46 lines
1.4 KiB
Rust
46 lines
1.4 KiB
Rust
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/// This ties two values T and U together, such that T does not move and cannot be used as long as
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/// there's an U. This essentially replaces the borrow checker's job for dependent values which
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/// need to be stored together in a struct {}, and is similar to what the 'rental' crate produces.
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pub struct Tied<T, U: ?Sized>(Option<Box<T>>, Option<Box<U>>);
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impl<T, U: ?Sized> Drop for Tied<T, U> {
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fn drop(&mut self) {
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// let's be explicit about order here!
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std::mem::drop(self.1.take());
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}
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}
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impl<T, U: ?Sized> Tied<T, U> {
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/// Takes an owner and a function producing the depending value. The owner will be inaccessible
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/// until the tied value is resolved. The dependent value is only accessible by reference.
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pub fn new<F>(owner: T, producer: F) -> Self
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where
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F: FnOnce(*mut T) -> Box<U>,
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{
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let mut owner = Box::new(owner);
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let dep = producer(&mut *owner);
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Tied(Some(owner), Some(dep))
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}
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pub fn into_boxed_inner(mut self) -> Box<T> {
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self.1 = None;
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self.0.take().unwrap()
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}
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pub fn into_inner(self) -> T {
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*self.into_boxed_inner()
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}
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}
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impl<T, U: ?Sized> AsRef<U> for Tied<T, U> {
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fn as_ref(&self) -> &U {
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self.1.as_ref().unwrap()
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}
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}
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impl<T, U: ?Sized> AsMut<U> for Tied<T, U> {
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fn as_mut(&mut self) -> &mut U {
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self.1.as_mut().unwrap()
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}
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}
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