st_::span fixes

move span.h to a proper place to make it available for the whole server

Reformat it.

Constuctors from a contigous container are fixed
to use cont.data() instead of cont.begin()

span<>::index_type is replaced with span<>::size_type

1 files changed, 141 insertions, 0 deletions

diff --git a/include/span.h b/include/span.h
new file mode 100644
index 00000000000..0ed0158088c
--- /dev/null
+++ b/include/span.h
@@ -0,0 +1,141 @@
+/*****************************************************************************
+
+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_
+{
+
+template <class ElementType> class span
+{
+public:
+  typedef ElementType element_type;
+  typedef ElementType 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;
+  typedef std::reverse_iterator<const_iterator> const_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(){};
+
+  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
+  {
+    assert(!empty());
+    return data_;
+  }
+
+  iterator begin() const { return data_; }
+  iterator end() const { return data_ + size_; }
+  reverse_iterator rbegin() const
+  {
+    return std::reverse_iterator<iterator>(std::advance(end(), -1));
+  }
+  reverse_iterator rend() const
+  {
+    return std::reverse_iterator<iterator>(std::advance(begin(), -1));
+  }
+
+private:
+  pointer data_;
+  size_type size_;
+};
+
+} // namespace st_