Struct CycleGuard 

pub struct CycleGuard { /* private fields */ }

A termination proof for a chain walk, paid for only by the chains that need one.

Under MAX_DELTA_LINKS links it is two integer operations and no allocation — the shape every ordinary read has always had. Past that depth it starts recording the archive offsets it has stood on, and a repeat is a cycle by definition rather than by a guess about how deep is too deep. The set is only ever entered on chains a corrupt pack or a long push history produced, so the hot path is unchanged; a legitimate chain of d links costs d - MAX_DELTA_LINKS u64 slots and nothing else.

It is one guard for both walkers (LAW 5): materialize_at here and GitStore::resolved_type_at in crate::serve, which followed the same links under a hand-written copy of the same ceiling.

Implementations

impl CycleGuard

pub fn new() -> Self

pub fn step(&mut self, at: u64) -> Result<()>

One link, standing at archive offset at. Err only when this walk has already stood there, which no acyclic chain can do.

pub fn links(&self) -> usize

How many links this walk has taken.

Trait Implementations

impl Default for CycleGuard

fn default() -> Self

Returns the “default value” for a type.