1 //---------------------------------------------------------------------------//
2 // Copyright (c) 2013 Kyle Lutz <kyle.r.lutz@gmail.com>
4 // Distributed under the Boost Software License, Version 1.0
5 // See accompanying file LICENSE_1_0.txt or copy at
6 // http://www.boost.org/LICENSE_1_0.txt
8 // See http://boostorg.github.com/compute for more information.
9 //---------------------------------------------------------------------------//
11 #ifndef BOOST_COMPUTE_ITERATOR_TRANSFORM_ITERATOR_HPP
12 #define BOOST_COMPUTE_ITERATOR_TRANSFORM_ITERATOR_HPP
17 #include <boost/config.hpp>
18 #include <boost/iterator/iterator_adaptor.hpp>
20 #include <boost/compute/functional.hpp>
21 #include <boost/compute/detail/meta_kernel.hpp>
22 #include <boost/compute/detail/is_buffer_iterator.hpp>
23 #include <boost/compute/detail/read_write_single_value.hpp>
24 #include <boost/compute/iterator/detail/get_base_iterator_buffer.hpp>
25 #include <boost/compute/type_traits/is_device_iterator.hpp>
26 #include <boost/compute/type_traits/result_of.hpp>
31 // forward declaration for transform_iterator
32 template<class InputIterator, class UnaryFunction>
33 class transform_iterator;
37 // meta-function returning the value_type for a transform_iterator
38 template<class InputIterator, class UnaryFunction>
39 struct make_transform_iterator_value_type
41 typedef typename std::iterator_traits<InputIterator>::value_type value_type;
43 typedef typename boost::compute::result_of<UnaryFunction(value_type)>::type type;
46 // helper class which defines the iterator_adaptor super-class
47 // type for transform_iterator
48 template<class InputIterator, class UnaryFunction>
49 class transform_iterator_base
52 typedef ::boost::iterator_adaptor<
53 ::boost::compute::transform_iterator<InputIterator, UnaryFunction>,
55 typename make_transform_iterator_value_type<InputIterator, UnaryFunction>::type,
56 typename std::iterator_traits<InputIterator>::iterator_category,
57 typename make_transform_iterator_value_type<InputIterator, UnaryFunction>::type
61 template<class InputIterator, class UnaryFunction, class IndexExpr>
62 struct transform_iterator_index_expr
65 make_transform_iterator_value_type<
70 transform_iterator_index_expr(const InputIterator &input_iter,
71 const UnaryFunction &transform_expr,
72 const IndexExpr &index_expr)
73 : m_input_iter(input_iter),
74 m_transform_expr(transform_expr),
75 m_index_expr(index_expr)
79 const InputIterator m_input_iter;
80 const UnaryFunction m_transform_expr;
81 const IndexExpr m_index_expr;
84 template<class InputIterator, class UnaryFunction, class IndexExpr>
85 inline meta_kernel& operator<<(meta_kernel &kernel,
86 const transform_iterator_index_expr<InputIterator,
90 return kernel << expr.m_transform_expr(expr.m_input_iter[expr.m_index_expr]);
93 } // end detail namespace
95 /// \class transform_iterator
96 /// \brief A transform iterator adaptor.
98 /// The transform_iterator adaptor applies a unary function to each element
99 /// produced from the underlying iterator when dereferenced.
101 /// For example, to copy from an input range to an output range while taking
102 /// the absolute value of each element:
104 /// \snippet test/test_transform_iterator.cpp copy_abs
106 /// \see buffer_iterator, make_transform_iterator()
107 template<class InputIterator, class UnaryFunction>
108 class transform_iterator :
109 public detail::transform_iterator_base<InputIterator, UnaryFunction>::type
113 detail::transform_iterator_base<InputIterator,
114 UnaryFunction>::type super_type;
115 typedef typename super_type::value_type value_type;
116 typedef typename super_type::reference reference;
117 typedef typename super_type::base_type base_type;
118 typedef typename super_type::difference_type difference_type;
119 typedef UnaryFunction unary_function;
121 transform_iterator(InputIterator iterator, UnaryFunction transform)
122 : super_type(iterator),
123 m_transform(transform)
127 transform_iterator(const transform_iterator<InputIterator,
128 UnaryFunction> &other)
129 : super_type(other.base()),
130 m_transform(other.m_transform)
134 transform_iterator<InputIterator, UnaryFunction>&
135 operator=(const transform_iterator<InputIterator,
136 UnaryFunction> &other)
139 super_type::operator=(other);
141 m_transform = other.m_transform;
147 ~transform_iterator()
151 size_t get_index() const
153 return super_type::base().get_index();
156 const buffer& get_buffer() const
158 return detail::get_base_iterator_buffer(*this);
161 template<class IndexExpression>
162 detail::transform_iterator_index_expr<InputIterator, UnaryFunction, IndexExpression>
163 operator[](const IndexExpression &expr) const
165 return detail::transform_iterator_index_expr<InputIterator,
167 IndexExpression>(super_type::base(),
173 friend class ::boost::iterator_core_access;
175 reference dereference() const
177 const context &context = super_type::base().get_buffer().get_context();
178 command_queue queue(context, context.get_device());
180 detail::meta_kernel k("read");
181 size_t output_arg = k.add_arg<value_type *>(memory_object::global_memory, "output");
182 k << "*output = " << m_transform(super_type::base()[k.lit(0)]) << ";";
184 kernel kernel = k.compile(context);
186 buffer output_buffer(context, sizeof(value_type));
188 kernel.set_arg(output_arg, output_buffer);
190 queue.enqueue_task(kernel);
192 return detail::read_single_value<value_type>(output_buffer, queue);
196 UnaryFunction m_transform;
199 /// Returns a transform_iterator for \p iterator with \p transform.
201 /// \param iterator the underlying iterator
202 /// \param transform the unary transform function
204 /// \return a \c transform_iterator for \p iterator with \p transform
206 /// For example, to create an iterator which returns the square-root of each
207 /// value in a \c vector<int>:
209 /// auto sqrt_iterator = make_transform_iterator(vec.begin(), sqrt<int>());
211 template<class InputIterator, class UnaryFunction>
212 inline transform_iterator<InputIterator, UnaryFunction>
213 make_transform_iterator(InputIterator iterator, UnaryFunction transform)
215 return transform_iterator<InputIterator,
216 UnaryFunction>(iterator, transform);
219 /// \internal_ (is_device_iterator specialization for transform_iterator)
220 template<class InputIterator, class UnaryFunction>
221 struct is_device_iterator<
222 transform_iterator<InputIterator, UnaryFunction> > : boost::true_type {};
224 } // end compute namespace
225 } // end boost namespace
227 #endif // BOOST_COMPUTE_ITERATOR_TRANSFORM_ITERATOR_HPP