intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 99 insertions, 0 deletions

diff --git a/library/cpp/messagebus/misc/weak_ptr.h b/library/cpp/messagebus/misc/weak_ptr.h
new file mode 100644
index 0000000000..70fdeb0e2a
--- /dev/null
+++ b/library/cpp/messagebus/misc/weak_ptr.h
@@ -0,0 +1,99 @@
+#pragma once
+
+#include <util/generic/ptr.h>
+#include <util/system/mutex.h>
+
+template <typename T>
+struct TWeakPtr;
+
+template <typename TSelf>
+struct TWeakRefCounted {
+    template <typename>
+    friend struct TWeakPtr;
+
+private:
+    struct TRef: public TAtomicRefCount<TRef> {
+        TMutex Mutex;
+        TSelf* Outer;
+
+        TRef(TSelf* outer)
+            : Outer(outer)
+        {
+        }
+
+        void Release() {
+            TGuard<TMutex> g(Mutex);
+            Y_ASSERT(!!Outer);
+            Outer = nullptr;
+        }
+
+        TIntrusivePtr<TSelf> Get() {
+            TGuard<TMutex> g(Mutex);
+            Y_ASSERT(!Outer || Outer->RefCount() > 0);
+            return Outer;
+        }
+    };
+
+    TAtomicCounter Counter;
+    TIntrusivePtr<TRef> RefPtr;
+
+public:
+    TWeakRefCounted()
+        : RefPtr(new TRef(static_cast<TSelf*>(this)))
+    {
+    }
+
+    void Ref() {
+        Counter.Inc();
+    }
+
+    void UnRef() {
+        if (Counter.Dec() == 0) {
+            RefPtr->Release();
+
+            // drop is to prevent dtor from reading it
+            RefPtr.Drop();
+
+            delete static_cast<TSelf*>(this);
+        }
+    }
+
+    void DecRef() {
+        Counter.Dec();
+    }
+
+    unsigned RefCount() const {
+        return Counter.Val();
+    }
+};
+
+template <typename T>
+struct TWeakPtr {
+private:
+    typedef TIntrusivePtr<typename T::TRef> TRefPtr;
+    TRefPtr RefPtr;
+
+public:
+    TWeakPtr() {
+    }
+
+    TWeakPtr(T* t) {
+        if (!!t) {
+            RefPtr = t->RefPtr;
+        }
+    }
+
+    TWeakPtr(TIntrusivePtr<T> t) {
+        if (!!t) {
+            RefPtr = t->RefPtr;
+        }
+    }
+
+    TIntrusivePtr<T> Get() {
+        if (!RefPtr) {
+            return nullptr;
+        } else {
+            return RefPtr->Get();
+        }
+    }
+};