std::basic_syncbuf(3)

NAME
std::basic_syncbuf - std::basic_syncbuf

Synopsis
   Defined in header <syncstream>
   template<
       class CharT,
       class Traits = std::char_traits<CharT>, (since C++20)
       class Allocator = std::allocator<CharT>
   > class basic_syncbuf : public std::basic_streambuf<CharT, Traits>
   std::basic_syncbuf is a wrapper for a std::basic_streambuf (provided at construction
   time as a pointer). It accumulates output in its own internal buffer, and atomically
   transmits its entire contents to the wrapped buffer on destruction and when
   explicitly requested, so that they appear as a contiguous sequence of characters. It
   guarantees that there are no data races and no interleaving of characters sent to
   the wrapped buffer as long as all other outputs made to the same buffer are made
   through, possibly different, instances of std::basic_syncbuf.
   Typical implementation of std::basic_syncbuf holds a pointer to the wrapped
   std::basic_streambuf, a boolean flag indicating whether the buffer will transmit its
   contents to the wrapped buffer on sync (flush), a boolean flag indicating a pending
   flush when the policy is to not emit on sync, an internal buffer that uses Allocator
   (such as std::string), and a pointer to a mutex used to synchronize emit between
   multiple threads accessing the same wrapped stream buffer (these mutexes may be in a
   hash map with pointers to std::basic_streambuf objects used as keys).
   Like other streambuf classes, std::basic_syncbuf is normally only accessed through
   the corresponding stream, std::osyncstream, not directly.
   Several typedefs for common character types are provided:
   Defined in header <syncstream>
   Type Definition
   std::syncbuf std::basic_syncbuf<char>
   std::wsyncbuf std::basic_syncbuf<wchar_t>

Member types
   Member type Definition
   char_type CharT
   traits_type Traits; the program is ill-formed if Traits::char_type is not
                  CharT.
   int_type Traits::int_type
   pos_type Traits::pos_type
   off_type Traits::off_type
   allocator_type Allocator
   streambuf_type std::basic_streambuf<CharT, Traits>

Member functions

Public member functions
   constructor constructs a basic_syncbuf object
                    (public member function)
   operator= assigns a basic_syncbuf object
                    (public member function)
   swap swaps two basic_syncbuf objects
                    (public member function)
   destructor destroys the basic_syncbuf and emits its internal buffer
                    (public member function)
                    atomically transmits the entire internal buffer to the wrapped
   emit streambuf
                    (public member function)
   get_wrapped retrieves the wrapped streambuf pointer
                    (public member function)
   get_allocator retrieves the allocator used by this basic_syncbuf
                    (public member function)
   set_emit_on_sync changes the current emit-on-sync policy
                    (public member function)

Protected member functions
                    either emits, or records a pending flush, depending on the current
   sync emit-on-sync policy
                    (public member function)

Non-member functions
   std::swap(std::basic_syncbuf) specializes the std::swap algorithm
   (C++20) (function template) Inherited from std::basic_streambuf

Member types
   Member type Definition
   char_type CharT
   traits_type Traits; the program is ill-formed if Traits::char_type is not
               CharT.
   int_type Traits::int_type
   pos_type Traits::pos_type
   off_type Traits::off_type

Member functions
   destructor destructs the basic_streambuf object
   [virtual] (virtual public member function of
                      std::basic_streambuf<CharT,Traits>)

Locales
                      invokes imbue()
   pubimbue (public member function of std::basic_streambuf<CharT,Traits>)
                      obtains a copy of the associated locale
   getloc (public member function of std::basic_streambuf<CharT,Traits>)

Positioning
                      invokes setbuf()
   pubsetbuf (public member function of std::basic_streambuf<CharT,Traits>)
                      invokes seekoff()
   pubseekoff (public member function of std::basic_streambuf<CharT,Traits>)
                      invokes seekpos()
   pubseekpos (public member function of std::basic_streambuf<CharT,Traits>)
                      invokes sync()
   pubsync (public member function of std::basic_streambuf<CharT,Traits>)

Get area
                      obtains the number of characters immediately available in the get
   in_avail area
                      (public member function of std::basic_streambuf<CharT,Traits>)
                      advances the input sequence, then reads one character without
   snextc advancing again
                      (public member function of std::basic_streambuf<CharT,Traits>)
   sbumpc reads one character from the input sequence and advances the
   stossc sequence
   (removed in C++17) (public member function of std::basic_streambuf<CharT,Traits>)
                      reads one character from the input sequence without advancing the
   sgetc sequence
                      (public member function of std::basic_streambuf<CharT,Traits>)
                      invokes xsgetn()
   sgetn (public member function of std::basic_streambuf<CharT,Traits>)

Put area
                      writes one character to the put area and advances the next
   sputc pointer
                      (public member function of std::basic_streambuf<CharT,Traits>)
                      invokes xsputn()
   sputn (public member function of std::basic_streambuf<CharT,Traits>)

Putback
                      puts one character back in the input sequence
   sputbackc (public member function of std::basic_streambuf<CharT,Traits>)
                      moves the next pointer in the input sequence back by one
   sungetc (public member function of std::basic_streambuf<CharT,Traits>)

Protected member functions
   constructor constructs a basic_streambuf object
                 (protected member function)
   operator= replaces a basic_streambuf object
   (C++11) (protected member function)
   swap swaps two basic_streambuf objects
   (C++11) (protected member function)

Locales
   imbue changes the associated locale
   [virtual] (virtual protected member function of
                 std::basic_streambuf<CharT,Traits>)

Positioning
   setbuf replaces the buffer with user-defined array, if permitted
   [virtual] (virtual protected member function of
                 std::basic_streambuf<CharT,Traits>)
                 repositions the next pointer in the input sequence, output sequence,
   seekoff or both, using relative addressing
   [virtual] (virtual protected member function of
                 std::basic_streambuf<CharT,Traits>)
                 repositions the next pointer in the input sequence, output sequence,
   seekpos or both using absolute addressing
   [virtual] (virtual protected member function of
                 std::basic_streambuf<CharT,Traits>)
   sync synchronizes the buffers with the associated character sequence
   [virtual] (virtual protected member function of
                 std::basic_streambuf<CharT,Traits>)

Get area
                 obtains the number of characters available for input in the associated
   showmanyc input sequence, if known
   [virtual] (virtual protected member function of
                 std::basic_streambuf<CharT,Traits>)
   underflow reads characters from the associated input sequence to the get area
   [virtual] (virtual protected member function of
                 std::basic_streambuf<CharT,Traits>)
                 reads characters from the associated input sequence to the get area
   uflow and advances the next pointer
   [virtual] (virtual protected member function of
                 std::basic_streambuf<CharT,Traits>)
   xsgetn reads multiple characters from the input sequence
   [virtual] (virtual protected member function of
                 std::basic_streambuf<CharT,Traits>)
   eback returns a pointer to the beginning, current character and the end of
   gptr the get area
   egptr (protected member function)
   gbump advances the next pointer in the input sequence
                 (protected member function)
                 repositions the beginning, next, and end pointers of the input
   setg sequence
                 (protected member function)

Put area
   xsputn writes multiple characters to the output sequence
   [virtual] (virtual protected member function of
                 std::basic_streambuf<CharT,Traits>)
   overflow writes characters to the associated output sequence from the put area
   [virtual] (virtual protected member function of
                 std::basic_streambuf<CharT,Traits>)
   pbase returns a pointer to the beginning, current character and the end of
   pptr the put area
   epptr (protected member function)
   pbump advances the next pointer of the output sequence
                 (protected member function)
                 repositions the beginning, next, and end pointers of the output
   setp sequence
                 (protected member function)

Putback
                 puts a character back into the input sequence, possibly modifying the
   pbackfail input sequence
   [virtual] (virtual protected member function of
                 std::basic_streambuf<CharT,Traits>)

Notes
   Feature-test macro Value Std Feature
   __cpp_lib_syncbuf 201803L (C++20) Synchronized buffered ostream (std::syncbuf,
                        std::osyncstream) and manipulators