Struct Cursor 

pub struct Cursor {
    pub stream: StreamId,
    pub seq: u64,
    pub hash: Hash,
}

A reader’s place in a stream: which stream, how far, and what the history up to there was.

The position is the last entry the reader has; reading “after” the cursor returns the entries that follow it. The identity and the link make the cursor checkable: the relay answers a cursor only if the stream is the same incarnation and its chain has the same link at that position. Otherwise it says which of the two failed, and the reader knows its copy and the relay’s have parted - rather than reading on from a place that no longer exists.

The text form, used in URLs, is <position>.<stream>.<link>:

use efema_proto::{Cursor, StreamId};

let start = Cursor::start(StreamId::from_bytes([0xab; 16]));
let text = start.to_string();
assert!(text.starts_with("0.abababab"));
assert_eq!(text.parse::<Cursor>().unwrap(), start);

Fields

stream: StreamId

The stream incarnation this cursor belongs to.

seq: u64

The position of the last entry the reader has; 0 before the first.

hash: Hash

The chain link at seq.

Implementations

impl Cursor

pub fn start(stream: StreamId) -> Self

The cursor before the first entry of stream: the reader knows the stream and has read nothing from it yet.

Trait Implementations

impl Clone for Cursor

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 Cursor

impl Debug for Cursor

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

Formats the value using the given formatter.

impl<'bytes, Ctx> Decode<'bytes, Ctx> for Cursor

fn decode( __d777: &mut Decoder<'bytes>, __ctx777: &mut Ctx, ) -> Result<Cursor, Error>

Decode a value using the given Decoder.

fn nil() -> Option<Self>

If possible, return a nil value of Self.

impl Display for Cursor

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

Formats the value using the given formatter.

impl<Ctx> Encode<Ctx> for Cursor

fn encode<__W777>( &self, __e777: &mut Encoder<__W777>, __ctx777: &mut Ctx, ) -> Result<(), Error<__W777::Error>>

where __W777: Write,

Encode a value of this type using the given Encoder.

fn is_nil(&self) -> bool

Is this value of Self a nil value?

impl Eq for Cursor

impl FromStr for Cursor

type Err = ParseCursorError

The associated error which can be returned from parsing.

fn from_str(s: &str) -> Result<Self, Self::Err>

Parses a string s to return a value of this type.

impl Hash for Cursor

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 Cursor

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for Cursor