Struct JournalLayout4 

#[repr(C, align(64))]
pub struct JournalLayout4 {
    pub header: LayoutHeader,
    pub initialized: IndexbusAtomicU32,
    pub pad0: u32,
    pub pad_to_64: [u8; 40],
    pub pub_pos: IndexbusAtomicU64,
    pub pad_pub_pos: [u8; 56],
    pub active_segment: IndexbusAtomicU32,
    pub pad_active_segment: [u8; 60],
    pub segments: [SegmentMeta; 3],
    pub sub_pos: [IndexbusAtomicU64; 4],
    pub pad_after_sub_pos: [u8; 32],
    pub segment_bufs: [[u8; 65536]; 3],
}

Concrete v1 journal layout:

• 3 segments
• 64KiB per segment
• 4 subscriber positions

This is a new region layout (v1 append-only) and must not reinterpret any existing region.

Fields

header: LayoutHeader

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

initialized: IndexbusAtomicU32

0 = uninitialized, 1 = initializing, 2 = initialized

pad0: u32

Padding (reserved).

pad_to_64: [u8; 40]

Pad to 64 so the first counter starts at offset 64.

pub_pos: IndexbusAtomicU64

Global publication position (monotonic bytes/records position; interpretation is lane-specific).

pad_pub_pos: [u8; 56]

Padding to keep pub_pos in its own cache line.

active_segment: IndexbusAtomicU32

Current active segment index (0..3).

pad_active_segment: [u8; 60]

Padding to keep active_segment in its own cache line.

segments: [SegmentMeta; 3]

Per-segment metadata.

sub_pos: [IndexbusAtomicU64; 4]

Per-subscriber positions.

pad_after_sub_pos: [u8; 32]

Pad so segment_bufs starts 64B-aligned.

segment_bufs: [[u8; 65536]; 3]

Segment buffers (64KiB each).

Implementations

impl JournalLayout4

pub const REQUIRED_CAPS: u32 = caps::INDEXBUS_CAP_SUPPORTS_JOURNAL

Capabilities required for this region to be considered compatible.