diff --git a/vulkan.d b/vulkan.d
index d8d4458..3d60f76 100644
--- a/vulkan.d
+++ b/vulkan.d
@@ -108,6 +108,14 @@ const VkFormat[] VK_IMAGE_FORMATS = [
 	VK_FORMAT_R8G8B8A8_UNORM,
 ];
 
+enum ShaderStage : VkShaderStageFlagBits
+{
+	None = cast(VkShaderStageFlagBits)0,
+	Vertex = VK_SHADER_STAGE_VERTEX_BIT,
+	Fragment = VK_SHADER_STAGE_FRAGMENT_BIT,
+	Compute = VK_SHADER_STAGE_COMPUTE_BIT,
+}
+
 enum InputRate : int
 {
 	Vertex = VK_VERTEX_INPUT_RATE_VERTEX,
diff --git a/vulkan_util.d b/vulkan_util.d
index a463380..47a5cef 100644
--- a/vulkan_util.d
+++ b/vulkan_util.d
@@ -263,11 +263,18 @@ AllocAlign(Arena* arena, u64 size, u64 alignment)
 void
 Reset(Arena* arena)
 {
+	memset(arena.mem, 0, arena.pos);
 	arena.pos = 0;
 }
 
 void
 Free(Arena* arena)
 {
-	(arena.mem);
+	MemFree(arena.mem, arena.length);
+}
+
+T 
+AlignPow2(T)(T v, T a)
+{
+	return (v + a - 1) & ~(a - 1);
 }