Enum writeable::LengthHint

pub enum LengthHint {
    Undefined,
    Exact(usize),
}

A hint to help consumers of Writeable pre-allocate bytes before they call write_to.

LengthHint implements std::ops::Add and similar traits for easy composition.

See this issue for more info: https://github.com/unicode-org/icu4x/issues/370.

Variants

Undefined

Default value: no hint is provided.

Exact(usize)

An exact length hint. This value is expected to equal the actual length from write_to.

Implementations

impl LengthHint

pub fn capacity(&self) -> usize

Returns a recommendation for the number of bytes to pre-allocate.

Examples

use writeable::Writeable;

fn pre_allocate_string(w: &impl Writeable) -> String {
    String::with_capacity(w.write_len().capacity())
}

pub fn is_zero(&self) -> bool

Returns whether the LengthHint indicates that the string is exactly 0 bytes long.

Trait Implementations

impl Add<LengthHint> for LengthHint

type Output = Self

The resulting type after applying the + operator.

fn add(self, other: LengthHint) -> Self

Performs the + operation.

impl Add<usize> for LengthHint

type Output = Self

The resulting type after applying the + operator.

fn add(self, other: usize) -> Self

Performs the + operation.

impl AddAssign<LengthHint> for LengthHint

fn add_assign(&mut self, other: Self)

Performs the += operation.

impl AddAssign<usize> for LengthHint

fn add_assign(&mut self, other: usize)

Performs the += operation.

impl Clone for LengthHint

fn clone(&self) -> LengthHint

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Copy for LengthHint

impl Debug for LengthHint

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

Formats the value using the given formatter.

impl Eq for LengthHint

impl PartialEq<LengthHint> for LengthHint

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

This method tests for self and other values to be equal, and is used by ==.

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

This method tests for !=.

impl StructuralEq for LengthHint

impl StructuralPartialEq for LengthHint

impl Sum<LengthHint> for LengthHint

fn sum<I>(iter: I) -> Self where
    I: Iterator<Item = LengthHint>, 

Method which takes an iterator and generates Self from the elements by “summing up” the items.

impl Sum<usize> for LengthHint

fn sum<I>(iter: I) -> Self where
    I: Iterator<Item = usize>, 

Method which takes an iterator and generates Self from the elements by “summing up” the items.