sdk: Add atomic operations groundwork

Signed-off-by: Chloe M. <chloe@mensia.org>

sdk/head/atomic.h

@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2026, Chloe M.
+ * Provided under the BSD-3 clause.
+ *
+ * Description: Atomic operations
+ * Author:      Chloe M.
+ */
+
+#ifndef _SDK_ATOMIC_H_
+#define _SDK_ATOMIC_H_ 1
+
+#include <stdef.h>
+
+static inline ULONG
+AtomicAddLongNv(volatile ULONG *Ptr, ULONG Value)
+{
+    return __sync_add_and_fetch(Ptr, Value);
+}
+
+static inline UQUAD
+AtomicAddQuadNv(volatile UQUAD *Ptr, UQUAD Value)
+{
+    return __sync_add_and_fetch(Ptr, Value);
+}
+
+static inline ULONG
+AtomicSubLongNv(volatile ULONG *Ptr, ULONG Value)
+{
+    return __sync_sub_and_fetch(Ptr, Value);
+}
+
+static inline ULONG
+AtomicSubQuadNv(volatile UQUAD *Ptr, UQUAD Value)
+{
+    return __sync_sub_and_fetch(Ptr, Value);
+}
+
+/* Atomic increment and fetch operations */
+#define AtomicIncLong(P) AtomicAddLongNv((P), 1)
+#define AtomicIncQuad(P) AtomicAddQuadNv((P), 1)
+
+/* Atomic decrement and fetch operations */
+#define AtomicDecLong(P) AtomicSubLongNv((P), 1)
+#define AtomicDecQuad(P) AtomicSubQuadNv((P), 1)
+
+#endif  /* !_SDK_ATOMIC_H_ */