X-Git-Url: http://git.liburcu.org/?p=userspace-rcu.git;a=blobdiff_plain;f=include%2Furcu%2Fref.h;fp=include%2Furcu%2Fref.h;h=e546da567120e086e5773950ac135d510900b4fc;hp=0000000000000000000000000000000000000000;hb=6893800a4d1cc14dff0395ddcd660a5138db183d;hpb=a59f39055b5ecb77b68cf78b9839aa9e8e4ec332

diff --git a/include/urcu/ref.h b/include/urcu/ref.h
new file mode 100644
index 0000000..e546da5
--- /dev/null
+++ b/include/urcu/ref.h
@@ -0,0 +1,98 @@
+#ifndef _URCU_REF_H
+#define _URCU_REF_H
+
+/*
+ * Userspace RCU - Reference counting
+ *
+ * Copyright (C) 2009 Novell Inc.
+ * Copyright (C) 2010 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * Author: Jan Blunck <jblunck@suse.de>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License version 2.1 as
+ * published by the Free  Software Foundation.
+ */
+
+#include <assert.h>
+#include <stdbool.h>
+#include <limits.h>
+#include <stdlib.h>
+#include <urcu/uatomic.h>
+
+struct urcu_ref {
+	long refcount; /* ATOMIC */
+};
+
+static inline void urcu_ref_set(struct urcu_ref *ref, long val)
+{
+	uatomic_set(&ref->refcount, val);
+}
+
+static inline void urcu_ref_init(struct urcu_ref *ref)
+{
+	urcu_ref_set(ref, 1);
+}
+
+static inline bool  __attribute__((warn_unused_result))
+		urcu_ref_get_safe(struct urcu_ref *ref)
+{
+	long old, _new, res;
+
+	old = uatomic_read(&ref->refcount);
+	for (;;) {
+		if (old == LONG_MAX) {
+			return false;	/* Failure. */
+		}
+		_new = old + 1;
+		res = uatomic_cmpxchg(&ref->refcount, old, _new);
+		if (res == old) {
+			return true;	/* Success. */
+		}
+		old = res;
+	}
+}
+
+static inline void urcu_ref_get(struct urcu_ref *ref)
+{
+	if (!urcu_ref_get_safe(ref))
+		abort();
+}
+
+static inline void urcu_ref_put(struct urcu_ref *ref,
+				void (*release)(struct urcu_ref *))
+{
+	long res = uatomic_sub_return(&ref->refcount, 1);
+	assert (res >= 0);
+	if (res == 0)
+		release(ref);
+}
+
+/*
+ * urcu_ref_get_unless_zero
+ *
+ * Allows getting a reference atomically if the reference count is not
+ * zero. Returns true if the reference is taken, false otherwise. This
+ * needs to be used in conjunction with another synchronization
+ * technique (e.g.  RCU or mutex) to ensure existence of the reference
+ * count. False is also returned in case incrementing the refcount would
+ * result in an overflow.
+ */
+static inline bool urcu_ref_get_unless_zero(struct urcu_ref *ref)
+{
+	long old, _new, res;
+
+	old = uatomic_read(&ref->refcount);
+	for (;;) {
+		if (old == 0 || old == LONG_MAX)
+			return false;	/* Failure. */
+		_new = old + 1;
+		res = uatomic_cmpxchg(&ref->refcount, old, _new);
+		if (res == old) {
+			return true;	/* Success. */
+		}
+		old = res;
+	}
+}
+
+#endif /* _URCU_REF_H */