fix string_literal

include/ylt/struct_pack/md5_constexpr.hpp

@@ -25,43 +25,27 @@
 
 namespace struct_pack {
 template <typename CharType, std::size_t Size>
-struct string_literal : public std::array<CharType, Size + 1> {
-  using base = std::array<CharType, Size + 1>;
-  using value_type = typename base::value_type;
-  using pointer = typename base::pointer;
-  using const_pointer = typename base::const_pointer;
-  using iterator = typename base::iterator;
-  using const_iterator = typename base::const_iterator;
-  using reference = typename base::const_pointer;
-  using const_reference = typename base::const_pointer;
-
+struct string_literal {
   constexpr string_literal() = default;
-  constexpr string_literal(const CharType (&value)[Size + 1]) {
-    // don't use std::copy_n here to support low version stdlibc++
-    for (size_t i = 0; i < Size + 1; ++i) {
-      (*this)[i] = value[i];
+
+  constexpr string_literal(const CharType (&value)[Size + 1]) : ar{} {
+    for (size_t i = 0; i <= Size; ++i) {
+      ar[i] = value[i];
     }
   }
 
   constexpr std::size_t size() const { return Size; }
 
   constexpr bool empty() const { return !Size; }
 
-  using base::begin;
-
-  constexpr auto end() { return base::end() - 1; }
+  constexpr char &operator[](std::size_t sz) { return ar[sz]; }
 
-  constexpr auto end() const { return base::end() - 1; }
+  constexpr const char &operator[](std::size_t sz) const { return ar[sz]; }
 
-  using base::data;
-  using base::operator[];
-  using base::at;
+  constexpr const char *data() const { return &ar[0]; }
 
  private:
-  using base::cbegin;
-  using base::cend;
-  using base::rbegin;
-  using base::rend;
+  CharType ar[Size + 1];
 };
 
 template <typename Char, std::size_t Size1, std::size_t Size2>
@@ -93,7 +77,6 @@ template <typename CharType, size_t Len1, size_t Len2>
 decltype(auto) constexpr operator+(string_literal<CharType, Len1> str1,
                                    string_literal<CharType, Len2> str2) {
   string_literal<CharType, Len1 + Len2> ret{};
-  // don't use std::copy_n here to support low version stdlibc++
   for (size_t i = 0; i < Len1; ++i) {
     ret[i] = str1[i];
   }