Enum CanHeader 

#[non_exhaustive]
pub enum CanHeader {
    Cid {
        seq: u8,
        node_id_bits: u16,
        alias: u16,
    },
    Rid {
        alias: u16,
    },
    Amd {
        alias: u16,
    },
    Ame {
        alias: u16,
    },
    Amr {
        alias: u16,
    },
    OtherControl {
        seq: u8,
        var: u16,
        alias: u16,
    },
    Message {
        mti: Mti,
        alias: u16,
    },
    Datagram {
        kind: MessageFrameType,
        dest: u16,
        alias: u16,
    },
    Stream {
        dest: u16,
        alias: u16,
    },
    Reserved {
        kind: u8,
        var: u16,
        alias: u16,
    },
}

A decoded CAN identifier.

CanHeader::decode interprets any 29-bit identifier and CanHeader::encode builds one; encode(decode(id)) == id for every identifier with bit 28 set. Every variant carries the source alias (bits 11-0), available uniformly through CanHeader::src_alias.

Bit 27	Bits 26-24	Bits 23-12	Variant
0	7, 6, 5, 4	Node ID chunk	Cid
0	0	0x700	Rid
0	0	0x701	Amd
0	0	0x702	Ame
0	0	0x703	Amr
0	other	other	OtherControl (e.g. error information reports)
1	1	CAN-MTI	Message
1	2-5	dest alias	Datagram
1	7	dest alias	Stream
1	0, 6	any	Reserved

use rolcb::can::CanHeader;
use rolcb::Mti;

let h = CanHeader::Message { mti: Mti::PCER, alias: 0x123 };
assert_eq!(h.encode(), 0x195B_4123);
assert_eq!(CanHeader::decode(0x195B_4123), h);
assert_eq!(CanHeader::Rid { alias: 0x285 }.encode(), 0x1070_0285);

The enum is #[non_exhaustive]: match it with a _ arm.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Cid

Check ID frame. seq is 7..=4; node_id_bits is the 12-bit chunk of the Node ID being reserved (7 = bits 47-36 … 4 = bits 11-0).

The first step of alias reservation. A node sends CID7, CID6, CID5, CID4 with its candidate alias, then waits 200 ms for objections. A node that already owns the alias answers with CanHeader::Rid. Build the whole set with cid_frames.

Fields

seq: u8

Sequence number 7, 6, 5 or 4 (bits 26-24).

node_id_bits: u16

The 12-bit slice of the Node ID this frame carries.

alias: u16

The alias being requested.

Rid

Reserve ID. Sent after the 200 ms CID wait to claim the alias, and by an alias owner to object to someone else’s CID for its alias.

Fields

alias: u16

The alias being reserved or defended.

Amd

Alias Map Definition. Data is the 6-byte Node ID. Announces “this alias now belongs to this Node ID”; the node becomes permitted to send messages. Also the reply to CanHeader::Ame.

Fields

alias: u16

The alias being mapped.

Ame

Alias Mapping Enquiry. With empty data, every permitted node replies with its AMD; with a 6-byte Node ID, only that node replies. Used by gateways and tools to rebuild their alias tables.

Fields

alias: u16

The alias of the node asking.

Amr

Alias Map Reset. Data is the 6-byte Node ID. The sender is giving up this alias (for example after a collision); others must forget the mapping and any partial multi-frame messages from it.

Fields

alias: u16

The alias being released.

OtherControl

Some other control frame (for example the error information report frames), passed through undecoded.

Fields

seq: u8

Bits 26-24.

var: u16

Bits 23-12.

alias: u16

Source alias.

Message

Global or addressed OpenLCB message.

For addressed MTIs the destination alias is not in the header but in the first two data bytes; see Message::to_frames.

Fields

mti: Mti

The message type (only the low 12 bits travel on CAN).

alias: u16

Source alias.

Datagram

Datagram frame addressed to dest.

Fields

kind: MessageFrameType

Which part of the datagram this frame is (only the four datagram variants of MessageFrameType are produced by decode).

dest: u16

Destination alias.

alias: u16

Source alias.

Stream

Stream data frame addressed to dest.

Fields

dest: u16

Destination alias.

alias: u16

Source alias.

Reserved

Reserved frame type.

Fields

kind: u8

The frame type, 0 or 6.

var: u16

Bits 23-12.

alias: u16

Source alias.

Implementations

impl CanHeader

pub fn decode(id: u32) -> CanHeader

Interpret a 29-bit identifier. Never fails: unrecognised values map to OtherControl or Reserved. Bit 28 is not checked.

pub fn encode(&self) -> u32

Build the 29-bit identifier (with the reserved bit 28 set).

A Datagram whose kind is not one of the four datagram variants is encoded as DatagramOnly. Every field is masked to its width (3 bits for seq/kind, 12 bits for aliases and the variable field), so an out-of-range value can never spill into a neighbouring field.

pub fn src_alias(&self) -> u16

The source alias, whatever the frame type.

Trait Implementations

impl Clone for CanHeader

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 CanHeader

impl Debug for CanHeader

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

Formats the value using the given formatter.

impl Eq for CanHeader

impl Hash for CanHeader

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for CanHeader

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for CanHeader