegate void DoThingDelegate(int pA, int pB);
[Resolvable("DoThing(int, int)")]
public static DoThingDelegate? DoThing;

[Resolvable("DoThing(int, int)")]
public static Action<int,int>? DoThing;

[Resolvable("DoThing(int, int)")]
public static Action<int,int>? DoThing;

GlatrixOP•3y ago

okay then thanks!! 🙂

Kouhai•3y ago

np 👍

Accord•3y ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ Importing functions by RVA instead of Name

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