| // Boost.Range library |
| // |
| // Copyright Neil Groves 2007. Use, modification and |
| // distribution is subject to 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) |
| // |
| // |
| // For more information, see http://www.boost.org/libs/range/ |
| // |
| #ifndef BOOST_RANGE_ADAPTOR_STRIDED_HPP_INCLUDED |
| #define BOOST_RANGE_ADAPTOR_STRIDED_HPP_INCLUDED |
| |
| #include <boost/range/adaptor/argument_fwd.hpp> |
| #include <boost/range/iterator_range.hpp> |
| #include <boost/iterator/iterator_adaptor.hpp> |
| #include <iterator> |
| |
| namespace boost |
| { |
| namespace range_detail |
| { |
| // strided_iterator for wrapping a forward traversal iterator |
| template<class BaseIterator, class Category> |
| class strided_iterator |
| : public iterator_adaptor< |
| strided_iterator<BaseIterator, Category> |
| , BaseIterator |
| , use_default |
| , boost::forward_traversal_tag |
| > |
| { |
| friend class ::boost::iterator_core_access; |
| |
| typedef iterator_adaptor< |
| strided_iterator<BaseIterator, Category> |
| , BaseIterator |
| , use_default |
| , boost::forward_traversal_tag |
| > super_t; |
| |
| public: |
| typedef BOOST_DEDUCED_TYPENAME std::iterator_traits<BaseIterator>::difference_type difference_type; |
| typedef BaseIterator base_iterator; |
| |
| strided_iterator() |
| : m_last() |
| , m_stride() |
| { |
| } |
| |
| strided_iterator(base_iterator first, base_iterator it, base_iterator last, difference_type stride) |
| : super_t(it) |
| , m_last(last) |
| , m_stride(stride) |
| { |
| } |
| |
| template<class OtherIterator> |
| strided_iterator(const strided_iterator<OtherIterator, Category>& other, |
| BOOST_DEDUCED_TYPENAME enable_if_convertible<OtherIterator, base_iterator>::type* = 0) |
| : super_t(other) |
| , m_last(other.base_end()) |
| , m_stride(other.get_stride()) |
| { |
| } |
| |
| base_iterator base_end() const { return m_last; } |
| difference_type get_stride() const { return m_stride; } |
| |
| private: |
| void increment() |
| { |
| base_iterator& it = this->base_reference(); |
| for (difference_type i = 0; (it != m_last) && (i < m_stride); ++i) |
| ++it; |
| } |
| |
| base_iterator m_last; |
| difference_type m_stride; |
| }; |
| |
| // strided_iterator for wrapping a bidirectional iterator |
| template<class BaseIterator> |
| class strided_iterator<BaseIterator, bidirectional_traversal_tag> |
| : public iterator_adaptor< |
| strided_iterator<BaseIterator, bidirectional_traversal_tag> |
| , BaseIterator |
| , use_default |
| , bidirectional_traversal_tag |
| > |
| { |
| friend class ::boost::iterator_core_access; |
| |
| typedef iterator_adaptor< |
| strided_iterator<BaseIterator, bidirectional_traversal_tag> |
| , BaseIterator |
| , use_default |
| , bidirectional_traversal_tag |
| > super_t; |
| public: |
| typedef BOOST_DEDUCED_TYPENAME std::iterator_traits<BaseIterator>::difference_type difference_type; |
| typedef BaseIterator base_iterator; |
| |
| strided_iterator() |
| : m_first() |
| , m_last() |
| , m_stride() |
| { |
| } |
| |
| strided_iterator(base_iterator first, base_iterator it, base_iterator last, difference_type stride) |
| : super_t(it) |
| , m_first(first) |
| , m_last(last) |
| , m_stride(stride) |
| { |
| } |
| |
| template<class OtherIterator> |
| strided_iterator(const strided_iterator<OtherIterator, bidirectional_traversal_tag>& other, |
| BOOST_DEDUCED_TYPENAME enable_if_convertible<OtherIterator, base_iterator>::type* = 0) |
| : super_t(other.base()) |
| , m_first(other.base_begin()) |
| , m_last(other.base_end()) |
| , m_stride(other.get_stride()) |
| { |
| } |
| |
| base_iterator base_begin() const { return m_first; } |
| base_iterator base_end() const { return m_last; } |
| difference_type get_stride() const { return m_stride; } |
| |
| private: |
| void increment() |
| { |
| base_iterator& it = this->base_reference(); |
| for (difference_type i = 0; (it != m_last) && (i < m_stride); ++i) |
| ++it; |
| } |
| |
| void decrement() |
| { |
| base_iterator& it = this->base_reference(); |
| for (difference_type i = 0; (it != m_first) && (i < m_stride); ++i) |
| --it; |
| } |
| |
| base_iterator m_first; |
| base_iterator m_last; |
| difference_type m_stride; |
| }; |
| |
| // strided_iterator implementation for wrapping a random access iterator |
| template<class BaseIterator> |
| class strided_iterator<BaseIterator, random_access_traversal_tag> |
| : public iterator_adaptor< |
| strided_iterator<BaseIterator, random_access_traversal_tag> |
| , BaseIterator |
| , use_default |
| , random_access_traversal_tag |
| > |
| { |
| friend class ::boost::iterator_core_access; |
| |
| typedef iterator_adaptor< |
| strided_iterator<BaseIterator, random_access_traversal_tag> |
| , BaseIterator |
| , use_default |
| , random_access_traversal_tag |
| > super_t; |
| public: |
| typedef BOOST_DEDUCED_TYPENAME super_t::difference_type difference_type; |
| typedef BaseIterator base_iterator; |
| |
| strided_iterator() |
| : m_first() |
| , m_last() |
| , m_index(0) |
| , m_stride() |
| { |
| } |
| |
| strided_iterator(BaseIterator first, BaseIterator it, BaseIterator last, difference_type stride) |
| : super_t(it) |
| , m_first(first) |
| , m_last(last) |
| , m_index(stride ? (it - first) / stride : 0) |
| , m_stride(stride) |
| { |
| } |
| |
| template<class OtherIterator> |
| strided_iterator(const strided_iterator<OtherIterator, random_access_traversal_tag>& other, |
| BOOST_DEDUCED_TYPENAME enable_if_convertible<OtherIterator, BaseIterator>::type* = 0) |
| : super_t(other.base()) |
| , m_first(other.base_begin()) |
| , m_last(other.base_end()) |
| , m_index(other.get_index()) |
| , m_stride(other.get_stride()) |
| { |
| } |
| |
| base_iterator base_begin() const { return m_first; } |
| base_iterator base_end() const { return m_last; } |
| difference_type get_stride() const { return m_stride; } |
| difference_type get_index() const { return m_index; } |
| |
| private: |
| void increment() |
| { |
| m_index += m_stride; |
| if (m_index < (m_last - m_first)) |
| this->base_reference() = m_first + m_index; |
| else |
| this->base_reference() = m_last; |
| } |
| |
| void decrement() |
| { |
| m_index -= m_stride; |
| if (m_index >= 0) |
| this->base_reference() = m_first + m_index; |
| else |
| this->base_reference() = m_first; |
| } |
| |
| void advance(difference_type offset) |
| { |
| offset *= m_stride; |
| m_index += offset; |
| if (m_index < 0) |
| this->base_reference() = m_first; |
| else if (m_index > (m_last - m_first)) |
| this->base_reference() = m_last; |
| else |
| this->base_reference() = m_first + m_index; |
| } |
| |
| template<class OtherIterator> |
| difference_type distance_to(const strided_iterator<OtherIterator, random_access_traversal_tag>& other, |
| BOOST_DEDUCED_TYPENAME enable_if_convertible<OtherIterator, BaseIterator>::type* = 0) const |
| { |
| if (other.base() >= this->base()) |
| return (other.base() - this->base() + (m_stride - 1)) / m_stride; |
| return (other.base() - this->base() - (m_stride - 1)) / m_stride; |
| } |
| |
| bool equal(const strided_iterator& other) const |
| { |
| return this->base() == other.base(); |
| } |
| |
| private: |
| base_iterator m_first; |
| base_iterator m_last; |
| difference_type m_index; |
| difference_type m_stride; |
| }; |
| |
| template<class BaseIterator, class Difference> inline |
| strided_iterator<BaseIterator, BOOST_DEDUCED_TYPENAME iterator_traversal<BaseIterator>::type> |
| make_strided_iterator(BaseIterator first, BaseIterator it, |
| BaseIterator last, Difference stride) |
| { |
| BOOST_ASSERT( stride >= 0 ); |
| typedef BOOST_DEDUCED_TYPENAME iterator_traversal<BaseIterator>::type traversal_tag; |
| return strided_iterator<BaseIterator, traversal_tag>(first, it, last, stride); |
| } |
| |
| template< class Rng |
| , class Category = BOOST_DEDUCED_TYPENAME iterator_traversal< |
| BOOST_DEDUCED_TYPENAME range_iterator<Rng>::type |
| >::type |
| > |
| class strided_range |
| : public iterator_range< |
| range_detail::strided_iterator< |
| BOOST_DEDUCED_TYPENAME range_iterator<Rng>::type, |
| Category |
| > |
| > |
| { |
| typedef range_detail::strided_iterator< |
| BOOST_DEDUCED_TYPENAME range_iterator<Rng>::type, |
| Category |
| > iter_type; |
| typedef iterator_range<iter_type> super_t; |
| public: |
| template<class Difference> |
| strided_range(Difference stride, Rng& rng) |
| : super_t(make_strided_iterator(boost::begin(rng), boost::begin(rng), boost::end(rng), stride), |
| make_strided_iterator(boost::begin(rng), boost::end(rng), boost::end(rng), stride)) |
| { |
| BOOST_ASSERT( stride >= 0 ); |
| } |
| }; |
| |
| template<class Difference> |
| class strided_holder : public holder<Difference> |
| { |
| public: |
| explicit strided_holder(Difference value) : holder<Difference>(value) {} |
| }; |
| |
| template<class Rng, class Difference> |
| inline strided_range<Rng> |
| operator|(Rng& rng, const strided_holder<Difference>& stride) |
| { |
| return strided_range<Rng>(stride.val, rng); |
| } |
| |
| template<class Rng, class Difference> |
| inline strided_range<const Rng> |
| operator|(const Rng& rng, const strided_holder<Difference>& stride) |
| { |
| return strided_range<const Rng>(stride.val, rng); |
| } |
| |
| } // namespace range_detail |
| |
| using range_detail::strided_range; |
| |
| namespace adaptors |
| { |
| |
| namespace |
| { |
| const range_detail::forwarder<range_detail::strided_holder> |
| strided = range_detail::forwarder<range_detail::strided_holder>(); |
| } |
| |
| template<class Range, class Difference> |
| inline strided_range<Range> |
| stride(Range& rng, Difference step) |
| { |
| return strided_range<Range>(step, rng); |
| } |
| |
| template<class Range, class Difference> |
| inline strided_range<const Range> |
| stride(const Range& rng, Difference step) |
| { |
| return strided_range<const Range>(step, rng); |
| } |
| |
| } // namespace 'adaptors' |
| } // namespace 'boost' |
| |
| #endif |