Struct ObjectHeader 

pub struct ObjectHeader {
    pub rc_count: u32,
    pub type_tag: TypeTag,
    pub flags: ObjectFlags,
    pub size_words: u16,
}

Header placed at the beginning of every heap-allocated object.

Layout:

• rc_count (u32): reference count
• type_tag (TypeTag): which kind of heap object
• flags (ObjectFlags): status flags
• size (u16): total object size in 8-byte words (max 512 KB)

Fields

rc_count: u32

Reference count.

type_tag: TypeTag

Type tag for the heap object.

flags: ObjectFlags

Object flags.

size_words: u16

Size of the object in 8-byte words.

Implementations

impl ObjectHeader

pub fn new(type_tag: TypeTag, size_words: u16) -> Self

Create a new object header.

pub fn inc_ref(&mut self)

Increment the reference count.

pub fn dec_ref(&mut self) -> bool

Decrement the reference count. Returns true if the count reaches zero.

pub fn is_unique(&self) -> bool

Check if the object has a single owner.

pub fn is_shared(&self) -> bool

Check if the object is shared.

pub fn size_bytes(&self) -> usize

Total size in bytes.

pub fn encode(&self) -> u64

Encode header into a u64 for compact storage.

pub fn decode(bits: u64) -> Option<Self>

Decode header from a u64.

Trait Implementations

impl Clone for ObjectHeader

fn clone(&self) -> ObjectHeader

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ObjectHeader

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

Formats the value using the given formatter.