| // 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_stride() | |
| { | |
| } | |
| strided_iterator(BaseIterator first, BaseIterator it, BaseIterator 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, 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_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(); | |
| if ((m_last - it) > m_stride) | |
| it += m_stride; | |
| else | |
| it = m_last; | |
| } | |
| void decrement() | |
| { | |
| base_iterator& it = this->base_reference(); | |
| if ((it - m_first) > m_stride) | |
| it -= m_stride; | |
| else | |
| it = m_first; | |
| } | |
| void advance(difference_type offset) | |
| { | |
| base_iterator& it = this->base_reference(); | |
| offset *= m_stride; | |
| if (offset >= 0) | |
| { | |
| if ((m_last - it) > offset) | |
| it += offset; | |
| else | |
| it = m_last; | |
| } | |
| else | |
| { | |
| if ((m_first - it) > offset) | |
| it += offset; | |
| else | |
| it = m_first; | |
| } | |
| } | |
| 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 other.base() == this->base(); | |
| } | |
| private: | |
| base_iterator m_first; | |
| base_iterator m_last; | |
| 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 |