Imported existing code

libraries/include/boost/coroutine/tuple_traits.hpp

@@ -0,0 +1,170 @@
+//  Copyright (c) 2006, Giovanni P. Deretta
+//
+//  This code may be used under either of the following two licences:
+//
+//  Permission is hereby granted, free of charge, to any person obtaining a copy 
+//  of this software and associated documentation files (the "Software"), to deal 
+//  in the Software without restriction, including without limitation the rights 
+//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 
+//  copies of the Software, and to permit persons to whom the Software is 
+//  furnished to do so, subject to the following conditions:
+//
+//  The above copyright notice and this permission notice shall be included in 
+//  all copies or substantial portions of the Software.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
+//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
+//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 
+//  THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
+//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
+//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN 
+//  THE SOFTWARE. OF SUCH DAMAGE.
+//
+//  Or:
+//
+//  Distributed under the Boost Software License, Version 1.0.
+//  (See accompanying file LICENSE_1_0.txt or copy at
+//  http://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef BOOST_COROUTINE_TUPLE_TRAITS_HPP_20060613
+#define BOOST_COROUTINE_TUPLE_TRAITS_HPP_20060613
+#include <boost/tuple/tuple.hpp>
+#include <boost/preprocessor/repetition/enum_binary_params.hpp>
+#include <boost/preprocessor/facilities/intercept.hpp>
+#include <boost/type_traits.hpp>
+#include <boost/mpl/eval_if.hpp>
+#include <boost/mpl/if.hpp>
+#include <boost/mpl/identity.hpp>
+#include <boost/mpl/bool.hpp>
+#include <boost/coroutine/detail/arg_max.hpp>
+
+namespace boost { namespace coroutines {
+  namespace detail {
+    /*
+     * NOTE & FIXME: coroutine_traits relies on the fact that we can construct a
+     * boost::tuple specifing more arguments of type null_type than
+     * required without generating an error. This is an undocumented
+     * 'feature' and doesn't actually  work for nullary tuples,
+     * so we need to detect this case and handle it with tuple_workaround.
+     * If ever boost::tuple is changed (for example by switching to fusion)
+     * tuple_workaround should be used in all cases to handle extra 
+     * parameters.
+     * The real solution would be to have an internal tuple
+     * type that derives from boost::tuple and handles all cases we care about.
+     * Or better, just use Boost.Fusion.
+     * In general the code in this file needs to be put in a better shape,
+     * eliminating all corner cases.
+     */
+
+    /* 
+     * A boost::tuple<> is not constructible from an arbitrary
+     * number of null_types (while non nullary tuples are).
+     * This class takes care of this assimmetry.
+     */
+    struct tuple_workaround : boost::tuple<> {
+#     define BOOST_COROUTINE_arg_null_typecr(z, n, unused)\
+	const boost::tuples::null_type&                   \
+      /**/
+	
+      tuple_workaround
+      (BOOST_PP_ENUM
+       (BOOST_COROUTINE_ARG_MAX, 
+	BOOST_COROUTINE_arg_null_typecr,
+	~)){}
+	
+      tuple_workaround(const tuple_workaround&) {}
+      tuple_workaround() {}
+#     undef BOOST_COROUTINE_arg_null_typecr
+    };
+  } /* detail */
+
+  // All tuple traits must be derived from this
+  // class to be correctly recognized.
+  struct tuple_traits_tag {};
+      
+  template<typename T>
+  struct get_length {
+   enum { length = T::length };
+  };
+
+  template<typename T>
+  struct is_nullary :  boost::mpl::bool_<boost::tuples::length<T>::value == 0> {  };
+
+  template<typename T>
+  struct is_singular : boost::mpl::bool_<boost::tuples::length<T>::value == 1> {  };
+
+  // Given a tuple_traits, makes a tuple of it
+  // Simply returns the internal tuple type, unless
+  // the tuple is nullary, then apply the nullary tuple workaround
+  template<typename T>
+  struct make_as_tuple :
+    boost::mpl::if_<
+    is_nullary<T>,
+      detail::tuple_workaround,
+      T
+    > {};
+
+  // Used to implement the next metafunction,
+  // Splitted in two parts to satisfy the compiler.
+  template<typename T>
+  struct step_2 :
+      boost::mpl::eval_if<
+      is_singular<T>,
+      boost::tuples::element<0, typename make_as_tuple<T>::type >,
+    boost::mpl::identity<typename make_as_tuple<T>::type> > { };
+
+  // Given a trait class return the internal tuple type modified 
+  // as a return value.
+  // The algorithm is as follow:
+  // - If the tuple is nullary returns 'void'. 
+  // - If it singular returns the first type
+  // - Else return the tuple itself.
+  template<typename T>
+  struct make_result_type :
+    boost::mpl::eval_if<
+    is_nullary<T>,
+    boost::mpl::identity<void>,
+    step_2<T> > { };
+
+  template<
+    BOOST_PP_ENUM_BINARY_PARAMS
+  (BOOST_COROUTINE_ARG_MAX,
+   typename T, 
+   = boost::tuples::null_type BOOST_PP_INTERCEPT)>
+  struct tuple_traits : tuple_traits_tag {
+  public:	
+
+    // This is the straightforward boost::tuple trait
+    // derived from the argument list. It is not 
+    // directly used in all cases.
+    typedef boost::tuple
+    <BOOST_PP_ENUM_PARAMS
+    (BOOST_COROUTINE_ARG_MAX, T)> internal_tuple_type;
+
+    // FIXME: Currently coroutine code does not use this typedef in all cases
+    // and expect it to be equal to boost::tuples::null_type
+    typedef boost::tuples::null_type null_type;
+    enum {length = boost::tuples::length<internal_tuple_type>::value};
+
+    // Return the element at the Indext'th position in the typelist.
+    // If the index is not less than the tuple length, it returns 
+    // null_type.
+    template<int Index> 
+    struct at : 
+      boost::mpl::eval_if_c<
+      Index < 
+      boost::tuples::length<typename tuple_traits::internal_tuple_type>::value,
+      boost::tuples::element<Index, typename tuple_traits::internal_tuple_type>,	
+      boost::mpl::identity<typename tuple_traits::null_type> >{};
+
+    typedef typename make_as_tuple<internal_tuple_type>::type
+    as_tuple;	
+
+    typedef typename make_result_type<internal_tuple_type>::type as_result;
+
+  };
+    
+  template<typename T>
+  struct is_tuple_traits : boost::is_base_of<tuple_traits_tag, T> {};
+} }
+#endif