Struct Header 

pub struct Header<E = ()> {
    pub version: u64,
    pub verifying_key: VerifyingKey,
    pub signature: Option<Signature>,
    pub payload_size: u64,
    pub payload_hash: Option<Hash>,
    pub timestamp: Timestamp,
    pub seq_num: SeqNum,
    pub backlink: Option<Hash>,
    pub extensions: E,
}

Header of a p2panda operation.

The header holds all metadata required to cryptographically secure and authenticate a message Body and, if required, apply ordering to collections of messages from the same or many authors.

Example

use p2panda_core::{Body, Header, Operation, SigningKey, Timestamp};

let signing_key = SigningKey::generate();

let body = Body::new("Hello, Sloth!".as_bytes());
let mut header = Header {
    version: 1,
    verifying_key: signing_key.verifying_key(),
    signature: None,
    payload_size: body.size(),
    payload_hash: Some(body.hash()),
    timestamp: Timestamp::now(),
    seq_num: 0,
    backlink: None,
    extensions: (),
};

// Sign the header with the author's private key.
header.sign(&signing_key);

Fields

version: u64

Operation format version, allowing backwards compatibility when specification changes.

verifying_key: VerifyingKey

Author of this operation.

signature: Option<Signature>

Signature by author over all fields in header, providing authenticity.

payload_size: u64

Number of bytes of the body of this operation, must be zero if no body is given.

payload_hash: Option<Hash>

Hash of the body of this operation, must be included if payload_size is non-zero and omitted otherwise.

Keeping the hash here allows us to delete the payload (off-chain data) while retaining the ability to check the signature of the header.

timestamp: Timestamp

Time in microseconds since the Unix epoch.

seq_num: SeqNum

Number of operations this author has published to this log, begins with 0 and is always incremented by 1 with each new operation by the same author.

backlink: Option<Hash>

Hash of the previous operation of the same author and log. Can be omitted if first operation in log.

extensions: E

Custom meta data.

Implementations

impl<E> Header<E>

where E: Extensions,

pub fn to_bytes(&self) -> Vec<u8>

Header encoded to bytes in CBOR format.

pub fn sign(&mut self, signing_key: &SigningKey)

Add a signature to the header using the provided SigningKey.

This method signs the byte representation of a header with any existing signature removed before adding back the newly generated signature.

pub fn verify(&self) -> bool

Verify that the signature contained in this Header was generated by the claimed public key.

pub fn hash(&self) -> Hash

BLAKE3 hash of the header bytes.

This hash is used as the unique identifier of an operation, aka the Operation Id.

pub fn extension<T>(&self) -> Option<T>

where E: Extension<T>,

Extract an extension value from the header.

Trait Implementations

impl<'arbitrary, E: Arbitrary<'arbitrary>> Arbitrary<'arbitrary> for Header<E>

fn arbitrary(u: &mut Unstructured<'arbitrary>) -> Result<Self>

Generate an arbitrary value of Self from the given unstructured data.

fn arbitrary_take_rest(u: Unstructured<'arbitrary>) -> Result<Self>

Generate an arbitrary value of Self from the entirety of the given unstructured data.

fn size_hint(depth: usize) -> (usize, Option<usize>)

Get a size hint for how many bytes out of an Unstructured this type needs to construct itself.

fn try_size_hint( depth: usize, ) -> Result<(usize, Option<usize>), MaxRecursionReached>

Get a size hint for how many bytes out of an Unstructured this type needs to construct itself.

impl<E> Borrow<Header<E>> for Operation<E>

fn borrow(&self) -> &Header<E>

Immutably borrows from an owned value.

impl<E: Clone> Clone for Header<E>

fn clone(&self) -> Header<E>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<E: Debug> Debug for Header<E>

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

Formats the value using the given formatter.

impl<E: Default> Default for Header<E>

fn default() -> Self

Returns the “default value” for a type.

impl<'de, E> Deserialize<'de> for Header<E>

where E: Deserialize<'de>,

fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>

where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl<E: PartialEq> PartialEq for Header<E>

fn eq(&self, other: &Header<E>) -> bool

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<E> Serialize for Header<E>

where E: Serialize,

fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>

where S: Serializer,

Serialize this value into the given Serde serializer.

impl TryFrom<&[u8]> for Header

type Error = DecodeError

The type returned in the event of a conversion error.

fn try_from(value: &[u8]) -> Result<Self, Self::Error>

Performs the conversion.

impl<E: Eq> Eq for Header<E>

impl<E> StructuralPartialEq for Header<E>