[−][src]Struct shared_arena::Arena
An arena
It can be sent to other threads but is not Sync
.
Pointers to the elements in the Arena
are shareable between
threads.
use shared_arena::Arena; let arena = Arena::new(); let foo = arena.alloc(1); let bar = std::thread::spawn(move || { let bar = arena.alloc(100); std::mem::drop(arena); bar }); // The values are still valid, even if the arena has been dropped // in the other thread assert_eq!(*bar.join().unwrap() + *foo, 101);
Implementations
impl<T: Sized> Arena<T>
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pub fn with_capacity(cap: usize) -> Arena<T>
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Constructs a new Arena
capable of holding at least cap
elements
Because the arena allocate by page of 63 elements, it might be able to
hold more elements than cap
.
The Arena will reallocate itself if there is not enough space when allocating (with alloc* functions)
Example
let arena = Arena::with_capacity(2048);
pub fn new() -> Arena<T>
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Constructs a new Arena
capable of holding exactly 63 elements
The Arena will reallocate itself if there is not enough space when allocating (with alloc* functions)
Example
let arena = Arena::new();
pub fn alloc(&self, value: T) -> ArenaBox<T>
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Writes a value in the arena, and returns an ArenaBox
pointing to that value.
Example
let arena = Arena::new(); let my_num: ArenaBox<u8> = arena.alloc(0xFF); assert_eq!(*my_num, 255);
pub fn alloc_with<F>(&self, initializer: F) -> ArenaBox<T> where
F: Fn(&mut MaybeUninit<T>) -> &T,
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F: Fn(&mut MaybeUninit<T>) -> &T,
Finds an empty space in the arena and calls the function initializer
with its argument pointing to that space.
It returns an ArenaBox
pointing to the newly initialized value.
The difference with alloc
is that it has the benefit of
avoiding intermediate copies of the value.
Safety
It is the caller responsability to initialize properly the value.
initializer
must return &T
, this is a way to ensure that
its parameter &mut MaybeUninit<T>
has been "consumed".
If initializer
returns a different reference than its parameter,
the function will panic.
When the ArenaBox
is dropped, the value is also
dropped. If the value is not initialized correctly, it will
drop an unitialized value, which is undefined behavior.
Example
struct MyData { a: usize } fn initialize_data<'a>(uninit: &'a mut MaybeUninit<MyData>, source: &MyData) -> &'a MyData { unsafe { let ptr = uninit.as_mut_ptr(); ptr::copy(source, ptr, 1); &*ptr } } let arena = Arena::<MyData>::new(); let source = MyData { a: 101 }; let data = arena.alloc_with(|uninit| { initialize_data(uninit, &source) }); assert!(data.a == 101);
pub fn alloc_arc(&self, value: T) -> ArenaArc<T>
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Writes a value in the arena, and returns an ArenaArc
pointing to that value.
Example
let arena = Arena::new(); let my_num: ArenaArc<u8> = arena.alloc_arc(0xFF); assert_eq!(*my_num, 255);
pub fn alloc_arc_with<F>(&self, initializer: F) -> ArenaArc<T> where
F: Fn(&mut MaybeUninit<T>) -> &T,
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F: Fn(&mut MaybeUninit<T>) -> &T,
Finds an empty space in the arena and calls the function initializer
with its argument pointing to that space.
It returns an ArenaArc
pointing to the newly initialized value.
The difference with alloc_arc
is that it has the benefit of
avoiding intermediate copies of the value.
Safety
It is the caller responsability to initialize properly the value.
initializer
must return &T
, this is a way to ensure that
its parameter &mut MaybeUninit<T>
has been "consumed".
If initializer
returns a different reference than its parameter,
the function will panic.
When all ArenaArc
pointing that value are dropped, the value
is also dropped. If the value is not initialized correctly, it will
drop an unitialized value, which is undefined behavior.
Example
struct MyData { a: usize } fn initialize_data<'a>(uninit: &'a mut MaybeUninit<MyData>, source: &MyData) -> &'a MyData { unsafe { let ptr = uninit.as_mut_ptr(); ptr::copy(source, ptr, 1); &*ptr } } let arena = Arena::<MyData>::new(); let source = MyData { a: 101 }; let data = arena.alloc_arc_with(|uninit| { initialize_data(uninit, &source) }); assert!(data.a == 101);
pub fn alloc_rc(&self, value: T) -> ArenaRc<T>
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Writes a value in the arena, and returns an ArenaRc
pointing to that value.
Example
let arena = Arena::new(); let my_num: ArenaRc<u8> = arena.alloc_rc(0xFF); assert_eq!(*my_num, 255);
pub fn alloc_rc_with<F>(&self, initializer: F) -> ArenaRc<T> where
F: Fn(&mut MaybeUninit<T>) -> &T,
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F: Fn(&mut MaybeUninit<T>) -> &T,
Finds an empty space in the arena and calls the function initializer
with its argument pointing to that space.
It returns an ArenaRc
pointing to the newly initialized value.
The difference with alloc_rc
is that it has the benefit of
avoiding intermediate copies of the value.
Safety
It is the caller responsability to initialize properly the value.
initializer
must return &T
, this is a way to ensure that
its parameter &mut MaybeUninit<T>
has been "consumed".
If initializer
returns a different reference than its parameter,
the function will panic.
When all ArenaRc
pointing that value are dropped, the value
is also dropped. If the value is not initialized correctly, it will
drop an unitialized value, which is undefined behavior.
Example
struct MyData { a: usize } fn initialize_data<'a>(uninit: &'a mut MaybeUninit<MyData>, source: &MyData) -> &'a MyData { unsafe { let ptr = uninit.as_mut_ptr(); ptr::copy(source, ptr, 1); &*ptr } } let arena = Arena::<MyData>::new(); let source = MyData { a: 101 }; let data = arena.alloc_rc_with(|uninit| { initialize_data(uninit, &source) }); assert!(data.a == 101);
pub fn shrink_to_fit(&self) -> bool
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Shrinks the capacity of the arena as much as possible.
It will drop all pages that are unused (no Arena{Box,Arc,Rc}
points to it).
If there is still one or more references to a page, the page
won't be dropped.
This is a slow function and it should not be called in a hot path.
The dedicated memory will be deallocated during this call.
Example
let mut arena = Arena::with_capacity(2048); let mut values = Vec::new(); assert_eq!(arena.stats(), (0, 2079)); for _ in 0..80 { values.push(arena.alloc(0xFF)); } arena.shrink_to_fit(); let (used, free) = arena.stats(); assert!(used == 80, free == 46);
pub fn stats(&self) -> (usize, usize)
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Returns a tuple of non-free and free spaces in the arena
This is a slow function and it should not be called in a hot path.
Example
let arena = Arena::new(); let item = arena.alloc(1); let (used, free) = arena.stats(); assert!(used == 1 && free == 62);
Trait Implementations
impl<T> Debug for Arena<T>
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impl<T: Sized> Default for Arena<T>
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impl<T: Sized> Drop for Arena<T>
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impl<T: Sized> Send for Arena<T>
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Auto Trait Implementations
impl<T> !RefUnwindSafe for Arena<T>
impl<T> !Sync for Arena<T>
impl<T> Unpin for Arena<T>
impl<T> !UnwindSafe for Arena<T>
Blanket Implementations
impl<T> Any for T where
T: 'static + ?Sized,
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T: 'static + ?Sized,
impl<T> Borrow<T> for T where
T: ?Sized,
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T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
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T: ?Sized,
fn borrow_mut(&mut self) -> &mut T
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impl<T> From<T> for T
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impl<T, U> Into<U> for T where
U: From<T>,
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U: From<T>,
impl<T, U> TryFrom<U> for T where
U: Into<T>,
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U: Into<T>,
type Error = Infallible
The type returned in the event of a conversion error.
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
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impl<T, U> TryInto<U> for T where
U: TryFrom<T>,
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U: TryFrom<T>,