Struct bound::Bound

pub struct Bound<G, U> { /* private fields */ }

Derive a struct from a reference and use it safely. The source is boxed, then a reference to it is used to construct the dependent data which is stored inline. This is not currently possible within Rust’s type system so we need to use unsafe code.

Usage

In abstract terms, the struct binds a lifetime and a dependent like so:

use bound::Bound;
// Struct with a lifetime parameter based on its reference field
struct Derived<'a>(&'a [usize]);
// Data that the struct must depend on
let data = vec![1, 2, 3];
let bound = Bound::new(data, |d| Derived(d.as_slice()));
// bound keeps alive the data and wraps the struct so that
// you just need to keep this struct in scope
assert_eq!(bound.wrapped().0, &[1, 2, 3]);

However you can only read the dependent this way. Writing the dependent can be unsound so it’s not allowed, but if the dependent is something like a mutex guard you can write through it. To be precise, Deref, DerefMut, AsRef and AsMut are all forwarded if the dependent implements them.

The canonical example is an Arc<RwLock>:

use std::sync::{Arc, RwLock};
use bound::Bound;
let shared_data = Arc::new(RwLock::new(1));
let mut writer = Bound::try_new(shared_data.clone(), |a| a.write()).expect("Failed to lock");
*writer = 2;

Normally you wouldn’t be able to pass around a RwLockWriteGuard, but because this is just a struct with no lifetime parameters, this works intuitively with a Bound.

Implementations

impl<'a, G, L: 'a> Bound<G, L>

pub fn new<F: FnOnce(&'a mut L) -> G>(source: L, func: F) -> Self

Bind data to a referrent

pub fn try_new<E, F>(source: L, func: F) -> Result<Self, Bound<E, L>>where
    F: FnOnce(&'a mut L) -> Result<G, E>,

Bind data to a referrent or a referrent error

pub async fn async_new<Fut, F>(source: L, func: F) -> Selfwhere
    Fut: IntoFuture<Output = G>,
    F: FnOnce(&'a mut L) -> Fut,

Bind data to an asynchronously obtained referrent

pub async fn async_try_new<E, Fut, F>(
    source: L,
    func: F
) -> Result<Self, Bound<E, L>>where
    Fut: IntoFuture<Output = Result<G, E>>,
    F: FnOnce(&'a mut L) -> Fut,

Bind data to an asynchronously obtained referrent or referrent error

pub fn unbind(self) -> Box<L>

Drop the referent and get back the source

pub fn wrapped(&self) -> &G

Access the wrapped struct

Trait Implementations

impl<T: ?Sized, G, L> AsMut<T> for Bound<G, L>where
    G: DerefMut + AsMut<T>,

fn as_mut(&mut self) -> &mut T

Converts this type into a mutable reference of the (usually inferred) input type.

impl<T: ?Sized, G, L> AsRef<T> for Bound<G, L>where
    G: AsRef<T>,

fn as_ref(&self) -> &T

Converts this type into a shared reference of the (usually inferred) input type.

impl<G, L> Debug for Bound<G, L>where
    G: Debug,

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T: ?Sized, G, U> Deref for Bound<G, U>where
    G: Deref<Target = T>,

type Target = T

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.

impl<T: ?Sized, G, U> DerefMut for Bound<G, U>where
    G: DerefMut<Target = T>,

fn deref_mut(&mut self) -> &mut Self::Target

Mutably dereferences the value.

impl<T: ?Sized, G, L> Display for Bound<G, L>where
    G: Deref<Target = T>,
    T: Display,

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<G, L> Drop for Bound<G, L>

Ensure that

• derived gets dropped before source_ptr
• source_ptr gets dropped

fn drop(&mut self)

Executes the destructor for this type.

impl<T: ?Sized, G, L> Hash for Bound<G, L>where
    G: Deref<Target = T>,
    T: Hash,

fn hash<H: Hasher>(&self, state: &mut H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)where
    H: Hasher,

Feeds a slice of this type into the given Hasher.

impl<T: ?Sized, G, L> Ord for Bound<G, L>where
    G: Deref<Target = T>,
    T: Ord,

fn cmp(&self, other: &Self) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Selfwhere
    Self: PartialOrd<Self>,

Restrict a value to a certain interval.

impl<T: ?Sized, G, L, T2: ?Sized, G2, L2> PartialEq<Bound<G2, L2>> for Bound<G, L>where
    G: Deref<Target = T>,
    G2: Deref<Target = T2>,
    T: PartialEq<T2>,

fn eq(&self, other: &Bound<G2, L2>) -> bool

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

fn ne(&self, other: &Bound<G2, L2>) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T: ?Sized, G, L, T2: ?Sized, G2, L2> PartialOrd<Bound<G2, L2>> for Bound<G, L>where
    G: Deref<Target = T>,
    G2: Deref<Target = T2>,
    T: PartialOrd<T2>,

fn partial_cmp(&self, other: &Bound<G2, L2>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<T: ?Sized, G, L> Eq for Bound<G, L>where
    G: Deref<Target = T>,
    T: Eq,