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