Struct ExtentItem 

pub struct ExtentItem {
    pub refs: u64,
    pub generation: u64,
    pub flags: ExtentFlags,
    pub tree_block_key: Option<DiskKey>,
    pub tree_block_level: Option<u8>,
    pub skinny_level: Option<u64>,
    pub inline_refs: Vec<InlineRef>,
}

Extent allocation record from the extent tree.

Tracks reference counts, ownership, and backreferences for a contiguous range of allocated disk space. Used for both data extents (EXTENT_ITEM) and metadata blocks (METADATA_ITEM with skinny metadata).

Fields

refs: u64

Number of references to this extent.

generation: u64

Generation when this extent was allocated.

flags: ExtentFlags

Whether this extent holds data or a tree block.

tree_block_key: Option<DiskKey>

For non-skinny tree block extents: the first key in the block.

tree_block_level: Option<u8>

For non-skinny tree block extents: the block’s tree level.

skinny_level: Option<u64>

For skinny metadata items: the tree level (from the key offset).

inline_refs: Vec<InlineRef>

Inline backreferences packed after the extent header.

Implementations

impl ExtentItem

pub const SKINNY_SIZE: usize = 33

Size of a skinny metadata extent item with one TREE_BLOCK_REF.

Layout: extent header (24) + inline ref type (1) + offset (8) = 33.

pub const NON_SKINNY_SIZE: usize = 51

Size of a non-skinny metadata extent item with tree_block_info and one TREE_BLOCK_REF.

Layout: extent header (24) + tree_block_info (18) + inline ref (9) = 51.

pub const DATA_INLINE_SIZE: usize = 53

Size of a data extent item with one inline EXTENT_DATA_REF.

Layout: extent header (24) + inline ref type (1) + data ref (28) = 53.

pub fn is_data(&self) -> bool

Returns true if this extent holds file data.

pub fn is_tree_block(&self) -> bool

Returns true if this extent holds a metadata tree block.

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

Parse an extent item from a raw byte buffer, using the item key to determine whether this is a skinny metadata item or a full extent item.

pub fn to_bytes_skinny(refs: u64, generation: u64, root_id: u64) -> Vec<u8>

Serialize a skinny metadata extent item (METADATA_ITEM) with a single TREE_BLOCK_REF inline backref (33 bytes).

pub fn to_bytes_non_skinny( refs: u64, generation: u64, root_id: u64, first_key: &DiskKey, level: u8, ) -> Vec<u8>

Serialize a non-skinny metadata extent item (EXTENT_ITEM) with tree_block_info and a TREE_BLOCK_REF inline backref (51 bytes).

pub fn to_bytes_data( refs: u64, generation: u64, root: u64, objectid: u64, offset: u64, count: u32, ) -> Vec<u8>

Serialize a data extent item (EXTENT_ITEM) with a single inline EXTENT_DATA_REF backref (53 bytes).

Trait Implementations

impl Clone for ExtentItem

fn clone(&self) -> ExtentItem

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ExtentItem

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

Formats the value using the given formatter.