Struct RootItem 

pub struct RootItem {

    pub inode_data: Vec<u8>,
    pub generation: u64,
    pub root_dirid: u64,
    pub bytenr: u64,
    pub byte_limit: u64,
    pub bytes_used: u64,
    pub last_snapshot: u64,
    pub flags: RootItemFlags,
    pub refs: u32,
    pub drop_progress: DiskKey,
    pub drop_level: u8,
    pub level: u8,
    pub generation_v2: u64,
    pub uuid: Uuid,
    pub parent_uuid: Uuid,
    pub received_uuid: Uuid,
    pub ctransid: u64,
    pub otransid: u64,
    pub stransid: u64,
    pub rtransid: u64,
    pub ctime: Timespec,
    pub otime: Timespec,
    pub stime: Timespec,
    pub rtime: Timespec,
}

Root item describing a tree (subvolume, snapshot, or internal tree).

Stored in the root tree with key (tree_objectid, ROOT_ITEM, 0). Contains the root block pointer, subvolume UUIDs, and transaction timestamps needed for snapshot management and send/receive.

Fields

inode_data: Vec<u8>

Raw bytes of the embedded btrfs_inode_item (160 bytes).

The on-disk ROOT_ITEM starts with an embedded inode describing the root directory of the subvolume. This is preserved as raw bytes to avoid losing data during parse/serialize round-trips, since the embedded inode fields are not otherwise tracked by this struct.

generation: u64

Generation when this root was last modified.

root_dirid: u64

Objectid of the root directory inode (always 256 for FS trees).

bytenr: u64

Logical bytenr of this tree’s root block.

byte_limit: u64

Quota byte limit (0 = unlimited).

bytes_used: u64

Bytes used by this tree.

last_snapshot: u64

Generation of the last snapshot taken from this subvolume.

flags: RootItemFlags

Root flags (RDONLY for read-only snapshots).

refs: u32

Reference count.

drop_progress: DiskKey

Progress key for in-progress drop operations.

drop_level: u8

Tree level of the drop progress.

level: u8

B-tree level of this tree’s root block.

generation_v2: u64

Extended generation (v2 root items, matches generation in practice).

uuid: Uuid

UUID of this subvolume.

parent_uuid: Uuid

UUID of the parent subvolume (for snapshots).

received_uuid: Uuid

UUID of the subvolume this was received from (for send/receive).

ctransid: u64

Transaction ID of the last change to this subvolume.

otransid: u64

Transaction ID when this subvolume was created.

stransid: u64

Transaction ID when this subvolume was sent.

rtransid: u64

Transaction ID when this subvolume was received.

ctime: Timespec

Time of the last change.

otime: Timespec

Creation time.

stime: Timespec

Time when sent.

rtime: Timespec

Time when received.

Implementations

impl RootItem

pub fn parse(data: &[u8]) -> Option<Self>

Parse a root item from a raw byte buffer. Handles both v1 (shorter) and v2 (full) root item formats gracefully, defaulting missing fields to zero/nil.

pub fn new_internal(generation: u64, bytenr: u64, level: u8) -> Self

Create a minimal root item for internal trees (not subvolumes).

Sets generation, bytenr, level, and refs=1. All other fields are zeroed/nil.

pub fn to_bytes(&self) -> Vec<u8>

Serialize to the on-disk byte representation (496 bytes).

Starts with a 160-byte zeroed inode_item, followed by root item fields, padded with zeros to 496 bytes total.

Trait Implementations

impl Clone for RootItem

fn clone(&self) -> RootItem

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for RootItem

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.