ext-boost/boost/iterator/iterator_adaptor.hpp

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// (C) Copyright David Abrahams 2002.
// (C) Copyright Jeremy Siek 2002.
// (C) Copyright Thomas Witt 2002.
// 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_ITERATOR_ADAPTOR_23022003THW_HPP
#define BOOST_ITERATOR_ADAPTOR_23022003THW_HPP
#include <boost/static_assert.hpp>
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#include <boost/core/use_default.hpp>
#include <boost/iterator/iterator_categories.hpp>
#include <boost/iterator/iterator_facade.hpp>
#include <boost/iterator/detail/enable_if.hpp>
#include <boost/mpl/and.hpp>
#include <boost/mpl/not.hpp>
#include <boost/mpl/or.hpp>
#include <boost/type_traits/is_same.hpp>
#include <boost/type_traits/is_convertible.hpp>
#ifdef BOOST_ITERATOR_REF_CONSTNESS_KILLS_WRITABILITY
# include <boost/type_traits/remove_reference.hpp>
#endif
#include <boost/type_traits/add_reference.hpp>
#include <boost/iterator/detail/config_def.hpp>
#include <boost/iterator/iterator_traits.hpp>
namespace boost {
namespace iterators {
// Used as a default template argument internally, merely to
// indicate "use the default", this can also be passed by users
// explicitly in order to specify that the default should be used.
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using boost::use_default;
} // namespace iterators
// the incompleteness of use_default causes massive problems for
// is_convertible (naturally). This workaround is fortunately not
// needed for vc6/vc7.
template<class To>
struct is_convertible<use_default,To>
: mpl::false_ {};
namespace iterators {
namespace detail
{
//
// Result type used in enable_if_convertible meta function.
// This can be an incomplete type, as only pointers to
// enable_if_convertible< ... >::type are used.
// We could have used void for this, but conversion to
// void* is just to easy.
//
struct enable_type;
}
//
// enable_if for use in adapted iterators constructors.
//
// In order to provide interoperability between adapted constant and
// mutable iterators, adapted iterators will usually provide templated
// conversion constructors of the following form
//
// template <class BaseIterator>
// class adapted_iterator :
// public iterator_adaptor< adapted_iterator<Iterator>, Iterator >
// {
// public:
//
// ...
//
// template <class OtherIterator>
// adapted_iterator(
// OtherIterator const& it
// , typename enable_if_convertible<OtherIterator, Iterator>::type* = 0);
//
// ...
// };
//
// enable_if_convertible is used to remove those overloads from the overload
// set that cannot be instantiated. For all practical purposes only overloads
// for constant/mutable interaction will remain. This has the advantage that
// meta functions like boost::is_convertible do not return false positives,
// as they can only look at the signature of the conversion constructor
// and not at the actual instantiation.
//
// enable_if_interoperable can be safely used in user code. It falls back to
// always enabled for compilers that don't support enable_if or is_convertible.
// There is no need for compiler specific workarounds in user code.
//
// The operators implementation relies on boost::is_convertible not returning
// false positives for user/library defined iterator types. See comments
// on operator implementation for consequences.
//
# if defined(BOOST_NO_IS_CONVERTIBLE) || defined(BOOST_NO_SFINAE)
template <class From, class To>
struct enable_if_convertible
{
typedef boost::iterators::detail::enable_type type;
};
# elif BOOST_WORKAROUND(_MSC_FULL_VER, BOOST_TESTED_AT(13102292))
// For some reason vc7.1 needs us to "cut off" instantiation
// of is_convertible in a few cases.
template<typename From, typename To>
struct enable_if_convertible
: iterators::enable_if<
mpl::or_<
is_same<From,To>
, is_convertible<From, To>
>
, boost::iterators::detail::enable_type
>
{};
# else
template<typename From, typename To>
struct enable_if_convertible
: iterators::enable_if<
is_convertible<From, To>
, boost::iterators::detail::enable_type
>
{};
# endif
//
// Default template argument handling for iterator_adaptor
//
namespace detail
{
// If T is use_default, return the result of invoking
// DefaultNullaryFn, otherwise return T.
template <class T, class DefaultNullaryFn>
struct ia_dflt_help
: mpl::eval_if<
is_same<T, use_default>
, DefaultNullaryFn
, mpl::identity<T>
>
{
};
// A metafunction which computes an iterator_adaptor's base class,
// a specialization of iterator_facade.
template <
class Derived
, class Base
, class Value
, class Traversal
, class Reference
, class Difference
>
struct iterator_adaptor_base
{
typedef iterator_facade<
Derived
# ifdef BOOST_ITERATOR_REF_CONSTNESS_KILLS_WRITABILITY
, typename boost::iterators::detail::ia_dflt_help<
Value
, mpl::eval_if<
is_same<Reference,use_default>
, iterator_value<Base>
, remove_reference<Reference>
>
>::type
# else
, typename boost::iterators::detail::ia_dflt_help<
Value, iterator_value<Base>
>::type
# endif
, typename boost::iterators::detail::ia_dflt_help<
Traversal
, iterator_traversal<Base>
>::type
, typename boost::iterators::detail::ia_dflt_help<
Reference
, mpl::eval_if<
is_same<Value,use_default>
, iterator_reference<Base>
, add_reference<Value>
>
>::type
, typename boost::iterators::detail::ia_dflt_help<
Difference, iterator_difference<Base>
>::type
>
type;
};
// workaround for aC++ CR JAGaf33512
template <class Tr1, class Tr2>
inline void iterator_adaptor_assert_traversal ()
{
BOOST_STATIC_ASSERT((is_convertible<Tr1, Tr2>::value));
}
}
//
// Iterator Adaptor
//
// The parameter ordering changed slightly with respect to former
// versions of iterator_adaptor The idea is that when the user needs
// to fiddle with the reference type it is highly likely that the
// iterator category has to be adjusted as well. Any of the
// following four template arguments may be ommitted or explicitly
// replaced by use_default.
//
// Value - if supplied, the value_type of the resulting iterator, unless
// const. If const, a conforming compiler strips constness for the
// value_type. If not supplied, iterator_traits<Base>::value_type is used
//
// Category - the traversal category of the resulting iterator. If not
// supplied, iterator_traversal<Base>::type is used.
//
// Reference - the reference type of the resulting iterator, and in
// particular, the result type of operator*(). If not supplied but
// Value is supplied, Value& is used. Otherwise
// iterator_traits<Base>::reference is used.
//
// Difference - the difference_type of the resulting iterator. If not
// supplied, iterator_traits<Base>::difference_type is used.
//
template <
class Derived
, class Base
, class Value = use_default
, class Traversal = use_default
, class Reference = use_default
, class Difference = use_default
>
class iterator_adaptor
: public boost::iterators::detail::iterator_adaptor_base<
Derived, Base, Value, Traversal, Reference, Difference
>::type
{
friend class iterator_core_access;
protected:
typedef typename boost::iterators::detail::iterator_adaptor_base<
Derived, Base, Value, Traversal, Reference, Difference
>::type super_t;
public:
iterator_adaptor() {}
explicit iterator_adaptor(Base const &iter)
: m_iterator(iter)
{
}
typedef Base base_type;
Base const& base() const
{ return m_iterator; }
protected:
// for convenience in derived classes
typedef iterator_adaptor<Derived,Base,Value,Traversal,Reference,Difference> iterator_adaptor_;
//
// lvalue access to the Base object for Derived
//
Base const& base_reference() const
{ return m_iterator; }
Base& base_reference()
{ return m_iterator; }
private:
//
// Core iterator interface for iterator_facade. This is private
// to prevent temptation for Derived classes to use it, which
// will often result in an error. Derived classes should use
// base_reference(), above, to get direct access to m_iterator.
//
typename super_t::reference dereference() const
{ return *m_iterator; }
template <
class OtherDerived, class OtherIterator, class V, class C, class R, class D
>
bool equal(iterator_adaptor<OtherDerived, OtherIterator, V, C, R, D> const& x) const
{
// Maybe readd with same_distance
// BOOST_STATIC_ASSERT(
// (detail::same_category_and_difference<Derived,OtherDerived>::value)
// );
return m_iterator == x.base();
}
typedef typename iterator_category_to_traversal<
typename super_t::iterator_category
>::type my_traversal;
# define BOOST_ITERATOR_ADAPTOR_ASSERT_TRAVERSAL(cat) \
boost::iterators::detail::iterator_adaptor_assert_traversal<my_traversal, cat>();
void advance(typename super_t::difference_type n)
{
BOOST_ITERATOR_ADAPTOR_ASSERT_TRAVERSAL(random_access_traversal_tag)
m_iterator += n;
}
void increment() { ++m_iterator; }
void decrement()
{
BOOST_ITERATOR_ADAPTOR_ASSERT_TRAVERSAL(bidirectional_traversal_tag)
--m_iterator;
}
template <
class OtherDerived, class OtherIterator, class V, class C, class R, class D
>
typename super_t::difference_type distance_to(
iterator_adaptor<OtherDerived, OtherIterator, V, C, R, D> const& y) const
{
BOOST_ITERATOR_ADAPTOR_ASSERT_TRAVERSAL(random_access_traversal_tag)
// Maybe readd with same_distance
// BOOST_STATIC_ASSERT(
// (detail::same_category_and_difference<Derived,OtherDerived>::value)
// );
return y.base() - m_iterator;
}
# undef BOOST_ITERATOR_ADAPTOR_ASSERT_TRAVERSAL
private: // data members
Base m_iterator;
};
} // namespace iterators
using iterators::iterator_adaptor;
using iterators::enable_if_convertible;
} // namespace boost
#include <boost/iterator/detail/config_undef.hpp>
#endif // BOOST_ITERATOR_ADAPTOR_23022003THW_HPP