Struct HopperHeader 

#[repr(C, packed(1))]
pub struct HopperHeader {
    pub disc: u8,
    pub version: u8,
    pub flags: u16,
    pub layout_id: [u8; 8],
    pub schema_epoch: u32,
}

The canonical 16-byte header at the start of a headered Hopper account.

The reserved header tail carries a schema_epoch: u32 so the runtime can distinguish schema-compatible minor versions from wire- incompatible revisions without bumping the single version byte.

byte 0     : disc (u8)
byte 1     : version (u8)
bytes 2-3  : flags (u16 LE)
bytes 4-11 : layout_id (first 8 bytes of canonical wire fingerprint)
bytes 12-15: schema_epoch (u32 LE), audit-added

schema_epoch defaults to 1 at account initialisation via init_header. Programs that publish a migration bump this field to advertise the new shape while retaining the same disc/version. Runtime header validation checks these values. Current generated headered clients compare the stored layout_id before decoding; compact clients use their separate size/discriminator path.

Fields

disc: u8

version: u8

flags: u16

layout_id: [u8; 8]

schema_epoch: u32

Schema-evolution epoch. Little-endian u32. 1 for freshly initialised headers; bumped by migration helpers.

Implementations

impl HopperHeader

pub const SIZE: usize = 16

The header is always 16 bytes.

pub fn from_bytes(data: &[u8]) -> Option<&Self>

Read a header from the start of a raw data slice.

pub fn from_bytes_mut(data: &mut [u8]) -> Option<&mut Self>

Read a mutable header from the start of a raw data slice.

Trait Implementations

impl Clone for HopperHeader

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for HopperHeader

impl Debug for HopperHeader

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

Formats the value using the given formatter.

impl Eq for HopperHeader

impl PartialEq for HopperHeader

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for HopperHeader