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+/*****************************************************************************
+
+Copyright (c) 2019, 2020 MariaDB Corporation.
+
+This program is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation; version 2 of the License.
+
+This program is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with
+this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA
+
+*****************************************************************************/
+
+#pragma once
+
+#include <cstddef>
+#include <iterator>
+
+namespace st_
+{
+
+namespace detail
+{
+
+template <class T> struct remove_cv
+{
+ typedef T type;
+};
+template <class T> struct remove_cv<const T>
+{
+ typedef T type;
+};
+template <class T> struct remove_cv<volatile T>
+{
+ typedef T type;
+};
+template <class T> struct remove_cv<const volatile T>
+{
+ typedef T type;
+};
+
+} // namespace detail
+
+template <class ElementType> class span
+{
+public:
+ typedef ElementType element_type;
+ typedef typename detail::remove_cv<ElementType>::type value_type;
+ typedef size_t size_type;
+ typedef ptrdiff_t difference_type;
+ typedef element_type *pointer;
+ typedef const element_type *const_pointer;
+ typedef element_type &reference;
+ typedef const element_type &const_reference;
+ typedef pointer iterator;
+ typedef const_pointer const_iterator;
+ typedef std::reverse_iterator<iterator> reverse_iterator;
+
+ span() : data_(NULL), size_(0) {}
+
+ span(pointer ptr, size_type count) : data_(ptr), size_(count) {}
+
+ span(pointer first, pointer last) : data_(first), size_(last - first) {}
+
+ template <size_t N> span(element_type (&arr)[N]) : data_(arr), size_(N) {}
+
+ template <class Container>
+ span(Container &cont) : data_(cont.data()), size_(cont.size())
+ {
+ }
+
+ template <class Container>
+ span(const Container &cont) : data_(cont.data()), size_(cont.size())
+ {
+ }
+
+ span(const span &other) : data_(other.data_), size_(other.size_) {}
+
+ ~span() = default;
+
+ span &operator=(const span &other)
+ {
+ data_= other.data();
+ size_= other.size();
+ return *this;
+ }
+
+ template <size_t Count> span<element_type> first() const
+ {
+ assert(!empty());
+ return span(data(), 1);
+ }
+ template <size_t Count> span<element_type> last() const
+ {
+ assert(!empty());
+ return span(data() + size() - 1, 1);
+ }
+
+ span<element_type> first(size_type count) const
+ {
+ assert(!empty());
+ return span(data(), 1);
+ }
+ span<element_type> last(size_type count) const
+ {
+ assert(!empty());
+ return span(data() + size() - 1, 1);
+ }
+ span<element_type> subspan(size_type offset, size_type count) const
+ {
+ assert(!empty());
+ assert(size() >= offset + count);
+ return span(data() + offset, count);
+ }
+
+ size_type size() const { return size_; }
+ size_type size_bytes() const { return size() * sizeof(ElementType); }
+ bool empty() const __attribute__((warn_unused_result))
+ {
+ return size() == 0;
+ }
+
+ reference operator[](size_type idx) const
+ {
+ assert(size() > idx);
+ return data()[idx];
+ }
+ reference front() const
+ {
+ assert(!empty());
+ return data()[0];
+ }
+ reference back() const
+ {
+ assert(!empty());
+ return data()[size() - 1];
+ }
+ pointer data() const { return data_; }
+
+ iterator begin() const { return data_; }
+ iterator end() const { return data_ + size_; }
+ reverse_iterator rbegin() const
+ {
+ return std::reverse_iterator<iterator>(end());
+ }
+ reverse_iterator rend() const
+ {
+ return std::reverse_iterator<iterator>(begin());
+ }
+
+private:
+ pointer data_;
+ size_type size_;
+};
+
+} // namespace st_