156 lines
4.3 KiB
C++
156 lines
4.3 KiB
C++
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/* Copyright 2016-2019 Joaquin M Lopez Munoz.
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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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*
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* See http://www.boost.org/libs/poly_collection for library home page.
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*/
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#ifndef BOOST_POLY_COLLECTION_DETAIL_STRIDE_ITERATOR_HPP
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#define BOOST_POLY_COLLECTION_DETAIL_STRIDE_ITERATOR_HPP
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#if defined(_MSC_VER)
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#pragma once
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#endif
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#include <boost/detail/workaround.hpp>
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#include <boost/iterator/iterator_facade.hpp>
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#include <type_traits>
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namespace boost{
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namespace poly_collection{
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namespace detail{
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/* random-access iterator to Value elements laid out stride *chars* apart */
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template<typename Value>
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class stride_iterator:
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public boost::iterator_facade<
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stride_iterator<Value>,
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Value,
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boost::random_access_traversal_tag
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>
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{
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public:
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stride_iterator()=default;
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stride_iterator(Value* p,std::size_t stride)noexcept:p{p},stride_{stride}{}
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stride_iterator(const stride_iterator&)=default;
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stride_iterator& operator=(const stride_iterator&)=default;
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template<
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typename NonConstValue,
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typename std::enable_if<
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std::is_same<Value,const NonConstValue>::value>::type* =nullptr
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>
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stride_iterator(const stride_iterator<NonConstValue>& x)noexcept:
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p{x.p},stride_{x.stride_}{}
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template<
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typename NonConstValue,
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typename std::enable_if<
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std::is_same<Value,const NonConstValue>::value>::type* =nullptr
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>
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stride_iterator& operator=(const stride_iterator<NonConstValue>& x)noexcept
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{
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p=x.p;stride_=x.stride_;
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return *this;
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}
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/* interoperability with [Derived]Value* */
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stride_iterator& operator=(Value* p_)noexcept{p=p_;return *this;}
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operator Value*()const noexcept{return p;}
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template<
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typename DerivedValue,
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typename std::enable_if<
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std::is_base_of<Value,DerivedValue>::value&&
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(std::is_const<Value>::value||!std::is_const<DerivedValue>::value)
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>::type* =nullptr
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>
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explicit stride_iterator(DerivedValue* x)noexcept:
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p{x},stride_{sizeof(DerivedValue)}{}
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#if BOOST_WORKAROUND(BOOST_GCC_VERSION,>=40900)||\
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BOOST_WORKAROUND(BOOST_CLANG,>=1)&&\
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(__clang_major__>3 || __clang_major__==3 && __clang_minor__ >= 8)
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/* https://github.com/boostorg/poly_collection/issues/15 */
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#define BOOST_POLY_COLLECTION_NO_SANITIZE
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/* UBSan seems not to be supported in some environments */
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#if defined(BOOST_GCC_VERSION)
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#pragma GCC diagnostic push
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#pragma GCC diagnostic ignored "-Wattributes"
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#elif defined(BOOST_CLANG)
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#pragma clang diagnostic push
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#pragma clang diagnostic ignored "-Wattributes"
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#endif
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#endif
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template<
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typename DerivedValue,
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typename std::enable_if<
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std::is_base_of<Value,DerivedValue>::value&&
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(!std::is_const<Value>::value||std::is_const<DerivedValue>::value)
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>::type* =nullptr
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>
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#if defined(BOOST_POLY_COLLECTION_NO_SANITIZE)
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__attribute__((no_sanitize("undefined")))
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#endif
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explicit operator DerivedValue*()const noexcept
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{return static_cast<DerivedValue*>(p);}
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#if defined(BOOST_POLY_COLLECTION_NO_SANITIZE)
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#if defined(BOOST_GCC_VERSION)
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#pragma GCC diagnostic pop
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#elif defined(BOOST_CLANG)
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#pragma clang diagnostic pop
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#endif
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#undef BOOST_POLY_COLLECTION_NO_SANITIZE
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#endif
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std::size_t stride()const noexcept{return stride_;}
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private:
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template<typename>
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friend class stride_iterator;
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using char_pointer=typename std::conditional<
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std::is_const<Value>::value,
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const char*,
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char*
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>::type;
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static char_pointer char_ptr(Value* p)noexcept
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{return reinterpret_cast<char_pointer>(p);}
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static Value* value_ptr(char_pointer p)noexcept
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{return reinterpret_cast<Value*>(p);}
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friend class boost::iterator_core_access;
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Value& dereference()const noexcept{return *p;}
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bool equal(const stride_iterator& x)const noexcept{return p==x.p;}
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void increment()noexcept{p=value_ptr(char_ptr(p)+stride_);}
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void decrement()noexcept{p=value_ptr(char_ptr(p)-stride_);}
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template<typename Integral>
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void advance(Integral n)noexcept
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{p=value_ptr(char_ptr(p)+n*(std::ptrdiff_t)stride_);}
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std::ptrdiff_t distance_to(const stride_iterator& x)const noexcept
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{return (char_ptr(x.p)-char_ptr(p))/(std::ptrdiff_t)stride_;}
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Value* p;
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std::size_t stride_;
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};
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} /* namespace poly_collection::detail */
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} /* namespace poly_collection */
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} /* namespace boost */
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#endif
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