Module snapshot 

Structs

FoldSnapshot

A fold snapshot: the folded state plus the per-partition offsets it folded through. as_of maps a partition id to the last offset folded into state (inclusive), matching the cursor’s per-partition offsets, so a multi-partition fold resumes correctly. Resume seeds the cursor at offset + 1 per partition, because the cursor takes the next offset to read (exclusive) while the snapshot records the last offset folded (inclusive).