This morning I stumbled upon a B-Tree Page API Example from Robert Sedgewick & Kevin Wayne (Algorithms 4/e).

Its in Java but can easily be transformed into C++:

"

public class Page<Key>

Page(boolean bottom) // create and open a page

void close() // close a page

void add(Key key) // add key into the (external) page

void  add(Page p) // open p and add an entry into this 

// (internal) page that associates 

// the smallest key in p with p

boolean  isExternal() // Is this page external?

boolean contains(Key key) // is key in the page?

Page next(Key key) // the subtree that could contain the key

boolean isFull() // has the page overflowed?

Page split() // move the highest-ranking half of the

// keys in the page to a new page

Iterable<Key> keys() // iterator for the keys on the page

“