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use {
crate::{InodeItem, Key, Time, UuidBytes},
byteorder::LE,
static_assertions::const_assert_eq,
zerocopy::{AsBytes, FromBytes, Unaligned, U32, U64},
};
/// Defines the location and parameters of the root of a b-tree.
#[derive(Copy, Clone, Debug, AsBytes, FromBytes, Unaligned)]
#[repr(C, packed)]
pub struct RootItem {
pub inode: InodeItem,
pub generation: U64<LE>,
pub root_dirid: U64<LE>,
pub bytenr: U64<LE>,
/// Currently unused. Always 0.
pub byte_limit: U64<LE>,
/// Currently unused.
pub bytes_used: U64<LE>,
/// The transaction ID of the last transaction that created a snapshot of this root.
pub last_snapshot: U64<LE>,
pub flags: U64<LE>,
/// Only 0 or 1. Historically contained a reference count.
pub refs: U32<LE>,
/// Contains the key of the last dropped item during subvolume removal or relocation.
///
/// Value will be zeroed out otherwise.
pub drop_progress: Key,
/// The tree level of the node referenced in [drop_progress](RootItem::drop_progress).
pub drop_level: u8,
/// The height of this root's tree.
pub level: u8,
/// Value to help determine whether this root has been modified by an older btrfs
/// implementation.
///
/// If the value is equal to [generation], the fields below are valid. Otherwise, this indicates
/// the fields are invalid but recoverable.
///
/// [generation]: RootItem::generation
pub generation_v2: U64<LE>,
/// The subvolume's UUID.
pub uuid: UuidBytes,
/// The parent's subvolume UUID.
///
/// This is used during send/receive.
pub parent_uuid: UuidBytes,
/// The received UUID.
///
/// This is used during send/receive.
pub received_uuid: UuidBytes,
/// The transaction ID of the last transaction that modified the tree.
///
/// Note: some operations like internal caches or relocation will not update this value.
pub ctransid: U64<LE>,
/// The transaction ID of the transaction that created the tree.
pub otransid: U64<LE>,
/// The transaction ID for the transaction that sent this subvolume.
///
/// This value is non-zero for a received subvolume.
pub stransid: U64<LE>,
/// The transaction ID for the transaction that received this subvolume.
///
/// This value is non-zero for a received subvolume.
pub rtransid: U64<LE>,
/// The timestamp of the [`ctransid`](RootItem::ctransid).
pub ctime: Time,
/// The timestamp of the [`otransid`](RootItem::otransid).
pub otime: Time,
/// The timestamp of the [`stransid`](RootItem::stransid).
pub stime: Time,
/// The timestamp of the [`rtransid`](RootItem::rtransid).
pub rtime: Time,
/// Currently unused. Reserved for future use.
pub _unused: [u64; 8],
}
const_assert_eq!(std::mem::size_of::<RootItem>(), 439);