Struct ChunkPreimage 

pub struct ChunkPreimage {
    pub preimage: [u8; 32],
    pub index: u8,
}

Payer → node released hash-chain preimage, advancing the lane’s claim by one chunk with no signature (ADR 003 §Hash-chain metering (PayWord), ADR 005 §Payment quantum and credit window).

Released after the payer has received and verified the chunk it pays for, so the payer’s exposure stays at zero. Preimage resistance makes the value self-proving: nobody derives keccak^(N−k−1)(s) from keccak^(N−k)(s) without the seed, so a deeper preimage is the receipt for every chunk below it.

Wire encoding

preimage ‖ index, 33 bytes flat — postcard writes a [u8; 32] raw and a u8 as one byte, so there is no length prefix and no varint. The byte IS the index, with no offset on send and no increment on receipt.

Index domain

Releasable indices are 1..=MAX_CHAIN_LENGTH. index == 0 is a protocol error — index 0 names chain_root and is the settlement case at redemption, so it proves nothing the voucher does not already say. It is rejected in band by the delivery handler as VoucherRejectReason::ChainIndexZero rather than at decode, so the payer learns why instead of seeing an opaque stream close. An index above MAX_CHAIN_LENGTH cannot be encoded at all: the walk is bounded at 255 hashes by the type, which is stronger than a runtime comparison.

Fields

preimage: [u8; 32]

The released value, keccak^(MAX_CHAIN_LENGTH − index) of the payer’s per-lane seed.

index: u8

Depth of preimage in the chain. Verified as keccak^(index − verified)(preimage) == tip against the receiving stream’s anchor.

Implementations

impl ChunkPreimage

pub const fn validate(&self) -> Result<(), MessageValidationError>

Always Ok. Both fields are fixed-width, so a decoded ChunkPreimage has no shape to check — and the one value invariant (index != 0) is deliberately not enforced here: it must surface as an in-band VoucherRejectReason::ChainIndexZero from the delivery handler, which holds the stream it has to answer on. Validating it here would collapse that reason into a decode failure and close the stream mute.

Present so ClientMessage::validate stays total over the enum, for the same reason ChunkData::validate is.

Errors

Never.

Trait Implementations

impl Clone for ChunkPreimage

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 ChunkPreimage

impl Debug for ChunkPreimage

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for ChunkPreimage

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Eq for ChunkPreimage

impl PartialEq for ChunkPreimage

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

Equality operator ==.

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

Inequality operator !=.

impl Serialize for ChunkPreimage

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for ChunkPreimage