Add file I forgot to commit

mehfooz09 · Feb 17, 2020 · ba78d23 · ba78d23
1 parent dcb19ff
commit ba78d23
Showing 1 changed file with 42 additions and 0 deletions.
diff --git a/util/refcount.h b/util/refcount.h
@@ -0,0 +1,42 @@
+#ifndef UTIL_REFCOUNT_H
+#define UTIL_REFCOUNT_H
+#include <stdatomic.h>
+
+// An industrial-strength refcounting implementation.
+// Safety first! Make sure to:
+// - Write a release for every retain
+// - Get exclusive access to the reference before retaining or releasing it
+
+struct refcount {
+    atomic_uint rc;
+};
+
+static inline void __refcount_init(struct refcount *refcount) {
+    refcount->rc = 1;
+}
+#define refcount_init(obj) __refcount_init(&(obj)->refcount)
+
+static inline int __refcount_get(struct refcount *refcount) {
+    return refcount->rc;
+}
+#define refcount_get(obj) __refcount_get(&(obj)->refcount)
+
+#define DECLARE_REFCOUNT(type) \
+    void type##_retain(struct type *obj); \
+    void type##_release(struct type *obj)
+
+#define __DEFINE_REFCOUNT(type, qualifiers) \
+    qualifiers struct type *type##_retain(struct type *obj) { \
+        obj->refcount.rc++; \
+        return obj; \
+    } \
+    static void type##_cleanup(struct type *obj); \
+    qualifiers void type##_release(struct type *obj) { \
+        if (--obj->refcount.rc == 0) \
+            type##_cleanup(obj); \
+    }
+
+#define DEFINE_REFCOUNT(type) __DEFINE_REFCOUNT(type, )
+#define DEFINE_REFCOUNT_STATIC(type) __DEFINE_REFCOUNT(type, static)
+
+#endif