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      std::basic_syncbuf

      From cppreference.com
      <cpp‎ |io
       
       
       
       
      Defined in header<syncstream>
      template<

         class CharT,
         class Traits=std::char_traits<CharT>,
         class Allocator=std::allocator<CharT>

      >class basic_syncbuf:publicstd::basic_streambuf<CharT, Traits>
      (since C++20)

      std::basic_syncbuf is a wrapper for astd::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 ofstd::basic_syncbuf.

      Typical implementation ofstd::basic_syncbuf holds a pointer to the wrappedstd::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 usesAllocator (such asstd::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 tostd::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::syncbufstd::basic_syncbuf<char>
      std::wsyncbufstd::basic_syncbuf<wchar_t>

      Contents

      [edit]Member types

      Member type Definition
      char_typeCharT[edit]
      traits_typeTraits; the program is ill-formed ifTraits::char_type is notCharT.[edit]
      int_typeTraits::int_type[edit]
      pos_typeTraits::pos_type[edit]
      off_typeTraits::off_type[edit]
      allocator_typeAllocator
      streambuf_typestd::basic_streambuf<CharT, Traits>

      [edit]Member functions

      Public member functions

      constructs abasic_syncbuf object
      (public member function)[edit]
      assigns abasic_syncbuf object
      (public member function)[edit]
      swaps twobasic_syncbuf objects
      (public member function)[edit]
      destroys thebasic_syncbuf and emits its internal buffer
      (public member function)[edit]
      atomically transmits the entire internal buffer to the wrapped streambuf
      (public member function)[edit]
      retrieves the wrapped streambuf pointer
      (public member function)[edit]
      retrieves the allocator used by thisbasic_syncbuf
      (public member function)[edit]
      changes the current emit-on-sync policy
      (public member function)[edit]

      Protected member functions

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

      [edit]Non-member functions

      specializes thestd::swap algorithm
      (function template)[edit]

      Inherited fromstd::basic_streambuf

      Member types

      Member type Definition
      char_typeCharT[edit]
      traits_typeTraits; the program is ill-formed ifTraits::char_type is notCharT.[edit]
      int_typeTraits::int_type[edit]
      pos_typeTraits::pos_type[edit]
      off_typeTraits::off_type[edit]

      Member functions

      [virtual]
      destructs thebasic_streambuf object
      (virtual public member function ofstd::basic_streambuf<CharT,Traits>)[edit]
      Locales
      changes the associated locale and invokesimbue()
      (public member function ofstd::basic_streambuf<CharT,Traits>)[edit]
      obtains a copy of the associated locale
      (public member function ofstd::basic_streambuf<CharT,Traits>)[edit]
      Positioning
      invokessetbuf()
      (public member function ofstd::basic_streambuf<CharT,Traits>)[edit]
      invokesseekoff()
      (public member function ofstd::basic_streambuf<CharT,Traits>)[edit]
      invokesseekpos()
      (public member function ofstd::basic_streambuf<CharT,Traits>)[edit]
      invokessync()
      (public member function ofstd::basic_streambuf<CharT,Traits>)[edit]
      Get area
      obtains the number of characters immediately available in the get area
      (public member function ofstd::basic_streambuf<CharT,Traits>)[edit]
      advances the input sequence, then reads one character without advancing again
      (public member function ofstd::basic_streambuf<CharT,Traits>)[edit]
      (removed in C++17)
      reads one character from the input sequence and advances the sequence
      (public member function ofstd::basic_streambuf<CharT,Traits>)[edit]
      reads one character from the input sequence without advancing the sequence
      (public member function ofstd::basic_streambuf<CharT,Traits>)[edit]
      invokesxsgetn()
      (public member function ofstd::basic_streambuf<CharT,Traits>)[edit]
      Put area
      writes one character to the put area and advances the next pointer
      (public member function ofstd::basic_streambuf<CharT,Traits>)[edit]
      invokesxsputn()
      (public member function ofstd::basic_streambuf<CharT,Traits>)[edit]
      Putback
      puts one character back in the input sequence
      (public member function ofstd::basic_streambuf<CharT,Traits>)[edit]
      moves the next pointer in the input sequence back by one
      (public member function ofstd::basic_streambuf<CharT,Traits>)[edit]

      Protected member functions

      constructs abasic_streambuf object
      (protected member function)[edit]
      (C++11)
      replaces abasic_streambuf object
      (protected member function)[edit]
      (C++11)
      swaps twobasic_streambuf objects
      (protected member function)[edit]
      Locales
      [virtual]
      reacts to a change of the associated locale
      (virtual protected member function ofstd::basic_streambuf<CharT,Traits>)[edit]
      Positioning
      [virtual]
      replaces the buffer with user-defined array, if permitted
      (virtual protected member function ofstd::basic_streambuf<CharT,Traits>)[edit]
      [virtual]
      repositions the next pointer in the input sequence, output sequence, or both, using relative addressing
      (virtual protected member function ofstd::basic_streambuf<CharT,Traits>)[edit]
      [virtual]
      repositions the next pointer in the input sequence, output sequence, or both using absolute addressing
      (virtual protected member function ofstd::basic_streambuf<CharT,Traits>)[edit]
      [virtual]
      synchronizes the buffers with the associated character sequence
      (virtual protected member function ofstd::basic_streambuf<CharT,Traits>)[edit]
      Get area
      [virtual]
      obtains the number of characters available for input in the associated input sequence, if known
      (virtual protected member function ofstd::basic_streambuf<CharT,Traits>)[edit]
      [virtual]
      reads characters from the associated input sequence to the get area
      (virtual protected member function ofstd::basic_streambuf<CharT,Traits>)[edit]
      [virtual]
      reads characters from the associated input sequence to the get area and advances the next pointer
      (virtual protected member function ofstd::basic_streambuf<CharT,Traits>)[edit]
      [virtual]
      reads multiple characters from the input sequence
      (virtual protected member function ofstd::basic_streambuf<CharT,Traits>)[edit]
      returns a pointer to the beginning, current character and the end of the get area
      (protected member function)[edit]
      advances the next pointer in the input sequence
      (protected member function)[edit]
      repositions the beginning, next, and end pointers of the input sequence
      (protected member function)[edit]
      Put area
      [virtual]
      writes multiple characters to the output sequence
      (virtual protected member function ofstd::basic_streambuf<CharT,Traits>)[edit]
      [virtual]
      writes characters to the associated output sequence from the put area
      (virtual protected member function ofstd::basic_streambuf<CharT,Traits>)[edit]
      returns a pointer to the beginning, current character and the end of the put area
      (protected member function)[edit]
      advances the next pointer of the output sequence
      (protected member function)[edit]
      repositions the beginning, next, and end pointers of the output sequence
      (protected member function)[edit]
      Putback
      [virtual]
      puts a character back into the input sequence, possibly modifying the input sequence
      (virtual protected member function ofstd::basic_streambuf<CharT,Traits>)[edit]

      [edit]Notes

      Feature-test macroValueStdFeature
      __cpp_lib_syncbuf201803L(C++20)Synchronized buffered ostream (std::syncbuf,std::osyncstream) and manipulators
      Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/io/basic_syncbuf&oldid=148138"

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