This Scheme code captures some of the buddy capability logic described here. It relies on a few non-standard Scheme features defined in SRFI 60. At the top lexical level are defined
is a useful debugging tool, not currently called.
is a print routine of large integers in binary and logarithmic form.
is a creator of functional but insecure sealer-unsealer pairs.
(desc k)
generates (top . catalog), for a address space of 2k cells. “top” is the capability for all cells and will presumably be closely held by whoever calls desc. “catalog” is a function that returns any of a universally available set of values and functions.
If C is the aforementioned catalog:
((C 'within) b c)
returns a bool indicating if all the cells available via b are available via c.
((C 'sub) b n)
returns a new capability to a subset of capability b.
((C 'locate) b c)
returns the range r of b within c if ((C 'within) b c). Otherwise it returns 0.
((C 'size) A)
returns a power of 2 which is the smallest invalid index into capability A.
(C 'zer)
returns the null capability with no valid indexes.
((C 'zer?) A)
iff A is the null capability.
((C 'eq?) A B)
iff A and B are the same capability.
If T = top = (car (desc k)) then ((C 'locate) x T) yields the real mid-pointer of the block accessed by x. Let (R x) be defined as ((C 'locate) x T) for this section. Let (S A n) be the storage cell accessed by applying index n to capability A. We can make several definitive claims with this notation.

If 0≤n<(size A) then