std::strstreambuf::setbuf(3)

NAME
std::strstreambuf::setbuf - std::strstreambuf::setbuf

Synopsis
   protected: (deprecated in C++98)
   virtual streambuf* setbuf( char* s, std::streamsize n ); (removed in C++26)
   If s is a null pointer and n is zero, this function has no effect.
   Otherwise, the effect is implementation-defined: some implementations do nothing,
   while some implementations deallocate the dynamic member array used as the buffer
   and begin using the user-supplied character array of size n, whose first element is
   pointed to by s.
   This function is protected virtual, it may only be called through pubsetbuf() or
   from member functions of a user-defined class derived from std::strstreambuf.

Parameters
   s - pointer to the first byte in the user-provided buffer
   n - the number of bytes in the user-provided buffer

Return value
   this

Example
   Implementation test to check if setbuf() is supported on a dynamic strstream (output
   obtained with Sun Studio): // Run this code
 #include <iostream>
 #include <strstream>
 int main()
 {
     char a[100] = {};
     std::strstream str;
     str.rdbuf()->pubsetbuf(a, sizeof a);
     str << "Test string" << std::ends;
     std::cout << "user-provided buffer holds \"" << a << "\"\n";
 }

Possible output:
 user-provided buffer holds "Test string"
   Defect reports
   The following behavior-changing defect reports were applied retroactively to
   previously published C++ standards.
     DR Applied to Behavior as published Correct behavior
                     the effect of setbuf() was "performs an
                     operation that is
   LWG 66 C++98 defined separately for each class derived the effect is
                     from strstreambuf", implementation-defined
                     but there are no classes derived from
                     strstreambuf

See also
   pubsetbuf invokes setbuf()
             (public member function of std::basic_streambuf<CharT,Traits>)
   setbuf replaces the buffer with user-defined array, if permitted
   [virtual] (virtual protected member function of std::basic_streambuf<CharT,Traits>)
   setbuf attempts to replace the controlled character sequence with an array
   [virtual] (virtual protected member function of
             std::basic_stringbuf<CharT,Traits,Allocator>)
   setbuf provides user-supplied buffer or turns this filebuf unbuffered
   [virtual] (virtual protected member function of std::basic_filebuf<CharT,Traits>)