[ostringstream]

# 31 Input/output library [[input.output]](./#input.output)

## 31.8 String-based streams [[string.streams]](string.streams#ostringstream)

### 31.8.4 Class template basic_ostringstream [ostringstream]

#### [31.8.4.1](#general) General [[ostringstream.general]](ostringstream.general)

[🔗](#lib:basic_ostringstream)

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]](#cons "31.8.4.2 Constructors"), 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 "31.8.4.3 Swap"), swapvoid swap(basic_ostringstream& rhs); // [[ostringstream.members]](#members "31.8.4.4 Member functions"), 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*};}

[1](#general-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L9325)

The classbasic_ostringstream<charT, traits, Allocator> supports writing objects of classbasic_string<​charT, traits, Allocator>[.](#general-1.sentence-1)

It uses abasic_stringbuf object to control the associated storage[.](#general-1.sentence-2)

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

- [(1.1)](#general-1.1)

*sb*, the stringbuf object[.](#general-1.sentence-3)

#### [31.8.4.2](#cons) Constructors [[ostringstream.cons]](ostringstream.cons)

[🔗](#lib:basic_ostringstream,constructor)

`explicit basic_ostringstream(ios_base::openmode which);
`

[1](#cons-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L9347)

*Effects*: Initializes the base class withbasic_ostream<charT, traits>(addressof(*sb*)) ([[ostream]](ostream "31.7.6.2 Class template basic_­ostream"))
and *sb* withbasic_stringbuf<charT, traits, Allocator>(which | ios_base​::​out) ([[stringbuf.cons]](stringbuf.cons "31.8.2.2 Constructors"))[.](#cons-1.sentence-1)

[🔗](#lib:basic_ostringstream,constructor_)

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

[2](#cons-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L9363)

*Effects*: Initializes the base class withbasic_ostream<charT, traits>(addressof(*sb*)) ([[ostream]](ostream "31.7.6.2 Class template basic_­ostream"))
and *sb* withbasic_stringbuf<charT, traits, Allocator>(s, which | ios_base​::​out)  
 ([[stringbuf.cons]](stringbuf.cons "31.8.2.2 Constructors"))[.](#cons-2.sentence-1)

[🔗](#lib:basic_ostringstream,constructor__)

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

[3](#cons-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L9377)

*Effects*: Initializes the base class withbasic_ostream<charT, traits>(addressof(*sb*)) ([[ostream]](ostream "31.7.6.2 Class template basic_­ostream"))
and *sb* withbasic_stringbuf<charT, traits, Allocator>(which | ios_base​::​out, a)  
 ([[stringbuf.cons]](stringbuf.cons "31.8.2.2 Constructors"))[.](#cons-3.sentence-1)

[🔗](#lib:basic_ostringstream,constructor___)

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

[4](#cons-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L9393)

*Effects*: Initializes the base class withbasic_ostream<charT, traits>(addressof(*sb*)) ([[ostream]](ostream "31.7.6.2 Class template basic_­ostream"))
and *sb* withbasic_stringbuf<charT, traits, Allocator>(std​::​move(s), which | ios_base​::​​out) ([[stringbuf.cons]](stringbuf.cons "31.8.2.2 Constructors"))[.](#cons-4.sentence-1)

[🔗](#lib:basic_ostringstream,constructor____)

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

[5](#cons-5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L9410)

*Effects*: Initializes the base class withbasic_ostream<charT, traits>(addressof(*sb*)) ([[ostream]](ostream "31.7.6.2 Class template basic_­ostream"))
and *sb* withbasic_stringbuf<charT, traits, Allocator>(s, which | ios_base​::​out, a)  
 ([[stringbuf.cons]](stringbuf.cons "31.8.2.2 Constructors"))[.](#cons-5.sentence-1)

[🔗](#lib:basic_ostringstream,constructor_____)

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

[6](#cons-6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L9427)

*Constraints*: is_same_v<SAlloc, Allocator> is false[.](#cons-6.sentence-1)

[7](#cons-7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L9431)

*Effects*: Initializes the base class withbasic_ostream<charT, traits>(addressof(*sb*)) ([[ostream]](ostream "31.7.6.2 Class template basic_­ostream"))
and *sb* withbasic_stringbuf<charT, traits, Allocator>(s, which | ios_base​::​out)  
 ([[stringbuf.cons]](stringbuf.cons "31.8.2.2 Constructors"))[.](#cons-7.sentence-1)

[🔗](#lib:basic_ostringstream,constructor______)

`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);
`

[8](#cons-8)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L9450)

Let which be ios_base​::​out for the overload with no parameter which, anda be Allocator() for the overload with no parameter a[.](#cons-8.sentence-1)

[9](#cons-9)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L9455)

*Constraints*: is_convertible_v<const T&, basic_string_view<charT, traits>> is true[.](#cons-9.sentence-1)

[10](#cons-10)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L9460)

*Effects*: Initializes the base class with addressof(*sb*), and
direct-non-list-initializes *sb* with t, which | ios_base​::​out, a[.](#cons-10.sentence-1)

[🔗](#lib:basic_ostringstream,constructor_______)

`basic_ostringstream(basic_ostringstream&& rhs);
`

[11](#cons-11)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L9472)

*Effects*: Move constructs from the rvalue rhs[.](#cons-11.sentence-1)

This
is accomplished by move constructing the base class, and the containedbasic_stringbuf[.](#cons-11.sentence-2)

Then calls basic_ostream<charT, traits>​::​set_rdbuf(addressof(*sb*)) to install the contained basic_stringbuf[.](#cons-11.sentence-3)

#### [31.8.4.3](#swap) Swap [[ostringstream.swap]](ostringstream.swap)

[🔗](#lib:swap,basic_ostringstream)

`void swap(basic_ostringstream& rhs);
`

[1](#swap-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L9489)

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

[🔗](#lib:swap,basic_ostringstream_)

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

[2](#swap-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L9506)

*Effects*: Equivalent to x.swap(y)[.](#swap-2.sentence-1)

#### [31.8.4.4](#members) Member functions [[ostringstream.members]](ostringstream.members)

[🔗](#lib:rdbuf,basic_ostringstream)

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

[1](#members-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L9519)

*Returns*: const_cast<basic_stringbuf<charT, traits, Allocator>*>(addressof(*sb*))[.](#members-1.sentence-1)

[🔗](#lib:str,basic_ostringstream)

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

[2](#members-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L9530)

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

[🔗](#lib:str,basic_ostringstream_)

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

[3](#members-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L9542)

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

[🔗](#lib:str,basic_ostringstream__)

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

[4](#members-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L9553)

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

[🔗](#lib:view,basic_ostringstream)

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

[5](#members-5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L9564)

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

[🔗](#lib:str,basic_ostringstream___)

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

[6](#members-6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L9575)

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

[🔗](#lib:str,basic_ostringstream____)

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

[7](#members-7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L9587)

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

[🔗](#lib:str,basic_ostringstream_____)

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

[8](#members-8)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L9598)

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

[🔗](#lib:str,basic_ostringstream______)

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

[9](#members-9)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L9610)

*Constraints*: is_convertible_v<const T&, basic_string_view<charT, traits>> is true[.](#members-9.sentence-1)

[10](#members-10)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L9615)

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