31 Input/output library [input.output]

31.8 String-based streams [string.streams]

31.8.4 Class template basic_ostringstream [ostringstream]

31.8.4.1 General [ostringstream.general]

namespace std { template<class charT, class traits = char_traits<charT>, class Allocator = allocator<charT>> class basic_ostringstream : public basic_ostream<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; // [ostringstream.cons], constructors basic_ostringstream() : basic_ostringstream(ios_base::out) {} explicit basic_ostringstream(ios_base::openmode which); explicit basic_ostringstream( const basic_string<charT, traits, Allocator>& s, ios_base::openmode which = ios_base::out); basic_ostringstream(ios_base::openmode which, const Allocator& a); explicit basic_ostringstream( basic_string<charT, traits, Allocator>&& s, ios_base::openmode which = ios_base::out); template<class SAlloc> basic_ostringstream( const basic_string<charT, traits, SAlloc>& s, const Allocator& a) : basic_ostringstream(s, ios_base::out, a) {} template<class SAlloc> basic_ostringstream( const basic_string<charT, traits, SAlloc>& s, ios_base::openmode which, const Allocator& a); template<class SAlloc> explicit basic_ostringstream( const basic_string<charT, traits, SAlloc>& s, ios_base::openmode which = ios_base::out); template<class T> explicit basic_ostringstream(const T& t, ios_base::openmode which = ios_base::out); template<class T> basic_ostringstream(const T& t, const Allocator& a); template<class T> basic_ostringstream(const T& t, ios_base::openmode which, const Allocator& a); basic_ostringstream(const basic_ostringstream&) = delete; basic_ostringstream(basic_ostringstream&& rhs); basic_ostringstream& operator=(const basic_ostringstream&) = delete; basic_ostringstream& operator=(basic_ostringstream&& rhs); // [ostringstream.swap], swap void swap(basic_ostringstream& rhs); // [ostringstream.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); template<class T> void str(const T& t); private: basic_stringbuf<charT, traits, Allocator> sb; // exposition only }; }

The class basic_ostringstream<charT, traits, Allocator> supports writing objects of class basic_string<charT, traits, Allocator>.

It uses a basic_stringbuf object to control the associated storage.

For the sake of exposition, the maintained data is presented here as:

(1.1)
sb, the stringbuf object.

31.8.4.2 Constructors [ostringstream.cons]

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explicit basic_ostringstream(ios_base::openmode which);

Effects: Initializes the base class with basic_ostream<charT, traits>(addressof(sb)) ([ostream]) and sb with basic_stringbuf<charT, traits, Allocator>(which | ios_base::out) ([stringbuf.cons]).

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explicit basic_ostringstream(
  const basic_string<charT, traits, Allocator>& s,
  ios_base::openmode which = ios_base::out);

Effects: Initializes the base class with basic_ostream<charT, traits>(addressof(sb)) ([ostream]) and sb with basic_stringbuf<charT, traits, Allocator>(s, which | ios_base::out)
([stringbuf.cons]).

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basic_ostringstream(ios_base::openmode which, const Allocator& a);

Effects: Initializes the base class with basic_ostream<charT, traits>(addressof(sb)) ([ostream]) and sb with basic_stringbuf<charT, traits, Allocator>(which | ios_base::out, a)
([stringbuf.cons]).

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explicit basic_ostringstream(
  basic_string<charT, traits, Allocator>&& s,
  ios_base::openmode which = ios_base::out);

Effects: Initializes the base class with basic_ostream<charT, traits>(addressof(sb)) ([ostream]) and sb with basic_stringbuf<charT, traits, Allocator>(std::move(s), which | ios_base::out) ([stringbuf.cons]).

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template<class SAlloc>
  basic_ostringstream(
    const basic_string<charT, traits, SAlloc>& s,
    ios_base::openmode which, const Allocator& a);

Effects: Initializes the base class with basic_ostream<charT, traits>(addressof(sb)) ([ostream]) and sb with basic_stringbuf<charT, traits, Allocator>(s, which | ios_base::out, a)
([stringbuf.cons]).

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template<class SAlloc>
  explicit basic_ostringstream(
    const basic_string<charT, traits, SAlloc>& s,
    ios_base::openmode which = ios_base::out);

Constraints: is_same_v<SAlloc,Allocator> is false.

Effects: Initializes the base class with basic_ostream<charT, traits>(addressof(sb)) ([ostream]) and sb with basic_stringbuf<charT, traits, Allocator>(s, which | ios_base::out)
([stringbuf.cons]).

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template<class T>
  explicit basic_ostringstream(const T& t, ios_base::openmode which = ios_base::out);
template<class T>
  basic_ostringstream(const T& t, const Allocator& a);
template<class T>
  basic_ostringstream(const T& t, ios_base::openmode which, const Allocator& a);

Let which be ios_base::out for the overload with no parameter which, and a be Allocator() for the overload with no parameter a.

Constraints: is_convertible_v<const T&, basic_string_view<charT, traits>> is true.

Effects: Initializes the base class with addressof(sb), and direct-non-list-initializes sb with t, which | ios_base::out, a.

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basic_ostringstream(basic_ostringstream&& rhs);

Effects: Move constructs from the rvalue rhs.

This is accomplished by move constructing the base class, and the contained basic_stringbuf.

Then calls basic_ostream<charT, traits>::set_rdbuf(addressof(sb)) to install the contained basic_stringbuf.

31.8.4.3 Swap [ostringstream.swap]

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void swap(basic_ostringstream& rhs);

Effects: Equivalent to: basic_ostream<charT, traits>::swap(rhs); sb.swap(rhs.sb);

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template<class charT, class traits, class Allocator>
  void swap(basic_ostringstream<charT, traits, Allocator>& x,
            basic_ostringstream<charT, traits, Allocator>& y);

Effects: Equivalent to x.swap(y).

31.8.4.4 Member functions [ostringstream.members]

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basic_stringbuf<charT, traits, Allocator>* rdbuf() const;

Returns: const_cast<basic_stringbuf<charT, traits, Allocator>*>(addressof(sb)).

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basic_string<charT, traits, Allocator> str() const &;

Effects: Equivalent to: return rdbuf()->str();

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template<class SAlloc>
  basic_string<charT,traits,SAlloc> str(const SAlloc& sa) const;

Effects: Equivalent to: return rdbuf()->str(sa);

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basic_string<charT,traits,Allocator> str() &&;

Effects: Equivalent to: return std::move(*rdbuf()).str();

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basic_string_view<charT, traits> view() const noexcept;

Effects: Equivalent to: return rdbuf()->view();

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

Effects: Equivalent to: rdbuf()->str(s);

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

Effects: Equivalent to: rdbuf()->str(s);

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void str(basic_string<charT, traits, Allocator>&& s);

Effects: Equivalent to: rdbuf()->str(std::move(s));

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template<class T>
  void str(const T& t);

Constraints: is_convertible_v<const T&, basic_string_view<charT, traits>> is true.

Effects: Equivalent to: rdbuf()->str(t);