#ifndef BOOST_CORE_SPAN_HPP
#define BOOST_CORE_SPAN_HPP
#include <boost/core/detail/assert.hpp>
#include <boost/core/data.hpp>
#include <array>
#include <iterator>
#include <type_traits>
namespace boost {
constexpr std::size_t dynamic_extent = static_cast<std::size_t>(-1);
template<class T, std::size_t E = dynamic_extent>
class span;
namespace detail {
template<class U, class T>
struct span_convertible {
static constexpr bool value = std::is_convertible<U(*)[], T(*)[]>::value;
};
template<std::size_t E, std::size_t N>
struct span_capacity {
static constexpr bool value = E == boost::dynamic_extent || E == N;
};
template<class T, std::size_t E, class U, std::size_t N>
struct span_compatible {
static constexpr bool value = span_capacity<E, N>::value &&
span_convertible<U, T>::value;
};
template<class T>
using span_uncvref = typename std::remove_cv<typename
std::remove_reference<T>::type>::type;
template<class>
struct span_is_span {
static constexpr bool value = false;
};
template<class T, std::size_t E>
struct span_is_span<boost::span<T, E> > {
static constexpr bool value = true;
};
template<class T>
struct span_is_array {
static constexpr bool value = false;
};
template<class T, std::size_t N>
struct span_is_array<std::array<T, N> > {
static constexpr bool value = true;
};
template<class T>
using span_ptr = decltype(boost::data(std::declval<T&>()));
template<class, class = void>
struct span_data { };
template<class T>
struct span_data<T,
typename std::enable_if<std::is_pointer<span_ptr<T> >::value>::type> {
typedef typename std::remove_pointer<span_ptr<T> >::type type;
};
template<class, class, class = void>
struct span_has_data {
static constexpr bool value = false;
};
template<class R, class T>
struct span_has_data<R, T, typename std::enable_if<span_convertible<typename
span_data<R>::type, T>::value>::type> {
static constexpr bool value = true;
};
template<class, class = void>
struct span_has_size {
static constexpr bool value = false;
};
template<class R>
struct span_has_size<R, typename
std::enable_if<std::is_convertible<decltype(std::declval<R&>().size()),
std::size_t>::value>::type> {
static constexpr bool value = true;
};
template<class R, class T>
struct span_is_range {
static constexpr bool value = (std::is_const<T>::value ||
std::is_lvalue_reference<R>::value) &&
!span_is_span<span_uncvref<R> >::value &&
!span_is_array<span_uncvref<R> >::value &&
!std::is_array<span_uncvref<R> >::value &&
span_has_data<R, T>::value &&
span_has_size<R>::value;
};
template<std::size_t E, std::size_t N>
struct span_implicit {
static constexpr bool value = E == boost::dynamic_extent ||
N != boost::dynamic_extent;
};
template<class T, std::size_t E, class U, std::size_t N>
struct span_copyable {
static constexpr bool value = (N == boost::dynamic_extent ||
span_capacity<E, N>::value) && span_convertible<U, T>::value;
};
template<std::size_t E, std::size_t O>
struct span_sub {
static constexpr std::size_t value = E == boost::dynamic_extent ?
boost::dynamic_extent : E - O;
};
template<class T, std::size_t E>
struct span_store {
constexpr span_store(T* p_, std::size_t) noexcept
: p(p_) { }
static constexpr std::size_t n = E;
T* p;
};
template<class T>
struct span_store<T, boost::dynamic_extent> {
constexpr span_store(T* p_, std::size_t n_) noexcept
: p(p_)
, n(n_) { }
T* p;
std::size_t n;
};
template<class T, std::size_t E>
struct span_bytes {
static constexpr std::size_t value = sizeof(T) * E;
};
template<class T>
struct span_bytes<T, boost::dynamic_extent> {
static constexpr std::size_t value = boost::dynamic_extent;
};
}
template<class T, std::size_t E>
class span {
public:
typedef T element_type;
typedef typename std::remove_cv<T>::type value_type;
typedef std::size_t size_type;
typedef std::ptrdiff_t difference_type;
typedef T* pointer;
typedef const T* const_pointer;
typedef T& reference;
typedef const T& const_reference;
typedef T* iterator;
typedef const T* const_iterator;
typedef std::reverse_iterator<T*> reverse_iterator;
typedef std::reverse_iterator<const T*> const_reverse_iterator;
static constexpr std::size_t extent = E;
template<std::size_t N = E,
typename std::enable_if<N == dynamic_extent || N == 0, int>::type = 0>
constexpr span() noexcept
: s_(0, 0) { }
template<class I,
typename std::enable_if<E == dynamic_extent &&
detail::span_convertible<I, T>::value, int>::type = 0>
constexpr span(I* f, size_type c)
: s_(f, c) { }
template<class I,
typename std::enable_if<E != dynamic_extent &&
detail::span_convertible<I, T>::value, int>::type = 0>
explicit constexpr span(I* f, size_type c)
: s_(f, c) { }
template<class I, class L,
typename std::enable_if<E == dynamic_extent &&
detail::span_convertible<I, T>::value, int>::type = 0>
constexpr span(I* f, L* l)
: s_(f, l - f) { }
template<class I, class L,
typename std::enable_if<E != dynamic_extent &&
detail::span_convertible<I, T>::value, int>::type = 0>
explicit constexpr span(I* f, L* l)
: s_(f, l - f) { }
template<std::size_t N,
typename std::enable_if<detail::span_capacity<E, N>::value,
int>::type = 0>
constexpr span(typename std::enable_if<true, T>::type (&a)[N]) noexcept
: s_(a, N) { }
template<class U, std::size_t N,
typename std::enable_if<detail::span_compatible<T, E, U, N>::value,
int>::type = 0>
constexpr span(std::array<U, N>& a) noexcept
: s_(a.data(), N) { }
template<class U, std::size_t N,
typename std::enable_if<detail::span_compatible<T, E, const U,
N>::value, int>::type = 0>
constexpr span(const std::array<U, N>& a) noexcept
: s_(a.data(), N) { }
template<class R,
typename std::enable_if<E == dynamic_extent &&
detail::span_is_range<R, T>::value, int>::type = 0>
constexpr span(R&& r) noexcept(noexcept(boost::data(r)) &&
noexcept(r.size()))
: s_(boost::data(r), r.size()) { }
template<class R,
typename std::enable_if<E != dynamic_extent &&
detail::span_is_range<R, T>::value, int>::type = 0>
explicit constexpr span(R&& r) noexcept(noexcept(boost::data(r)) &&
noexcept(r.size()))
: s_(boost::data(r), r.size()) { }
template<class U, std::size_t N,
typename std::enable_if<detail::span_implicit<E, N>::value &&
detail::span_copyable<T, E, U, N>::value, int>::type = 0>
constexpr span(const span<U, N>& s) noexcept
: s_(s.data(), s.size()) { }
template<class U, std::size_t N,
typename std::enable_if<!detail::span_implicit<E, N>::value &&
detail::span_copyable<T, E, U, N>::value, int>::type = 0>
explicit constexpr span(const span<U, N>& s) noexcept
: s_(s.data(), s.size()) { }
template<std::size_t C>
constexpr span<T, C> first() const {
static_assert(C <= E, "Count <= Extent");
return span<T, C>(s_.p, C);
}
template<std::size_t C>
constexpr span<T, C> last() const {
static_assert(C <= E, "Count <= Extent");
return span<T, C>(s_.p + (s_.n - C), C);
}
template<std::size_t O, std::size_t C = dynamic_extent>
constexpr typename std::enable_if<C == dynamic_extent,
span<T, detail::span_sub<E, O>::value> >::type subspan() const {
static_assert(O <= E, "Offset <= Extent");
return span<T, detail::span_sub<E, O>::value>(s_.p + O, s_.n - O);
}
template<std::size_t O, std::size_t C = dynamic_extent>
constexpr typename std::enable_if<C != dynamic_extent,
span<T, C> >::type subspan() const {
static_assert(O <= E && C <= E - O,
"Offset <= Extent && Count <= Extent - Offset");
return span<T, C>(s_.p + O, C);
}
constexpr span<T, dynamic_extent> first(size_type c) const {
return BOOST_CORE_DETAIL_ASSERT(c <= size()),
span<T, dynamic_extent>(s_.p, c);
}
constexpr span<T, dynamic_extent> last(size_type c) const {
return BOOST_CORE_DETAIL_ASSERT(c <= size()),
span<T, dynamic_extent>(s_.p + (s_.n - c), c);
}
constexpr span<T, dynamic_extent> subspan(size_type o,
size_type c = dynamic_extent) const {
return BOOST_CORE_DETAIL_ASSERT(o <= size() &&
(c == dynamic_extent || c + o <= size())),
span<T, dynamic_extent>(s_.p + o,
c == dynamic_extent ? s_.n - o : c);
}
constexpr size_type size() const noexcept {
return s_.n;
}
constexpr size_type size_bytes() const noexcept {
return s_.n * sizeof(T);
}
constexpr bool empty() const noexcept {
return s_.n == 0;
}
constexpr reference operator[](size_type i) const {
return BOOST_CORE_DETAIL_ASSERT(i < size()), s_.p[i];
}
constexpr reference front() const {
return BOOST_CORE_DETAIL_ASSERT(!empty()), *s_.p;
}
constexpr reference back() const {
return BOOST_CORE_DETAIL_ASSERT(!empty()), s_.p[s_.n - 1];
}
constexpr pointer data() const noexcept {
return s_.p;
}
constexpr iterator begin() const noexcept {
return s_.p;
}
constexpr iterator end() const noexcept {
return s_.p + s_.n;
}
constexpr reverse_iterator rbegin() const noexcept {
return reverse_iterator(s_.p + s_.n);
}
constexpr reverse_iterator rend() const noexcept {
return reverse_iterator(s_.p);
}
constexpr const_iterator cbegin() const noexcept {
return s_.p;
}
constexpr const_iterator cend() const noexcept {
return s_.p + s_.n;
}
constexpr const_reverse_iterator crbegin() const noexcept {
return const_reverse_iterator(s_.p + s_.n);
}
constexpr const_reverse_iterator crend() const noexcept {
return const_reverse_iterator(s_.p);
}
private:
detail::span_store<T, E> s_;
};
#if defined(BOOST_NO_CXX17_INLINE_VARIABLES)
template<class T, std::size_t E>
constexpr std::size_t span<T, E>::extent;
#endif
#ifdef __cpp_deduction_guides
template<class I, class L>
span(I*, L) -> span<I>;
template<class T, std::size_t N>
span(T(&)[N]) -> span<T, N>;
template<class T, std::size_t N>
span(std::array<T, N>&) -> span<T, N>;
template<class T, std::size_t N>
span(const std::array<T, N>&) -> span<const T, N>;
template<class R>
span(R&&) -> span<typename detail::span_data<R>::type>;
template<class T, std::size_t E>
span(span<T, E>) -> span<T, E>;
#endif
#ifdef __cpp_lib_byte
template<class T, std::size_t E>
inline span<const std::byte, detail::span_bytes<T, E>::value>
as_bytes(span<T, E> s) noexcept
{
return span<const std::byte, detail::span_bytes<T,
E>::value>(reinterpret_cast<const std::byte*>(s.data()),
s.size_bytes());
}
template<class T, std::size_t E>
inline typename std::enable_if<!std::is_const<T>::value,
span<std::byte, detail::span_bytes<T, E>::value> >::type
as_writable_bytes(span<T, E> s) noexcept
{
return span<std::byte, detail::span_bytes<T,
E>::value>(reinterpret_cast<std::byte*>(s.data()), s.size_bytes());
}
#endif
}
#endif