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.

Tuple Fields of Exact

0: usize

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.

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

Performs copy-assignment from source.

impl Debug for LengthHint

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

Formats the value using the given formatter.

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 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.

impl Copy for LengthHint

impl Eq for LengthHint

impl StructuralEq for LengthHint

impl StructuralPartialEq for LengthHint