I want use function (not kernel) like this: (C++)

Code :
void doSome(float4 &a, float4 &b)
{
  a.x = ... do something ...
  a.y = ... do something ...
  a.z = ... do something ...
  a.w = ... do something ...
  b = ... do something ...
}

How i may write this on OpenCL?
I try some variants with pointers, search in spec, but i dont find answer.