Utilities/std/cm/string_view

// -*-c++-*-
// vim: set ft=cpp:

/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
   file Copyright.txt or https://cmake.org/licensing for details.  */
#pragma once

#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> // IWYU pragma: export
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