[stringbuf.general]

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

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

### 31.8.2 Class template basic_stringbuf [[stringbuf]](stringbuf#general)

#### 31.8.2.1 General [stringbuf.general]

[ð](#lib:basic_stringbuf)

namespace std {template<class charT, class traits = char_traits<charT>, class Allocator = allocator<charT>>class basic_stringbuf : public basic_streambuf<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; // [[stringbuf.cons]](stringbuf.cons "31.8.2.2 Constructors"), constructors basic_stringbuf() : basic_stringbuf(ios_base::in | ios_base::out) {}explicit basic_stringbuf(ios_base::openmode which); explicit basic_stringbuf(const basic_string<charT, traits, Allocator>& s,
 ios_base::openmode which = ios_base::in | ios_base::out); explicit basic_stringbuf(const Allocator& a): basic_stringbuf(ios_base::in | ios_base::out, a) {} basic_stringbuf(ios_base::openmode which, const Allocator& a); explicit basic_stringbuf( basic_string<charT, traits, Allocator>&& s,
 ios_base::openmode which = ios_base::in | ios_base::out); template<class SAlloc> basic_stringbuf(const basic_string<charT, traits, SAlloc>& s, const Allocator& a): basic_stringbuf(s, ios_base::in | ios_base::out, a) {}template<class SAlloc> basic_stringbuf(const basic_string<charT, traits, SAlloc>& s,
 ios_base::openmode which, const Allocator& a); template<class SAlloc>explicit basic_stringbuf(const basic_string<charT, traits, SAlloc>& s,
 ios_base::openmode which = ios_base::in | ios_base::out); template<class T>explicit basic_stringbuf(const T& t,
 ios_base::openmode which = ios_base::in | ios_base::out); template<class T> basic_stringbuf(const T& t, const Allocator& a); template<class T> basic_stringbuf(const T& t, ios_base::openmode which, const Allocator& a);
 basic_stringbuf(const basic_stringbuf&) = delete;
 basic_stringbuf(basic_stringbuf&& rhs);
 basic_stringbuf(basic_stringbuf&& rhs, const Allocator& a); // [[stringbuf.assign]](stringbuf.assign "31.8.2.3 Assignment and swap"), assignment and swap basic_stringbuf& operator=(const basic_stringbuf&) = delete;
 basic_stringbuf& operator=(basic_stringbuf&& rhs); void swap(basic_stringbuf& rhs) noexcept(*see below*); // [[stringbuf.members]](stringbuf.members "31.8.2.4 Member functions"), getters and setters allocator_type get_allocator() const noexcept;

 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); protected:// [[stringbuf.virtuals]](stringbuf.virtuals "31.8.2.5 Overridden virtual functions"), overridden virtual functions int_type underflow() override;
 int_type pbackfail(int_type c = traits::eof()) override;
 int_type overflow (int_type c = traits::eof()) override;
 basic_streambuf<charT, traits>* setbuf(charT*, streamsize) override;

 pos_type seekoff(off_type off, ios_base::seekdir way,
 ios_base::openmode which = ios_base::in | ios_base::out) override;
 pos_type seekpos(pos_type sp,
 ios_base::openmode which = ios_base::in | ios_base::out) override; private: ios_base::openmode *mode*; // *exposition only* basic_string<charT, traits, Allocator> *buf*; // *exposition only*void *init-buf-ptrs*(); // *exposition only*};}

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L8113)

The classbasic_stringbuf is derived frombasic_streambuf to associate possibly the input sequence and possibly
the output sequence with a sequence of arbitrary[*characters*](#def:characters)[.](#1.sentence-1)

The sequence can be initialized from, or made available as, an object of classbasic_string[.](#1.sentence-2)

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L8124)

For the sake of exposition,
the maintained data and internal pointer initialization is presented here as:

- [(2.1)](#2.1)

  ios_base​::​openmode *mode*, has in set if the input sequence can be read, and out set if the output sequence can be written[.](#2.1.sentence-1)

- [(2.2)](#2.2)

  basic_string<charT, traits, Allocator> *buf* contains the underlying character sequence[.](#2.2.sentence-1)

- [(2.3)](#2.3)

  *init-buf-ptrs*() sets the base class'
 get area ([[streambuf.get.area]](streambuf.get.area "31.6.3.4.2 Get area access")) and
 put area ([[streambuf.put.area]](streambuf.put.area "31.6.3.4.3 Put area access")) pointers
 after initializing, moving from, or assigning to *buf* accordingly[.](#2.3.sentence-1)
