10#include <userver/utils/assert.hpp>
12USERVER_NAMESPACE_BEGIN
19struct TypeIdentityImpl final {
24using TypeIdentity =
typename TypeIdentityImpl<T>::type;
33 using value_type = std::remove_cv_t<T>;
35 constexpr span()
noexcept : span(
nullptr,
nullptr) {}
37 constexpr span(T* begin, T* end)
noexcept : begin_(begin), end_(end) {
38 UASSERT((begin !=
nullptr && end !=
nullptr && begin <= end) || (begin ==
nullptr && end ==
nullptr));
41 constexpr span(T* begin, std::size_t size)
noexcept : begin_(begin), end_(begin + size) {
42 UASSERT(begin !=
nullptr || size == 0);
45#if defined(__GNUC__) && !defined(__clang__)
47#pragma GCC diagnostic push
48#pragma GCC diagnostic ignored "-Winit-list-lifetime"
51 template <
typename Void =
void,
typename = std::enable_if_t<std::is_const_v<T> && std::is_void_v<Void>>>
52 constexpr span(std::initializer_list<value_type> il) : begin_(il.begin()), end_(il.end()) {}
53#if defined(__GNUC__) && !defined(__clang__)
55#pragma GCC diagnostic pop
61 typename = std::enable_if_t<
63 (std::is_lvalue_reference_v<Container> || std::is_const_v<T>)&&
65 !std::is_same_v<std::remove_cv_t<std::remove_reference_t<Container>>, span> &&
67 std::is_convertible_v<
decltype(std::data(std::declval<Container&>())), T*>>>
69 constexpr span(Container&& cont)
noexcept : span(std::data(cont), std::size(cont)) {}
71 template <std::size_t Size>
72 constexpr span(impl::TypeIdentity<T> (&array)[Size])
noexcept
73 : span(std::data(array), std::size(array)) {}
75 constexpr T* begin()
const noexcept {
return begin_; }
76 constexpr T* end()
const noexcept {
return end_; }
78 constexpr T* data()
const noexcept {
return begin_; }
79 constexpr std::size_t size()
const noexcept {
return end_ - begin_; }
80 constexpr bool empty()
const noexcept {
return size() == 0; }
82 constexpr span<T> first(std::size_t count)
const noexcept {
83 UASSERT(count <= size());
84 return span{begin_, begin_ + count};
87 constexpr span<T> last(std::size_t count)
const noexcept {
88 UASSERT(count <= size());
89 return span{end_ - count, end_};
92 constexpr span<T> subspan(std::size_t offset)
const noexcept {
93 UASSERT(offset <= size());
94 return span{begin_ + offset, end_};
97 constexpr span<T> subspan(
101 UASSERT(offset + count <= size());
102 return span{begin_ + offset, begin_ + offset + count};
105 constexpr T& operator[](std::size_t index)
const noexcept {
106 UASSERT(index < size());
107 return begin_[index];
115template <
typename Container>
116span(Container&& cont) -> span<std::remove_reference_t<
decltype(*std::begin(cont))>>;
120span<
const std::byte>
as_bytes(span<T> s)
noexcept {
121 const auto*
const data =
reinterpret_cast<
const std::byte*>(s.data());
122 return {data, data + s.size() *
sizeof(T)};
126template <
typename T,
typename = std::enable_if_t<!std::is_const_v<T>>>
128 auto*
const data =
reinterpret_cast<std::byte*>(s.data());
129 return {data, data + s.size() *
sizeof(T)};
142template <
typename T,
typename Enabler>
143struct range_const_iterator;
146struct range_const_iterator<USERVER_NAMESPACE::utils::span<T>,
void> {
147 using type =
typename USERVER_NAMESPACE::utils::span<T>::iterator;