Module segment_lease 

RAII-leased typed segment guards.

SegmentBorrowRegistry records live byte-range borrows. SegmentLease owns one registry entry and removes it on drop. SegRef and SegRefMut pair that lease with an account-data guard, allowing sequential access after the previous guard is dropped while rejecting incompatible live ranges.

For example, both mutations below are sequential because the first guard is dropped before the second is acquired:

{ let mut b = ctx.segment_mut::<WireU64>(0, BAL)?; *b += amount; }
{ let mut b = ctx.segment_mut::<WireU64>(0, BAL)?; *b += more;   }

Representation

SegmentLease stores a raw pointer to the registry plus a PhantomData<&'a mut SegmentBorrowRegistry>. A raw pointer avoids extending a Rust &mut borrow of the entire context through the returned segment guard. The lifetime marker ties the lease to the registry borrow, and Drop performs an exact entry release without allocation.

Why a wrapper, not a field on Ref/RefMut

The canonical hopper_runtime::Ref / RefMut are kept flat on Solana ({ptr, state_ptr} = 2 words, see borrow.rs). Adding a registry pointer to them would expand the representation for all access paths, including the whole-account load() path that doesn’t touch the segment registry. Keeping the lease as a separate wrapper leaves load() at two words while segment access carries the additional lease pointer.

Structs

SegRef

Shared typed segment guard: a Ref<T> paired with a SegmentLease that releases the registry entry on drop.

SegRefMut

Exclusive typed segment guard.

SegmentLease

RAII lease on one registered entry in a SegmentBorrowRegistry.

SegmentsMut

A guard over several disjoint typed sub-ranges of one account, returned by AccountView::split_segments_mut.