intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 42 insertions, 0 deletions

diff --git a/library/cpp/threading/queue/mpmc_unordered_ring.h b/library/cpp/threading/queue/mpmc_unordered_ring.h
new file mode 100644
index 0000000000..5042f7528e
--- /dev/null
+++ b/library/cpp/threading/queue/mpmc_unordered_ring.h
@@ -0,0 +1,42 @@
+#pragma once
+
+/*
+  It's not a general purpose queue.
+  No order guarantee, but it mostly ordered.
+  Items may stuck in almost empty queue.
+  Use UnsafeScanningPop to pop all stuck items.
+  Almost wait-free for producers and consumers.
+ */
+
+#include <util/system/atomic.h>
+#include <util/generic/ptr.h>
+
+namespace NThreading {
+    struct TMPMCUnorderedRing {
+    public:
+        static constexpr ui16 MAX_PUSH_TRIES = 4;
+        static constexpr ui16 MAX_POP_TRIES = 4;
+
+        TMPMCUnorderedRing(size_t size);
+
+        bool Push(void* msg, ui16 retryCount = MAX_PUSH_TRIES) noexcept;
+        void StubbornPush(void* msg) {
+            while (!WeakPush(msg)) {
+            }
+        }
+
+        void* Pop() noexcept;
+
+        void* UnsafeScanningPop(ui64* last) noexcept;
+
+    private:
+        bool WeakPush(void* msg) noexcept;
+
+        size_t RingSize;
+        TArrayPtr<void*> RingBuffer;
+        ui64 WritePawl = 0;
+        ui64 WriteFront = 0;
+        ui64 ReadPawl = 0;
+        ui64 ReadFront = 0;
+    };
+}