Trait orx_fixed_vec::prelude::PinnedVec

pub trait PinnedVec<T> {
    // Required methods
    fn clear(&mut self);
    fn capacity(&self) -> usize;
    fn extend_from_slice(&mut self, other: &[T])
       where T: Clone;
    fn get(&self, index: usize) -> Option<&T>;
    fn get_mut(&mut self, index: usize) -> Option<&mut T>;
    unsafe fn get_unchecked(&self, index: usize) -> &T;
    unsafe fn get_unchecked_mut(&mut self, index: usize) -> &mut T;
    fn is_empty(&self) -> bool;
    fn len(&self) -> usize;
    fn push(&mut self, value: T);
    unsafe fn unsafe_insert(&mut self, index: usize, element: T);
    unsafe fn unsafe_remove(&mut self, index: usize) -> T;
    unsafe fn unsafe_pop(&mut self) -> Option<T>;
    unsafe fn unsafe_swap(&mut self, a: usize, b: usize);
    unsafe fn unsafe_truncate(&mut self, len: usize);
    unsafe fn unsafe_clone(&self) -> Self
       where T: Clone;
    fn partial_eq<S>(&self, other: S) -> bool
       where S: AsRef<[T]>,
             T: PartialEq<T>;
    fn debug(&self, f: &mut Formatter<'_>) -> Result<(), Error>
       where T: Debug;
}

A vector of elements of T which differs from the std::vec::Vec by the following feature:

• memory location of an element already pushed to the collection never changes and remains valid unless:
  • the vector is dropped,
  • the vector is cleared, resized or truncated,
  • any element is inserted into the vector,
  • any element is removed or popped from the vector.

Or, more briefly, pushing or extending the vector does not change memory locations of already added elements, and hence, the corresponding references remain valid.

Safety

This trait can be considered as a marker trait: its methods are relevant for the useful ‘vec’-related side of the trait, rather than the pinned side. The implementing struct must guarantee that pushing or extending the vector does not cause the memory locations of already added elements to change.

Required Methods

fn clear(&mut self)

Clears the vector, removing all values.

Note that this method has no effect on the allocated capacity of the vector.

Safety

clear operation is safe both when T: NotSelfReferencingVecItem or T: SelfReferencingVecItem.

The prior is obvious; the reason why T: SelfReferencingVecItem is safe is as follows:

• elements holding references to each other will be cleaned all together; hence, none of them can have an invalid reference;
• we cannot have a reference to a vector element defined before the clear, since clear requires a mut reference.

fn capacity(&self) -> usize

Returns the total number of elements the vector can hold without reallocating.

fn extend_from_slice(&mut self, other: &[T])where T: Clone,

Clones and appends all elements in a slice to the Vec.

Iterates over the slice other, clones each element, and then appends it to this Vec. The other slice is traversed in-order.

Note that this function is same as extend except that it is specialized to work with slices instead. If and when Rust gets specialization this function will likely be deprecated (but still available).

fn get(&self, index: usize) -> Option<&T>

Returns a reference to an element with the given index, returns None if the index is out of bounds.

fn get_mut(&mut self, index: usize) -> Option<&mut T>

Returns a mutable reference to an element with the given index, returns None if the index is out of bounds.

unsafe fn get_unchecked(&self, index: usize) -> &T

Returns a reference to an element or subslice, without doing bounds checking.

For a safe alternative see [get].

Safety

Calling this method with an out-of-bounds index is [undefined behavior] even if the resulting reference is not used.

unsafe fn get_unchecked_mut(&mut self, index: usize) -> &mut T

Returns a mutable reference to an element or subslice, without doing bounds checking.

For a safe alternative see [get_mut].

Safety

Calling this method with an out-of-bounds index is [undefined behavior] even if the resulting reference is not used.

fn is_empty(&self) -> bool

Returns true if the vector contains no elements.

fn len(&self) -> usize

Returns the number of elements in the vector, also referred to as its ‘length’.

fn push(&mut self, value: T)

Appends an element to the back of a collection.

unsafe fn unsafe_insert(&mut self, index: usize, element: T)

Inserts an element at position index within the vector, shifting all elements after it to the right.

Panics

Panics if index >= len.

Safety

This operation is unsafe when T is not NotSelfRefVecItem. To pick the conservative approach, every T which does not implement NotSelfRefVecItem is assumed to be a vector item referencing other vector items.

insert is unsafe since insertion of a new element at an arbitrary position of the vector typically changes the positions of already existing elements.

When the elements are holding references to other elements of the vector, this change in positions makes the references invalid.

On the other hand, any vector implementing PinnedVec<T> where T: NotSelfRefVecItem implements PinnedVecSimple<T> which implements the safe version of this method.

unsafe fn unsafe_remove(&mut self, index: usize) -> T

Removes and returns the element at position index within the vector, shifting all elements after it to the left.

Panics

Panics if index is out of bounds.

Safety

This operation is unsafe when T is not NotSelfRefVecItem. To pick the conservative approach, every T which does not implement NotSelfRefVecItem is assumed to be a vector item referencing other vector items.

remove is unsafe since removal of an element at an arbitrary position of the vector typically changes the positions of already existing elements.

Further, it is possible that at least one of the remaining elements is pointing to the element which is being removed.

On the other hand, any vector implementing PinnedVec<T> where T: NotSelfRefVecItem implements PinnedVecSimple<T> which implements the safe version of this method.

unsafe fn unsafe_pop(&mut self) -> Option<T>

Removes the last element from a vector and returns it, or None if it is empty.

Safety

This operation is unsafe when T is not NotSelfRefVecItem. To pick the conservative approach, every T which does not implement NotSelfRefVecItem is assumed to be a vector item referencing other vector items.

pop is unsafe since it is possible that at least one of the remaining elements is pointing to the last element which is being popped.

On the other hand, any vector implementing PinnedVec<T> where T: NotSelfRefVecItem implements PinnedVecSimple<T> which implements the safe version of this method.

unsafe fn unsafe_swap(&mut self, a: usize, b: usize)

Swaps two elements in the slice.

If a equals to b, it’s guaranteed that elements won’t change value.

Arguments

• a - The index of the first element
• b - The index of the second element

Safety

This operation is unsafe when T is not NotSelfRefVecItem. To pick the conservative approach, every T which does not implement NotSelfRefVecItem is assumed to be a vector item referencing other vector items.

swap is unsafe since it is possible that other elements are referencing one of the elements to be swapped. The swap operation does not lead to an undefined behavior in the classical sense; however, would invalidate the inter-elements-references.

On the other hand, any vector implementing PinnedVec<T> where T: NotSelfRefVecItem implements PinnedVecSimple<T> which implements the safe version of this method.

unsafe fn unsafe_truncate(&mut self, len: usize)

Shortens the vector, keeping the first len elements and dropping the rest.

If len is greater than the vector’s current length, this has no effect.

Safety

This operation is unsafe when T is not NotSelfRefVecItem. To pick the conservative approach, every T which does not implement NotSelfRefVecItem is assumed to be a vector item referencing other vector items.

truncate is unsafe since it is possible that remaining elements are referencing to elements which are dropped by the truncate method.

On the other hand, any vector implementing PinnedVec<T> where T: NotSelfRefVecItem implements PinnedVecSimple<T> which implements the safe version of this method.

unsafe fn unsafe_clone(&self) -> Selfwhere T: Clone,

Creates and returns a clone of the vector.

Safety

This operation is unsafe when T is not NotSelfRefVecItem. To pick the conservative approach, every T which does not implement NotSelfRefVecItem is assumed to be a vector item referencing other vector items.

To understand why clone is unsafe when T is not NotSelfRefVecItem, consider the following example.

• let vec be the initial vector with self referencing vector elements.
• let cl be the clone of A; i.e., ’let cl = vec.clone()`.
• In this case, elements of cl are pointing to elements of vec.
  • This is not correct, as these references are to be kept internal to the vector.
  • Furthermore, if vec is dropped, cl elements will contain invalid references leading to UB.

fn partial_eq<S>(&self, other: S) -> boolwhere S: AsRef<[T]>, T: PartialEq<T>,

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

fn debug(&self, f: &mut Formatter<'_>) -> Result<(), Error>where T: Debug,

Formats the value using the given formatter.

Implementors

impl<T> PinnedVec<T> for FixedVec<T>