Pointers from function argument as host data (memory allocation)

Say I want to add two vectors as in example two. In the example, memory space is allocated and host data is created inside the code:

    float*       h_a = (float*) calloc(LENGTH, sizeof(float));       // a vector
    float*       h_b = (float*) calloc(LENGTH, sizeof(float));  // a vector
     int i = 0;
     int count = LENGTH;
     for(i = 0; i < count; i++){
        h_a[i] = rand() / (float)RAND_MAX;
        h_b[i] = rand() / (float)RAND_MAX;
    }

I'm trying to pass vectors a and b from R. They are passed as arguments to the main function as: vadd(double *a, double *b, int *n) (in RI have to change mainfor some other name like vadd). I allocate memory and I dereference the arguments as:

int i = 0;
    int count = LENGTH;
    for(i = 0; i < count; i++){
        h_a[i] = a[i];
        h_b[i] = b[i];
    }

This dereferencing procedure is taking too much time. Is there a way so that these pointers passed as arguments to the function are set as host data directly without the loop? Something like:

h_a = *a; h_b = *b;