std::basic_stringbuf(3cxx) on Linux
The text fc08549c419c, as Debian 6.0 (Squeeze) shipped it.
The actual work of input and output (for std::string). This class associates either or both of its input and output sequences with a sequence of characters, which can be initialized from, or made available as, a std::basic_string. (Paraphrased from [27.7.1]/1.).