Struct StateLayout 

#[repr(C)]
pub struct StateLayout<const STATE_MAX: usize> {
    pub header: LayoutHeader,
    pub seq: IndexbusAtomicU64,
    pub len: IndexbusAtomicU32,
    pub pad: IndexbusAtomicU32,
    pub data: [u8; STATE_MAX],
}

State stream region base layout (generic over max bytes).

Note: C header generation typically uses a concrete STATE_MAX (see StateLayout256).

IMPORTANT: This generic layout does not include trailing padding for appended sections. For C headers and append-only wake sections, prefer a concrete exported layout like StateLayout256 which includes explicit 64B padding.

Initialization protocol (v1)

Most IndexBus layouts use a cross-process initialization state machine initialized: 0 (uninit) / 1 (initializing) / 2 (initialized).

The state-stream layout is intentionally different: it uses the seq field itself as the writer protocol (even = stable, odd = write-in-progress). A fresh, initialized region starts with seq = 0 (stable). There is no separate initialized field in v1.

Fields

header: LayoutHeader

Common region header (magic/version/capabilities/layout size).

seq: IndexbusAtomicU64

Sequence protocol:

• even = stable
• odd = writer in progress

len: IndexbusAtomicU32

Current payload length in bytes.

pad: IndexbusAtomicU32

Padding (reserved).

data: [u8; STATE_MAX]

State payload bytes (up to len).

Implementations

impl<const STATE_MAX: usize> StateLayout<STATE_MAX>

pub const REQUIRED_CAPS: u32 = caps::INDEXBUS_CAP_SUPPORTS_STATE

Capabilities required for this region to be considered compatible.