#[repr(C)]pub struct OwnedArray<T, const N: usize> {
ptr: NonNull<T>,
_phantom: PhantomData<T>,
}Expand description
A struct that basically replaces a Box<[T; N]>, but which cbindgen can
understand.
Every OwnedArray is allocation-backed with N fully-constructed
elements; there is no empty or moved-from state.
We could rely on the struct layout of Box<[T; N]>. Per the Box
documentation, Box<T> has the same ABI as *mut T, and since [T; N] is
Sized, that’s a thin pointer (unlike Box<[T]>, which is fat):
https://doc.rust-lang.org/std/boxed/index.html#memory-layout
But handling Box with cbindgen both in structs and argument positions
more generally is a bit tricky.
This is useful when generated cbindgen code has circular references that
can only be broken by indirection through boxed objects. When a type needs
two, three, or a similar small number of such objects of the same kind,
OwnedArray<T, N> is more ergonomic and efficient than holding N
separate boxed values: it uses a single allocation and a single thin
pointer instead of N of each.
Compared to OwnedSlice<T>, OwnedArray<T, N> does not store the length
at runtime, N is part of the type, so the struct is a single
pointer-word instead of two. For types used as enum variant payloads, this
reduces the enclosing enum’s footprint. The length can also be statically
checked, wrong-length values are unrepresentable, so consumers don’t need
need runtime length assertions.
cbindgen:derive-eq=false cbindgen:derive-neq=false
Fields§
§ptr: NonNull<T>§_phantom: PhantomData<T>Implementations§
Methods from Deref<Target = [T; N]>§
1.57.0 · Sourcepub fn as_slice(&self) -> &[T]
pub fn as_slice(&self) -> &[T]
Returns a slice containing the entire array. Equivalent to &s[..].
1.57.0 · Sourcepub fn as_mut_slice(&mut self) -> &mut [T]
pub fn as_mut_slice(&mut self) -> &mut [T]
Returns a mutable slice containing the entire array. Equivalent to
&mut s[..].
1.77.0 · Sourcepub fn each_ref(&self) -> [&T; N]
pub fn each_ref(&self) -> [&T; N]
Borrows each element and returns an array of references with the same
size as self.
§Example
let floats = [3.1, 2.7, -1.0];
let float_refs: [&f64; 3] = floats.each_ref();
assert_eq!(float_refs, [&3.1, &2.7, &-1.0]);This method is particularly useful if combined with other methods, like
map. This way, you can avoid moving the original
array if its elements are not Copy.
let strings = ["Ferris".to_string(), "♥".to_string(), "Rust".to_string()];
let is_ascii = strings.each_ref().map(|s| s.is_ascii());
assert_eq!(is_ascii, [true, false, true]);
// We can still access the original array: it has not been moved.
assert_eq!(strings.len(), 3);1.77.0 · Sourcepub fn each_mut(&mut self) -> [&mut T; N]
pub fn each_mut(&mut self) -> [&mut T; N]
Borrows each element mutably and returns an array of mutable references
with the same size as self.
§Example
let mut floats = [3.1, 2.7, -1.0];
let float_refs: [&mut f64; 3] = floats.each_mut();
*float_refs[0] = 0.0;
assert_eq!(float_refs, [&mut 0.0, &mut 2.7, &mut -1.0]);
assert_eq!(floats, [0.0, 2.7, -1.0]);Sourcepub fn split_array_ref<const M: usize>(&self) -> (&[T; M], &[T])
🔬This is a nightly-only experimental API. (split_array)
pub fn split_array_ref<const M: usize>(&self) -> (&[T; M], &[T])
split_array)Divides one array reference into two at an index.
The first will contain all indices from [0, M) (excluding
the index M itself) and the second will contain all
indices from [M, N) (excluding the index N itself).
§Panics
Panics if M > N.
§Examples
#![feature(split_array)]
let v = [1, 2, 3, 4, 5, 6];
{
let (left, right) = v.split_array_ref::<0>();
assert_eq!(left, &[]);
assert_eq!(right, &[1, 2, 3, 4, 5, 6]);
}
{
let (left, right) = v.split_array_ref::<2>();
assert_eq!(left, &[1, 2]);
assert_eq!(right, &[3, 4, 5, 6]);
}
{
let (left, right) = v.split_array_ref::<6>();
assert_eq!(left, &[1, 2, 3, 4, 5, 6]);
assert_eq!(right, &[]);
}Sourcepub fn split_array_mut<const M: usize>(&mut self) -> (&mut [T; M], &mut [T])
🔬This is a nightly-only experimental API. (split_array)
pub fn split_array_mut<const M: usize>(&mut self) -> (&mut [T; M], &mut [T])
split_array)Divides one mutable array reference into two at an index.
The first will contain all indices from [0, M) (excluding
the index M itself) and the second will contain all
indices from [M, N) (excluding the index N itself).
§Panics
Panics if M > N.
§Examples
#![feature(split_array)]
let mut v = [1, 0, 3, 0, 5, 6];
let (left, right) = v.split_array_mut::<2>();
assert_eq!(left, &mut [1, 0][..]);
assert_eq!(right, &mut [3, 0, 5, 6]);
left[1] = 2;
right[1] = 4;
assert_eq!(v, [1, 2, 3, 4, 5, 6]);Sourcepub fn rsplit_array_ref<const M: usize>(&self) -> (&[T], &[T; M])
🔬This is a nightly-only experimental API. (split_array)
pub fn rsplit_array_ref<const M: usize>(&self) -> (&[T], &[T; M])
split_array)Divides one array reference into two at an index from the end.
The first will contain all indices from [0, N - M) (excluding
the index N - M itself) and the second will contain all
indices from [N - M, N) (excluding the index N itself).
§Panics
Panics if M > N.
§Examples
#![feature(split_array)]
let v = [1, 2, 3, 4, 5, 6];
{
let (left, right) = v.rsplit_array_ref::<0>();
assert_eq!(left, &[1, 2, 3, 4, 5, 6]);
assert_eq!(right, &[]);
}
{
let (left, right) = v.rsplit_array_ref::<2>();
assert_eq!(left, &[1, 2, 3, 4]);
assert_eq!(right, &[5, 6]);
}
{
let (left, right) = v.rsplit_array_ref::<6>();
assert_eq!(left, &[]);
assert_eq!(right, &[1, 2, 3, 4, 5, 6]);
}Sourcepub fn rsplit_array_mut<const M: usize>(&mut self) -> (&mut [T], &mut [T; M])
🔬This is a nightly-only experimental API. (split_array)
pub fn rsplit_array_mut<const M: usize>(&mut self) -> (&mut [T], &mut [T; M])
split_array)Divides one mutable array reference into two at an index from the end.
The first will contain all indices from [0, N - M) (excluding
the index N - M itself) and the second will contain all
indices from [N - M, N) (excluding the index N itself).
§Panics
Panics if M > N.
§Examples
#![feature(split_array)]
let mut v = [1, 0, 3, 0, 5, 6];
let (left, right) = v.rsplit_array_mut::<4>();
assert_eq!(left, &mut [1, 0]);
assert_eq!(right, &mut [3, 0, 5, 6][..]);
left[1] = 2;
right[1] = 4;
assert_eq!(v, [1, 2, 3, 4, 5, 6]);