Struct unsized_vec::UnsizedVec

pub struct UnsizedVec<T: ?Sized> { /* private fields */ }

Like Vec, but can store unsized values.

Memory layout

When T is a Sized type, the memory layout is more or less the same as Vec<T>; pointer to a heap allocation, as well as a usize each for length and capacity. Elements are laid out in order, one after the other.

When T is a slice, there are two heap allocations. The first is to the slices themsleves; they are laid out end-to-end, one after the other, with no padding in between. The second heap allocation is to a list of offsets, to store where each element begins and ends.

When T is neither of the above, there are still two allocations. The first allocation still contains the elements of the vector laid out end-to-end, but now every element is padded to at least the alignment of the most-aligned element in the UnsizedVec. For this reason, adding a new element to the Vec with a larger alignment than any of the elements already in it will add new padding to all the existing elements, which will involve a lot of copying and probably a reallocation. If you want to avoid excessive copies, use the UnsizedVec::with_byte_capacity_align function to set the padding up front.

In the third case, the second allocation, in addition to storing offsets, also stores the pointer metadata of each element.

Example

#![feature(unsized_fn_params)]
use core::fmt::Debug;
use unsized_vec::{*, emplace::box_new_with};

// `Box::new()` necessary only to coerce the values to trait objects.
let obj: Box<dyn Debug> = Box::new(1);
let obj_2: Box<dyn Debug> = Box::new((97_u128, "oh noes"));
let mut vec: UnsizedVec<dyn Debug> = unsized_vec![*obj, *obj_2];
for traitobj in &vec {
    dbg!(traitobj);
};

assert_eq!(vec.len(), 2);

let popped = box_new_with(|e| vec.pop_unwrap(e));
dbg!(&*popped);

assert_eq!(vec.len(), 1);

Implementations

impl<T: ?Sized> UnsizedVec<T>

pub fn new() -> Self

Make a new, empty UnsizedVec.

pub fn with_byte_capacity_align(byte_capacity: usize, align: usize) -> Self

Make a new UnsizedVec with at least the the given capacity and alignment. (align is ignored for Aligned types).

Panics

Panics if align is not a power of two.

pub fn push(&mut self, elem: T)

Add element to end of the vec.

pub fn insert(&mut self, index: usize, elem: T)

Insert element into vec at given index, shifting following elements to the right.

pub fn pop_unwrap(&mut self, emplacer: &mut Emplacer<T>)

Remove an element from the end of the vec. This returns the element, which is unsized, through the “emplacer” mechanism. Call box_new_with(|e| your_unsized_vec.pop_unwrap(e)) to get the element boxed.

Panics

Panics if len is 0.

pub fn remove(&mut self, index: usize, emplacer: &mut Emplacer<T>)

Remove the element at the given index, shifting those after it to the left. This returns the element, which is unsized, through the “emplacer” mechanism. Call box_new_with(|e| your_unsized_vec.remove(index, e)) to get the element boxed.

Doesn’t shink the allocation, and doesn’t reduce alignment.

Panics

Panics if index is out of bounds.

pub fn len(&self) -> usize

pub fn byte_capacity(&self) -> usize

pub fn align(&self) -> usize

pub fn is_empty(&self) -> bool

pub fn iter(&self) -> UnsizedVecIter<'_, T>

pub fn iter_mut(&mut self) -> UnsizedVecIterMut<'_, T>

Trait Implementations

impl<T: ?Sized + Clone> Clone for UnsizedVec<T>

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 + Debug> Debug for UnsizedVec<T>

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

Formats the value using the given formatter.

impl<T: ?Sized> Default for UnsizedVec<T>

fn default() -> Self

Returns the “default value” for a type.

impl<T: ?Sized> Drop for UnsizedVec<T>

fn drop(&mut self)

Executes the destructor for this type.

impl<T: ?Sized + Hash> Hash for UnsizedVec<T>

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> Index<usize> for UnsizedVec<T>

type Output = T

The returned type after indexing.

fn index(&self, index: usize) -> &Self::Output

Performs the indexing (container[index]) operation.

impl<T: ?Sized> IndexMut<usize> for UnsizedVec<T>

fn index_mut(&mut self, index: usize) -> &mut Self::Output

Performs the mutable indexing (container[index]) operation.

impl<'a, T: ?Sized + 'a> IntoIterator for &'a UnsizedVec<T>

type Item = &'a T

The type of the elements being iterated over.

type IntoIter = UnsizedVecIter<'a, T>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl<'a, T: ?Sized + 'a> IntoIterator for &'a mut UnsizedVec<T>

type Item = &'a mut T

The type of the elements being iterated over.

type IntoIter = UnsizedVecIterMut<'a, T>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl<T: ?Sized + Ord> Ord for UnsizedVec<T>

fn cmp(&self, other: &Self) -> 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) -> Selfwhere
    Self: PartialOrd<Self>,

Restrict a value to a certain interval.

impl<T: ?Sized + PartialEq<U>, U: ?Sized> PartialEq<UnsizedVec<U>> for UnsizedVec<T>

fn eq(&self, other: &UnsizedVec<U>) -> bool

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

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

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T: ?Sized + PartialOrd<U>, U: ?Sized> PartialOrd<UnsizedVec<U>> for UnsizedVec<T>

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

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

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

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

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

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

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

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

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

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

impl<T: ?Sized + Eq> Eq for UnsizedVec<T>

impl<T: ?Sized + Send> Send for UnsizedVec<T>

impl<T: ?Sized + Sync> Sync for UnsizedVec<T>