Revisit C# binding

[anakrish]

Refactor code to address #539 (comment) and other issues.
Also make performance improvements.

[billknye]

I'm seeing memory leaks in the C# bindings, unsure if it already known. Experimenting with this, I ran the dotnet benchmarks and noticed huge memory usage. Simple naive usage at the very least seems to slowly leak memory. I could definitely be doing something wrong, I'm using the NuGet from this action output;

using Regorus;

for (int i = 0; i < 1_000_000; i++)
{
    using var engine = new Engine();
    engine.AddPolicy(
        "test.rego",
        "package test\nx = 1\nmessage = `Hello`");

    _ = engine.EvalRule("data.test.message");

    if (i % 1_000 == 0)
    {
        Console.WriteLine($"{i} {Environment.WorkingSet}");
    }
}

Output:

395000 4681183232 // 4+gb here, continues to grow

Adapting a different test to see if a more realistic usage scenario, with a loop like below, shows the managed memory being allocated and cleaned up (as expected) but the total memory continues to grow:

for (int i = 0; i < 1_000_000; i++)
{
    using var vm = new Rvm();

    vm.LoadProgram(rehydrated);
    vm.SetDataJson(Test.Data);
    vm.SetInputJson(Test.Input);

    _ = vm.Execute();

    if (i % 1_000 == 0)
    {
        Console.WriteLine($"{i} {Environment.WorkingSet} {GC.GetTotalMemory(false)}");
    }
}

Output:

421000 1857249280 11668176
422000 1861640192 12268528
423000 1865871360 12868880
424000 1870192640 895392
425000 1874526208 1495744

[anakrish]

@billknye Thanks for reporting this. I will investigate.

[anakrish]

@billknye Thanks for reporting this. It was. a memory leak due to the rust objects not getting freed. Created a separate issue #570 to track it and a fix in #571