zstring_view.hh

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#ifndef ZSTRING_VIEW_HH
#define ZSTRING_VIEW_HH
 
#include <cassert>
#include <cstring>
#include <iostream>
#include <string>
#include <string_view>
#include <type_traits>
 
class zstring_view
{
public:
        using size_type = size_t;
        using const_iterator = const char*;
 
        static constexpr auto npos = std::string_view::npos;
 
        /*constexpr*/ zstring_view(const char* s)
                : dat(s), siz(size_type(strlen(s))) {}
        constexpr zstring_view(const char* s, size_t n)
                : dat(s), siz(n) { assert(s[n] == '\0'); }
        /*constexpr*/ zstring_view(const std::string& s)
                : dat(s.c_str()), siz(s.size()) {}
 
        [[nodiscard]] constexpr auto begin() const { return dat; }
        [[nodiscard]] constexpr auto end()   const { return dat + siz; }
 
        [[nodiscard]] constexpr auto size()  const { return siz; }
        [[nodiscard]] constexpr auto empty() const { return siz == 0; }
 
        [[nodiscard]] constexpr char operator[](size_type i) const {
                assert(i < siz);
                return dat[i];
        }
        [[nodiscard]] constexpr char front() const { return *dat; }
        [[nodiscard]] constexpr char back() const { return *(dat + siz - 1); }
        [[nodiscard]] constexpr const char* data()  const { return dat; }
        [[nodiscard]] constexpr const char* c_str() const { return dat; }
 
        [[nodiscard]] constexpr auto find(char c, size_type pos = 0) const {
                return view().find(c, pos);
        }
 
        [[nodiscard]] constexpr zstring_view substr(size_type pos) const {
                assert(pos <= siz);
                return {dat + pos, siz - pos};
        }
 
        [[nodiscard]] constexpr bool starts_with(std::string_view sv) const {
                return view().starts_with(sv);
        }
        [[nodiscard]] constexpr bool starts_with(char c) const {
                return view().starts_with(c);
        }
        [[nodiscard]] constexpr bool starts_with(const char* s) const {
                return view().starts_with(s);
        }
        [[nodiscard]] constexpr bool ends_with(std::string_view sv) const {
                return view().ends_with(sv);
        }
        [[nodiscard]] constexpr bool ends_with(char c) const {
                return view().ends_with(c);
        }
        [[nodiscard]] constexpr bool ends_with(const char* s) const {
                return view().ends_with(s);
        }
 
        [[nodiscard]] explicit operator std::string() const {
                return {dat, siz};
        }
        [[nodiscard]] constexpr std::string_view view() const {
                return {dat, siz};
        }
        [[nodiscard]] constexpr /*implicit*/ operator std::string_view() const {
                return view();
        }
 
private:
        const char* dat;
        size_type siz;
};
 
static_assert(std::is_trivially_destructible_v<zstring_view>);
static_assert(std::is_trivially_copyable_v<zstring_view>);
static_assert(std::is_trivially_copy_constructible_v<zstring_view>);
static_assert(std::is_trivially_move_constructible_v<zstring_view>);
static_assert(std::is_trivially_assignable_v<zstring_view, zstring_view>);
static_assert(std::is_trivially_copy_assignable_v<zstring_view>);
static_assert(std::is_trivially_move_assignable_v<zstring_view>);
 
[[nodiscard]] constexpr auto begin(const zstring_view& x) { return x.begin(); }
[[nodiscard]] constexpr auto end  (const zstring_view& x) { return x.end();   }
 
[[nodiscard]] constexpr bool operator==(const zstring_view& x, const zstring_view& y) {
        return std::string_view(x) == std::string_view(y);
}
[[nodiscard]] inline bool operator==(const zstring_view& x, const std::string& y) {
        return std::string_view(x) == std::string_view(y);
}
[[nodiscard]] constexpr bool operator==(const zstring_view& x, const std::string_view& y) {
        return std::string_view(x) == y;
}
[[nodiscard]] constexpr bool operator==(const zstring_view& x, const char* y) {
        return std::string_view(x) == std::string_view(y);
}
 
inline std::ostream& operator<<(std::ostream& os, const zstring_view& str)
{
        os << std::string_view(str);
        return os;
}
#endif