string_view

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std::basic_string_view (C++17)	read-only string view (class template)
std::string_view	std::basic_string_view<char>
std::wstring_view	std::basic_string_view<wchar_t>
std::u16string_view	std::basic_string_view<char16_t>
std::u32string_view	std::basic_string_view<char32_t>
std::hash<std::string_view>std::hash<std::wstring_view>std::hash<std::u16string_view>std::hash<std::u32string_view> (C++17)	hash support for string views (class template specialization)

功能

operator==operator!=operatoroperator<=operator>=	lexicographically compares two string views (function template)
operator<<	performs stream output on string views (function template)

简介

二次

namespace std {
 
// class template basic_string_view
template<class charT, class traits = char_traits<charT>>
class basic_string_view;
 
// non-member comparison functions
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 bool operator!=(basic_string_view<charT, traits> x,
                          basic_string_view<charT, traits> y) noexcept;
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 bool operator> (basic_string_view<charT, traits> x,
                          basic_string_view<charT, traits> y) noexcept;
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 bool operator>=(basic_string_view<charT, traits> x,
                          basic_string_view<charT, traits> y) noexcept;
/* sufficient additional overloads of comparison functions */
 
// inserters and extractors
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 names
typedef basic_string_view<char> string_view;
typedef basic_string_view<char16_t> u16string_view;
typedef basic_string_view<char32_t> u32string_view;
typedef basic_string_view<wchar_t> wstring_view;
 
inline namespace literals {
inline namespace string_view_literals {
// suffix for basic_string_view literals
constexpr string_view operator "" sv(const char* 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;
}
}
 
// hash support
template<class T> struct hash;
template<> struct hash<string_view>;
template<> struct hash<u16string_view>;
template<> struct hash<u32string_view>;
template<> struct hash<wstring_view>;
 
template<class charT, class traits = char_traits<charT>>
class basic_string_view {
public:
// types
typedef traits traits_type;
typedef charT value_type;
typedef charT* pointer;
typedef const charT* const_pointer;
typedef charT& reference;
typedef const charT& const_reference;
typedef implementation-defined const_iterator;
typedef const_iterator iterator;
typedef reverse_iterator<const_iterator> const_reverse_iterator;
typedef const_reverse_iterator reverse_iterator;
typedef size_t size_type;
typedef ptrdiff_t difference_type;
static constexpr size_type npos = size_type(-1
 
// construction and assignment
constexpr basic_string_view() noexcept;
constexpr basic_string_view(const basic_string_view&) noexcept = default;
basic_string_view &operator=(const basic_string_view&) noexcept = default;
template <class Allocator>
basic_string_view(const basic_string<charT, traits, Allocator>& str) noexcept;
constexpr basic_string_view(const charT* str
constexpr basic_string_view(const charT* str, size_type len
 
// iterator support
constexpr const_iterator begin() const noexcept;
constexpr const_iterator end() const noexcept;
constexpr const_iterator cbegin() const noexcept;
constexpr const_iterator cend() const noexcept;
const_reverse_iterator rbegin() const noexcept;
const_reverse_iterator rend() const noexcept;
const_reverse_iterator crbegin() const noexcept;
const_reverse_iterator crend() const noexcept;
 
// capacity
constexpr size_type size() const noexcept;
constexpr size_type length() const noexcept;
constexpr size_type max_size() const noexcept;
constexpr bool empty() const noexcept;
 
// element access
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;
 
// modifiers
constexpr void remove_prefix(size_type n
constexpr void remove_suffix(size_type n
constexpr void swap(basic_string_view& s) noexcept;
 
// string operations
template <class Allocator>
explicit operator basic_string<charT, traits, Allocator>() const;
template <class Allocator = allocator<charT>>
basic_string<charT, traits, Allocator> to_string(const Allocator& a = Allocator()) const;
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 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_; // exposition only
size_type size_; // exposition only
};
 
} // namespace std

二次

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