Включение простейшего span из boost

src/myx/base/span.hpp

@@ -0,0 +1,215 @@
+//
+// Copyright (c) 2016-2019 Vinnie Falco (vinnie dot falco at gmail dot com)
+//
+// 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)
+//
+// Official repository: https://github.com/boostorg/beast
+//
+
+#ifndef BOOST_BEAST_CORE_SPAN_HPP
+#define BOOST_BEAST_CORE_SPAN_HPP
+
+#include <boost/beast/core/detail/config.hpp>
+#include <boost/beast/core/detail/type_traits.hpp>
+#include <algorithm>
+#include <iterator>
+#include <string>
+#include <type_traits>
+
+namespace boost {
+namespace beast {
+
+/** A range of bytes expressed as a ContiguousContainer
+
+    This class implements a non-owning reference to a storage
+    area of a certain size and having an underlying integral
+    type with size of 1.
+
+    @tparam T The type pointed to by span iterators
+*/
+template<class T>
+class span
+{
+    T* data_ = nullptr;
+    std::size_t size_ = 0;
+
+public:
+    /// The type of value, including cv qualifiers
+    using element_type = T;
+
+    /// The type of value of each span element
+    using value_type = typename std::remove_const<T>::type;
+
+    /// The type of integer used to index the span
+    using index_type = std::ptrdiff_t;
+
+    /// A pointer to a span element
+    using pointer = T*;
+
+    /// A reference to a span element
+    using reference = T&;
+
+    /// The iterator used by the container
+    using iterator = pointer;
+
+    /// The const pointer used by the container
+    using const_pointer = T const*;
+
+    /// The const reference used by the container
+    using const_reference = T const&;
+
+    /// The const iterator used by the container
+    using const_iterator = const_pointer;
+
+    /// Constructor
+    span() = default;
+
+    /// Constructor
+    span(span const&) = default;
+
+    /// Assignment
+    span& operator=(span const&) = default;
+
+    /** Constructor
+
+        @param data A pointer to the beginning of the range of elements
+
+        @param size The number of elements pointed to by `data`
+    */
+    span(T* data, std::size_t size)
+        : data_(data), size_(size)
+    {
+    }
+
+    /** Constructor
+
+        @param container The container to construct from
+    */
+    template<class ContiguousContainer
+#if ! BOOST_BEAST_DOXYGEN
+        , class = typename std::enable_if<
+          detail::is_contiguous_container<
+                ContiguousContainer, T>::value>::type
+#endif
+    >
+    explicit
+    span(ContiguousContainer&& container)
+        : data_(container.data())
+        , size_(container.size())
+    {
+    }
+
+#if ! BOOST_BEAST_DOXYGEN
+    template<class CharT, class Traits, class Allocator>
+    explicit
+    span(std::basic_string<CharT, Traits, Allocator>& s)
+        : data_(&s[0])
+        , size_(s.size())
+    {
+    }
+
+    template<class CharT, class Traits, class Allocator>
+    explicit
+    span(std::basic_string<CharT, Traits, Allocator> const& s)
+        : data_(s.data())
+        , size_(s.size())
+    {
+    }
+#endif
+
+    /** Assignment
+
+        @param container The container to assign from
+    */
+    template<class ContiguousContainer>
+#if BOOST_BEAST_DOXYGEN
+    span&
+#else
+    typename std::enable_if<detail::is_contiguous_container<
+        ContiguousContainer, T>::value,
+    span&>::type
+#endif
+    operator=(ContiguousContainer&& container)
+    {
+        data_ = container.data();
+        size_ = container.size();
+        return *this;
+    }
+
+#if ! BOOST_BEAST_DOXYGEN
+    template<class CharT, class Traits, class Allocator>
+    span&
+    operator=(std::basic_string<
+        CharT, Traits, Allocator>& s)
+    {
+        data_ = &s[0];
+        size_ = s.size();
+        return *this;
+    }
+
+    template<class CharT, class Traits, class Allocator>
+    span&
+    operator=(std::basic_string<
+        CharT, Traits, Allocator> const& s)
+    {
+        data_ = s.data();
+        size_ = s.size();
+        return *this;
+    }
+#endif
+
+    /// Returns `true` if the span is empty
+    bool
+    empty() const
+    {
+        return size_ == 0;
+    }
+
+    /// Returns a pointer to the beginning of the span
+    T*
+    data() const
+    {
+        return data_;
+    }
+
+    /// Returns the number of elements in the span
+    std::size_t
+    size() const
+    {
+        return size_;
+    }
+
+    /// Returns an iterator to the beginning of the span
+    const_iterator
+    begin() const
+    {
+        return data_;
+    }
+
+    /// Returns an iterator to the beginning of the span
+    const_iterator
+    cbegin() const
+    {
+        return data_;
+    }
+
+    /// Returns an iterator to one past the end of the span
+    const_iterator
+    end() const
+    {
+        return data_ + size_;
+    }
+
+    /// Returns an iterator to one past the end of the span
+    const_iterator
+    cend() const
+    {
+        return data_ + size_;
+    }
+};
+
+} // beast
+} // boost
+
+#endif