Enum Count 

pub enum Count {
    Normal(u64),
    Backfilled(i64),
}

Sequence number locating a PDU in a room timeline.

Valid normal counts range from zero through i64::MAX, while valid backfilled counts range from i64::MIN through zero. Ordering compares their signed representations, with zero shared by both variants.

Variants

Normal(u64)

Sequence assigned to an event in the normal timeline.

Normal counts advance forward as new local or federated events are appended. Valid values do not exceed i64::MAX.

Backfilled(i64)

Sequence assigned to an event in the backfilled timeline.

Valid backfilled counts occupy the nonpositive signed ordering range.

Implementations

impl Count

pub fn to_be_bytes(self) -> [u8; 8]

Encodes the count’s integer bits in big-endian order.

Normal values retain their unsigned representation. Backfilled values are reinterpreted as unsigned two’s-complement bits before encoding.

Panics

Panics in debug builds if a positive Backfilled value was constructed directly.

pub fn from_unsigned(unsigned: u64) -> Self

Interprets unsigned integer bits as a signed timeline count.

Values with the high bit set become negative backfilled counts. Other positive values become normal counts, while zero becomes backfilled zero.

pub fn from_signed(signed: i64) -> Self

Classifies a signed integer as a normal or backfilled count.

Positive values become normal counts. Zero and negative values become backfilled counts.

pub fn into_unsigned(self) -> u64

Converts the count to its unsigned integer bit representation.

Backfilled values are reinterpreted using two’s-complement bits. The variant information is not retained in the returned integer.

Panics

Panics in debug builds if a positive Backfilled value was constructed directly.

pub fn into_signed(self) -> i64

Converts the count to the signed representation used for ordering.

Valid normal values cast into the nonnegative signed domain, while valid backfilled values retain their signed count. Direct construction outside the documented ranges violates the ordering invariant.

Panics

Panics in debug builds if a positive Backfilled value was constructed directly.

pub fn into_normal(self) -> Self

Converts a count to a normal-timeline position.

Existing normal counts are preserved. Any backfilled count maps to the beginning of the normal timeline at zero.

Panics

Panics in debug builds if a positive Backfilled value was constructed directly.

pub fn checked_inc(self, dir: Direction) -> Result<Self, Error>

Advances or retreats the count by one without integer overflow.

Forward movement adds one and backward movement subtracts one. The original variant is preserved, so callers must avoid crossing that variant’s valid timeline range.

pub fn checked_add(self, add: u64) -> Result<Self, Error>

Adds an unsigned offset without integer overflow.

Backfilled offsets are cast to i64 and must not exceed i64::MAX. Callers must keep the resulting variant within its documented range; integer overflow returns an arithmetic error.

pub fn checked_sub(self, sub: u64) -> Result<Self, Error>

Subtracts an unsigned offset without integer underflow.

Backfilled offsets are cast to i64 and must not exceed i64::MAX. Callers must keep the resulting variant within its documented range; integer underflow returns an arithmetic error.

pub fn saturating_inc(self, dir: Direction) -> Self

Advances or retreats the count by one with saturation.

Forward movement adds one and backward movement subtracts one. Saturation uses the integer boundary of the existing variant and does not prevent a backfilled value from crossing zero.

pub fn saturating_add(self, add: u64) -> Self

Adds an unsigned offset with saturation at the integer boundary.

Backfilled offsets are cast to i64 and must not exceed i64::MAX. Saturation uses the underlying integer boundary and does not repair a result outside the variant’s documented range.

pub fn saturating_sub(self, sub: u64) -> Self

Subtracts an unsigned offset with saturation at the integer boundary.

Backfilled offsets are cast to i64 and must not exceed i64::MAX. Saturation uses the underlying integer boundary and does not repair a result outside the variant’s documented range.

pub const fn min() -> Self

Returns the earliest valid timeline count.

The minimum is a backfilled count at i64::MIN. It sorts before every other valid count.

pub const fn max() -> Self

Returns the latest valid timeline count.

The maximum is a normal count at i64::MAX. This keeps the value within the signed domain used by ordering.

pub(crate) fn debug_assert_valid(&self)

Trait Implementations

impl Clone for Count

fn clone(&self) -> Count

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for Count

impl Debug for Count

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

Formats the value using the given formatter.

impl Default for Count

fn default() -> Self

Returns the “default value” for a type.

impl Display for Count

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

Formats the value using the given formatter.

impl Eq for Count

impl From<i64> for Count

fn from(signed: i64) -> Self

Converts to this type from the input type.

impl From<u64> for Count

fn from(unsigned: u64) -> Self

Converts to this type from the input type.

impl FromStr for Count

type Err = Error

The associated error which can be returned from parsing.

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

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

impl Hash for Count

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 Ord for Count

fn cmp(&self, other: &Self) -> 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.

impl PartialEq for Count

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

Equality operator ==.

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

Inequality operator !=.

impl PartialOrd for Count

fn partial_cmp(&self, other: &Self) -> 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 Count