Add NCE code

src/Ryujinx.Cpu/Nce/NceThreadTable.cs

@@ -0,0 +1,97 @@
+using Ryujinx.Memory;
+using System;
+using System.Runtime.CompilerServices;
+
+namespace Ryujinx.Cpu.Nce
+{
+    static class NceThreadTable
+    {
+        private const int MaxThreads = 4096;
+
+        private struct Entry
+        {
+            public IntPtr ThreadId;
+            public IntPtr NativeContextPtr;
+
+            public Entry(IntPtr threadId, IntPtr nativeContextPtr)
+            {
+                ThreadId = threadId;
+                NativeContextPtr = nativeContextPtr;
+            }
+        }
+
+        private static MemoryBlock _block;
+
+        public static IntPtr EntriesPointer => _block.Pointer + 8;
+
+        static NceThreadTable()
+        {
+            _block = new MemoryBlock((ulong)Unsafe.SizeOf<Entry>() * MaxThreads + 8UL);
+            _block.Write(0UL, 0UL);
+        }
+
+        public static int Register(IntPtr threadId, IntPtr nativeContextPtr)
+        {
+            Span<Entry> entries = GetStorage();
+
+            lock (_block)
+            {
+                ref ulong currentThreadCount = ref GetThreadsCount();
+
+                for (int i = 0; i < MaxThreads; i++)
+                {
+                    if (entries[i].ThreadId == IntPtr.Zero)
+                    {
+                        entries[i] = new Entry(threadId, nativeContextPtr);
+
+                        if (currentThreadCount < (ulong)i + 1)
+                        {
+                            currentThreadCount = (ulong)i + 1;
+                        }
+
+                        return i;
+                    }
+                }
+            }
+
+            throw new Exception($"Number of active threads exceeds limit of {MaxThreads}.");
+        }
+
+        public static void Unregister(int tableIndex)
+        {
+            Span<Entry> entries = GetStorage();
+
+            lock (_block)
+            {
+                if (entries[tableIndex].ThreadId != IntPtr.Zero)
+                {
+                    entries[tableIndex] = default;
+
+                    ulong currentThreadCount = GetThreadsCount();
+
+                    for (int i = (int)currentThreadCount - 1; i >= 0; i--)
+                    {
+                        if (entries[i].ThreadId != IntPtr.Zero)
+                        {
+                            break;
+                        }
+
+                        currentThreadCount = (ulong)i;
+                    }
+
+                    GetThreadsCount() = currentThreadCount;
+                }
+            }
+        }
+
+        private static ref ulong GetThreadsCount()
+        {
+            return ref _block.GetRef<ulong>(0UL);
+        }
+
+        private static unsafe Span<Entry> GetStorage()
+        {
+            return new Span<Entry>((void*)_block.GetPointer(8UL, (ulong)Unsafe.SizeOf<Entry>() * MaxThreads), MaxThreads);
+        }
+    }
+}