C++: getting the address of the start of an std::vector?
c++, pointers, vector
Solution
I guess you'd just have to check.
Perhaps a utility function:
template <class T, class Alloc>
T* data(std::vector<T, Alloc>& vec)
{
return vec.empty() ? 0 : &vec[0];
}
template <class T, class Alloc>
const T* data(const std::vector<T, Alloc>& vec)
{
return vec.empty() ? 0 : &vec[0];
}
Problem
Sometimes it is useful to use the starting address of an `std::vector` and temporarily treat that address as the address of a regularly allocated buffer. For instance replace this: ``` char* buf = new char[size]; fillTheBuffer(buf, size); useTheBuffer(buf, size); delete[] buf; ``` With This: ``` vector<char> buf(size); fillTheBuffer(&buf[0], size); useTheBuffer(&buf[0], size); ``` The advantage of this is of course that the buffer is deallocated automatically and I don't have to worry about the `delete[]`. The problem I'm having with this is when size == 0. In that case the first version works ok. An empty buffer is "allocated" and the subsequent functions do nothing size they get size == 0. The second version however fails if size == 0 since calling `buf[0]` may rightly contain an assertion that `0 < size`. So is there an alternative to the idiom `&buf[0]` that returns the address of the start of the vector even if the vector is empty? I've also considered using `buf.begin()` but according to the standard it isn't even guaranteed to return a pointer.