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Showing content from https://timsong-cpp.github.io/cppwp/n4659/string.view.template below:

[string.view.template]

24 Strings library [strings] 24.4 String view classes [string.view] 24.4.2 Class template basic_string_view [string.view.template]

template<class charT, class traits = char_traits<charT>>
class basic_string_view {
public:
    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         = implementation-defined;   using iterator               = const_iterator;228
  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);

    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);

    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;

    constexpr size_type size() const noexcept;
  constexpr size_type length() const noexcept;
  constexpr size_type max_size() const noexcept;
  constexpr bool empty() const noexcept;

    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;

    constexpr void remove_prefix(size_type n);
  constexpr void remove_suffix(size_type n);
  constexpr void swap(basic_string_view& s) noexcept;

    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_;   size_type size_;     };

In every specialization basic_string_view<charT, traits>, the type traits shall satisfy the character traits requirements ([char.traits]), and the type traits::char_type shall name the same type as charT.

24.4.2.1 Construction and assignment [string.view.cons]

constexpr basic_string_view() noexcept;

Effects: Constructs an empty basic_string_view.

Postconditions: size_ == 0 and data_ == nullptr.

constexpr basic_string_view(const charT* str);

Requires: [str, str + traits::length(str)) is a valid range.

Effects: Constructs a basic_string_view, with the postconditions in Table 64.

Table

—

basic_string_view(const charT*)

effects

Element Value data_ str size_ traits::length(str)

Complexity: O(traits::length(str)).

constexpr basic_string_view(const charT* str, size_type len);

Requires: [str, str + len) is a valid range.

Effects: Constructs a basic_string_view, with the postconditions in Table 65.

Table

—

basic_string_view(const charT*, size_type)

effects

Element Value data_ str size_ len 24.4.2.2 Iterator support [string.view.iterators]

using const_iterator = implementation-defined;

For a basic_string_view str, any operation that invalidates a pointer in the range [str.data(), str.data() + str.size()) invalidates pointers, iterators, and references returned from str's methods.

constexpr const_iterator begin() const noexcept; constexpr const_iterator cbegin() const noexcept;

Returns: An iterator such that

if !empty(), &*begin() == data_,
otherwise, an unspecified value such that [begin(), end()) is a valid range.

constexpr const_iterator end() const noexcept; constexpr const_iterator cend() const noexcept;

Returns: begin() + size().

constexpr const_reverse_iterator rbegin() const noexcept; constexpr const_reverse_iterator crbegin() const noexcept;

Returns: const_reverse_iterator(end()).

constexpr const_reverse_iterator rend() const noexcept; constexpr const_reverse_iterator crend() const noexcept;

Returns: const_reverse_iterator(begin()).

24.4.2.3 Capacity [string.view.capacity]

constexpr size_type size() const noexcept;

constexpr size_type length() const noexcept;

constexpr size_type max_size() const noexcept;

Returns: The largest possible number of char-like objects that can be referred to by a basic_string_view.

constexpr bool empty() const noexcept;

24.4.2.4 Element access [string.view.access]

constexpr const_reference operator[](size_type pos) const;

[ Note: Unlike basic_string::operator[], basic_string_view::operator[](size()) has undefined behavior instead of returning charT(). — end note ]

constexpr const_reference at(size_type pos) const;

Throws: out_of_range if pos >= size().

constexpr const_reference front() const;

constexpr const_reference back() const;

Returns: data_[size() - 1].

constexpr const_pointer data() const noexcept;

[ Note: Unlike basic_string::data() and string literals, data() may return a pointer to a buffer that is not null-terminated. Therefore it is typically a mistake to pass data() to a function that takes just a const charT* and expects a null-terminated string. — end note ]

24.4.2.5 Modifiers [string.view.modifiers]

constexpr void remove_prefix(size_type n);

Effects: Equivalent to: data_ += n; size_ -= n;

constexpr void remove_suffix(size_type n);

Effects: Equivalent to: size_ -= n;

constexpr void swap(basic_string_view& s) noexcept;

Effects: Exchanges the values of *this and s.

24.4.2.6 String operations [string.view.ops]

size_type copy(charT* s, size_type n, size_type pos = 0) const;

Let rlen be the smaller of n and size() - pos.

Throws: out_of_range if pos > size().

Requires: [s, s + rlen) is a valid range.

Effects: Equivalent to traits::copy(s, data() + pos, rlen).

constexpr basic_string_view substr(size_type pos = 0, size_type n = npos) const;

Let rlen be the smaller of n and size() - pos.

Throws: out_of_range if pos > size().

Effects: Determines rlen, the effective length of the string to reference.

Returns: basic_string_view(data() + pos, rlen).

constexpr int compare(basic_string_view str) const noexcept;

Let rlen be the smaller of size() and str.size().

Effects: Determines rlen, the effective length of the strings to compare. The function then compares the two strings by calling traits::compare(data(), str.data(), rlen).

Returns: The nonzero result if the result of the comparison is nonzero. Otherwise, returns a value as indicated in Table 66.

Table

—

compare()

results

Condition Return Value size() < str.size() < 0 size() == str.size() 0 size() > str.size() > 0

constexpr int compare(size_type pos1, size_type n1, basic_string_view str) const;

Effects: Equivalent to: return substr(pos1, n1).compare(str);

constexpr int compare(size_type pos1, size_type n1, basic_string_view str, size_type pos2, size_type n2) const;

Effects: Equivalent to: return substr(pos1, n1).compare(str.substr(pos2, n2));

constexpr int compare(const charT* s) const;

Effects: Equivalent to: return compare(basic_string_view(s));

constexpr int compare(size_type pos1, size_type n1, const charT* s) const;

Effects: Equivalent to: return substr(pos1, n1).compare(basic_string_view(s));

constexpr int compare(size_type pos1, size_type n1, const charT* s, size_type n2) const;

Effects: Equivalent to: return substr(pos1, n1).compare(basic_string_view(s, n2));

24.4.2.7 Searching [string.view.find]

This section specifies the basic_string_view member functions named find, rfind, find_first_of, find_last_of, find_first_not_of, and find_last_not_of.

Member functions in this section have complexity O(size() * str.size()) at worst, although implementations are encouraged to do better.

Each member function of the form

constexpr return-type F(const charT* s, size_type pos);

is equivalent to return F(basic_string_view(s), pos);

Each member function of the form

constexpr return-type F(const charT* s, size_type pos, size_type n);

is equivalent to return F(basic_string_view(s, n), pos);

Each member function of the form

constexpr return-type F(charT c, size_type pos);

is equivalent to return F(basic_string_view(&c, 1), pos);

constexpr size_type find(basic_string_view str, size_type pos = 0) const noexcept;

Let xpos be the lowest position, if possible, such that the following conditions hold:

pos <= xpos
xpos + str.size() <= size()
traits::eq(at(xpos + I), str.at(I)) for all elements I of the string referenced by str.

Effects: Determines xpos.