static inline
    SilcBool silc_atomic_cas_pointer(SilcAtomicPointer *atomic,
                                     void *old_ptr, void *new_ptr);

    Performs compare and swap (CAS).  Atomically compares if the variable
    `atomic' has the pointer `old_ptr' and in that case swaps it with the
    pointer `new_ptr'.  Returns TRUE if the old pointer was same and it was
    swapped and FALSE if it differed and was not swapped.