# Standard library header <sstream>

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< cpp‎ | header

This header is part of the Input/Output library.

### Classes
basic_stringbuf | implements raw string device (class template)
basic_istringstream | implements high-level string stream input operations (class template)
basic_ostringstream | implements high-level string stream output operations (class template)
basic_stringstream | implements high-level string stream input/output operations (class template)
`stringbuf` | std::basic_stringbuf<char> (typedef)
`wstringbuf` | std::basic_stringbuf<wchar_t> (typedef)
`istringstream` | std::basic_istringstream<char> (typedef)
`wistringstream` | std::basic_istringstream<wchar_t> (typedef)
`ostringstream` | std::basic_ostringstream<char> (typedef)
`wostringstream` | std::basic_ostringstream<wchar_t> (typedef)
`stringstream` | std::basic_stringstream<char> (typedef)
`wstringstream` | std::basic_stringstream<wchar_t> (typedef)
### Functions
std::swap(std::basic_stringbuf) (C++11) | specializes the std::swap algorithm (function template)
std::swap(std::basic_istringstream) (C++11) | specializes the std::swap algorithm (function template)
std::swap(std::basic_ostringstream) (C++11) | specializes the std::swap algorithm (function template)
std::swap(std::basic_stringstream) (C++11) | specializes the std::swap algorithm (function template)

### Synopsis

    namespace std {
      template<class CharT, class Traits = char_traits<CharT>,
               class Allocator = allocator<CharT>>
        class basic_stringbuf;

      using stringbuf  = basic_stringbuf<char>;
      using wstringbuf = basic_stringbuf<wchar_t>;

      template<class CharT, class Traits = char_traits<CharT>,
               class Allocator = allocator<CharT>>
        class basic_istringstream;

      using istringstream  = basic_istringstream<char>;
      using wistringstream = basic_istringstream<wchar_t>;

      template<class CharT, class Traits = char_traits<CharT>,
               class Allocator = allocator<CharT>>
        class basic_ostringstream;
      using ostringstream  = basic_ostringstream<char>;
      using wostringstream = basic_ostringstream<wchar_t>;

      template<class CharT, class Traits = char_traits<CharT>,
               class Allocator = allocator<CharT>>
        class basic_stringstream;
      using stringstream  = basic_stringstream<char>;
      using wstringstream = basic_stringstream<wchar_t>;
    }

#### Class template std::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;

        // 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);
        basic_stringbuf(const basic_stringbuf&) = delete;
        basic_stringbuf(basic_stringbuf&& rhs);
        basic_stringbuf(basic_stringbuf&& rhs, const Allocator& a);

        // assign and swap
        basic_stringbuf& operator=(const basic_stringbuf&) = delete;
        basic_stringbuf& operator=(basic_stringbuf&& rhs);
        void swap(basic_stringbuf& rhs) noexcept(see below);

        // 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);

      protected:
        // 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
      };

      template<class CharT, class Traits, class Allocator>
        void swap(basic_stringbuf<CharT, Traits, Allocator>& x,
                  basic_stringbuf<CharT, Traits, Allocator>& y) noexcept(noexcept(x.swap(y)));
    }

#### Class template std::basic_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;

        // 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&) = delete;
        basic_istringstream(basic_istringstream&& rhs);

        // assign and swap
        basic_istringstream& operator=(const basic_istringstream&) = delete;
        basic_istringstream& operator=(basic_istringstream&& rhs);
        void swap(basic_istringstream& rhs);

        // 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);
    }

#### Class template std::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;

        // 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);
        basic_ostringstream(const basic_ostringstream&) = delete;
        basic_ostringstream(basic_ostringstream&& rhs);

        // assign and swap
        basic_ostringstream& operator=(const basic_ostringstream&) = delete;
        basic_ostringstream& operator=(basic_ostringstream&& rhs);
        void swap(basic_ostringstream& rhs);

        // 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_ostringstream<CharT, Traits, Allocator>& x,
                  basic_ostringstream<CharT, Traits, Allocator>& y);
    }

#### Class template std::basic_stringstream

    namespace std {
      template<class CharT, class Traits = char_traits<CharT>,
               class Allocator = allocator<CharT>>
      class basic_stringstream : public basic_iostream<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;

        // constructors
        basic_stringstream() : basic_stringstream(ios_base::out | ios_base::in) {}
        explicit basic_stringstream(ios_base::openmode which);
        explicit basic_stringstream(
          const basic_string<CharT, Traits, Allocator>& s,
          ios_base::openmode which = ios_base::out | ios_base::in);
        basic_stringstream(ios_base::openmode which, const Allocator& a);
        explicit basic_stringstream(
          basic_string<CharT, Traits, Allocator>&& s,
          ios_base::openmode which = ios_base::out | ios_base::in);
        template<class SAlloc>
          basic_stringstream(
            const basic_string<CharT, Traits, SAlloc>& s, const Allocator& a)
            : basic_stringstream(s, ios_base::out | ios_base::in, a) {}
        template<class SAlloc>
          basic_stringstream(
            const basic_string<CharT, Traits, SAlloc>& s,
            ios_base::openmode which, const Allocator& a);
        template<class SAlloc>
          explicit basic_stringstream(
            const basic_string<CharT, Traits, SAlloc>& s,
            ios_base::openmode which = ios_base::out | ios_base::in);
        basic_stringstream(const basic_stringstream&) = delete;
        basic_stringstream(basic_stringstream&& rhs);

        // assign and swap
        basic_stringstream& operator=(const basic_stringstream&) = delete;
        basic_stringstream& operator=(basic_stringstream&& rhs);
        void swap(basic_stringstream& rhs);

        // 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> sb;  // exposition only
      };

      template<class CharT, class Traits, class Allocator>
        void swap(basic_stringstream<CharT, Traits, Allocator>& x,
                  basic_stringstream<CharT, Traits, Allocator>& y);
    }

### Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR | Applied to | Behavior as published | Correct behavior
--- | --- | --- | ---
LWG 170 | C++98 | the definitions of `traits_type` were missing in the synopses of std::basic_ostringstream and std::basic_stringstream | added
LWG 251 | C++98 | the definitions of `allocator_type` were missing in the synopses of std::basic_stringbuf, std::basic_istringstream std::basic_ostringstream and std::basic_stringstream | added

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