intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 125 insertions, 0 deletions

diff --git a/library/cpp/threading/queue/tune.h b/library/cpp/threading/queue/tune.h
new file mode 100644
index 0000000000..50fc3dc17c
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+++ b/library/cpp/threading/queue/tune.h
@@ -0,0 +1,125 @@
+#pragma once
+
+/*
+  Motivation: consider you have a template class with many parameters
+  with default associations
+
+  template <typename A = TDefA,
+            typename B = TDefB,
+            typename C = TDefC,
+            typename D = TDefD>
+  class TExample {
+  };
+
+  consider you would like to provide easy to use interface to tune all
+  these parameters in position independed manner,
+  In that case TTune would be helpful for you.
+
+  How to use:
+  First step: declare a struct with all default associations
+
+  struct TDefaultTune {
+      using TStructA = TDefA;
+      using TStructB = TDefB;
+      using TStructC = TDefC;
+      using TStructD = TDefD;
+  };
+
+  Second step: declare helper names visible to a user
+
+  DeclareTuneTypeParam(TTuneParamA, TStructA);
+  DeclareTuneTypeParam(TTuneParamB, TStructB);
+  DeclareTuneTypeParam(TTuneParamC, TStructC);
+  DeclareTuneTypeParam(TTuneParamD, TStructD);
+
+  Third step: declare TExample this way:
+
+  template <typename...TParams>
+  class TExample {
+      using TMyParams = TTune<TDefaultTune, TParams...>;
+
+      using TActualA = TMyParams::TStructA;
+      using TActualB = TMyParams::TStructB;
+      ...
+  };
+
+  TTune<TDefaultTune, TParams...> is a struct with the default parameteres
+  taken from TDefaultTune and overridden from "TParams...".
+
+  for example:  "TTune<TDefaultTune, TTuneParamC<TUserClass>>"
+  will be virtually the same as:
+
+  struct TTunedClass {
+      using TStructA = TDefA;
+      using TStructB = TDefB;
+      using TStructC = TUserClass;
+      using TStructD = TDefD;
+  };
+
+  From now on you can tune your TExample in the following manner:
+
+  using TCustomClass =
+      TExample <TTuneParamA<TUserStruct1>, TTuneParamD<TUserStruct2>>;
+
+  You can also tweak constant expressions in your TDefaultTune.
+  Consider you have:
+
+  struct TDefaultTune {
+      static constexpr ui32 MySize = 42;
+  };
+
+  declare an interface to modify the parameter this way:
+
+  DeclareTuneValueParam(TStructSize, ui32, MySize);
+
+  and tweak your class:
+
+  using TTwiceBigger = TExample<TStructSize<84>>;
+
+ */
+
+#define DeclareTuneTypeParam(TParamName, InternalName) \
+    template <typename TNewType>                       \
+    struct TParamName {                                \
+        template <typename TBase>                      \
+        struct TApply: public TBase {                  \
+            using InternalName = TNewType;             \
+        };                                             \
+    }
+
+#define DeclareTuneValueParam(TParamName, TValueType, InternalName) \
+    template <TValueType NewValue>                                  \
+    struct TParamName {                                             \
+        template <typename TBase>                                   \
+        struct TApply: public TBase {                               \
+            static constexpr TValueType InternalName = NewValue;    \
+        };                                                          \
+    }
+
+#define DeclareTuneContainer(TParamName, InternalName)              \
+    template <template <typename, typename...> class TNewContainer> \
+    struct TParamName {                                             \
+        template <typename TBase>                                   \
+        struct TApply: public TBase {                               \
+            template <typename TElem, typename... TRest>            \
+            using InternalName = TNewContainer<TElem, TRest...>;    \
+        };                                                          \
+    }
+
+namespace NTunePrivate {
+    template <typename TBase, typename... TParams>
+    struct TFold;
+
+    template <typename TBase>
+    struct TFold<TBase>: public TBase {
+    };
+
+    template <typename TBase, typename TFirstArg, typename... TRest>
+    struct TFold<TBase, TFirstArg, TRest...>
+       : public TFold<typename TFirstArg::template TApply<TBase>, TRest...> {
+    };
+}
+
+template <typename TDefault, typename... TParams>
+struct TTune: public NTunePrivate::TFold<TDefault, TParams...> {
+};