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◆ main openmsx / src / utils / zstring_view.hh
5.2 KiB · C++ · last changed chore(): initial commit 1 month ago source blame history raw
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#ifndef ZSTRING_VIEW_HH
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#define ZSTRING_VIEW_HH
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#include <cassert>
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#include <cstring>
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#include <iostream>
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#include <string>
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#include <string_view>
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#include <type_traits>
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/**
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 * Like std::string_view, but with the extra guarantee that it refers to a
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 * zero-terminated string. In other words it has this additional invariant:
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 *    data()[size()] == '\0'
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 *
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 * Current version only implements a subset of the std::string_view API. That
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 * is because:
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 * - Some functions cannot be implemented (those that trim the tail).
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 * - Most were not yet required. We can implement those on demand.
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 */
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class zstring_view
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{
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public:
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	using size_type = size_t;
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	using const_iterator = const char*;
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	static constexpr auto npos = std::string_view::npos;
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	constexpr zstring_view()
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		: dat(nullptr), siz(0) {}
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	constexpr zstring_view(const char* s)
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		: dat(s), siz(std::char_traits<char>::length(s)) {}
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	constexpr zstring_view(const char* s, size_t n)
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		: dat(s), siz(n) { assert(s[n] == '\0'); }
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	constexpr zstring_view(const std::string& s)
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		: dat(s.c_str()), siz(s.size()) {}
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	[[nodiscard]] constexpr auto begin() const { return dat; }
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	[[nodiscard]] constexpr auto end()   const { return dat + siz; }
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	[[nodiscard]] constexpr auto size()  const { return siz; }
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	[[nodiscard]] constexpr auto empty() const { return siz == 0; }
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	[[nodiscard]] constexpr char operator[](size_type i) const {
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		assert(i < siz);
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		return dat[i];
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	}
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	[[nodiscard]] constexpr char front() const { return *dat; }
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	[[nodiscard]] constexpr char back() const { return *(dat + siz - 1); }
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	[[nodiscard]] constexpr const char* data()  const { return dat; }
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	[[nodiscard]] constexpr const char* c_str() const { return dat; }
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	[[nodiscard]] constexpr auto find(char c, size_type pos = 0) const {
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		return view().find(c, pos);
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	}
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	[[nodiscard]] constexpr auto find(const char* s, size_type pos = 0) const {
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		return view().find(s, pos);
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	}
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	[[nodiscard]] constexpr zstring_view substr(size_type pos) const {
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		assert(pos <= siz);
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		return {dat + pos, siz - pos};
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	}
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	[[nodiscard]] constexpr std::string_view substr(size_type pos, size_type count) const {
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		assert(pos <= siz);
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		return view().substr(pos, count);
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	}
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	constexpr void remove_prefix(size_type n) {
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		assert(n <= siz);
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		siz -= n;
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		dat += n;
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	}
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	[[nodiscard]] constexpr bool starts_with(std::string_view sv) const {
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		return view().starts_with(sv);
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	}
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	[[nodiscard]] constexpr bool starts_with(char c) const {
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		return view().starts_with(c);
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	}
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	[[nodiscard]] constexpr bool starts_with(const char* s) const {
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		return view().starts_with(s);
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	}
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	[[nodiscard]] constexpr bool ends_with(std::string_view sv) const {
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		return view().ends_with(sv);
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	}
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	[[nodiscard]] constexpr bool ends_with(char c) const {
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		return view().ends_with(c);
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	}
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	[[nodiscard]] constexpr bool ends_with(const char* s) const {
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		return view().ends_with(s);
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	}
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	[[nodiscard]] constexpr bool contains(std::string_view sv) const {
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		return view().contains(sv);
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	}
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	[[nodiscard]] constexpr bool contains(char c) const {
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		return view().contains(c);
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	}
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	[[nodiscard]] constexpr bool contains(const char* s) const {
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		return view().contains(s);
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	}
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	[[nodiscard]] explicit operator std::string() const {
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		return {dat, siz};
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	}
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	[[nodiscard]] constexpr std::string_view view() const {
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		return {dat, siz};
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	}
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	[[nodiscard]] explicit(false) constexpr operator std::string_view() const {
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		return view();
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	}
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	[[nodiscard]] constexpr friend bool operator==(const zstring_view& x, const zstring_view& y) {
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		return std::string_view(x) == std::string_view(y);
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	}
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	[[nodiscard]] friend bool operator==(const zstring_view& x, const std::string& y) {
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		return std::string_view(x) == std::string_view(y);
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	}
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	[[nodiscard]] constexpr friend bool operator==(const zstring_view& x, const std::string_view& y) {
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		return std::string_view(x) == y;
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	}
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	[[nodiscard]] constexpr friend bool operator==(const zstring_view& x, const char* y) {
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		return std::string_view(x) == std::string_view(y);
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	}
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	[[nodiscard]] constexpr friend auto operator<=>(const zstring_view& x, const zstring_view& y) {
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		return std::string_view(x) <=> std::string_view(y);
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	}
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	[[nodiscard]] friend auto operator<=>(const zstring_view& x, const std::string& y) {
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		return std::string_view(x) <=> std::string_view(y);
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	}
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	[[nodiscard]] constexpr friend auto operator<=>(const zstring_view& x, const std::string_view& y) {
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		return std::string_view(x) <=> y;
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	}
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	[[nodiscard]] constexpr friend auto operator<=>(const zstring_view& x, const char* y) {
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		return std::string_view(x) <=> std::string_view(y);
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	}
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	friend std::ostream& operator<<(std::ostream& os, const zstring_view& str)
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	{
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		os << std::string_view(str);
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		return os;
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	}
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private:
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	const char* dat;
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	size_type siz;
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};
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static_assert(std::is_trivially_destructible_v<zstring_view>);
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static_assert(std::is_trivially_copyable_v<zstring_view>);
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static_assert(std::is_trivially_copy_constructible_v<zstring_view>);
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static_assert(std::is_trivially_move_constructible_v<zstring_view>);
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static_assert(std::is_trivially_assignable_v<zstring_view, zstring_view>);
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static_assert(std::is_trivially_copy_assignable_v<zstring_view>);
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static_assert(std::is_trivially_move_assignable_v<zstring_view>);
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[[nodiscard]] constexpr auto begin(const zstring_view& x) { return x.begin(); }
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[[nodiscard]] constexpr auto end  (const zstring_view& x) { return x.end();   }
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#endif