C++ vectors to pointers

vector_to_pointer2.cpp

#include <iostream>
#include <string>
#include <vector>
#include <memory>
using namespace std;


template<class T>
void test_function(T ***c, const size_t size_x, const size_t size_y, const size_t size_z)
{

}

template<class T>
void test_function(T **c, const size_t size_x, const size_t size_y)
{

}

template<class T>
void test_function(T *c, const size_t size_x)
{

}


template<class T>
T*** get_pointer_from_vector(vector<vector<vector<T>>> &input_data, const size_t size_x, const size_t size_y)
{
    vector<vector<T*>> ptr_array2(size_x, vector<T*>(size_y));
    vector<T**> ptr_array1(size_x);

    for (size_t i = 0; i < size_x; i++)
    {
        for (size_t j = 0; j < size_y; j++)
            ptr_array2[i][j] = input_data[i][j].data();

        ptr_array1[i] = ptr_array2[i].data();
    }

    T*** legacy_ptr = ptr_array1.data();

    return legacy_ptr;
}

template<class T>
T** get_pointer_from_vector(vector<vector<T>>& input_data, const size_t size_x)
{
    vector<T*> row_ptrs(size_x);

    for (size_t i = 0; i < size_x; i++)
        row_ptrs[i] = input_data[i].data();

    T** legacy_ptr = row_ptrs.data();

    return legacy_ptr;
}

template<class T>
T* get_pointer_from_vector(vector<T>& input_data)
{
    T* legacy_ptr = input_data.data();

    return legacy_ptr;
}


int main(void)
{
    const size_t dim1 = 2, dim2 = 2, dim3 = 3;

    vector<vector<vector<int>>> data3(dim1, vector<vector<int>>(dim2, vector<int>(dim3)));
    test_function(get_pointer_from_vector(data3, dim1, dim2), dim1, dim2, dim3);
    
    vector<vector<char>> data2(dim1, vector<char>(dim2));
    test_function(get_pointer_from_vector(data2, dim1), dim1, dim2);

    vector<double> data1(dim1);
    test_function(get_pointer_from_vector(data1), dim1);

	return 0;
}