cpp/io/basic streambuf/basic streambuf

@1@ Constructs the object, initializes the six pointer members (,, , , , and ) to null pointer values, and the locale member to , a copy of the global C++ locale at the time of construction. @2@ Constructs a copy of, initializing the six pointers and the locale object with the copies of the values held by. Note that this is a shallow copy: the pointers of the newly-constructed basic_streambuf are pointing into the same character array as the pointers of.

Both constructors are protected, and are only called by the concrete streambuf classes, such as std, std, or std.