标准库头文件 <string_view>
此头文件是字符串库的一部分。
包含 | |
| (C++20) |
三路比较运算符支持 |
类 | |
| (C++17) |
只读的字符串视图 (类模板) |
| std::string_view (C++17) | std::basic_string_view<char> |
| std::u8string_view (C++20) | std::basic_string_view<char8_t> |
| std::u16string_view (C++17) | std::basic_string_view<char16_t> |
| std::u32string_view (C++17) | std::basic_string_view<char32_t> |
| std::wstring_view (C++17) | std::basic_string_view<wchar_t> |
| string_view 的散列支持 (类模板特化) | |
前置声明 | |
| 定义于头文件
<functional> | |
| (C++11) |
散列函数对象 (类模板) |
函数 | |
| (C++20 中移除)(C++20 中移除)(C++20 中移除)(C++20 中移除)(C++20 中移除)(C++20) |
以字典序比较两个字符串视图 (函数模板) |
| 进行字符串视图的流输出 (函数模板) | |
| 交换两个对象的值 (函数模板) | |
范围访问 | |
| (C++11)(C++14) |
返回指向容器或数组起始的迭代器 (函数模板) |
| (C++11)(C++14) |
返回指向容器或数组结尾的迭代器 (函数模板) |
| (C++14) |
返回指向一个容器或数组的逆向迭代器 (函数模板) |
| (C++14) |
返回容器或数组的逆向尾迭代器 (函数模板) |
| (C++17)(C++20) |
返回容器或数组的大小 (函数模板) |
| (C++17) |
检查容器是否为空 (函数模板) |
| (C++17) |
获得指向底层数组的指针 (函数模板) |
字面量 | |
| 定义于内联命名空间
std::literals::string_view_literals | |
| (C++17) |
创建一个字符数组字面量的字符串视图 (函数) |
概要
#include <compare> namespace std { // 类模板 basic_string_view template<class CharT, class Traits = char_traits<CharT>> class basic_string_view; template<class CharT, class Traits> inline constexpr bool ranges::enable_view<basic_string_view<CharT, Traits>> = true; template<class CharT, class Traits> inline constexpr bool ranges::enable_borrowed_range<basic_string_view<CharT, Traits>> = true; // 非成员函数 template<class CharT, class Traits> constexpr bool operator==(basic_string_view<CharT, Traits> x, basic_string_view<CharT, Traits> y) noexcept; template<class CharT, class Traits> constexpr /* 见描述 */ operator<=>(basic_string_view<CharT, Traits> x, basic_string_view<CharT, Traits> y) noexcept; // 充足的比较函数额外重载 // 插入器与提取器 template<class CharT, class Traits> basic_ostream<CharT, Traits>& operator<<(basic_ostream<CharT, Traits>& os, basic_string_view<CharT, Traits> str); // basic_string_view typedef 名 using string_view = basic_string_view<char>; using u8string_view = basic_string_view<char8_t>; using u16string_view = basic_string_view<char16_t>; using u32string_view = basic_string_view<char32_t>; using wstring_view = basic_string_view<wchar_t>; // 散列支持 template<class T> struct hash; template<> struct hash<string_view>; template<> struct hash<u8string_view>; template<> struct hash<u16string_view>; template<> struct hash<u32string_view>; template<> struct hash<wstring_view>; inline namespace literals { inline namespace string_view_literals { // basic_string_view 字面量的后缀 constexpr string_view operator""sv(const char* str, size_t len) noexcept; constexpr u8string_view operator""sv(const char8_t* str, size_t len) noexcept; constexpr u16string_view operator""sv(const char16_t* str, size_t len) noexcept; constexpr u32string_view operator""sv(const char32_t* str, size_t len) noexcept; constexpr wstring_view operator""sv(const wchar_t* str, size_t len) noexcept; } } }
类模板 std::basic_string_view
namespace std { template<class CharT, class Traits = char_traits<CharT>> class basic_string_view { public: // 类型 using Traits_type = Traits; using value_type = CharT; using pointer = value_type*; using const_pointer = const value_type*; using reference = value_type&; using const_reference = const value_type&; using const_iterator = /* 由实现定义 */ using iterator = const_iterator; using const_reverse_iterator = reverse_iterator<const_iterator>; using reverse_iterator = const_reverse_iterator; using size_type = size_t; using difference_type = ptrdiff_t; static constexpr size_type npos = size_type(-1); // 构造与赋值 constexpr basic_string_view() noexcept; constexpr basic_string_view(const basic_string_view&) noexcept = default; constexpr basic_string_view& operator=(const basic_string_view&) noexcept = default; constexpr basic_string_view(const CharT* str); constexpr basic_string_view(const CharT* str, size_type len); template<class It, class End> constexpr basic_string_view(It begin, End end); // 迭代器支持 constexpr const_iterator begin() const noexcept; constexpr const_iterator end() const noexcept; constexpr const_iterator cbegin() const noexcept; constexpr const_iterator cend() const noexcept; constexpr const_reverse_iterator rbegin() const noexcept; constexpr const_reverse_iterator rend() const noexcept; constexpr const_reverse_iterator crbegin() const noexcept; constexpr const_reverse_iterator crend() const noexcept; // 容量 constexpr size_type size() const noexcept; constexpr size_type length() const noexcept; constexpr size_type max_size() const noexcept; [[nodiscard]] constexpr bool empty() const noexcept; // 元素访问 constexpr const_reference operator[](size_type pos) const; constexpr const_reference at(size_type pos) const; constexpr const_reference front() const; constexpr const_reference back() const; constexpr const_pointer data() const noexcept; // 修改器 constexpr void remove_prefix(size_type n); constexpr void remove_suffix(size_type n); constexpr void swap(basic_string_view& s) noexcept; // 字符串操作 constexpr size_type copy(CharT* s, size_type n, size_type pos = 0) const; constexpr basic_string_view substr(size_type pos = 0, size_type n = npos) const; constexpr int compare(basic_string_view s) const noexcept; constexpr int compare(size_type pos1, size_type n1, basic_string_view s) const; constexpr int compare(size_type pos1, size_type n1, basic_string_view s, size_type pos2, size_type n2) const; constexpr int compare(const CharT* s) const; constexpr int compare(size_type pos1, size_type n1, const CharT* s) const; constexpr int compare(size_type pos1, size_type n1, const CharT* s, size_type n2) const; constexpr bool starts_with(basic_string_view x) const noexcept; constexpr bool starts_with(CharT x) const noexcept; constexpr bool starts_with(const CharT* x) const; constexpr bool ends_with(basic_string_view x) const noexcept; constexpr bool ends_with(CharT x) const noexcept; constexpr bool ends_with(const CharT* x) const; // 搜索 constexpr size_type find(basic_string_view s, size_type pos = 0) const noexcept; constexpr size_type find(CharT c, size_type pos = 0) const noexcept; constexpr size_type find(const CharT* s, size_type pos, size_type n) const; constexpr size_type find(const CharT* s, size_type pos = 0) const; constexpr size_type rfind(basic_string_view s, size_type pos = npos) const noexcept; constexpr size_type rfind(CharT c, size_type pos = npos) const noexcept; constexpr size_type rfind(const CharT* s, size_type pos, size_type n) const; constexpr size_type rfind(const CharT* s, size_type pos = npos) const; constexpr size_type find_first_of(basic_string_view s, size_type pos = 0) const noexcept; constexpr size_type find_first_of(CharT c, size_type pos = 0) const noexcept; constexpr size_type find_first_of(const CharT* s, size_type pos, size_type n) const; constexpr size_type find_first_of(const CharT* s, size_type pos = 0) const; constexpr size_type find_last_of(basic_string_view s, size_type pos = npos) const noexcept; constexpr size_type find_last_of(CharT c, size_type pos = npos) const noexcept; constexpr size_type find_last_of(const CharT* s, size_type pos, size_type n) const; constexpr size_type find_last_of(const CharT* s, size_type pos = npos) const; constexpr size_type find_first_not_of(basic_string_view s, size_type pos = 0) const noexcept; constexpr size_type find_first_not_of(CharT c, size_type pos = 0) const noexcept; constexpr size_type find_first_not_of(const CharT* s, size_type pos, size_type n) const; constexpr size_type find_first_not_of(const CharT* s, size_type pos = 0) const; constexpr size_type find_last_not_of(basic_string_view s, size_type pos = npos) const noexcept; constexpr size_type find_last_not_of(CharT c, size_type pos = npos) const noexcept; constexpr size_type find_last_not_of(const CharT* s, size_type pos, size_type n) const; constexpr size_type find_last_not_of(const CharT* s, size_type pos = npos) const; private: const_pointer data_; // 仅用于阐释 size_type size_; // 仅用于阐释 }; // 推导指引 template<class It, class End> basic_string_view(It, End) -> basic_string_view<iter_value_t<It>>; }