std::basic_streambuf::setp(3)

NAME
std::basic_streambuf::setp - std::basic_streambuf::setp

Synopsis
   protected:
   void setp( char_type* pbeg, char_type* pend );
   Sets the values of the pointers defining the put area. Specifically, after the call
   pbase() == pbeg, pptr() == pbeg, epptr() == pend.

Parameters
   pbeg - pointer to the new beginning of the put area
   pend - pointer to the new end of the put area

Return value
   (none)

Example
// Run this code
 #include <array>
 #include <cstddef>
 #include <iostream>
 // Buffer for std::ostream implemented by std::array
 template<std::size_t size, class CharT = char>
 struct ArrayedStreamBuffer : std::basic_streambuf<CharT>
 {
     using Base = std::basic_streambuf<CharT>;
     using char_type = typename Base::char_type;
     ArrayedStreamBuffer()
     {
         // put area pointers to work with 'buffer'
         Base::setp(buffer.data(), buffer.data() + size);
     }
     void print_buffer()
     {
         for (char_type i : buffer)
         {
             if (i == 0)
                 std::cout << "\\0";
             else
                 std::cout << i;
             std::cout << ' ';
         }
         std::cout << '\n';
     }
 private:
     std::array<char_type, size> buffer{}; // value-initialize buffer
 };
 int main()
 {
     ArrayedStreamBuffer<10> streambuf;
     std::ostream stream(&streambuf);
     stream << "hello";
     stream << ",";
     streambuf.print_buffer();
 }

Output:
 h e l l o , \0 \0 \0 \0

See also
   setg repositions the beginning, next, and end pointers of the input sequence
        (protected member function)