Struct smallbox::SmallBox

pub struct SmallBox<T: ?Sized, Space> { /* fields omitted */ }

An optimized box that store value on stack or on heap depending on its size

Methods

impl<T: ?Sized, Space> SmallBox<T, Space>

pub fn new(val: T) -> SmallBox<T, Space> where
    T: Sized, 

Box value on stack or on heap depending on its size.

Example

use smallbox::SmallBox;
use smallbox::space::*;

let small: SmallBox<_, S4> = SmallBox::new([0usize; 2]);
let large: SmallBox<_, S4> = SmallBox::new([1usize; 8]);

assert_eq!(small.len(), 2);
assert_eq!(large[7], 1);

assert!(large.is_heap() == true);

pub fn resize<ToSpace>(self) -> SmallBox<T, ToSpace>

Change the capacity of SmallBox.

This method may move stack-allocated data from stack to heap when inline space is not sufficient. And once the data is moved to heap, it'll never be moved again.

Example

use smallbox::SmallBox;
use smallbox::space::{S2, S4};

let s: SmallBox::<_, S4> = SmallBox::new([0usize; 4]);
let m: SmallBox::<_, S2> = s.resize();

pub fn is_heap(&self) -> bool

Returns true if data is allocated on heap.

Example

use smallbox::SmallBox;
use smallbox::space::S1;

let stacked: SmallBox::<usize, S1> = SmallBox::new(0usize);
assert!(!stacked.is_heap());

let heaped: SmallBox::<(usize, usize), S1> = SmallBox::new((0usize, 1usize));
assert!(heaped.is_heap());

pub fn into_inner(self) -> T where
    T: Sized, 

Consumes the SmallBox and returns ownership of the boxed value

Examples

use smallbox::SmallBox;
use smallbox::space::S1;

let stacked : SmallBox<_, S1> = SmallBox::new([21usize]);
let val = stacked.into_inner();
assert_eq!(val[0], 21);

let boxed : SmallBox<_, S1> = SmallBox::new(vec![21, 56, 420]);
let val = boxed.into_inner();
assert_eq!(val[1], 56);

impl<Space> SmallBox<dyn Any, Space>

pub fn downcast<T: Any>(self) -> Result<SmallBox<T, Space>, Self>

Attempt to downcast the box to a concrete type.

Examples

#[macro_use]
extern crate smallbox;

use std::any::Any;
use smallbox::SmallBox;
use smallbox::space::*;

fn print_if_string(value: SmallBox<dyn Any, S1>) {
    if let Ok(string) = value.downcast::<String>() {
        println!("String ({}): {}", string.len(), string);
    }
}

fn main() {
    let my_string = "Hello World".to_string();
    print_if_string(smallbox!(my_string));
    print_if_string(smallbox!(0i8));
}

impl<Space> SmallBox<dyn Any + Send, Space>

pub fn downcast<T: Any>(self) -> Result<SmallBox<T, Space>, Self>

Attempt to downcast the box to a concrete type.

Examples

#[macro_use]
extern crate smallbox;

use std::any::Any;
use smallbox::SmallBox;
use smallbox::space::*;

fn print_if_string(value: SmallBox<dyn Any, S1>) {
    if let Ok(string) = value.downcast::<String>() {
        println!("String ({}): {}", string.len(), string);
    }
}

fn main() {
    let my_string = "Hello World".to_string();
    print_if_string(smallbox!(my_string));
    print_if_string(smallbox!(0i8));
}

Trait Implementations

impl<T: ?Sized + Send, Space> Send for SmallBox<T, Space>

impl<T: ?Sized + Sync, Space> Sync for SmallBox<T, Space>

impl<T: ?Sized, Space> Drop for SmallBox<T, Space>

fn drop(&mut self)

Executes the destructor for this type.

impl<T: Clone, Space> Clone for SmallBox<T, Space> where
    T: Sized, 

fn clone(&self) -> Self

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<T: ?Sized + Eq, Space> Eq for SmallBox<T, Space>

impl<T: ?Sized + Ord, Space> Ord for SmallBox<T, Space>

fn cmp(&self, other: &SmallBox<T, Space>) -> Ordering

This method returns an Ordering between self and other.

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

Compares and returns the maximum of two values.

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

Compares and returns the minimum of two values.

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

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

Restrict a value to a certain interval.

impl<T: ?Sized + PartialEq, Space> PartialEq<SmallBox<T, Space>> for SmallBox<T, Space>

fn eq(&self, other: &SmallBox<T, Space>) -> bool

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

fn ne(&self, other: &SmallBox<T, Space>) -> bool

This method tests for !=.

impl<T: ?Sized + PartialOrd, Space> PartialOrd<SmallBox<T, Space>> for SmallBox<T, Space>

fn partial_cmp(&self, other: &SmallBox<T, Space>) -> Option<Ordering>

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

fn lt(&self, other: &SmallBox<T, Space>) -> bool

This method tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &SmallBox<T, Space>) -> bool

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

fn ge(&self, other: &SmallBox<T, Space>) -> bool

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

fn gt(&self, other: &SmallBox<T, Space>) -> bool

This method tests greater than (for self and other) and is used by the > operator.

impl<T: ?Sized + Display, Space> Display for SmallBox<T, Space>

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

Formats the value using the given formatter.

impl<T: ?Sized + Debug, Space> Debug for SmallBox<T, Space>

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

Formats the value using the given formatter.

impl<T: ?Sized, Space> Deref for SmallBox<T, Space>

type Target = T

The resulting type after dereferencing.

fn deref(&self) -> &T

Dereferences the value.

impl<T: ?Sized, Space> DerefMut for SmallBox<T, Space>

fn deref_mut(&mut self) -> &mut T

Mutably dereferences the value.

impl<T: ?Sized + Hash, Space> Hash for SmallBox<T, Space>

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, 

Feeds a slice of this type into the given [Hasher].

impl<T: ?Sized, Space> Pointer for SmallBox<T, Space>

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

Formats the value using the given formatter.