std::ostrstream::rdbuf
From cppreference.com
                    
                                        
                    < cpp | io | ostrstream
                    
                                                            
                    
|   strstreambuf* rdbuf() const;  | 
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Returns a pointer to the associated std::strstreambuf, casting away its constness (despite the const qualifier on the member function)
[edit] Parameters
(none)
[edit] Return value
Pointer to the associated std::strsteambuf, with constness cast away.
[edit] Example
#include <strstream> int main() { const std::ostrstream buf; std::strstreambuf* ptr = buf.rdbuf(); }