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// Extracted from the scopeguard crate
use core::{
mem::ManuallyDrop,
ops::{Deref, DerefMut},
ptr,
};
pub struct ScopeGuard<T, F>
where
F: FnMut(&mut T),
{
dropfn: F,
value: T,
}
#[inline]
pub fn guard<T, F>(value: T, dropfn: F) -> ScopeGuard<T, F>
where
F: FnMut(&mut T),
{
ScopeGuard { dropfn, value }
}
impl<T, F> ScopeGuard<T, F>
where
F: FnMut(&mut T),
{
#[inline]
pub fn into_inner(guard: Self) -> T {
// Cannot move out of Drop-implementing types, so
// ptr::read the value out of a ManuallyDrop<Self>
// Don't use mem::forget as that might invalidate value
let guard = ManuallyDrop::new(guard);
unsafe {
let value = ptr::read(&guard.value);
// read the closure so that it is dropped
let _ = ptr::read(&guard.dropfn);
value
}
}
}
impl<T, F> Deref for ScopeGuard<T, F>
where
F: FnMut(&mut T),
{
type Target = T;
#[inline]
fn deref(&self) -> &T {
&self.value
}
}
impl<T, F> DerefMut for ScopeGuard<T, F>
where
F: FnMut(&mut T),
{
#[inline]
fn deref_mut(&mut self) -> &mut T {
&mut self.value
}
}
impl<T, F> Drop for ScopeGuard<T, F>
where
F: FnMut(&mut T),
{
#[inline]
fn drop(&mut self) {
(self.dropfn)(&mut self.value);
}
}