1use crate::clone::TrivialClone;
2use crate::ptr;
3
4pub(super) trait SpecFill<T> {
5 fn spec_fill(&mut self, value: T);
6}
7
8impl<T: Clone> SpecFill<T> for [T] {
9 default fn spec_fill(&mut self, value: T) {
10 if let Some((last: &mut T, elems: &mut [T])) = self.split_last_mut() {
11 for el: &mut T in elems {
12 el.clone_from(&value);
13 }
14
15 *last = value
16 }
17 }
18}
19
20impl<T: TrivialClone> SpecFill<T> for [T] {
21 default fn spec_fill(&mut self, value: T) {
22 for item: &mut T in self.iter_mut() {
23 // SAFETY: `TrivialClone` indicates that this is equivalent to
24 // calling `Clone::clone`
25 *item = unsafe { ptr::read(&value) };
26 }
27 }
28}
29
30impl SpecFill<u8> for [u8] {
31 fn spec_fill(&mut self, value: u8) {
32 // SAFETY: The pointer is derived from a reference, so it's writable.
33 unsafe {
34 crate::intrinsics::write_bytes(self.as_mut_ptr(), val:value, self.len());
35 }
36 }
37}
38
39impl SpecFill<i8> for [i8] {
40 fn spec_fill(&mut self, value: i8) {
41 // SAFETY: The pointer is derived from a reference, so it's writable.
42 unsafe {
43 crate::intrinsics::write_bytes(self.as_mut_ptr(), val:value.cast_unsigned(), self.len());
44 }
45 }
46}
47
48macro spec_fill_int {
49 ($($type:ty)*) => {$(
50 impl SpecFill<$type> for [$type] {
51 #[inline]
52 fn spec_fill(&mut self, value: $type) {
53 // We always take this fastpath in Miri for long slices as the manual `for`
54 // loop can be prohibitively slow.
55 if (cfg!(miri) && self.len() > 32) || crate::intrinsics::is_val_statically_known(value) {
56 let bytes = value.to_ne_bytes();
57 if value == <$type>::from_ne_bytes([bytes[0]; size_of::<$type>()]) {
58 // SAFETY: The pointer is derived from a reference, so it's writable.
59 unsafe {
60 crate::intrinsics::write_bytes(self.as_mut_ptr(), bytes[0], self.len());
61 }
62 return;
63 }
64 }
65 for item in self.iter_mut() {
66 *item = value;
67 }
68 }
69 }
70 )*}
71}
72
73spec_fill_int! { u16 i16 u32 i32 u64 i64 u128 i128 usize isize }
74