ADOFAIRenderer/Util/StreamUtil.cs

using System;
using System.IO;

namespace ADOFAIRenderer.Util
{
    public static class StreamUtil
    {
        public static void WriteNativePtrToStream(IntPtr nativePtr, int length, Stream destinationStream)
        {
            if (nativePtr == IntPtr.Zero)
                throw new ArgumentNullException(nameof(nativePtr));
            if (length <= 0) return;

            unsafe
            {
                // Create an unmanaged memory stream that wraps the native pointer
                // (This does not allocate new memory; it references the existing pointer)
                using var unmanagedStream = new UnmanagedMemoryStream((byte*)nativePtr, length);
                // Copy the data directly into your target stream
                unmanagedStream.CopyTo(destinationStream);
            }
        }
    }
}