commit 22e84cb07053853a9ead94350fcd856dd82f47e1
from: Aleksey Ryndin <continue@to.any-key.press>
date: Fri Aug 11 16:01:20 2023 UTC

Return to C++11, use span<> from https://github.com/tcbrindle/span

commit - 24c27acbf4be5ebfb6b64cd7697facc9219c500f
commit + 22e84cb07053853a9ead94350fcd856dd82f47e1
blob - d970243ef62291dfabea388e5760d215099c7676
blob + 313082479108a8f36277c1ba6d8cb506e91fe54f
--- shared/transport.cc
+++ shared/transport.cc
@@ -15,7 +15,7 @@ using config_t = std::unique_ptr<struct tls_config, de
 constexpr auto protocols = TLS_PROTOCOL_TLSv1_2 | TLS_PROTOCOL_TLSv1_3;
 
 
-std::span<char> read(not_null<struct tls *> ctx, std::span<char> buff)
+tcb::span<char> read(not_null<struct tls *> ctx, tcb::span<char> buff)
 {
     ssize_t ret{};
     for (; ; )
@@ -36,9 +36,9 @@ std::span<char> read(not_null<struct tls *> ctx, std::
                     error::g_log << "Error: " << last_error << std::endl;
             }
         );
-        return std::span<char>{};
+        return tcb::span<char>{};
     }
-    return std::span<char>{&buff[0], static_cast<size_t>(ret)};
+    return tcb::span<char>{&buff[0], static_cast<size_t>(ret)};
 }
 
 
@@ -142,11 +142,11 @@ void accept(
 }
 
 
-std::span<char> read_request(not_null<struct tls *> ctx, std::array<char, MAX_REQUEST_LENGTH> &buffer)
+tcb::span<char> read_request(not_null<struct tls *> ctx, std::array<char, MAX_REQUEST_LENGTH> &buffer)
 {
     const auto request = read(ctx, buffer);
     if (!request.size())
-        return std::span<char>{};
+        return tcb::span<char>{};
 
     for (auto current = request.begin(); current < request.end(); ++current)
     {
@@ -157,15 +157,15 @@ std::span<char> read_request(not_null<struct tls *> ct
         if (*current == CRLF[0] && *next == CRLF[1])
         {
             // > servers MUST ignore anything sent after the first occurrence of a <CR><LF>.
-            return std::span<char>{&request[0], static_cast<size_t>(current - request.begin())};
+            return tcb::span<char>{&request[0], static_cast<size_t>(current - request.begin())};
         }
     }
     error::occurred("Parse request", error::none{});
-    return std::span<char>{};
+    return tcb::span<char>{};
 }
 
 
-bool send_response(not_null<struct tls *> ctx, std::array<char, 2> status, std::span<const char> meta)
+bool send_response(not_null<struct tls *> ctx, std::array<char, 2> status, tcb::span<const char> meta)
 {
     // > <STATUS><SPACE><META><CR><LF>
     std::array<char, status.size() + SPACE.size() + MAX_META_LENGTH + CRLF.size()> buff;
@@ -176,11 +176,11 @@ bool send_response(not_null<struct tls *> ctx, std::ar
     current = std::copy(meta.begin(), meta.end(), current);
     current = std::copy(CRLF.cbegin(), CRLF.cend(), current);
 
-    return send(ctx, std::span<char const>{&buff[0], static_cast<size_t>(current - buff.begin())});
+    return send(ctx, tcb::span<char const>{&buff[0], static_cast<size_t>(current - buff.begin())});
 }
 
 
-bool send(not_null<struct tls *> ctx, std::span<const char> buff)
+bool send(not_null<struct tls *> ctx, tcb::span<const char> buff)
 {
     ssize_t ret{0};
     while (buff.size() > 0)
@@ -189,7 +189,7 @@ bool send(not_null<struct tls *> ctx, std::span<const 
         if (ret == TLS_WANT_POLLIN || ret == TLS_WANT_POLLOUT)
             continue;
         break;
-        buff = std::span<const char>{&buff[ret], buff.size() - ret};
+        buff = tcb::span<const char>{&buff[ret], buff.size() - ret};
     }
     if (ret == -1)
     {
blob - /dev/null
blob + fdc3a988a4c2ec5322deee7dc8fc3955f2ccb995 (mode 644)
--- /dev/null
+++ shared/span.hpp
@@ -0,0 +1,618 @@
+
+/*
+This is an implementation of C++20's std::span
+http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/n4820.pdf
+*/
+
+//          Copyright Tristan Brindle 2018.
+// Distributed under the Boost Software License, Version 1.0.
+//    (See accompanying file ../../LICENSE_1_0.txt or copy at
+//          https://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef TCB_SPAN_HPP_INCLUDED
+#define TCB_SPAN_HPP_INCLUDED
+
+#include <array>
+#include <cstddef>
+#include <cstdint>
+#include <type_traits>
+
+#ifndef TCB_SPAN_NO_EXCEPTIONS
+// Attempt to discover whether we're being compiled with exception support
+#if !(defined(__cpp_exceptions) || defined(__EXCEPTIONS) || defined(_CPPUNWIND))
+#define TCB_SPAN_NO_EXCEPTIONS
+#endif
+#endif
+
+#ifndef TCB_SPAN_NO_EXCEPTIONS
+#include <cstdio>
+#include <stdexcept>
+#endif
+
+// Various feature test macros
+
+#ifndef TCB_SPAN_NAMESPACE_NAME
+#define TCB_SPAN_NAMESPACE_NAME tcb
+#endif
+
+#if __cplusplus >= 201703L || (defined(_MSVC_LANG) && _MSVC_LANG >= 201703L)
+#define TCB_SPAN_HAVE_CPP17
+#endif
+
+#if __cplusplus >= 201402L || (defined(_MSVC_LANG) && _MSVC_LANG >= 201402L)
+#define TCB_SPAN_HAVE_CPP14
+#endif
+
+namespace TCB_SPAN_NAMESPACE_NAME {
+
+// Establish default contract checking behavior
+#if !defined(TCB_SPAN_THROW_ON_CONTRACT_VIOLATION) &&                          \
+    !defined(TCB_SPAN_TERMINATE_ON_CONTRACT_VIOLATION) &&                      \
+    !defined(TCB_SPAN_NO_CONTRACT_CHECKING)
+#if defined(NDEBUG) || !defined(TCB_SPAN_HAVE_CPP14)
+#define TCB_SPAN_NO_CONTRACT_CHECKING
+#else
+#define TCB_SPAN_TERMINATE_ON_CONTRACT_VIOLATION
+#endif
+#endif
+
+#if defined(TCB_SPAN_THROW_ON_CONTRACT_VIOLATION)
+struct contract_violation_error : std::logic_error {
+    explicit contract_violation_error(const char* msg) : std::logic_error(msg)
+    {}
+};
+
+inline void contract_violation(const char* msg)
+{
+    throw contract_violation_error(msg);
+}
+
+#elif defined(TCB_SPAN_TERMINATE_ON_CONTRACT_VIOLATION)
+[[noreturn]] inline void contract_violation(const char* /*unused*/)
+{
+    std::terminate();
+}
+#endif
+
+#if !defined(TCB_SPAN_NO_CONTRACT_CHECKING)
+#define TCB_SPAN_STRINGIFY(cond) #cond
+#define TCB_SPAN_EXPECT(cond)                                                  \
+    cond ? (void) 0 : contract_violation("Expected " TCB_SPAN_STRINGIFY(cond))
+#else
+#define TCB_SPAN_EXPECT(cond)
+#endif
+
+#if defined(TCB_SPAN_HAVE_CPP17) || defined(__cpp_inline_variables)
+#define TCB_SPAN_INLINE_VAR inline
+#else
+#define TCB_SPAN_INLINE_VAR
+#endif
+
+#if defined(TCB_SPAN_HAVE_CPP14) ||                                            \
+    (defined(__cpp_constexpr) && __cpp_constexpr >= 201304)
+#define TCB_SPAN_HAVE_CPP14_CONSTEXPR
+#endif
+
+#if defined(TCB_SPAN_HAVE_CPP14_CONSTEXPR)
+#define TCB_SPAN_CONSTEXPR14 constexpr
+#else
+#define TCB_SPAN_CONSTEXPR14
+#endif
+
+#if defined(TCB_SPAN_HAVE_CPP14_CONSTEXPR) &&                                  \
+    (!defined(_MSC_VER) || _MSC_VER > 1900)
+#define TCB_SPAN_CONSTEXPR_ASSIGN constexpr
+#else
+#define TCB_SPAN_CONSTEXPR_ASSIGN
+#endif
+
+#if defined(TCB_SPAN_NO_CONTRACT_CHECKING)
+#define TCB_SPAN_CONSTEXPR11 constexpr
+#else
+#define TCB_SPAN_CONSTEXPR11 TCB_SPAN_CONSTEXPR14
+#endif
+
+#if defined(TCB_SPAN_HAVE_CPP17) || defined(__cpp_deduction_guides)
+#define TCB_SPAN_HAVE_DEDUCTION_GUIDES
+#endif
+
+#if defined(TCB_SPAN_HAVE_CPP17) || defined(__cpp_lib_byte)
+#define TCB_SPAN_HAVE_STD_BYTE
+#endif
+
+#if defined(TCB_SPAN_HAVE_CPP17) || defined(__cpp_lib_array_constexpr)
+#define TCB_SPAN_HAVE_CONSTEXPR_STD_ARRAY_ETC
+#endif
+
+#if defined(TCB_SPAN_HAVE_CONSTEXPR_STD_ARRAY_ETC)
+#define TCB_SPAN_ARRAY_CONSTEXPR constexpr
+#else
+#define TCB_SPAN_ARRAY_CONSTEXPR
+#endif
+
+#ifdef TCB_SPAN_HAVE_STD_BYTE
+using byte = std::byte;
+#else
+using byte = unsigned char;
+#endif
+
+#if defined(TCB_SPAN_HAVE_CPP17)
+#define TCB_SPAN_NODISCARD [[nodiscard]]
+#else
+#define TCB_SPAN_NODISCARD
+#endif
+
+TCB_SPAN_INLINE_VAR constexpr std::size_t dynamic_extent = SIZE_MAX;
+
+template <typename ElementType, std::size_t Extent = dynamic_extent>
+class span;
+
+namespace detail {
+
+template <typename E, std::size_t S>
+struct span_storage {
+    constexpr span_storage() noexcept = default;
+
+    constexpr span_storage(E* p_ptr, std::size_t /*unused*/) noexcept
+       : ptr(p_ptr)
+    {}
+
+    E* ptr = nullptr;
+    static constexpr std::size_t size = S;
+};
+
+template <typename E>
+struct span_storage<E, dynamic_extent> {
+    constexpr span_storage() noexcept = default;
+
+    constexpr span_storage(E* p_ptr, std::size_t p_size) noexcept
+        : ptr(p_ptr), size(p_size)
+    {}
+
+    E* ptr = nullptr;
+    std::size_t size = 0;
+};
+
+// Reimplementation of C++17 std::size() and std::data()
+#if defined(TCB_SPAN_HAVE_CPP17) ||                                            \
+    defined(__cpp_lib_nonmember_container_access)
+using std::data;
+using std::size;
+#else
+template <class C>
+constexpr auto size(const C& c) -> decltype(c.size())
+{
+    return c.size();
+}
+
+template <class T, std::size_t N>
+constexpr std::size_t size(const T (&)[N]) noexcept
+{
+    return N;
+}
+
+template <class C>
+constexpr auto data(C& c) -> decltype(c.data())
+{
+    return c.data();
+}
+
+template <class C>
+constexpr auto data(const C& c) -> decltype(c.data())
+{
+    return c.data();
+}
+
+template <class T, std::size_t N>
+constexpr T* data(T (&array)[N]) noexcept
+{
+    return array;
+}
+
+template <class E>
+constexpr const E* data(std::initializer_list<E> il) noexcept
+{
+    return il.begin();
+}
+#endif // TCB_SPAN_HAVE_CPP17
+
+#if defined(TCB_SPAN_HAVE_CPP17) || defined(__cpp_lib_void_t)
+using std::void_t;
+#else
+template <typename...>
+using void_t = void;
+#endif
+
+template <typename T>
+using uncvref_t =
+    typename std::remove_cv<typename std::remove_reference<T>::type>::type;
+
+template <typename>
+struct is_span : std::false_type {};
+
+template <typename T, std::size_t S>
+struct is_span<span<T, S>> : std::true_type {};
+
+template <typename>
+struct is_std_array : std::false_type {};
+
+template <typename T, std::size_t N>
+struct is_std_array<std::array<T, N>> : std::true_type {};
+
+template <typename, typename = void>
+struct has_size_and_data : std::false_type {};
+
+template <typename T>
+struct has_size_and_data<T, void_t<decltype(detail::size(std::declval<T>())),
+                                   decltype(detail::data(std::declval<T>()))>>
+    : std::true_type {};
+
+template <typename C, typename U = uncvref_t<C>>
+struct is_container {
+    static constexpr bool value =
+        !is_span<U>::value && !is_std_array<U>::value &&
+        !std::is_array<U>::value && has_size_and_data<C>::value;
+};
+
+template <typename T>
+using remove_pointer_t = typename std::remove_pointer<T>::type;
+
+template <typename, typename, typename = void>
+struct is_container_element_type_compatible : std::false_type {};
+
+template <typename T, typename E>
+struct is_container_element_type_compatible<
+    T, E,
+    typename std::enable_if<
+        !std::is_same<
+            typename std::remove_cv<decltype(detail::data(std::declval<T>()))>::type,
+            void>::value &&
+        std::is_convertible<
+            remove_pointer_t<decltype(detail::data(std::declval<T>()))> (*)[],
+            E (*)[]>::value
+        >::type>
+    : std::true_type {};
+
+template <typename, typename = size_t>
+struct is_complete : std::false_type {};
+
+template <typename T>
+struct is_complete<T, decltype(sizeof(T))> : std::true_type {};
+
+} // namespace detail
+
+template <typename ElementType, std::size_t Extent>
+class span {
+    static_assert(std::is_object<ElementType>::value,
+                  "A span's ElementType must be an object type (not a "
+                  "reference type or void)");
+    static_assert(detail::is_complete<ElementType>::value,
+                  "A span's ElementType must be a complete type (not a forward "
+                  "declaration)");
+    static_assert(!std::is_abstract<ElementType>::value,
+                  "A span's ElementType cannot be an abstract class type");
+
+    using storage_type = detail::span_storage<ElementType, Extent>;
+
+public:
+    // constants and types
+    using element_type = ElementType;
+    using value_type = typename std::remove_cv<ElementType>::type;
+    using size_type = std::size_t;
+    using difference_type = std::ptrdiff_t;
+    using pointer = element_type*;
+    using const_pointer = const element_type*;
+    using reference = element_type&;
+    using const_reference = const element_type&;
+    using iterator = pointer;
+    using reverse_iterator = std::reverse_iterator<iterator>;
+
+    static constexpr size_type extent = Extent;
+
+    // [span.cons], span constructors, copy, assignment, and destructor
+    template <
+        std::size_t E = Extent,
+        typename std::enable_if<(E == dynamic_extent || E <= 0), int>::type = 0>
+    constexpr span() noexcept
+    {}
+
+    TCB_SPAN_CONSTEXPR11 span(pointer ptr, size_type count)
+        : storage_(ptr, count)
+    {
+        TCB_SPAN_EXPECT(extent == dynamic_extent || count == extent);
+    }
+
+    TCB_SPAN_CONSTEXPR11 span(pointer first_elem, pointer last_elem)
+        : storage_(first_elem, last_elem - first_elem)
+    {
+        TCB_SPAN_EXPECT(extent == dynamic_extent ||
+                        last_elem - first_elem ==
+                            static_cast<std::ptrdiff_t>(extent));
+    }
+
+    template <std::size_t N, std::size_t E = Extent,
+              typename std::enable_if<
+                  (E == dynamic_extent || N == E) &&
+                      detail::is_container_element_type_compatible<
+                          element_type (&)[N], ElementType>::value,
+                  int>::type = 0>
+    constexpr span(element_type (&arr)[N]) noexcept : storage_(arr, N)
+    {}
+
+    template <typename T, std::size_t N, std::size_t E = Extent,
+              typename std::enable_if<
+                  (E == dynamic_extent || N == E) &&
+                      detail::is_container_element_type_compatible<
+                          std::array<T, N>&, ElementType>::value,
+                  int>::type = 0>
+    TCB_SPAN_ARRAY_CONSTEXPR span(std::array<T, N>& arr) noexcept
+        : storage_(arr.data(), N)
+    {}
+
+    template <typename T, std::size_t N, std::size_t E = Extent,
+              typename std::enable_if<
+                  (E == dynamic_extent || N == E) &&
+                      detail::is_container_element_type_compatible<
+                          const std::array<T, N>&, ElementType>::value,
+                  int>::type = 0>
+    TCB_SPAN_ARRAY_CONSTEXPR span(const std::array<T, N>& arr) noexcept
+        : storage_(arr.data(), N)
+    {}
+
+    template <
+        typename Container, std::size_t E = Extent,
+        typename std::enable_if<
+            E == dynamic_extent && detail::is_container<Container>::value &&
+                detail::is_container_element_type_compatible<
+                    Container&, ElementType>::value,
+            int>::type = 0>
+    constexpr span(Container& cont)
+        : storage_(detail::data(cont), detail::size(cont))
+    {}
+
+    template <
+        typename Container, std::size_t E = Extent,
+        typename std::enable_if<
+            E == dynamic_extent && detail::is_container<Container>::value &&
+                detail::is_container_element_type_compatible<
+                    const Container&, ElementType>::value,
+            int>::type = 0>
+    constexpr span(const Container& cont)
+        : storage_(detail::data(cont), detail::size(cont))
+    {}
+
+    constexpr span(const span& other) noexcept = default;
+
+    template <typename OtherElementType, std::size_t OtherExtent,
+              typename std::enable_if<
+                  (Extent == dynamic_extent || OtherExtent == dynamic_extent ||
+                   Extent == OtherExtent) &&
+                      std::is_convertible<OtherElementType (*)[],
+                                          ElementType (*)[]>::value,
+                  int>::type = 0>
+    constexpr span(const span<OtherElementType, OtherExtent>& other) noexcept
+        : storage_(other.data(), other.size())
+    {}
+
+    ~span() noexcept = default;
+
+    TCB_SPAN_CONSTEXPR_ASSIGN span&
+    operator=(const span& other) noexcept = default;
+
+    // [span.sub], span subviews
+    template <std::size_t Count>
+    TCB_SPAN_CONSTEXPR11 span<element_type, Count> first() const
+    {
+        TCB_SPAN_EXPECT(Count <= size());
+        return {data(), Count};
+    }
+
+    template <std::size_t Count>
+    TCB_SPAN_CONSTEXPR11 span<element_type, Count> last() const
+    {
+        TCB_SPAN_EXPECT(Count <= size());
+        return {data() + (size() - Count), Count};
+    }
+
+    template <std::size_t Offset, std::size_t Count = dynamic_extent>
+    using subspan_return_t =
+        span<ElementType, Count != dynamic_extent
+                              ? Count
+                              : (Extent != dynamic_extent ? Extent - Offset
+                                                          : dynamic_extent)>;
+
+    template <std::size_t Offset, std::size_t Count = dynamic_extent>
+    TCB_SPAN_CONSTEXPR11 subspan_return_t<Offset, Count> subspan() const
+    {
+        TCB_SPAN_EXPECT(Offset <= size() &&
+                        (Count == dynamic_extent || Offset + Count <= size()));
+        return {data() + Offset,
+                Count != dynamic_extent ? Count : size() - Offset};
+    }
+
+    TCB_SPAN_CONSTEXPR11 span<element_type, dynamic_extent>
+    first(size_type count) const
+    {
+        TCB_SPAN_EXPECT(count <= size());
+        return {data(), count};
+    }
+
+    TCB_SPAN_CONSTEXPR11 span<element_type, dynamic_extent>
+    last(size_type count) const
+    {
+        TCB_SPAN_EXPECT(count <= size());
+        return {data() + (size() - count), count};
+    }
+
+    TCB_SPAN_CONSTEXPR11 span<element_type, dynamic_extent>
+    subspan(size_type offset, size_type count = dynamic_extent) const
+    {
+        TCB_SPAN_EXPECT(offset <= size() &&
+                        (count == dynamic_extent || offset + count <= size()));
+        return {data() + offset,
+                count == dynamic_extent ? size() - offset : count};
+    }
+
+    // [span.obs], span observers
+    constexpr size_type size() const noexcept { return storage_.size; }
+
+    constexpr size_type size_bytes() const noexcept
+    {
+        return size() * sizeof(element_type);
+    }
+
+    TCB_SPAN_NODISCARD constexpr bool empty() const noexcept
+    {
+        return size() == 0;
+    }
+
+    // [span.elem], span element access
+    TCB_SPAN_CONSTEXPR11 reference operator[](size_type idx) const
+    {
+        TCB_SPAN_EXPECT(idx < size());
+        return *(data() + idx);
+    }
+
+    TCB_SPAN_CONSTEXPR11 reference front() const
+    {
+        TCB_SPAN_EXPECT(!empty());
+        return *data();
+    }
+
+    TCB_SPAN_CONSTEXPR11 reference back() const
+    {
+        TCB_SPAN_EXPECT(!empty());
+        return *(data() + (size() - 1));
+    }
+
+    constexpr pointer data() const noexcept { return storage_.ptr; }
+
+    // [span.iterators], span iterator support
+    constexpr iterator begin() const noexcept { return data(); }
+
+    constexpr iterator end() const noexcept { return data() + size(); }
+
+    TCB_SPAN_ARRAY_CONSTEXPR reverse_iterator rbegin() const noexcept
+    {
+        return reverse_iterator(end());
+    }
+
+    TCB_SPAN_ARRAY_CONSTEXPR reverse_iterator rend() const noexcept
+    {
+        return reverse_iterator(begin());
+    }
+
+private:
+    storage_type storage_{};
+};
+
+#ifdef TCB_SPAN_HAVE_DEDUCTION_GUIDES
+
+/* Deduction Guides */
+template <class T, size_t N>
+span(T (&)[N])->span<T, N>;
+
+template <class T, size_t N>
+span(std::array<T, N>&)->span<T, N>;
+
+template <class T, size_t N>
+span(const std::array<T, N>&)->span<const T, N>;
+
+template <class Container>
+span(Container&)->span<typename std::remove_reference<
+    decltype(*detail::data(std::declval<Container&>()))>::type>;
+
+template <class Container>
+span(const Container&)->span<const typename Container::value_type>;
+
+#endif // TCB_HAVE_DEDUCTION_GUIDES
+
+template <typename ElementType, std::size_t Extent>
+constexpr span<ElementType, Extent>
+make_span(span<ElementType, Extent> s) noexcept
+{
+    return s;
+}
+
+template <typename T, std::size_t N>
+constexpr span<T, N> make_span(T (&arr)[N]) noexcept
+{
+    return {arr};
+}
+
+template <typename T, std::size_t N>
+TCB_SPAN_ARRAY_CONSTEXPR span<T, N> make_span(std::array<T, N>& arr) noexcept
+{
+    return {arr};
+}
+
+template <typename T, std::size_t N>
+TCB_SPAN_ARRAY_CONSTEXPR span<const T, N>
+make_span(const std::array<T, N>& arr) noexcept
+{
+    return {arr};
+}
+
+template <typename Container>
+constexpr span<typename std::remove_reference<
+    decltype(*detail::data(std::declval<Container&>()))>::type>
+make_span(Container& cont)
+{
+    return {cont};
+}
+
+template <typename Container>
+constexpr span<const typename Container::value_type>
+make_span(const Container& cont)
+{
+    return {cont};
+}
+
+template <typename ElementType, std::size_t Extent>
+span<const byte, ((Extent == dynamic_extent) ? dynamic_extent
+                                             : sizeof(ElementType) * Extent)>
+as_bytes(span<ElementType, Extent> s) noexcept
+{
+    return {reinterpret_cast<const byte*>(s.data()), s.size_bytes()};
+}
+
+template <
+    class ElementType, size_t Extent,
+    typename std::enable_if<!std::is_const<ElementType>::value, int>::type = 0>
+span<byte, ((Extent == dynamic_extent) ? dynamic_extent
+                                       : sizeof(ElementType) * Extent)>
+as_writable_bytes(span<ElementType, Extent> s) noexcept
+{
+    return {reinterpret_cast<byte*>(s.data()), s.size_bytes()};
+}
+
+template <std::size_t N, typename E, std::size_t S>
+constexpr auto get(span<E, S> s) -> decltype(s[N])
+{
+    return s[N];
+}
+
+} // namespace TCB_SPAN_NAMESPACE_NAME
+
+namespace std {
+
+template <typename ElementType, size_t Extent>
+class tuple_size<TCB_SPAN_NAMESPACE_NAME::span<ElementType, Extent>>
+    : public integral_constant<size_t, Extent> {};
+
+template <typename ElementType>
+class tuple_size<TCB_SPAN_NAMESPACE_NAME::span<
+    ElementType, TCB_SPAN_NAMESPACE_NAME::dynamic_extent>>; // not defined
+
+template <size_t I, typename ElementType, size_t Extent>
+class tuple_element<I, TCB_SPAN_NAMESPACE_NAME::span<ElementType, Extent>> {
+public:
+    static_assert(Extent != TCB_SPAN_NAMESPACE_NAME::dynamic_extent &&
+                      I < Extent,
+                  "");
+    using type = ElementType;
+};
+
+} // end namespace std
+
+#endif // TCB_SPAN_HPP_INCLUDED
blob - 73cdc0d8a6131b9393b5dcd70420546bffd0f6a3
blob + b7518fc07c0e247aef385cbc777f032258efc06c
--- shared/transport.h
+++ shared/transport.h
@@ -6,7 +6,7 @@
 #include <unique_fd>
 
 #include <array>
-#include <span>
+#include <span.hpp>
 
 #include <tls.h>
 
@@ -39,8 +39,9 @@ class accepted_context : non_copiable
 public:
     struct value
     {
-        int m_fd{-1};
-        struct tls *m_ctx{nullptr};
+        int m_fd;
+        struct tls *m_ctx;
+        value(int fd = -1, struct tls *ctx = nullptr) : m_fd{fd}, m_ctx{ctx} {}
     };
 
     accepted_context(int fd = -1, struct tls *ctx = nullptr) { reset(value{fd, ctx}); }
@@ -82,15 +83,15 @@ void accept(
 
 
 /** Read genimi request and return url (empty url - error) */
-std::span<char> read_request(not_null<struct tls *> ctx, std::array<char, MAX_REQUEST_LENGTH> &buffer);
+tcb::span<char> read_request(not_null<struct tls *> ctx, std::array<char, MAX_REQUEST_LENGTH> &buffer);
 
 
 /** Write gemini response */
-bool send_response(not_null<struct tls *> ctx, std::array<char, 2> status, std::span<const char> meta);
+bool send_response(not_null<struct tls *> ctx, std::array<char, 2> status, tcb::span<const char> meta);
 
 
 /** Send raw bytes */
-bool send(not_null<struct tls *> ctx, std::span<const char> buff);
+bool send(not_null<struct tls *> ctx, tcb::span<const char> buff);
 
 
 }   // namespace transport
blob - 50d12fd6adfe4e61ca5b62655d187117f60b628d
blob + ec616dd3564f0010d8c801009f3d6de7524b98cb
--- vostokd/Makefile
+++ vostokd/Makefile
@@ -1,4 +1,4 @@
-CXXFLAGS	= -Wall -Wextra -std=c++20
+CXXFLAGS	= -Wall -Wextra -std=c++11
 CXXFLAGS	+= -I${.CURDIR}/../shared
 CXXFLAGS	+= -ltls
 
@@ -8,6 +8,7 @@ HXXFILES        += ${.PATH}../shared/zstring
 HXXFILES        += ${.PATH}../shared/unique_fd
 HXXFILES        += ${.PATH}../shared/non_copiable
 HXXFILES        += ${.PATH}../shared/unique_fd
+HXXFILES        += ${.PATH}../shared/span.hpp
 CXXFILES	+= ${.PATH}../shared/transport.cc
 HXXFILES	+= ${.PATH}../shared/transport.h
 CXXFILES	+= ${.PATH}../shared/error.cc
blob - 05c0100fbe7c3827ea489de80b145de1e22516ff
blob + 0030360c072f273bef80ef452d9b0f9985ae2d5c
--- vostokd/vostokd.cc
+++ vostokd/vostokd.cc
@@ -21,10 +21,9 @@ namespace
 
 /** Remove null terminating character and return as span */
 template <std::size_t N>
-constexpr std::span<const char> cut_null(const char (&arr)[N])
+constexpr tcb::span<const char> cut_null(const char (&arr)[N])
 {
-    static_assert(N > 0);
-    return std::span<const char>{&arr[0], N - 1};
+    return tcb::span<const char>{&arr[0], N - 1};
 }
 
 
@@ -125,7 +124,7 @@ void client_thread(transport::accepted_context::value 
     }
 
     // > If <META> is an empty string, the MIME type MUST default to "text/gemini; charset=utf-8".
-    transport::send_response(ctx.get_ctx(), transport::STATUS_20_SUCCESS, std::span<const char>{});
+    transport::send_response(ctx.get_ctx(), transport::STATUS_20_SUCCESS, tcb::span<const char>{});
     static const char content[] = "# Vostok server\r\n\r\n...work-in-progress...";
     transport::send(ctx.get_ctx(), cut_null(content));
 }