add thread local scratch allocator

alloc.d

@@ -9,8 +9,16 @@ import std.stdio;
 import core.stdc.string : memset;
 import core.memory;
 
+static Scratch g_scratch;
+
 const DEFAULT_ALIGNMENT = (void *).sizeof * 2;
 
+struct Scratch
+{
+	Arena arena;
+	bool  init;
+}
+
 struct ArenaPool
 {
 	u8* mem;
@@ -173,7 +181,32 @@ FreeArray(T)(T[] arr)
 	pureFree(arr.ptr);
 }
 
-void Free(T)(T* ptr)
+void 
+Free(T)(T* ptr)
 {
 	pureFree(ptr);
 }
+
+void
+ResetScratch(u64 size)
+{
+	if (!g_scratch.init)
+	{
+		g_scratch.arena = CreateArena(size);
+		g_scratch.init = true;
+	}
+
+	Reset(&g_scratch.arena);
+}
+
+T*
+ScratchAlloc(T)()
+{
+	return Alloc!(T)(&g_scratch.arena);
+}
+
+T[]
+ScratchAlloc(T)(u64 count)
+{
+	return AllocArray!(T)(&g_scratch.arena, count);
+}