156 lines
4.7 KiB
C++
156 lines
4.7 KiB
C++
// Copyright (c) 2006, Giovanni P. Deretta
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//
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// This code may be used under either of the following two licences:
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"), to deal
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// in the Software without restriction, including without limitation the rights
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// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the Software is
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// furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in
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// all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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// THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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// THE SOFTWARE. OF SUCH DAMAGE.
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//
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// Or:
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//
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// Distributed under the Boost Software License, Version 1.0.
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// (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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#ifndef BOOST_COROUTINE_GENERATOR_HPP_20060812
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#define BOOST_COROUTINE_GENERATOR_HPP_20060812
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#include <iterator>
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#include <boost/optional.hpp>
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#include <boost/none.hpp>
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#include <boost/coroutine/shared_coroutine.hpp>
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namespace boost { namespace coroutines {
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namespace detail {
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template<typename T>
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class tag {};
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class empty {};
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template<typename Category, typename ValueType>
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struct make_std_iterator {
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typedef std::iterator<Category,
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ValueType,
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std::ptrdiff_t,
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BOOST_DEDUCED_TYPENAME boost::remove_reference<ValueType>::type *, //pointer
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BOOST_DEDUCED_TYPENAME boost::remove_reference<ValueType>::type & //reference
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> type;
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};
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}
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// This simple class implement generators (a simple
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// subset of coroutines) in the form of an InputIterator
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// interface. It also models to the AdaptableGenerator concept.
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// Finally it is ConvertibleToBool.
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template<typename ValueType,
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typename Coroutine =
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shared_coroutine<ValueType()> >
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class generator : public boost::mpl::eval_if<boost::is_same<ValueType, void>,
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boost::mpl::identity<detail::empty>,
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detail::make_std_iterator<
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std::input_iterator_tag,
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typename Coroutine::result_type> >::type {
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typedef void(generator::*safe_bool)();
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typedef ValueType internal_value_type;
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public:
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typedef Coroutine coroutine_type;
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typedef BOOST_DEDUCED_TYPENAME
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coroutine_type::result_type result_type;
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typedef result_type value_type;
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typedef BOOST_DEDUCED_TYPENAME coroutine_type::self self;
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generator() {}
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template<typename Functor>
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generator(Functor f) :
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m_coro(f),
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m_val(assign(detail::tag<result_type>())){};
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generator(const generator& rhs) :
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m_coro(rhs.m_coro),
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m_val(rhs.m_val) {}
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value_type operator*() {
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return *m_val;
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}
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generator& operator++() {
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m_val = assign(detail::tag<result_type>());
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return *this;
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}
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generator operator++(int) {
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generator t(*this);
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++(*this);
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return t;
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}
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friend
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bool operator==(const generator& lhs, const generator& rhs) {
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return lhs.m_val == rhs.m_val;
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}
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friend
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bool operator != (const generator& lhs, const generator & rhs) {
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return !(lhs == rhs);
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}
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operator safe_bool () const {
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return m_val? &generator::safe_bool_true: 0;
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}
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value_type operator()() {
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return *(*this)++;
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}
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private:
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void safe_bool_true () {};
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// hack to handle correctly void result types.
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struct optional_void {
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optional_void() : m_result(true) {}
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optional_void(boost::none_t) : m_result(false) {}
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void operator*() const {}
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operator bool() const { return m_result; };
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bool m_result;
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};
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typedef BOOST_DEDUCED_TYPENAME
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boost::mpl::if_<boost::is_same<value_type, void>,
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optional_void,
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boost::optional<value_type> >::type optional_type;
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template<typename T>
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optional_type assign(detail::tag<T>) {
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return m_coro? m_coro(std::nothrow): boost::none;
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}
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optional_type assign(detail::tag<void>) {
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return m_coro? (m_coro(std::nothrow), optional_type()): boost::none;
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}
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// There is a possible EBO here. May be use compressed pair.
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coroutine_type m_coro;
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optional_type m_val;
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};
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} }
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#endif
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