string::data
Return the underlying character array directly.
Synopsis
char*
data() noexcept; (1)
char const*
data() const noexcept; (2)Description
Returns a pointer to the underlying array serving as storage. The value returned is such that the range [data(), data() + size()) is always a valid range, even if the container is empty.
| The value returned from this function is never equal to  | 
Complexity
Constant.
Exception Safety
No-throw guarantee.