char* str();
Returns a pointer to the internal character array. If the stream was built with the void-argument constructor, then str freezes the array. You must not send characters to a frozen stream, and you are responsible for deleting the array. You can unfreeze the the stream by calling rdbuf->freeze( 0 ).
If the stream was built with the constructor that specified the buffer, then the pointer contains the same address as the array used to construct the ostrstream object.