Struct CompressedClusterReadGuard 

pub(super) struct CompressedClusterReadGuard<'a> {
    host_offset: HostOffset,
    length: NonZero<u64>,
    cluster_bits: u32,
    _lock: RwLockEitherGuard<'a, ()>,
}

Read guard for a compressed cluster.

Readers generally do not need to lock L2 tables: Modifications replace mappings atomically, and allocations referenced by a (data) mapping are not freed while the image can be accessed concurrently. However, allocations referenced by compressed mappings may be freed when they are replaced (by concurrent writes), so the L2 table must not be modified from looking up the compressed mapping until its data has been read. This guard ensures that.

Fields

host_offset: HostOffset

Offset of the compressed data.

length: NonZero<u64>

Upper limit on the number of bytes that comprise the compressed data.

cluster_bits: u32

log2 of the cluster size.

_lock: RwLockEitherGuard<'a, ()>

Held lock on the L2 table, preventing modifications.

Implementations

impl<'a> CompressedClusterReadGuard<'a>

pub fn new( l2_table: &L2Table, cluster: GuestCluster, lock: RwLockEitherGuard<'a, ()>, ) -> Result<Option<Self>>

Create a new guard for reading compressed data from the given cluster, under lock, which prevents concurrent modifications of that cluster.

lock must be a read or write lock on L2Table.writer_lock.

Return None if cluster is not compressed (checked under the guard).

pub async fn read_compressed<S: Storage>( &self, storage: &S, buf: &mut [u8], ) -> Result<()>

Read the compressed cluster.

Read the compressed data from storage (which must be the image’s data file) and decompress it into buf (which must have a length of exactly one cluster).

Trait Implementations

impl<'a> Debug for CompressedClusterReadGuard<'a>

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

Formats the value using the given formatter.