1 files changed, 54 insertions, 0 deletions
diff --git a/src/basic/refcnt.h b/src/basic/refcnt.h
new file mode 100644
index 0000000..40f9a84
--- /dev/null
+++ b/src/basic/refcnt.h
@@ -0,0 +1,54 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+#pragma once
+
+/* A type-safe atomic refcounter.
+ *
+ * DO NOT USE THIS UNLESS YOU ACTUALLY CARE ABOUT THREAD SAFETY! */
+
+typedef struct {
+        volatile unsigned _value;
+} RefCount;
+
+#define REFCNT_GET(r) ((r)._value)
+#define REFCNT_INC(r) (__sync_add_and_fetch(&(r)._value, 1))
+#define REFCNT_DEC(r) (__sync_sub_and_fetch(&(r)._value, 1))
+
+#define REFCNT_INIT ((RefCount) { ._value = 1 })
+
+#define _DEFINE_ATOMIC_REF_FUNC(type, name, scope)                    \
+        scope type *name##_ref(type *p) {                               \
+                if (!p)                                                 \
+                        return NULL;                                    \
+                                                                        \
+                assert_se(REFCNT_INC(p->n_ref) >= 2);                   \
+                return p;                                               \
+        }
+
+#define _DEFINE_ATOMIC_UNREF_FUNC(type, name, free_func, scope)       \
+        scope type *name##_unref(type *p) {                             \
+                if (!p)                                                 \
+                        return NULL;                                    \
+                                                                        \
+                if (REFCNT_DEC(p->n_ref) > 0)                           \
+                        return NULL;                                    \
+                                                                        \
+                return free_func(p);                                    \
+        }
+
+#define DEFINE_ATOMIC_REF_FUNC(type, name)    \
+        _DEFINE_ATOMIC_REF_FUNC(type, name,)
+#define DEFINE_PUBLIC_ATOMIC_REF_FUNC(type, name)     \
+        _DEFINE_ATOMIC_REF_FUNC(type, name, _public_)
+
+#define DEFINE_ATOMIC_UNREF_FUNC(type, name, free_func)       \
+        _DEFINE_ATOMIC_UNREF_FUNC(type, name, free_func,)
+#define DEFINE_PUBLIC_ATOMIC_UNREF_FUNC(type, name, free_func)        \
+        _DEFINE_ATOMIC_UNREF_FUNC(type, name, free_func, _public_)
+
+#define DEFINE_ATOMIC_REF_UNREF_FUNC(type, name, free_func)   \
+        DEFINE_ATOMIC_REF_FUNC(type, name);                   \
+        DEFINE_ATOMIC_UNREF_FUNC(type, name, free_func);
+
+#define DEFINE_PUBLIC_ATOMIC_REF_UNREF_FUNC(type, name, free_func)   \
+        DEFINE_PUBLIC_ATOMIC_REF_FUNC(type, name);                   \
+        DEFINE_PUBLIC_ATOMIC_UNREF_FUNC(type, name, free_func);