Struct Cursor 

pub struct Cursor(/* private fields */);

How far a scan has got, and the number the client holds between calls.

It is a position in the keyspace and not a position in memory. Two calls a week apart with the same cursor resume at the same place, even if every segment in the index has split in between.

Implementations

impl Cursor

pub const START: Cursor

The start of a walk, and the same value as the end of one.

pub const fn from_raw(raw: u64) -> Cursor

The cursor a client sent, whatever it sent.

Any number is a valid cursor. A made up one resumes somewhere arbitrary and answers keys from there, which is what Redis does and is the only behaviour that does not require the server to remember every cursor it has ever handed out.

pub const fn raw(self) -> u64

The number to hand the client.

pub const fn is_end(self) -> bool

Whether the walk is over.

pub const fn stripe(self) -> usize

Which index of several this cursor was walking.

The index itself never reads this and never writes it. It is here because the number a client holds has one bit budget and the layer above needs a field in it, and a field handed out in two places is a field that collides. See the module docs for the rest of the shape.

pub const fn with_stripe(self, stripe: usize) -> Cursor

The same cursor with a stripe number written into it.

A number too big for the field is masked down rather than refused, and nothing can hand one over: the field holds STRIPE_BITS bits and that is what the width above it is capped at.

pub const fn without_stripe(self) -> Cursor

The same cursor with the stripe number taken back out.

What the index is handed, so that a walk of one stripe cannot tell it is one of several. Which also means that a cursor holding nothing but a stripe number is the start of that stripe.

Trait Implementations

impl Clone for Cursor

fn clone(&self) -> Cursor

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 Default for Cursor

fn default() -> Cursor

Returns the “default value” for a type.

impl Eq for Cursor

impl From<Cursor> for u64

fn from(c: Cursor) -> u64

Converts to this type from the input type.

impl From<u64> for Cursor

fn from(raw: u64) -> Cursor

Converts to this type from the input type.

impl Ord for Cursor

fn cmp(&self, other: &Cursor) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

fn clamp_to<R>(self, range: R) -> Self

where Self: Sized, R: ClampBounds<Self>,

🔬This is a nightly-only experimental API. (clamp_to)

Restrict a value to a certain range.

impl PartialEq for Cursor

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

Equality operator ==.

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

Inequality operator !=.

impl PartialOrd for Cursor

fn partial_cmp(&self, other: &Cursor) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

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

Tests less than (for self and other) and is used by the < operator.

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

Tests less than or equal to (for self and other) and is used by the <= operator.

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

Tests greater than (for self and other) and is used by the > operator.

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

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl StructuralPartialEq for Cursor