forked from boostorg/iterator
138 lines
4.8 KiB
C++
138 lines
4.8 KiB
C++
#ifndef BOOST_ITERATOR_TRAITS_HPP
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#define BOOST_ITERATOR_TRAITS_HPP
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#include <boost/config.hpp>
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#include <boost/type_traits/conversion_traits.hpp>
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#include <boost/type_traits/cv_traits.hpp>
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#include <boost/pending/ct_if.hpp>
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#include <boost/detail/iterator.hpp>
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namespace boost {
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// Traversal Categories
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struct single_pass_iterator_tag { };
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struct forward_iterator_tag : public single_pass_iterator_tag { };
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struct bidirectional_iterator_tag : public forward_iterator_tag { };
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struct random_access_iterator_tag : public bidirectional_iterator_tag { };
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// Return Type Categories
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struct readable_iterator_tag { };
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struct writable_iterator_tag { };
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struct mutable_lvalue_iterator_tag : virtual public writable_iterator_tag,
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virtual public readable_iterator_tag { };
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struct constant_lvalue_iterator_tag : public readable_iterator_tag { };
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struct error_iterator_tag { };
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// Inherit from iterator_base if your iterator defines its own
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// return_category and traversal_category. Otherwise, the "old style"
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// iterator category will be mapped to the return_category and
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// traversal_category.
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struct new_iterator_base { };
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namespace detail {
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struct iter_traits_from_nested_types {
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template <typename Iterator> struct bind {
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typedef typename Iterator::value_type value_type;
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typedef typename Iterator::reference reference;
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typedef typename Iterator::pointer pointer;
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typedef typename Iterator::difference_type difference_type;
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typedef typename Iterator::return_category return_category;
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typedef typename Iterator::traversal_category traversal_category;
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};
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};
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template <typename ValueType>
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struct choose_lvalue_return {
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typedef typename ct_if<is_const<ValueType>::value,
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boost::constant_lvalue_iterator_tag,
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boost::mutable_lvalue_iterator_tag>::type type;
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};
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template <typename Category, typename ValueType>
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struct iter_category_to_return {
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typedef typename ct_if<
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is_convertible<Category*, std::forward_iterator_tag*>::value,
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typename choose_lvalue_return<ValueType>::type,
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typename ct_if<
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is_convertible<Category*, std::input_iterator_tag*>::value,
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boost::readable_iterator_tag,
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typename ct_if<
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is_convertible<Category*, std::output_iterator_tag*>::value,
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boost::writable_iterator_tag,
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boost::error_iterator_tag
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>::type
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>::type
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>::type type;
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};
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template <typename Category>
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struct iter_category_to_traversal {
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typedef typename ct_if<
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is_convertible<Category*, std::random_access_iterator_tag*>::value,
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boost::random_access_iterator_tag,
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typename ct_if<
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is_convertible<Category*, std::bidirectional_iterator_tag*>::value,
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boost::bidirectional_iterator_tag,
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typename ct_if<
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is_convertible<Category*, std::forward_iterator_tag*>::value,
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boost::forward_iterator_tag,
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boost::single_pass_iterator_tag>::type
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>::type
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>::type type;
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};
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struct iter_traits_from_old_traits {
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template <typename Iterator> class bind {
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typedef boost::detail::iterator_traits<Iterator> OldTraits;
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typedef typename OldTraits::iterator_category Cat;
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public:
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typedef typename OldTraits::value_type value_type;
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typedef typename OldTraits::reference reference;
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typedef typename OldTraits::pointer pointer;
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typedef typename OldTraits::difference_type difference_type;
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typedef iter_category_to_return<Cat,value_type>::type return_category;
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typedef iter_category_to_traversal<Cat>::type traversal_category;
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};
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};
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template <typename Iterator>
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class choose_iter_traits {
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typedef typename ct_if<is_convertible<Iterator*,
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new_iterator_base*>::value,
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iter_traits_from_nested_types,
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iter_traits_from_old_traits>::type Choice;
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public:
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typedef typename Choice:: template bind<Iterator> type;
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};
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} // namespace detail
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template <typename Iterator>
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class iterator_traits
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: public detail::choose_iter_traits<Iterator>::type { };
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#if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
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template <typename T>
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struct iterator_traits<T*>
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{
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typedef T value_type;
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typedef T& reference;
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typedef T* pointer;
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typedef std::ptrdiff_t difference_type;
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typedef typename ct_if<is_const<T>::value,
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boost::constant_lvalue_iterator_tag,
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boost::mutable_lvalue_iterator_tag>::type
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return_category;
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typedef boost::random_access_iterator_tag traversal_category;
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};
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#endif
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} // namespace boost
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#endif // BOOST_ITERATOR_TRAITS_HPP
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