Jeff Thompson | ef2d5a4 | 2013-08-22 19:09:24 -0700 | [diff] [blame] | 1 | // Copyright David Abrahams 2003. Use, modification and distribution is |
| 2 | // subject to the Boost Software License, Version 1.0. (See accompanying |
| 3 | // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) |
Jeff Thompson | 2491bd6 | 2013-10-15 17:10:24 -0700 | [diff] [blame] | 4 | #ifndef FACADE_ITERATOR_CATEGORY_NDNBOOST_DWA20031118_HPP |
| 5 | # define FACADE_ITERATOR_CATEGORY_NDNBOOST_DWA20031118_HPP |
Jeff Thompson | ef2d5a4 | 2013-08-22 19:09:24 -0700 | [diff] [blame] | 6 | |
| 7 | # include <ndnboost/iterator/iterator_categories.hpp> |
| 8 | |
| 9 | # include <ndnboost/mpl/or.hpp> // used in iterator_tag inheritance logic |
| 10 | # include <ndnboost/mpl/and.hpp> |
| 11 | # include <ndnboost/mpl/if.hpp> |
| 12 | # include <ndnboost/mpl/eval_if.hpp> |
| 13 | # include <ndnboost/mpl/identity.hpp> |
| 14 | # include <ndnboost/mpl/assert.hpp> |
| 15 | |
| 16 | # include <ndnboost/type_traits/is_same.hpp> |
| 17 | # include <ndnboost/type_traits/is_const.hpp> |
| 18 | # include <ndnboost/type_traits/is_reference.hpp> |
| 19 | # include <ndnboost/type_traits/is_convertible.hpp> |
| 20 | |
| 21 | # include <ndnboost/type_traits/is_same.hpp> |
| 22 | |
| 23 | # include <ndnboost/iterator/detail/config_def.hpp> // try to keep this last |
| 24 | |
Jeff Thompson | 3d613fd | 2013-10-15 15:39:04 -0700 | [diff] [blame] | 25 | # ifdef NDNBOOST_ITERATOR_REF_CONSTNESS_KILLS_WRITABILITY |
Jeff Thompson | ef2d5a4 | 2013-08-22 19:09:24 -0700 | [diff] [blame] | 26 | # include <ndnboost/detail/indirect_traits.hpp> |
| 27 | # endif |
| 28 | |
| 29 | // |
| 30 | // iterator_category deduction for iterator_facade |
| 31 | // |
| 32 | |
| 33 | // forward declaration |
| 34 | namespace ndnboost { struct use_default; } |
| 35 | |
| 36 | namespace ndnboost { namespace detail { |
| 37 | |
| 38 | struct input_output_iterator_tag |
| 39 | : std::input_iterator_tag |
| 40 | { |
| 41 | // Using inheritance for only input_iterator_tag helps to avoid |
| 42 | // ambiguities when a stdlib implementation dispatches on a |
| 43 | // function which is overloaded on both input_iterator_tag and |
| 44 | // output_iterator_tag, as STLPort does, in its __valid_range |
| 45 | // function. I claim it's better to avoid the ambiguity in these |
| 46 | // cases. |
| 47 | operator std::output_iterator_tag() const |
| 48 | { |
| 49 | return std::output_iterator_tag(); |
| 50 | } |
| 51 | }; |
| 52 | |
| 53 | // |
| 54 | // True iff the user has explicitly disabled writability of this |
| 55 | // iterator. Pass the iterator_facade's Value parameter and its |
| 56 | // nested ::reference type. |
| 57 | // |
| 58 | template <class ValueParam, class Reference> |
| 59 | struct iterator_writability_disabled |
Jeff Thompson | 3d613fd | 2013-10-15 15:39:04 -0700 | [diff] [blame] | 60 | # ifdef NDNBOOST_ITERATOR_REF_CONSTNESS_KILLS_WRITABILITY // Adding Thomas' logic? |
Jeff Thompson | ef2d5a4 | 2013-08-22 19:09:24 -0700 | [diff] [blame] | 61 | : mpl::or_< |
| 62 | is_const<Reference> |
| 63 | , ndnboost::detail::indirect_traits::is_reference_to_const<Reference> |
| 64 | , is_const<ValueParam> |
| 65 | > |
| 66 | # else |
| 67 | : is_const<ValueParam> |
| 68 | # endif |
| 69 | {}; |
| 70 | |
| 71 | |
| 72 | // |
| 73 | // Convert an iterator_facade's traversal category, Value parameter, |
| 74 | // and ::reference type to an appropriate old-style category. |
| 75 | // |
| 76 | // If writability has been disabled per the above metafunction, the |
| 77 | // result will not be convertible to output_iterator_tag. |
| 78 | // |
| 79 | // Otherwise, if Traversal == single_pass_traversal_tag, the following |
| 80 | // conditions will result in a tag that is convertible both to |
| 81 | // input_iterator_tag and output_iterator_tag: |
| 82 | // |
| 83 | // 1. Reference is a reference to non-const |
| 84 | // 2. Reference is not a reference and is convertible to Value |
| 85 | // |
| 86 | template <class Traversal, class ValueParam, class Reference> |
| 87 | struct iterator_facade_default_category |
| 88 | : mpl::eval_if< |
| 89 | mpl::and_< |
| 90 | is_reference<Reference> |
| 91 | , is_convertible<Traversal,forward_traversal_tag> |
| 92 | > |
| 93 | , mpl::eval_if< |
| 94 | is_convertible<Traversal,random_access_traversal_tag> |
| 95 | , mpl::identity<std::random_access_iterator_tag> |
| 96 | , mpl::if_< |
| 97 | is_convertible<Traversal,bidirectional_traversal_tag> |
| 98 | , std::bidirectional_iterator_tag |
| 99 | , std::forward_iterator_tag |
| 100 | > |
| 101 | > |
| 102 | , typename mpl::eval_if< |
| 103 | mpl::and_< |
| 104 | is_convertible<Traversal, single_pass_traversal_tag> |
| 105 | |
| 106 | // check for readability |
| 107 | , is_convertible<Reference, ValueParam> |
| 108 | > |
| 109 | , mpl::identity<std::input_iterator_tag> |
| 110 | , mpl::identity<Traversal> |
| 111 | > |
| 112 | > |
| 113 | { |
| 114 | }; |
| 115 | |
| 116 | // True iff T is convertible to an old-style iterator category. |
| 117 | template <class T> |
| 118 | struct is_iterator_category |
| 119 | : mpl::or_< |
| 120 | is_convertible<T,std::input_iterator_tag> |
| 121 | , is_convertible<T,std::output_iterator_tag> |
| 122 | > |
| 123 | { |
| 124 | }; |
| 125 | |
| 126 | template <class T> |
| 127 | struct is_iterator_traversal |
| 128 | : is_convertible<T,incrementable_traversal_tag> |
| 129 | {}; |
| 130 | |
| 131 | // |
| 132 | // A composite iterator_category tag convertible to Category (a pure |
| 133 | // old-style category) and Traversal (a pure traversal tag). |
| 134 | // Traversal must be a strict increase of the traversal power given by |
| 135 | // Category. |
| 136 | // |
| 137 | template <class Category, class Traversal> |
| 138 | struct iterator_category_with_traversal |
| 139 | : Category, Traversal |
| 140 | { |
Jeff Thompson | 3d613fd | 2013-10-15 15:39:04 -0700 | [diff] [blame] | 141 | # if !NDNBOOST_WORKAROUND(NDNBOOST_MSVC, <= 1300) |
Jeff Thompson | ef2d5a4 | 2013-08-22 19:09:24 -0700 | [diff] [blame] | 142 | // Make sure this isn't used to build any categories where |
| 143 | // convertibility to Traversal is redundant. Should just use the |
| 144 | // Category element in that case. |
Jeff Thompson | 3d613fd | 2013-10-15 15:39:04 -0700 | [diff] [blame] | 145 | NDNBOOST_MPL_ASSERT_NOT(( |
Jeff Thompson | ef2d5a4 | 2013-08-22 19:09:24 -0700 | [diff] [blame] | 146 | is_convertible< |
| 147 | typename iterator_category_to_traversal<Category>::type |
| 148 | , Traversal |
| 149 | >)); |
| 150 | |
Jeff Thompson | 3d613fd | 2013-10-15 15:39:04 -0700 | [diff] [blame] | 151 | NDNBOOST_MPL_ASSERT((is_iterator_category<Category>)); |
| 152 | NDNBOOST_MPL_ASSERT_NOT((is_iterator_category<Traversal>)); |
| 153 | NDNBOOST_MPL_ASSERT_NOT((is_iterator_traversal<Category>)); |
| 154 | # if !NDNBOOST_WORKAROUND(NDNBOOST_MSVC, NDNBOOST_TESTED_AT(1310)) |
| 155 | NDNBOOST_MPL_ASSERT((is_iterator_traversal<Traversal>)); |
Jeff Thompson | ef2d5a4 | 2013-08-22 19:09:24 -0700 | [diff] [blame] | 156 | # endif |
| 157 | # endif |
| 158 | }; |
| 159 | |
| 160 | // Computes an iterator_category tag whose traversal is Traversal and |
| 161 | // which is appropriate for an iterator |
| 162 | template <class Traversal, class ValueParam, class Reference> |
| 163 | struct facade_iterator_category_impl |
| 164 | { |
Jeff Thompson | 3d613fd | 2013-10-15 15:39:04 -0700 | [diff] [blame] | 165 | # if !NDNBOOST_WORKAROUND(NDNBOOST_MSVC, <= 1300) |
| 166 | NDNBOOST_MPL_ASSERT_NOT((is_iterator_category<Traversal>)); |
Jeff Thompson | ef2d5a4 | 2013-08-22 19:09:24 -0700 | [diff] [blame] | 167 | # endif |
| 168 | |
| 169 | typedef typename iterator_facade_default_category< |
| 170 | Traversal,ValueParam,Reference |
| 171 | >::type category; |
| 172 | |
| 173 | typedef typename mpl::if_< |
| 174 | is_same< |
| 175 | Traversal |
| 176 | , typename iterator_category_to_traversal<category>::type |
| 177 | > |
| 178 | , category |
| 179 | , iterator_category_with_traversal<category,Traversal> |
| 180 | >::type type; |
| 181 | }; |
| 182 | |
| 183 | // |
| 184 | // Compute an iterator_category for iterator_facade |
| 185 | // |
| 186 | template <class CategoryOrTraversal, class ValueParam, class Reference> |
| 187 | struct facade_iterator_category |
| 188 | : mpl::eval_if< |
| 189 | is_iterator_category<CategoryOrTraversal> |
| 190 | , mpl::identity<CategoryOrTraversal> // old-style categories are fine as-is |
| 191 | , facade_iterator_category_impl<CategoryOrTraversal,ValueParam,Reference> |
| 192 | > |
| 193 | { |
| 194 | }; |
| 195 | |
| 196 | }} // namespace ndnboost::detail |
| 197 | |
| 198 | # include <ndnboost/iterator/detail/config_undef.hpp> |
| 199 | |
Jeff Thompson | 2491bd6 | 2013-10-15 17:10:24 -0700 | [diff] [blame] | 200 | #endif // FACADE_ITERATOR_CATEGORY_NDNBOOST_DWA20031118_HPP |