351 lines
13 KiB
C++
351 lines
13 KiB
C++
// Boost.Range library
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//
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// Copyright Neil Groves 2007. Use, modification and
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// distribution is subject to the Boost Software License, Version
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// 1.0. (See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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//
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//
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// For more information, see http://www.boost.org/libs/range/
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//
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#ifndef BOOST_RANGE_ADAPTOR_STRIDED_HPP_INCLUDED
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#define BOOST_RANGE_ADAPTOR_STRIDED_HPP_INCLUDED
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#include <boost/range/adaptor/argument_fwd.hpp>
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#include <boost/range/iterator_range.hpp>
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#include <boost/iterator/iterator_adaptor.hpp>
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#include <iterator>
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namespace boost
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{
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namespace range_detail
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{
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// strided_iterator for wrapping a forward traversal iterator
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template<class BaseIterator, class Category>
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class strided_iterator
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: public iterator_adaptor<
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strided_iterator<BaseIterator, Category>
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, BaseIterator
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, use_default
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, boost::forward_traversal_tag
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>
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{
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friend class ::boost::iterator_core_access;
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typedef iterator_adaptor<
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strided_iterator<BaseIterator, Category>
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, BaseIterator
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, use_default
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, boost::forward_traversal_tag
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> super_t;
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public:
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typedef BOOST_DEDUCED_TYPENAME std::iterator_traits<BaseIterator>::difference_type difference_type;
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typedef BaseIterator base_iterator;
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strided_iterator()
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: m_last()
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, m_stride()
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{
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}
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strided_iterator(base_iterator first, base_iterator it, base_iterator last, difference_type stride)
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: super_t(it)
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, m_last(last)
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, m_stride(stride)
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{
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}
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template<class OtherIterator>
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strided_iterator(const strided_iterator<OtherIterator, Category>& other,
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BOOST_DEDUCED_TYPENAME enable_if_convertible<OtherIterator, base_iterator>::type* = 0)
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: super_t(other)
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, m_last(other.base_end())
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, m_stride(other.get_stride())
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{
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}
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base_iterator base_end() const { return m_last; }
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difference_type get_stride() const { return m_stride; }
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private:
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void increment()
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{
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base_iterator& it = this->base_reference();
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for (difference_type i = 0; (it != m_last) && (i < m_stride); ++i)
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++it;
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}
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base_iterator m_last;
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difference_type m_stride;
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};
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// strided_iterator for wrapping a bidirectional iterator
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template<class BaseIterator>
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class strided_iterator<BaseIterator, bidirectional_traversal_tag>
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: public iterator_adaptor<
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strided_iterator<BaseIterator, bidirectional_traversal_tag>
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, BaseIterator
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, use_default
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, bidirectional_traversal_tag
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>
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{
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friend class ::boost::iterator_core_access;
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typedef iterator_adaptor<
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strided_iterator<BaseIterator, bidirectional_traversal_tag>
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, BaseIterator
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, use_default
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, bidirectional_traversal_tag
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> super_t;
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public:
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typedef BOOST_DEDUCED_TYPENAME std::iterator_traits<BaseIterator>::difference_type difference_type;
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typedef BaseIterator base_iterator;
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strided_iterator()
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: m_first()
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, m_last()
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, m_stride()
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{
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}
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strided_iterator(base_iterator first, base_iterator it, base_iterator last, difference_type stride)
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: super_t(it)
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, m_first(first)
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, m_last(last)
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, m_stride(stride)
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{
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}
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template<class OtherIterator>
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strided_iterator(const strided_iterator<OtherIterator, bidirectional_traversal_tag>& other,
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BOOST_DEDUCED_TYPENAME enable_if_convertible<OtherIterator, base_iterator>::type* = 0)
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: super_t(other.base())
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, m_first(other.base_begin())
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, m_last(other.base_end())
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, m_stride(other.get_stride())
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{
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}
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base_iterator base_begin() const { return m_first; }
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base_iterator base_end() const { return m_last; }
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difference_type get_stride() const { return m_stride; }
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private:
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void increment()
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{
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base_iterator& it = this->base_reference();
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for (difference_type i = 0; (it != m_last) && (i < m_stride); ++i)
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++it;
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}
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void decrement()
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{
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base_iterator& it = this->base_reference();
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for (difference_type i = 0; (it != m_first) && (i < m_stride); ++i)
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--it;
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}
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base_iterator m_first;
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base_iterator m_last;
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difference_type m_stride;
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};
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// strided_iterator implementation for wrapping a random access iterator
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template<class BaseIterator>
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class strided_iterator<BaseIterator, random_access_traversal_tag>
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: public iterator_adaptor<
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strided_iterator<BaseIterator, random_access_traversal_tag>
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, BaseIterator
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, use_default
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, random_access_traversal_tag
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>
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{
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friend class ::boost::iterator_core_access;
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typedef iterator_adaptor<
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strided_iterator<BaseIterator, random_access_traversal_tag>
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, BaseIterator
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, use_default
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, random_access_traversal_tag
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> super_t;
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public:
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typedef BOOST_DEDUCED_TYPENAME super_t::difference_type difference_type;
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typedef BaseIterator base_iterator;
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strided_iterator()
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: m_first()
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, m_last()
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, m_index(0)
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, m_stride()
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{
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}
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strided_iterator(BaseIterator first, BaseIterator it, BaseIterator last, difference_type stride)
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: super_t(it)
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, m_first(first)
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, m_last(last)
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, m_index(stride ? (it - first) / stride : 0)
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, m_stride(stride)
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{
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}
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template<class OtherIterator>
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strided_iterator(const strided_iterator<OtherIterator, random_access_traversal_tag>& other,
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BOOST_DEDUCED_TYPENAME enable_if_convertible<OtherIterator, BaseIterator>::type* = 0)
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: super_t(other.base())
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, m_first(other.base_begin())
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, m_last(other.base_end())
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, m_index(other.get_index())
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, m_stride(other.get_stride())
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{
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}
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base_iterator base_begin() const { return m_first; }
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base_iterator base_end() const { return m_last; }
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difference_type get_stride() const { return m_stride; }
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difference_type get_index() const { return m_index; }
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private:
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void increment()
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{
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m_index += m_stride;
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if (m_index < (m_last - m_first))
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this->base_reference() = m_first + m_index;
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else
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this->base_reference() = m_last;
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}
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void decrement()
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{
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m_index -= m_stride;
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if (m_index >= 0)
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this->base_reference() = m_first + m_index;
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else
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this->base_reference() = m_first;
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}
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void advance(difference_type offset)
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{
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offset *= m_stride;
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m_index += offset;
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if (m_index < 0)
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this->base_reference() = m_first;
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else if (m_index > (m_last - m_first))
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this->base_reference() = m_last;
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else
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this->base_reference() = m_first + m_index;
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}
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template<class OtherIterator>
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difference_type distance_to(const strided_iterator<OtherIterator, random_access_traversal_tag>& other,
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BOOST_DEDUCED_TYPENAME enable_if_convertible<OtherIterator, BaseIterator>::type* = 0) const
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{
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if (other.base() >= this->base())
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return (other.base() - this->base() + (m_stride - 1)) / m_stride;
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return (other.base() - this->base() - (m_stride - 1)) / m_stride;
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}
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bool equal(const strided_iterator& other) const
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{
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return this->base() == other.base();
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}
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private:
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base_iterator m_first;
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base_iterator m_last;
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difference_type m_index;
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difference_type m_stride;
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};
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template<class BaseIterator, class Difference> inline
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strided_iterator<BaseIterator, BOOST_DEDUCED_TYPENAME iterator_traversal<BaseIterator>::type>
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make_strided_iterator(BaseIterator first, BaseIterator it,
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BaseIterator last, Difference stride)
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{
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BOOST_ASSERT( stride >= 0 );
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typedef BOOST_DEDUCED_TYPENAME iterator_traversal<BaseIterator>::type traversal_tag;
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return strided_iterator<BaseIterator, traversal_tag>(first, it, last, stride);
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}
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template< class Rng
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, class Category = BOOST_DEDUCED_TYPENAME iterator_traversal<
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BOOST_DEDUCED_TYPENAME range_iterator<Rng>::type
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>::type
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>
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class strided_range
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: public iterator_range<
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range_detail::strided_iterator<
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BOOST_DEDUCED_TYPENAME range_iterator<Rng>::type,
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Category
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>
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>
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{
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typedef range_detail::strided_iterator<
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BOOST_DEDUCED_TYPENAME range_iterator<Rng>::type,
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Category
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> iter_type;
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typedef iterator_range<iter_type> super_t;
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public:
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template<class Difference>
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strided_range(Difference stride, Rng& rng)
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: super_t(make_strided_iterator(boost::begin(rng), boost::begin(rng), boost::end(rng), stride),
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make_strided_iterator(boost::begin(rng), boost::end(rng), boost::end(rng), stride))
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{
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BOOST_ASSERT( stride >= 0 );
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}
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};
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template<class Difference>
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class strided_holder : public holder<Difference>
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{
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public:
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explicit strided_holder(Difference value) : holder<Difference>(value) {}
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};
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template<class Rng, class Difference>
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inline strided_range<Rng>
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operator|(Rng& rng, const strided_holder<Difference>& stride)
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{
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return strided_range<Rng>(stride.val, rng);
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}
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template<class Rng, class Difference>
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inline strided_range<const Rng>
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operator|(const Rng& rng, const strided_holder<Difference>& stride)
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{
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return strided_range<const Rng>(stride.val, rng);
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}
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} // namespace range_detail
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using range_detail::strided_range;
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namespace adaptors
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{
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namespace
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{
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const range_detail::forwarder<range_detail::strided_holder>
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strided = range_detail::forwarder<range_detail::strided_holder>();
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}
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template<class Range, class Difference>
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inline strided_range<Range>
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stride(Range& rng, Difference step)
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{
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return strided_range<Range>(step, rng);
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}
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template<class Range, class Difference>
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inline strided_range<const Range>
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stride(const Range& rng, Difference step)
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{
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return strided_range<const Range>(step, rng);
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}
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} // namespace 'adaptors'
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} // namespace 'boost'
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#endif
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