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use std::ops::{Deref, DerefMut};
pub struct BorrowMut<'a, T: 'a> {
inner: &'a mut Vec<T>
}
impl<'a, T> Deref for BorrowMut<'a, T> {
type Target = Vec<T>;
fn deref(&self) -> &Self::Target { self.inner }
}
impl<'a, T> DerefMut for BorrowMut<'a, T> {
fn deref_mut(&mut self) -> &mut Self::Target { self.inner }
}
impl<'a, T> Drop for BorrowMut<'a, T> {
fn drop(&mut self){
self.inner.clear();
}
}
pub struct TmpVec<U> {
inner: Vec<U>
}
impl<U> Default for TmpVec<U> {
fn default() -> Self { Self::new() }
}
impl<U> TmpVec<U> {
pub fn new() -> Self { TmpVec{ inner: Vec::new() } }
pub fn with_capacity(cap: usize) -> Self { TmpVec{ inner: Vec::with_capacity(cap) } }
pub fn borrow_mut<T>(&mut self) -> BorrowMut<T> {
use std::mem;
assert_eq!(mem::size_of::<T>(), mem::size_of::<U>());
assert_eq!(mem::align_of::<T>(), mem::align_of::<U>());
unsafe { self.inner.set_len(0); }
BorrowMut{ inner: unsafe { mem::transmute(&mut self.inner) } }
}
}
impl<U> Drop for TmpVec<U> {
fn drop(&mut self){
unsafe { self.inner.set_len(0); }
}
}