intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 53 insertions, 0 deletions

diff --git a/library/cpp/messagebus/latch.h b/library/cpp/messagebus/latch.h
new file mode 100644
index 0000000000..373f4c0e13
--- /dev/null
+++ b/library/cpp/messagebus/latch.h
@@ -0,0 +1,53 @@
+#pragma once
+
+#include <util/system/condvar.h>
+#include <util/system/mutex.h>
+
+class TLatch {
+private:
+    // 0 for unlocked, 1 for locked
+    TAtomic Locked;
+    TMutex Mutex;
+    TCondVar CondVar;
+
+public:
+    TLatch()
+        : Locked(0)
+    {
+    }
+
+    void Wait() {
+        // optimistic path
+        if (AtomicGet(Locked) == 0) {
+            return;
+        }
+
+        TGuard<TMutex> guard(Mutex);
+        while (AtomicGet(Locked) == 1) {
+            CondVar.WaitI(Mutex);
+        }
+    }
+
+    bool TryWait() {
+        return AtomicGet(Locked) == 0;
+    }
+
+    void Unlock() {
+        // optimistic path
+        if (AtomicGet(Locked) == 0) {
+            return;
+        }
+
+        TGuard<TMutex> guard(Mutex);
+        AtomicSet(Locked, 0);
+        CondVar.BroadCast();
+    }
+
+    void Lock() {
+        AtomicSet(Locked, 1);
+    }
+
+    bool IsLocked() {
+        return AtomicGet(Locked);
+    }
+};