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[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 "31.8.4.2Constructors"), 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 "31.8.4.3Swap"), swapvoid swap(basic_ostringstream& rhs); // [[ostringstream.members]](#members "31.8.4.4Member 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 "31.7.6.2Class template basic_­ostream"))
and *sb* withbasic_stringbuf<charT, traits, Allocator>(which | ios_base::out) ([[stringbuf.cons]](stringbuf.cons "31.8.2.2Constructors"))[.](#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 "31.7.6.2Class template basic_­ostream"))
and *sb* withbasic_stringbuf<charT, traits, Allocator>(s, which | ios_base::out)
([[stringbuf.cons]](stringbuf.cons "31.8.2.2Constructors"))[.](#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 "31.7.6.2Class template basic_­ostream"))
and *sb* withbasic_stringbuf<charT, traits, Allocator>(which | ios_base::out, a)
([[stringbuf.cons]](stringbuf.cons "31.8.2.2Constructors"))[.](#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 "31.7.6.2Class template basic_­ostream"))
and *sb* withbasic_stringbuf<charT, traits, Allocator>(std::move(s), which | ios_base::out) ([[stringbuf.cons]](stringbuf.cons "31.8.2.2Constructors"))[.](#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 "31.7.6.2Class template basic_­ostream"))
and *sb* withbasic_stringbuf<charT, traits, Allocator>(s, which | ios_base::out, a)
([[stringbuf.cons]](stringbuf.cons "31.8.2.2Constructors"))[.](#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 "31.7.6.2Class template basic_­ostream"))
and *sb* withbasic_stringbuf<charT, traits, Allocator>(s, which | ios_base::out)
([[stringbuf.cons]](stringbuf.cons "31.8.2.2Constructors"))[.](#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);