string_view.hpp

/*
MIT License
 
Copyright (c) 2024 mguludag
 
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
 
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
 
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/
 
#ifndef STRING_STRING_VIEW_HPP
#define STRING_STRING_VIEW_HPP
 
#include <cstring>
#include <ostream>
#include <string>
 
#include "mgutility/_common/definitions.hpp"
 
namespace mgutility {
 
#if MGUTILITY_CPLUSPLUS < 201703L
 
namespace detail {
constexpr auto strlen_constexpr(const char *str, size_t sz = 0) noexcept
    -> size_t {
  return str[sz] == '\0' ? sz : strlen_constexpr(str, ++sz);
}
} // namespace detail
 
template <typename Char = char> class basic_string_view {
public:
  constexpr inline basic_string_view() noexcept : data_(""), size_(0) {}
 
  constexpr inline basic_string_view(const Char *str) noexcept
      : data_(str), size_(detail::strlen_constexpr(str)) {}
 
  constexpr inline basic_string_view(
      const std::basic_string<Char> &str) noexcept
      : data_(str.c_str()), size_(str.size()) {}
 
  constexpr inline basic_string_view(const Char *str, size_t len) noexcept
      : data_(str), size_(len) {}
 
  constexpr inline basic_string_view(const basic_string_view &other)
      : data_(other.data_), size_(other.size_) {}
 
  constexpr inline basic_string_view(basic_string_view &&other) noexcept
      : data_(std::move(other.data_)), size_(std::move(other.size_)) {}
 
  MGUTILITY_CNSTXPR inline basic_string_view<Char> &
  operator=(const basic_string_view &other) noexcept {
    data_ = other.data_;
    size_ = other.size_;
    return *this;
  }
 
  MGUTILITY_CNSTXPR inline basic_string_view<Char> &
  operator=(basic_string_view &&other) noexcept {
    data_ = std::move(other.data_);
    size_ = std::move(other.size_);
    return *this;
  }
 
  constexpr inline const Char operator[](size_t index) const noexcept {
    return data_[index];
  }
 
  constexpr inline const Char *begin() const noexcept { return data_; }
 
  constexpr inline const Char *end() const noexcept { return (data_ + size_); }
 
  constexpr inline bool empty() const noexcept { return size_ < 1; }
 
  constexpr inline size_t size() const noexcept { return size_; }
 
  constexpr inline const Char *data() const noexcept { return data_; }
 
  constexpr inline basic_string_view<Char>
  substr(size_t begin, size_t len = 0U) const noexcept {
    return basic_string_view<Char>(data_ + begin,
                                   len == 0U ? size_ - begin : len);
  }
 
  constexpr inline size_t rfind(Char c, size_t pos = npos) const noexcept {
    return (pos == npos ? pos = size_ : pos = pos), c == data_[pos] ? pos
                                                    : pos == 0U
                                                        ? npos
                                                        : rfind(c, --pos);
  }
 
  constexpr inline size_t find(Char c, size_t pos = 0) const noexcept {
    return c == data_[pos] ? pos : pos < size_ ? find(c, ++pos) : npos;
  }
 
  constexpr friend inline bool
  operator==(basic_string_view<Char> lhs,
             basic_string_view<Char> rhs) noexcept {
    return (lhs.size_ == rhs.size_) &&
           std::strncmp(lhs.data_, rhs.data_, lhs.size_) == 0;
  }
 
  constexpr friend inline bool operator==(basic_string_view<Char> lhs,
                                          const Char *rhs) noexcept {
    return (lhs.size_ == detail::strlen_constexpr(rhs)) &&
           std::strncmp(lhs.data_, rhs, lhs.size_) == 0;
  }
 
  constexpr friend inline bool
  operator!=(basic_string_view<Char> lhs,
             basic_string_view<Char> rhs) noexcept {
    return !(lhs == rhs);
  }
 
  constexpr friend inline bool operator!=(basic_string_view<Char> lhs,
                                          const Char *rhs) noexcept {
    return !(lhs == rhs);
  }
 
  inline operator std::string() { return std::string(data_, size_); }
 
  inline operator std::string() const { return std::string(data_, size_); }
 
  friend inline std::ostream &operator<<(std::ostream &os,
                                         const basic_string_view<Char> &sv) {
    for (auto c : sv) {
      os << c;
    }
    return os;
  }
 
  static constexpr auto npos = -1;
 
private:
  size_t size_;
  const Char *data_;
};
 
using string_view = basic_string_view<char>;
 
#else
#include <string_view>
 
using string_view = std::string_view;
 
#endif
 
} // namespace mgutility
 
#endif // STRING_STRING_VIEW_HPP