PorygonSharp/PorygonSharp/EvaluateResult.cs

using System;
using System.Runtime.InteropServices;
using System.Text;
using PorygonSharp.EvalValues;

namespace PorygonSharp
{
    internal struct EvaluateResult : IDisposable
    {
        [StructLayout(LayoutKind.Sequential)]
        private struct EvaluateResultInternal
        {
            public readonly IntPtr Value;
            public readonly byte Result;
            public readonly IntPtr ErrorMessage;
            public readonly long ErrorSize;
        }

        private readonly IntPtr _ptr;
        private readonly EvaluateResultInternal _internal;
        public EvaluateResult(IntPtr ptr)
        {
            _ptr = ptr;
            _internal = Marshal.PtrToStructure<EvaluateResultInternal>(ptr);
        }

        public EvalValue GetValue()
        {
            return new EvalValue(_internal.Value);
        }

        public bool IsSuccess()
        {
            return _internal.Result == 0;
        }

        public string GetError()
        {
            var nameArr = new byte[_internal.ErrorSize];
            for (var i = 0; i < _internal.ErrorSize; i++)
                nameArr[i] = Marshal.ReadByte(_internal.ErrorMessage, i);
            return $"Error length: {_internal.ErrorSize}" +  Encoding.UTF8.GetString(nameArr);
        }

        public void Dispose()
        {
            Marshal.FreeHGlobal(_ptr);
        }
        
        [DllImport("PorygonLang", EntryPoint = "GetResultError", CallingConvention = CallingConvention.Cdecl)]
        private static extern string GetErrorMessage(IntPtr ptr);

    }
}