Struct rustc_data_structures::owning_ref::OwningRef

source · 
pub struct OwningRef<O, T: ?Sized> {
    owner: O,
    reference: *const T,
}
Expand description

An owning reference.

This wraps an owner O and a reference &T pointing at something reachable from O::Target while keeping the ability to move self around.

The owner is usually a pointer that points at some base type.

For more details and examples, see the module and method docs.

Fields§

§owner: O§reference: *const T

Implementations§

Creates a new owning reference from an owner initialized to the direct dereference of it.

Example
use rustc_data_structures::owning_ref::OwningRef;

fn main() {
    let owning_ref = OwningRef::new(Box::new(42));
    assert_eq!(*owning_ref, 42);
}

Like new, but doesn’t require O to implement the StableAddress trait. Instead, the caller is responsible to make the same promises as implementing the trait.

This is useful for cases where coherence rules prevents implementing the trait without adding a dependency to this crate in a third-party library.

Converts self into a new owning reference that points at something reachable from the previous one.

This can be a reference to a field of U, something reachable from a field of U, or even something unrelated with a 'static lifetime.

Example
use rustc_data_structures::owning_ref::OwningRef;

fn main() {
    let owning_ref = OwningRef::new(Box::new([1, 2, 3, 4]));

    // create an owning reference that points at the
    // third element of the array.
    let owning_ref = owning_ref.map(|array| &array[2]);
    assert_eq!(*owning_ref, 3);
}

Tries to convert self into a new owning reference that points at something reachable from the previous one.

This can be a reference to a field of U, something reachable from a field of U, or even something unrelated with a 'static lifetime.

Example
use rustc_data_structures::owning_ref::OwningRef;

fn main() {
    let owning_ref = OwningRef::new(Box::new([1, 2, 3, 4]));

    // create an owning reference that points at the
    // third element of the array.
    let owning_ref = owning_ref.try_map(|array| {
        if array[2] == 3 { Ok(&array[2]) } else { Err(()) }
    });
    assert_eq!(*owning_ref.unwrap(), 3);
}

Converts self into a new owning reference with a different owner type.

The new owner type needs to still contain the original owner in some way so that the reference into it remains valid. This function is marked unsafe because the user needs to manually uphold this guarantee.

Converts self into a new owning reference where the owner is wrapped in an additional Box<O>.

This can be used to safely erase the owner of any OwningRef<O, T> to an OwningRef<Box<Erased>, T>.

Erases the concrete base type of the owner with a trait object.

This allows mixing of owned references with different owner base types.

Example
use rustc_data_structures::owning_ref::{OwningRef, Erased};

fn main() {
    // N.B., using the concrete types here for explicitness.
    // For less verbose code type aliases like `BoxRef` are provided.

    let owning_ref_a: OwningRef<Box<[i32; 4]>, [i32; 4]>
        = OwningRef::new(Box::new([1, 2, 3, 4]));

    let owning_ref_b: OwningRef<Box<Vec<(i32, bool)>>, Vec<(i32, bool)>>
        = OwningRef::new(Box::new(vec![(0, false), (1, true)]));

    let owning_ref_a: OwningRef<Box<[i32; 4]>, i32>
        = owning_ref_a.map(|a| &a[0]);

    let owning_ref_b: OwningRef<Box<Vec<(i32, bool)>>, i32>
        = owning_ref_b.map(|a| &a[1].0);

    let owning_refs: [OwningRef<Box<dyn Erased>, i32>; 2]
        = [owning_ref_a.erase_owner(), owning_ref_b.erase_owner()];

    assert_eq!(*owning_refs[0], 1);
    assert_eq!(*owning_refs[1], 1);
}

Erases the concrete base type of the owner with a trait object which implements Send.

This allows mixing of owned references with different owner base types.

Erases the concrete base type of the owner with a trait object which implements Send and Sync.

This allows mixing of owned references with different owner base types.

A getter for the underlying owner.

Discards the reference and retrieves the owner.

Trait Implementations§

Converts this type into a shared reference of the (usually inferred) input type.
Immutably borrows from an owned value. Read more
Returns a copy of the value. Read more
Performs copy-assignment from source. Read more
Formats the value using the given formatter. Read more
The resulting type after dereferencing.
Dereferences the value.
Converts to this type from the input type.
Converts to this type from the input type.
Feeds this value into the given Hasher. Read more
Feeds a slice of this type into the given Hasher. Read more
This method returns an Ordering between self and other. Read more
Compares and returns the maximum of two values. Read more
Compares and returns the minimum of two values. Read more
Restrict a value to a certain interval. Read more
This method tests for self and other values to be equal, and is used by ==. Read more
This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason. Read more
This method returns an ordering between self and other values if one exists. Read more
This method tests less than (for self and other) and is used by the < operator. Read more
This method tests less than or equal to (for self and other) and is used by the <= operator. Read more
This method tests greater than (for self and other) and is used by the > operator. Read more
This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more

Auto Trait Implementations§

Blanket Implementations§

Gets the TypeId of self. Read more
Immutably borrows from an owned value. Read more
Mutably borrows from an owned value. Read more

Returns the argument unchanged.

Calls U::from(self).

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

The resulting type after obtaining ownership.
Creates owned data from borrowed data, usually by cloning. Read more
Uses borrowed data to replace owned data, usually by cloning. Read more
The type returned in the event of a conversion error.
Performs the conversion.
The type returned in the event of a conversion error.
Performs the conversion.

Layout§

Note: Unable to compute type layout, possibly due to this type having generic parameters. Layout can only be computed for concrete, fully-instantiated types.