intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 65 insertions, 0 deletions

diff --git a/util/generic/scope.h b/util/generic/scope.h
new file mode 100644
index 0000000000..b2c33af61e
--- /dev/null
+++ b/util/generic/scope.h
@@ -0,0 +1,65 @@
+#pragma once
+
+#include <util/system/compiler.h>
+#include <util/system/defaults.h>
+
+#include <utility>
+
+namespace NPrivate {
+    template <typename F>
+    class TScopeGuard {
+    public:
+        TScopeGuard(const F& function)
+            : Function_{function}
+        {
+        }
+
+        TScopeGuard(F&& function)
+            : Function_{std::move(function)}
+        {
+        }
+
+        TScopeGuard(TScopeGuard&&) = default;
+        TScopeGuard(const TScopeGuard&) = default;
+
+        ~TScopeGuard() {
+            Function_();
+        }
+
+    private:
+        F Function_;
+    };
+
+    struct TMakeGuardHelper {
+        template <class F>
+        TScopeGuard<F> operator|(F&& function) const {
+            return std::forward<F>(function);
+        }
+    };
+}
+
+// \brief `Y_SCOPE_EXIT(captures) { body };`
+//
+// General implementaion of RAII idiom (resource acquisition is initialization). Executes
+// function upon return from the current scope.
+//
+// @note expects `body` to provide no-throw guarantee, otherwise whenever an exception
+// is thrown and leaves the outermost block of `body`, the function `std::terminate` is called.
+// @see http://drdobbs.com/184403758 for detailed motivation.
+#define Y_SCOPE_EXIT(...) const auto Y_GENERATE_UNIQUE_ID(scopeGuard) Y_DECLARE_UNUSED = ::NPrivate::TMakeGuardHelper{} | [__VA_ARGS__]() mutable -> void
+
+// \brief `Y_DEFER { body };`
+//
+// Same as `Y_SCOPE_EXIT` but doesn't require user to provide capture-list explicitly (it
+// implicitly uses `[&]` capture). Have same requirements for `body`.
+//
+// Inspired by `defer` statement in languages like Swift and Go.
+//
+// \code
+// auto item = s.pop();
+// bool ok = false;
+// Y_DEFER { if (!ok) { s.push(std::move(item)); } };
+// ... try handle `item` ...
+// ok = true;
+// \endcode
+#define Y_DEFER Y_SCOPE_EXIT(&)