C++ the good parts — std::swap – Page 4

What is Pointer Rewiring aka Relinking?

Since a “pointer” is a much-feared word, let’s clarify what is pointer rewiring/relinking. That is the idiom used to speed up nontrivial types of moving. You do not move them, you swap their internals.

Let’s visualize this function

// overload for pointers to int

inline void rewire( int * A, int * B )

{

int * temp = A ;

A = B ;

B = temp ;

}

Watch carefully.

That is the situation upon entering the rewiring function. Then:

1	T * temp = a ;

And then this:

a = b

This is where “pointer to A” loses its address. It is rewired to the same value as pointer B. Lastly:

b = temp;

Now B is rewired to the “value A”. Effectively pointers A and B have exchanged addresses of the values they have been pointing to. The pointers themselves have changed. They have been “rewired”.