cmstd: Modernize CMake system headers

Provide a standardized way to handle the C++ "standard" headers
customized to be used with current CMake C++ standard constraints.
Offer under directory `cm` headers which can be used as direct
replacements of the standard ones.  For example:

    #include <cm/string_view>

can be used safely for CMake development in place of the `<string_view>`
standard header.

Fixes: #19491

1 files changed, 0 insertions, 217 deletions

diff --git a/Source/cm_string_view.hxx b/Source/cm_string_view.hxx
deleted file mode 100644
index 04de797..0000000
--- a/Source/cm_string_view.hxx
+++ /dev/null
@@ -1,217 +0,0 @@
-/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
-   file Copyright.txt or https://cmake.org/licensing for details.  */
-#ifndef cm_string_view_hxx
-#define cm_string_view_hxx
-
-#include "cmConfigure.h" // IWYU pragma: keep
-
-#if __cplusplus >= 201703L || defined(_MSVC_LANG) && _MSVC_LANG >= 201703L
-#  define CMake_HAVE_CXX_STRING_VIEW
-#endif
-
-#ifdef CMake_HAVE_CXX_STRING_VIEW
-#  include <string_view>
-namespace cm {
-using std::string_view;
-}
-#else
-#  include <cstddef>
-#  include <functional>
-#  include <iosfwd>
-#  include <iterator>
-#  include <string>
-
-namespace cm {
-
-class string_view
-{
-public:
-  using traits_type = std::string::traits_type;
-  using value_type = char;
-  using pointer = char*;
-  using const_pointer = const char*;
-  using reference = char&;
-  using const_reference = char const&;
-  using const_iterator = const char*;
-  using iterator = const_iterator;
-  using const_reverse_iterator = std::reverse_iterator<const_iterator>;
-  using reverse_iterator = const_reverse_iterator;
-  using size_type = std::string::size_type;
-  using difference_type = std::string::difference_type;
-
-  static size_type const npos = static_cast<size_type>(-1);
-
-  string_view() noexcept = default;
-  string_view(string_view const&) noexcept = default;
-
-  string_view(const char* s, size_t count) noexcept
-    : data_(s)
-    , size_(count)
-  {
-  }
-
-  string_view(const char* s) noexcept
-    : data_(s)
-    , size_(traits_type::length(s))
-  {
-  }
-
-  // C++17 does not define this constructor.  Instead it defines
-  // a conversion operator on std::string to create a string_view.
-  // Since this implementation is used in C++11, std::string does
-  // not have that conversion.
-  string_view(std::string const& s) noexcept
-    : data_(s.data())
-    , size_(s.size())
-  {
-  }
-
-  // C++17 does not define this conversion.  Instead it defines
-  // a constructor on std::string that can take a string_view.
-  // Since this implementation is used in C++11, std::string does
-  // not have that constructor.
-  explicit operator std::string() const { return std::string(data_, size_); }
-
-  string_view& operator=(string_view const&) = default;
-
-  const_iterator begin() const noexcept { return data_; }
-  const_iterator end() const noexcept { return data_ + size_; }
-  const_iterator cbegin() const noexcept { return begin(); }
-  const_iterator cend() const noexcept { return end(); }
-
-  const_reverse_iterator rbegin() const noexcept
-  {
-    return const_reverse_iterator(end());
-  }
-  const_reverse_iterator rend() const noexcept
-  {
-    return const_reverse_iterator(begin());
-  }
-  const_reverse_iterator crbegin() const noexcept { return rbegin(); }
-  const_reverse_iterator crend() const noexcept { return rend(); }
-
-  const_reference operator[](size_type pos) const noexcept
-  {
-    return data_[pos];
-  }
-  const_reference at(size_type pos) const;
-  const_reference front() const noexcept { return data_[0]; }
-  const_reference back() const noexcept { return data_[size_ - 1]; }
-  const_pointer data() const noexcept { return data_; }
-
-  size_type size() const noexcept { return size_; }
-  size_type length() const noexcept { return size_; }
-  size_type max_size() const noexcept { return npos - 1; }
-  bool empty() const noexcept { return size_ == 0; }
-
-  void remove_prefix(size_type n) noexcept
-  {
-    data_ += n;
-    size_ -= n;
-  }
-  void remove_suffix(size_type n) noexcept { size_ -= n; }
-  void swap(string_view& v) noexcept
-  {
-    string_view tmp = v;
-    v = *this;
-    *this = tmp;
-  }
-
-  size_type copy(char* dest, size_type count, size_type pos = 0) const;
-  string_view substr(size_type pos = 0, size_type count = npos) const;
-
-  int compare(string_view v) const noexcept;
-  int compare(size_type pos1, size_type count1, string_view v) const;
-  int compare(size_type pos1, size_type count1, string_view v, size_type pos2,
-              size_type count2) const;
-  int compare(const char* s) const;
-  int compare(size_type pos1, size_type count1, const char* s) const;
-  int compare(size_type pos1, size_type count1, const char* s,
-              size_type count2) const;
-
-  size_type find(string_view v, size_type pos = 0) const noexcept;
-  size_type find(char c, size_type pos = 0) const noexcept;
-  size_type find(const char* s, size_type pos, size_type count) const;
-  size_type find(const char* s, size_type pos = 0) const;
-
-  size_type rfind(string_view v, size_type pos = npos) const noexcept;
-  size_type rfind(char c, size_type pos = npos) const noexcept;
-  size_type rfind(const char* s, size_type pos, size_type count) const;
-  size_type rfind(const char* s, size_type pos = npos) const;
-
-  size_type find_first_of(string_view v, size_type pos = 0) const noexcept;
-  size_type find_first_of(char c, size_type pos = 0) const noexcept;
-  size_type find_first_of(const char* s, size_type pos, size_type count) const;
-  size_type find_first_of(const char* s, size_type pos = 0) const;
-
-  size_type find_last_of(string_view v, size_type pos = npos) const noexcept;
-  size_type find_last_of(char c, size_type pos = npos) const noexcept;
-  size_type find_last_of(const char* s, size_type pos, size_type count) const;
-  size_type find_last_of(const char* s, size_type pos = npos) const;
-
-  size_type find_first_not_of(string_view v, size_type pos = 0) const noexcept;
-  size_type find_first_not_of(char c, size_type pos = 0) const noexcept;
-  size_type find_first_not_of(const char* s, size_type pos,
-                              size_type count) const;
-  size_type find_first_not_of(const char* s, size_type pos = 0) const;
-
-  size_type find_last_not_of(string_view v, size_type pos = npos) const
-    noexcept;
-  size_type find_last_not_of(char c, size_type pos = npos) const noexcept;
-  size_type find_last_not_of(const char* s, size_type pos,
-                             size_type count) const;
-  size_type find_last_not_of(const char* s, size_type pos = npos) const;
-
-private:
-  const char* data_ = nullptr;
-  size_type size_ = 0;
-};
-
-std::ostream& operator<<(std::ostream& o, string_view v);
-
-std::string& operator+=(std::string& s, string_view v);
-
-inline bool operator==(string_view l, string_view r) noexcept
-{
-  return l.compare(r) == 0;
-}
-
-inline bool operator!=(string_view l, string_view r) noexcept
-{
-  return l.compare(r) != 0;
-}
-
-inline bool operator<(string_view l, string_view r) noexcept
-{
-  return l.compare(r) < 0;
-}
-
-inline bool operator<=(string_view l, string_view r) noexcept
-{
-  return l.compare(r) <= 0;
-}
-
-inline bool operator>(string_view l, string_view r) noexcept
-{
-  return l.compare(r) > 0;
-}
-
-inline bool operator>=(string_view l, string_view r) noexcept
-{
-  return l.compare(r) >= 0;
-}
-}
-
-namespace std {
-
-template <>
-struct hash<cm::string_view>
-{
-  using argument_type = cm::string_view;
-  using result_type = size_t;
-  result_type operator()(argument_type const& s) const noexcept;
-};
-}
-
-#endif
-#endif