EndReading function returns a const char_type pointer to the element just beyond the last element of the string's internal buffer.
const char_type* EndReading() const;
It is generally illegal to dereference the returned pointer, unless it is known that the string's internal buffer is null-terminated. The
NS_CStringGetData function can be used to determine if a
nsACString instance has null-terminated storage.
BeginReading for an example.