DroplessArena in rustc_arena - Rust
Description: An arena that can hold objects of multiple different types that impl `Copy` and/or satisfy `!mem::needs_drop`.

Skip to main content

## DroplessArena

# Struct DroplessArena

Source

    pub struct DroplessArena {
        pub(crate) start: Cell<*mut u8>,
        pub(crate) end: Cell<*mut u8>,
        pub(crate) chunks: RefCell<Vec<ArenaChunk>>,
    }

Expand description

An arena that can hold objects of multiple different types that impl `Copy` and/or satisfy `!mem::needs_drop`.

## Fields§

§`start: Cell<*mut u8>`

A pointer to the start of the free space.

§`end: Cell<*mut u8>`

A pointer to the end of free space.

The allocation proceeds downwards from the end of the chunk towards the start. (This is slightly simpler and faster than allocating upwards, see https://fitzgeraldnick.com/2019/11/01/always-bump-downwards.html.) When this pointer crosses the start pointer, a new chunk is allocated.

This is kept aligned to DROPLESS_ALIGNMENT.

§`chunks: RefCell<Vec<ArenaChunk>>`

A vector of arena chunks.

## Implementations§

Source§

### impl DroplessArena

Source

#### pub(crate) fn grow(&self, layout: Layout)

Source

#### pub fn alloc_raw(&self, layout: Layout) -> *mut u8

Source

#### pub fn alloc<T>(&self, object: T) -> &mut T

Source

#### pub fn alloc_slice<T>(&self, slice: &[T]) -> &mut [T]
where T: Copy,

Allocates a slice of objects that are copied into the `DroplessArena`, returning a mutable reference to it. Will panic if passed a zero-sized type.

Panics:

- Zero-sized types
- Zero-length slices

Source

#### pub fn alloc_str(&self, string: &str) -> &str

Allocates a string slice that is copied into the `DroplessArena`, returning a reference to it. Will panic if passed an empty string.

Panics:

- Zero-length string

Source

#### pub(crate) unsafe fn write_from_iter<T, I: Iterator<Item = T>>( &self, iter: I, len: usize, mem: *mut T, ) -> &mut [T]

##### §Safety

The caller must ensure that `mem` is valid for writes up to `size_of::<T>() * len`, and that that memory stays allocated and not shared for the lifetime of `self`. This must hold even if `iter.next()` allocates onto `self`.

Source

#### pub fn alloc_from_iter<T, I: IntoIterator<Item = T>>(&self, iter: I) -> &mut [T]

Source

#### pub fn try_alloc_from_iter<T, E>( &self, iter: impl IntoIterator<Item = Result<T, E>>, ) -> Result<&mut [T], E>

## Trait Implementations§

Source§

### impl Default for DroplessArena

Source§

#### fn default() -> DroplessArena

Returns the “default value” for a type. Read more
Source§

### impl Send for DroplessArena

## Auto Trait Implementations§

§

### impl !Freeze for DroplessArena

§

### impl !RefUnwindSafe for DroplessArena

§

### impl !Sync for DroplessArena

§

### impl Unpin for DroplessArena

§

### impl UnsafeUnpin for DroplessArena

§

### impl UnwindSafe for DroplessArena

## Blanket Implementations§

Source§

### impl<T> Any for T
where T: 'static + ?Sized,

Source§

#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more
Source§

### impl<T> Borrow<T> for T
where T: ?Sized,

Source§

#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
Source§

### impl<T> BorrowMut<T> for T
where T: ?Sized,

Source§

#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
Source§

### impl<T> From<T> for T

Source§

#### fn from(t: T) -> T

Returns the argument unchanged.

Source§

### impl<T, U> Into<U> for T
where U: From<T>,

Source§

#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

Source§

### impl<T, U> TryFrom<U> for T
where U: Into<T>,

Source§

#### type Error = Infallible

The type returned in the event of a conversion error.
Source§

#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
Source§

### impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

Source§

#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
Source§

#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.

## Layout§

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain `repr(...)` attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 48 bytes