1 use core::alloc::Layout;
2 use core::mem;
3
4 /// Aborts the process.
5 ///
6 /// To abort, this function simply panics while panicking.
abort() -> !7 pub(crate) fn abort() -> ! {
8 struct Panic;
9
10 impl Drop for Panic {
11 fn drop(&mut self) {
12 panic!("aborting the process");
13 }
14 }
15
16 let _panic = Panic;
17 panic!("aborting the process");
18 }
19
20 /// Calls a function and aborts if it panics.
21 ///
22 /// This is useful in unsafe code where we can't recover from panics.
23 #[inline]
abort_on_panic<T>(f: impl FnOnce() -> T) -> T24 pub(crate) fn abort_on_panic<T>(f: impl FnOnce() -> T) -> T {
25 struct Bomb;
26
27 impl Drop for Bomb {
28 fn drop(&mut self) {
29 abort();
30 }
31 }
32
33 let bomb = Bomb;
34 let t = f();
35 mem::forget(bomb);
36 t
37 }
38
39 /// Returns the layout for `a` followed by `b` and the offset of `b`.
40 ///
41 /// This function was adapted from the currently unstable `Layout::extend()`:
42 /// https://doc.rust-lang.org/nightly/std/alloc/struct.Layout.html#method.extend
43 #[inline]
extend(a: Layout, b: Layout) -> (Layout, usize)44 pub(crate) fn extend(a: Layout, b: Layout) -> (Layout, usize) {
45 let new_align = a.align().max(b.align());
46 let pad = padding_needed_for(a, b.align());
47
48 let offset = a.size().checked_add(pad).unwrap();
49 let new_size = offset.checked_add(b.size()).unwrap();
50
51 let layout = Layout::from_size_align(new_size, new_align).unwrap();
52 (layout, offset)
53 }
54
55 /// Returns the padding after `layout` that aligns the following address to `align`.
56 ///
57 /// This function was adapted from the currently unstable `Layout::padding_needed_for()`:
58 /// https://doc.rust-lang.org/nightly/std/alloc/struct.Layout.html#method.padding_needed_for
59 #[inline]
padding_needed_for(layout: Layout, align: usize) -> usize60 pub(crate) fn padding_needed_for(layout: Layout, align: usize) -> usize {
61 let len = layout.size();
62 let len_rounded_up = len.wrapping_add(align).wrapping_sub(1) & !align.wrapping_sub(1);
63 len_rounded_up.wrapping_sub(len)
64 }
65