Trait Table

pub trait Table: Sized {
    type InternalEntry: TableEntry;
    type Entry: Copy;

    const NAME: &'static str;
    const MAX_ENTRIES: usize;

    // Required methods
    fn from_data(data: Box<[Self::InternalEntry]>, header: &Header) -> Self;
    fn entries(&self) -> usize;
    fn get_ref(&self, index: usize) -> Option<&Self::InternalEntry>;
    fn get(&self, index: usize) -> Self::Entry;
    fn get_cluster(&self) -> Option<HostCluster>;
    fn get_offset(&self) -> Option<HostOffset>;
    fn set_cluster(&mut self, cluster: HostCluster);
    fn unset_cluster(&mut self);
    fn cluster_bits(&self) -> u32;
    fn is_modified(&self) -> bool;
    fn clear_modified(&self);
    fn set_modified(&self);

    // Provided methods
    fn byte_size(&self) -> usize { ... }
    fn cluster_count(&self) -> ClusterCount { ... }
    async fn load<S: Storage>(
        image: &S,
        header: &Header,
        cluster: HostCluster,
        entries: usize,
    ) -> Result<Self> { ... }
    async fn write<S: Storage>(&self, image: &S) -> Result<()> { ... }
    async fn write_entry<S: Storage>(
        &self,
        image: &S,
        index: usize,
    ) -> Result<()> { ... }
}

Generic trait for qcow2 metadata tables (L1, L2, refcount table).

Required Associated Constants

const NAME: &'static str

User-readable struct name.

const MAX_ENTRIES: usize

Maximum allowable number of entries.

Required Associated Types

type InternalEntry: TableEntry

Internal type for each table entry.

type Entry: Copy

Externally visible type for each table entry.

Required Methods

fn from_data(data: Box<[Self::InternalEntry]>, header: &Header) -> Self

Create a new table with the given contents

fn entries(&self) -> usize

Number of entries.

fn get_ref(&self, index: usize) -> Option<&Self::InternalEntry>

Get the given entry (as reference).

fn get(&self, index: usize) -> Self::Entry

Get the given entry (copied).

fn get_cluster(&self) -> Option<HostCluster>

Get this table’s (first) cluster in the image file.

fn get_offset(&self) -> Option<HostOffset>

Get this table’s offset in the image file.

fn set_cluster(&mut self, cluster: HostCluster)

Set this table’s (first) cluster in the image file (for writing).

fn unset_cluster(&mut self)

Remove the table’s association with any cluster in the image file.

fn cluster_bits(&self) -> u32

Return log2 of the cluster size.

All tables store this anyway.

fn is_modified(&self) -> bool

Check whether this table has been modified since it was last written.

fn clear_modified(&self)

Clear the modified flag.

fn set_modified(&self)

Set the modified flag.

Provided Methods

fn byte_size(&self) -> usize

Table size in bytes.

fn cluster_count(&self) -> ClusterCount

Number of clusters used by this table.

async fn load<S: Storage>( image: &S, header: &Header, cluster: HostCluster, entries: usize, ) -> Result<Self>

Load a table from the image file.

async fn write<S: Storage>(&self, image: &S) -> Result<()>

Write a table to the image file.

Callers must ensure the table is copied, i.e. its refcount is 1.

async fn write_entry<S: Storage>(&self, image: &S, index: usize) -> Result<()>

Write at least the given single (modified) entry to the image file.

Potentially writes more of the table, if alignment requirements ask for that.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors

impl Table for L1Table

const NAME: &'static str = "L1 table"

const MAX_ENTRIES: usize = 4_194_304usize

type InternalEntry = L1Entry

type Entry = L1Entry

impl Table for L2Table

const NAME: &'static str = "L2 table"

const MAX_ENTRIES: usize = 262_144usize

type InternalEntry = AtomicL2Entry

type Entry = L2Entry

impl Table for RefTable

const NAME: &'static str = "Refcount table"

const MAX_ENTRIES: usize = 4_194_304usize

type InternalEntry = RefTableEntry

type Entry = RefTableEntry