Struct BTreeHeader 

pub struct BTreeHeader {
    pub magic: u64,
    pub root: AtomicU32,
    pub node_count: AtomicU32,
    pub capacity: u64,
    pub len: AtomicU64,
    pub free_head: AtomicU32,
    pub version: AtomicU64,
    /* private fields */
}

Fields

magic: u64

root: AtomicU32

node_count: AtomicU32

capacity: u64

len: AtomicU64

free_head: AtomicU32

Head of the single-writer free list (NIL = empty); merged/removed nodes are recycled here so deletes reclaim slots.

version: AtomicU64

Global seqlock. A writer makes it odd for the duration of a structural mutation (insert/remove) and even after; readers retry the whole search if it changes or is odd, so concurrent reads never observe a torn tree. Single-writer, multi-reader.