X-Git-Url: https://gerrit.opnfv.org/gerrit/gitweb?a=blobdiff_plain;f=src%2Fceph%2Fsrc%2Fcommon%2Finline_variant.h;fp=src%2Fceph%2Fsrc%2Fcommon%2Finline_variant.h;h=bd55a59116cda06fe69cf9bef28429b7a654cdf9;hb=812ff6ca9fcd3e629e49d4328905f33eee8ca3f5;hp=0000000000000000000000000000000000000000;hpb=15280273faafb77777eab341909a3f495cf248d9;p=stor4nfv.git

diff --git a/src/ceph/src/common/inline_variant.h b/src/ceph/src/common/inline_variant.h
new file mode 100644
index 0000000..bd55a59
--- /dev/null
+++ b/src/ceph/src/common/inline_variant.h
@@ -0,0 +1,210 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:4; indent-tabs-mode:t -*-
+// vim: ts=8 sw=4 smarttab
+/*
+ * Copied from:
+ * https://github.com/exclipy/inline_variant_visitor/blob/master/inline_variant.hpp
+ */
+
+#ifndef INLINE_VARIANT_H
+#define INLINE_VARIANT_H
+
+#include <boost/function_types/function_arity.hpp>
+#include <boost/fusion/algorithm/transformation/transform.hpp>
+#include <boost/mpl/contains.hpp>
+#include <boost/mpl/map.hpp>
+#include <boost/mpl/vector.hpp>
+#include <boost/mpl/range_c.hpp>
+
+#include "function_signature.h"
+
+namespace detail {
+
+// A metafunction class for getting the argument type from a unary function or functor type
+struct function_arg_extractor
+{
+    // Function is either a function type like void(int const&), or a functor - eg. a class with void operator(int)
+    // Sets type to the argument type with the constness and referenceness stripped (eg. int)
+    template <typename Function>
+    struct apply
+    {
+    private:
+        typedef typename boost::remove_const< typename boost::remove_reference<Function>::type >::type bare_type;
+        typedef typename signature_of<bare_type>::type normalized_function_type;
+        typedef typename boost::function_types::function_arity<normalized_function_type>::type arity;
+        typedef typename boost::function_types::parameter_types<normalized_function_type>::type parameter_types;
+        typedef typename boost::function_types::result_type<normalized_function_type>::type result_type;
+
+        BOOST_STATIC_ASSERT_MSG((arity::value == 1), "make_visitor called with a non-unary function");
+
+        typedef typename boost::mpl::front<parameter_types>::type parameter_type;
+    public:
+        typedef typename boost::remove_const< typename boost::remove_reference<parameter_type>::type >::type type;
+    };
+};
+
+struct make_pair
+{
+    template <typename AType, typename Ind>
+    struct apply {
+	typedef boost::mpl::pair<AType, Ind> type;
+    };
+};
+
+// A metafunction class that asserts the second argument is in Allowed, and returns void
+template<typename Allowed>
+struct check_in
+{
+    template <typename Type1, typename Type2>
+    struct apply
+    {
+    private:
+        BOOST_STATIC_ASSERT_MSG((boost::mpl::contains<Allowed, typename boost::mpl::first<Type2>::type>::value),
+                "make_visitor called with spurious handler functions");
+    public:
+        typedef void type;
+    };
+};
+
+template <typename Seq>
+struct as_map
+{
+private:
+    struct insert_helper {
+	template <typename M, typename P>
+	struct apply
+	{
+	    typedef typename boost::mpl::insert<
+		M,
+		P>::type type;
+	};
+    };
+public:
+    typedef typename boost::mpl::fold<Seq, boost::mpl::map0<>, insert_helper>::type type;
+};
+
+// A functor template suitable for passing into apply_visitor.  The constructor accepts the list of handler functions,
+// which are then exposed through a set of operator()s
+template <typename Result, typename Variant, typename... Functions>
+struct generic_visitor : boost::static_visitor<Result>, boost::noncopyable
+{
+private:
+    typedef generic_visitor<Result, Variant, Functions...> type;
+
+    // Compute the function_map type
+    typedef boost::mpl::vector<Functions...> function_types;
+    typedef typename boost::mpl::transform<function_types, function_arg_extractor>::type arg_types;
+    typedef typename boost::mpl::transform<
+        arg_types,
+	boost::mpl::range_c<int, 0, boost::mpl::size<arg_types>::value>,
+	make_pair
+	>::type pair_list;
+    typedef typename as_map<pair_list>::type fmap;
+
+    // Check that the argument types are unique
+    BOOST_STATIC_ASSERT_MSG((boost::mpl::size<fmap>::value == boost::mpl::size<arg_types>::value),
+            "make_visitor called with non-unique argument types for handler functions");
+
+    // Check that there aren't any argument types not in the variant types
+    typedef typename boost::mpl::fold<fmap, void, check_in<typename Variant::types> >::type dummy;
+
+    boost::fusion::vector<Functions...> fvec;
+
+
+    template <typename T>
+    Result apply_helper(const T& object, boost::mpl::true_) const {
+	typedef typename boost::mpl::at<fmap, T>::type Ind;
+        return boost::fusion::at<Ind>(fvec)(object);
+    }
+
+    template <typename T>
+    Result apply_helper(const T& object, boost::mpl::false_) const {
+        return Result();
+    }
+
+    BOOST_MOVABLE_BUT_NOT_COPYABLE(generic_visitor)
+
+public:
+    generic_visitor(BOOST_RV_REF(type) other)
+    :
+        fvec(boost::move(other.fvec))
+    {
+    }
+    generic_visitor(Functions&&... functions)
+    :
+        fvec(std::forward<Functions>(functions)...)
+    {
+    }
+
+    template <typename T>
+    Result operator()(const T& object) const {
+        typedef typename boost::mpl::has_key<fmap, T>::type correct_key;
+        BOOST_STATIC_ASSERT_MSG(correct_key::value,
+            "make_visitor called without specifying handlers for all required types");
+        return apply_helper(object, correct_key());
+    }
+};
+
+// A metafunction class for getting the return type of a function
+struct function_return_extractor
+{
+    template <typename Function>
+    struct apply : boost::function_types::result_type<typename signature_of<Function>::type>
+    {
+    };
+};
+
+// A metafunction class that asserts the two arguments are the same and returns the first one
+struct check_same
+{
+    template <typename Type1, typename Type2>
+    struct apply
+    {
+    private:
+        BOOST_STATIC_ASSERT_MSG((boost::is_same<Type1, Type2>::value),
+                "make_visitor called with functions of differing return types");
+    public:
+        typedef Type1 type;
+    };
+};
+
+// A metafunction for getting the required generic_visitor type for the set of Functions
+template <typename Variant, typename... Functions>
+struct get_generic_visitor
+{
+private:
+    typedef boost::mpl::vector<Functions...> function_types;
+    typedef typename boost::mpl::transform<
+        function_types,
+        boost::remove_const< boost::remove_reference<boost::mpl::_1> >
+    >::type bare_function_types;
+    typedef typename boost::mpl::transform<bare_function_types, function_return_extractor>::type return_types;
+
+public:
+    // Set result_type to the return type of the first function
+    typedef typename boost::mpl::front<return_types>::type result_type;
+    typedef generic_visitor<result_type, Variant, Functions...> type;
+
+private:
+    // Assert that every return type is the same as the first one
+    typedef typename boost::mpl::fold<return_types, result_type, check_same>::type dummy;
+};
+
+// Accepts a set of functions and returns an object suitable for apply_visitor
+template <typename Variant, typename... Functions>
+auto make_visitor(BOOST_RV_REF(Functions)... functions)
+    -> typename detail::get_generic_visitor<Variant, Functions...>::type
+{
+    return typename detail::get_generic_visitor<Variant, Functions...>::type(boost::forward<Functions>(functions)...);
+}
+
+}
+
+template <typename Variant, typename... Functions>
+auto match(Variant const& variant, BOOST_RV_REF(Functions)... functions)
+    -> typename detail::get_generic_visitor<Variant, Functions...>::result_type
+{
+    return boost::apply_visitor(detail::make_visitor<Variant>(
+        boost::forward<Functions>(functions)...), variant);
+}
+
+#endif