New cpp folder structure

Signed-off-by: Alexander Borsuk <me@alex.bio>

libs/base/cancellable.hpp

@@ -0,0 +1,56 @@
+#pragma once
+
+#include <chrono>
+#include <mutex>
+#include <optional>
+#include <string>
+
+namespace base
+{
+// This is a helper thread-safe class which can be mixed in
+// classes which represent some cancellable activities.
+class Cancellable
+{
+public:
+  enum class Status
+  {
+    Active,
+    CancelCalled,
+    DeadlineExceeded,
+  };
+
+  Cancellable() = default;
+
+  virtual ~Cancellable() {}
+
+  // Marks current activity as not cancelled.
+  // Resets the deadline if it was present.
+  virtual void Reset();
+
+  // Marks current activity as cancelled.
+  virtual void Cancel();
+
+  // Sets a deadline after which the activity is cancelled.
+  virtual void SetDeadline(std::chrono::steady_clock::time_point const & t);
+
+  // Updates the status.
+  // Returns true iff current activity has been cancelled (either by the call
+  // to Cancel or by timeout).
+  virtual bool IsCancelled() const;
+
+  // Updates the status of current activity and returns its value.
+  virtual Status CancellationStatus() const;
+
+private:
+  // Checks whether |m_deadline| has exceeded. Must be called with |m_mutex| locked.
+  void CheckDeadline() const;
+
+  mutable std::mutex m_mutex;
+
+  mutable Status m_status = Status::Active;
+
+  std::optional<std::chrono::steady_clock::time_point> m_deadline;
+};
+
+std::string DebugPrint(Cancellable::Status status);
+}  // namespace base