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zeroed out boxes

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Lokathor 2019-09-20 09:01:23 -06:00
parent 427893ab9b
commit 876da036e4
1 changed files with 25 additions and 0 deletions
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25
src/allocation.rs
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@ -2,6 +2,8 @@
use super::*;
use alloc::{boxed::Box, rc::Rc, sync::Arc, vec::Vec};
use alloc::alloc::Layout;
use alloc::alloc::alloc_zeroed;
/// As [`try_cast_box`](try_cast_box), but unwraps for you.
#[inline]
@ -31,6 +33,29 @@ pub fn try_cast_box<A: Pod, B: Pod>(input: Box<A>) -> Result<Box<B>, (PodCastErr
}
}
/// Allocates a `Box<T>` with all of the contents being zeroed out.
///
/// This is not the same as using `Box::new(T::zeroed())`. With this function
/// the contents of the box never exists on the stack, so this can create very
/// large boxes without fear of a stack overflow.
#[inline]
pub fn try_zeroed_box<T: Zeroable>() -> Result<Box<T>,()> {
let layout = Layout::from_size_align(size_of::<T>(), align_of::<T>()).unwrap();
let ptr = unsafe { alloc_zeroed(layout) };
if ptr.is_null() {
// we don't know what the error is because `alloc_zeroed` is a dumb API
Err(())
} else {
Box::<T>::from_raw(ptr)
}
}
/// As [`try_zeroed_box`], but unwraps for you.
#[inline]
pub fn zeroed_box<T: Zeroable>() -> Box<T> {
try_zeroed_box().unwrap()
}
/// As [`try_cast_vec`](try_cast_vec), but unwraps for you.
#[inline]
pub fn cast_vec<A: Pod, B: Pod>(input: Vec<A>) -> Vec<B> {