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- //---------------------------------------------------------------------------//
- // Copyright (c) 2015 Jakub Szuppe <j.szuppe@gmail.com>
- //
- // 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
- //
- // See http://boostorg.github.com/compute for more information.
- //---------------------------------------------------------------------------//
- #ifndef BOOST_COMPUTE_ITERATOR_STRIDED_ITERATOR_HPP
- #define BOOST_COMPUTE_ITERATOR_STRIDED_ITERATOR_HPP
- #include <cstddef>
- #include <iterator>
- #include <boost/config.hpp>
- #include <boost/iterator/iterator_adaptor.hpp>
- #include <boost/compute/functional.hpp>
- #include <boost/compute/detail/meta_kernel.hpp>
- #include <boost/compute/detail/is_buffer_iterator.hpp>
- #include <boost/compute/detail/read_write_single_value.hpp>
- #include <boost/compute/iterator/detail/get_base_iterator_buffer.hpp>
- #include <boost/compute/type_traits/is_device_iterator.hpp>
- #include <boost/compute/type_traits/result_of.hpp>
- namespace boost {
- namespace compute {
- // forward declaration for strided_iterator
- template<class Iterator>
- class strided_iterator;
- namespace detail {
- // helper class which defines the iterator_adaptor super-class
- // type for strided_iterator
- template<class Iterator>
- class strided_iterator_base
- {
- public:
- typedef ::boost::iterator_adaptor<
- ::boost::compute::strided_iterator<Iterator>,
- Iterator,
- typename std::iterator_traits<Iterator>::value_type,
- typename std::iterator_traits<Iterator>::iterator_category
- > type;
- };
- // helper class for including stride value in index expression
- template<class IndexExpr, class Stride>
- struct stride_expr
- {
- stride_expr(const IndexExpr &expr, const Stride &stride)
- : m_index_expr(expr),
- m_stride(stride)
- {
- }
- const IndexExpr m_index_expr;
- const Stride m_stride;
- };
- template<class IndexExpr, class Stride>
- inline stride_expr<IndexExpr, Stride> make_stride_expr(const IndexExpr &expr,
- const Stride &stride)
- {
- return stride_expr<IndexExpr, Stride>(expr, stride);
- }
- template<class IndexExpr, class Stride>
- inline meta_kernel& operator<<(meta_kernel &kernel,
- const stride_expr<IndexExpr, Stride> &expr)
- {
- // (expr.m_stride * (expr.m_index_expr))
- return kernel << "(" << static_cast<ulong_>(expr.m_stride)
- << " * (" << expr.m_index_expr << "))";
- }
- template<class Iterator, class Stride, class IndexExpr>
- struct strided_iterator_index_expr
- {
- typedef typename std::iterator_traits<Iterator>::value_type result_type;
- strided_iterator_index_expr(const Iterator &input_iter,
- const Stride &stride,
- const IndexExpr &index_expr)
- : m_input_iter(input_iter),
- m_stride(stride),
- m_index_expr(index_expr)
- {
- }
- const Iterator m_input_iter;
- const Stride m_stride;
- const IndexExpr m_index_expr;
- };
- template<class Iterator, class Stride, class IndexExpr>
- inline meta_kernel& operator<<(meta_kernel &kernel,
- const strided_iterator_index_expr<Iterator,
- Stride,
- IndexExpr> &expr)
- {
- return kernel << expr.m_input_iter[make_stride_expr(expr.m_index_expr, expr.m_stride)];
- }
- } // end detail namespace
- /// \class strided_iterator
- /// \brief An iterator adaptor with adjustable iteration step.
- ///
- /// The strided iterator adaptor skips over multiple elements each time
- /// it is incremented or decremented.
- ///
- /// \see buffer_iterator, make_strided_iterator(), make_strided_iterator_end()
- template<class Iterator>
- class strided_iterator :
- public detail::strided_iterator_base<Iterator>::type
- {
- public:
- typedef typename
- detail::strided_iterator_base<Iterator>::type super_type;
- typedef typename super_type::value_type value_type;
- typedef typename super_type::reference reference;
- typedef typename super_type::base_type base_type;
- typedef typename super_type::difference_type difference_type;
- strided_iterator(Iterator iterator, difference_type stride)
- : super_type(iterator),
- m_stride(static_cast<difference_type>(stride))
- {
- // stride must be greater than zero
- BOOST_ASSERT_MSG(stride > 0, "Stride must be greater than zero");
- }
- strided_iterator(const strided_iterator<Iterator> &other)
- : super_type(other.base()),
- m_stride(other.m_stride)
- {
- }
- strided_iterator<Iterator>&
- operator=(const strided_iterator<Iterator> &other)
- {
- if(this != &other){
- super_type::operator=(other);
- m_stride = other.m_stride;
- }
- return *this;
- }
- ~strided_iterator()
- {
- }
- size_t get_index() const
- {
- return super_type::base().get_index();
- }
- const buffer& get_buffer() const
- {
- return detail::get_base_iterator_buffer(*this);
- }
- template<class IndexExpression>
- detail::strided_iterator_index_expr<Iterator, difference_type, IndexExpression>
- operator[](const IndexExpression &expr) const
- {
- typedef
- typename detail::strided_iterator_index_expr<Iterator,
- difference_type,
- IndexExpression>
- StridedIndexExprType;
- return StridedIndexExprType(super_type::base(),m_stride, expr);
- }
- private:
- friend class ::boost::iterator_core_access;
- reference dereference() const
- {
- return reference();
- }
- bool equal(const strided_iterator<Iterator> &other) const
- {
- return (other.m_stride == m_stride)
- && (other.base_reference() == this->base_reference());
- }
- void increment()
- {
- std::advance(super_type::base_reference(), m_stride);
- }
- void decrement()
- {
- std::advance(super_type::base_reference(),-m_stride);
- }
- void advance(typename super_type::difference_type n)
- {
- std::advance(super_type::base_reference(), n * m_stride);
- }
- difference_type distance_to(const strided_iterator<Iterator> &other) const
- {
- return std::distance(this->base_reference(), other.base_reference()) / m_stride;
- }
- private:
- difference_type m_stride;
- };
- /// Returns a strided_iterator for \p iterator with \p stride.
- ///
- /// \param iterator the underlying iterator
- /// \param stride the iteration step for strided_iterator
- ///
- /// \return a \c strided_iterator for \p iterator with \p stride.
- ///
- /// For example, to create an iterator which iterates over every other
- /// element in a \c vector<int>:
- /// \code
- /// auto strided_iterator = make_strided_iterator(vec.begin(), 2);
- /// \endcode
- template<class Iterator>
- inline strided_iterator<Iterator>
- make_strided_iterator(Iterator iterator,
- typename std::iterator_traits<Iterator>::difference_type stride)
- {
- return strided_iterator<Iterator>(iterator, stride);
- }
- /// Returns a strided_iterator which refers to element that would follow
- /// the last element accessible through strided_iterator for \p first iterator
- /// with \p stride.
- ///
- /// Parameter \p stride must be greater than zero.
- ///
- /// \param first the iterator referring to the first element accessible
- /// through strided_iterator for \p first with \p stride
- /// \param last the iterator referring to the last element that may be
- //// accessible through strided_iterator for \p first with \p stride
- /// \param stride the iteration step
- ///
- /// \return a \c strided_iterator referring to element that would follow
- /// the last element accessible through strided_iterator for \p first
- /// iterator with \p stride.
- ///
- /// It can be helpful when iterating over strided_iterator:
- /// \code
- /// // vec.size() may not be divisible by 3
- /// auto strided_iterator_begin = make_strided_iterator(vec.begin(), 3);
- /// auto strided_iterator_end = make_strided_iterator_end(vec.begin(), vec.end(), 3);
- ///
- /// // copy every 3rd element to result
- /// boost::compute::copy(
- /// strided_iterator_begin,
- /// strided_iterator_end,
- /// result.begin(),
- /// queue
- /// );
- /// \endcode
- template<class Iterator>
- strided_iterator<Iterator>
- make_strided_iterator_end(Iterator first,
- Iterator last,
- typename std::iterator_traits<Iterator>::difference_type stride)
- {
- typedef typename std::iterator_traits<Iterator>::difference_type difference_type;
- // calculate distance from end to the last element that would be
- // accessible through strided_iterator.
- difference_type range = std::distance(first, last);
- difference_type d = (range - 1) / stride;
- d *= stride;
- d -= range;
- // advance from end to the element that would follow the last
- // accessible element
- Iterator end_for_strided_iterator = last;
- std::advance(end_for_strided_iterator, d + stride);
- return strided_iterator<Iterator>(end_for_strided_iterator, stride);
- }
- /// \internal_ (is_device_iterator specialization for strided_iterator)
- template<class Iterator>
- struct is_device_iterator<strided_iterator<Iterator> > : boost::true_type {};
- } // end compute namespace
- } // end boost namespace
- #endif // BOOST_COMPUTE_ITERATOR_STRIDED_ITERATOR_HPP
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