New creates a PortAllocator over a net.PortRange, calling allocatorFactory to construct the backing store.

NewFromSnapshot allocates a PortAllocator and initializes it from a snapshot.

NewInMemory creates an in-memory allocator.

Creates a portAllocationOperation, tracking a set of allocations & releases If dryRun is specified, never actually allocate or release anything.

Encapsulates the semantics of a port allocation 'transaction': It is better to leak ports than to double-allocate them, so we allocate immediately, but defer release.

Interface manages the allocation of ports out of a range.