29 Input/output library [input.output]

29.8 String-based streams [string.streams]

29.8.3 Class template basic_­istringstream [istringstream]

namespace std {
  template<class charT, class traits = char_traits<charT>,
           class Allocator = allocator<charT>>
  class basic_istringstream : public basic_istream<charT, traits> {
  public:
    using char_type      = charT;
    using int_type       = typename traits::int_type;
    using pos_type       = typename traits::pos_type;
    using off_type       = typename traits::off_type;
    using traits_type    = traits;
    using allocator_type = Allocator;

    // [istringstream.cons], constructors
    basic_istringstream() : basic_istringstream(ios_base::in) {}
    explicit basic_istringstream(ios_base::openmode which);
    explicit basic_istringstream(
      const basic_string<charT, traits, Allocator>& s,
      ios_base::openmode which = ios_base::in);
    basic_istringstream(ios_base::openmode which, const Allocator& a);
    explicit basic_istringstream(
      basic_string<charT, traits, Allocator>&& s,
      ios_base::openmode which = ios_base::in);
    template<class SAlloc>
      basic_istringstream(
        const basic_string<charT, traits, SAlloc>& s, const Allocator& a)
        : basic_istringstream(s, ios_base::in, a) {}
    template<class SAlloc>
      basic_istringstream(
        const basic_string<charT, traits, SAlloc>& s,
        ios_base::openmode which, const Allocator& a);
    template<class SAlloc>
      explicit basic_istringstream(
        const basic_string<charT, traits, SAlloc>& s,
        ios_base::openmode which = ios_base::in);
    basic_istringstream(const basic_istringstream& rhs) = delete;
    basic_istringstream(basic_istringstream&& rhs);

    // [istringstream.assign], assign and swap
    basic_istringstream& operator=(const basic_istringstream& rhs) = delete;
    basic_istringstream& operator=(basic_istringstream&& rhs);
    void swap(basic_istringstream& rhs);

    // [istringstream.members], members
    basic_stringbuf<charT, traits, Allocator>* rdbuf() const;
    basic_string<charT, traits, Allocator> str() const &;
    template<class SAlloc>
      basic_string<charT,traits,SAlloc> str(const SAlloc& sa) const;
    basic_string<charT, traits, Allocator> str() &&;
    basic_string_view<charT, traits> view() const noexcept;

    void str(const basic_string<charT, traits, Allocator>& s);
    template<class SAlloc>
      void str(const basic_string<charT, traits, SAlloc>& s);
    void str(basic_string<charT, traits, Allocator>&& s);

  private:
    basic_stringbuf<charT, traits, Allocator> sb; // exposition only
  };

  template<class charT, class traits, class Allocator>
    void swap(basic_istringstream<charT, traits, Allocator>& x,
              basic_istringstream<charT, traits, Allocator>& y);
}
The class basic_­istringstream<charT, traits, Allocator> supports reading objects of class basic_­string<​charT, traits, Allocator>.
It uses a basic_­stringbuf<charT, traits, Allocator> object to control the associated storage.
For the sake of exposition, the maintained data is presented here as:
  • sb, the stringbuf object.

29.8.3.1 Constructors [istringstream.cons]

explicit basic_istringstream(ios_base::openmode which);
Effects: Initializes the base class with basic_­istream<charT, traits>(addressof(sb)) ([istream]) and sb with basic_­stringbuf<charT, traits, Allocator>(which | ios_­base​::​in) ([stringbuf.cons]).
explicit basic_istringstream( const basic_string<charT, traits, Allocator>& s, ios_base::openmode which = ios_base::in);
Effects: Initializes the base class with basic_­istream<charT, traits>(addressof(sb)) ([istream]) and sb with basic_­stringbuf<charT, traits, Allocator>(s, which | ios_­base​::​in)
([stringbuf.cons]).
basic_istringstream(ios_base::openmode which, const Allocator& a);
Effects: Initializes the base class with basic_­istream<charT, traits>(addressof(sb)) ([istream]) and sb with basic_­stringbuf<charT, traits, Allocator>(which | ios_­base​::​in, a) ([stringbuf.cons]).
explicit basic_istringstream( basic_string<charT, traits, Allocator>&& s, ios_base::openmode which = ios_base::in);
Effects: Initializes the base class with basic_­istream<charT, traits>(addressof(sb)) ([istream]) and sb with basic_­stringbuf<charT, traits, Allocator>(std​::​move(s), which | ios_­base​::​​in) ([stringbuf.cons]).
template<class SAlloc> basic_istringstream( const basic_string<charT, traits, SAlloc>& s, ios_base::openmode which, const Allocator& a);
Effects: Initializes the base class with basic_­istream<charT, traits>(addressof(sb)) ([istream]) and sb with basic_­stringbuf<charT, traits, Allocator>(s, which | ios_­base​::​in, a)
([stringbuf.cons]).
template<class SAlloc> explicit basic_istringstream( const basic_string<charT, traits, SAlloc>& s, ios_base::openmode which = ios_base::in);
Effects: Initializes the base class with basic_­istream<charT, traits>(addressof(sb)) ([istream]) and sb with basic_­stringbuf<charT, traits, Allocator>(s, which | ios_­base​::​in) ([stringbuf.cons]).
basic_istringstream(basic_istringstream&& rhs);
Effects: Move constructs from the rvalue rhs.
This is accomplished by move constructing the base class, and the contained basic_­stringbuf.
Next basic_­istream<charT, traits>​::​set_­rdbuf(addressof(sb)) is called to install the contained basic_­stringbuf.

29.8.3.2 Assignment and swap [istringstream.assign]

basic_istringstream& operator=(basic_istringstream&& rhs);
Effects: Move assigns the base and members of *this from the base and corresponding members of rhs.
Returns: *this.
void swap(basic_istringstream& rhs);
Effects: Equivalent to:
basic_istream<charT, traits>::swap(rhs);
sb.swap(rhs.sb);
template<class charT, class traits, class Allocator> void swap(basic_istringstream<charT, traits, Allocator>& x, basic_istringstream<charT, traits, Allocator>& y);
Effects: As if by x.swap(y).

29.8.3.3 Member functions [istringstream.members]

basic_stringbuf<charT, traits, Allocator>* rdbuf() const;
Returns: const_­cast<basic_­stringbuf<charT, traits, Allocator>*>(addressof(sb)).
basic_string<charT, traits, Allocator> str() const &;
Effects: Equivalent to: return rdbuf()->str();
template<class SAlloc> basic_string<charT,traits,SAlloc> str(const SAlloc& sa) const;
Effects: Equivalent to: return rdbuf()->str(sa);
basic_string<charT,traits,Allocator> str() &&;
Effects: Equivalent to: return std​::​move(*rdbuf()).str();
basic_string_view<charT, traits> view() const noexcept;
Effects: Equivalent to: return rdbuf()->view();
void str(const basic_string<charT, traits, Allocator>& s);
Effects: Equivalent to: rdbuf()->str(s);
template<class SAlloc> void str(const basic_string<charT, traits, SAlloc>& s);
Effects: Equivalent to: rdbuf()->str(s);
void str(basic_string<charT, traits, Allocator>&& s);
Effects: Equivalent to: rdbuf()->str(std​::​move(s));