rust/library/core/src/slice/specialize.rs
The8472 dd166da8f8 generalize slice::fill specialization for byte-sized items
This should also improve cross-crate inlining since the method is generic
2021-03-18 00:25:20 +01:00

35 lines
955 B
Rust

use crate::mem::{size_of, transmute_copy};
use crate::ptr::write_bytes;
pub(super) trait SpecFill<T> {
fn spec_fill(&mut self, value: T);
}
impl<T: Clone> SpecFill<T> for [T] {
default fn spec_fill(&mut self, value: T) {
if let Some((last, elems)) = self.split_last_mut() {
for el in elems {
el.clone_from(&value);
}
*last = value
}
}
}
impl<T: Copy> SpecFill<T> for [T] {
fn spec_fill(&mut self, value: T) {
if size_of::<T>() == 1 {
// SAFETY: The size_of check above ensures that values are 1 byte wide, as required
// for the transmute and write_bytes
unsafe {
let value: u8 = transmute_copy(&value);
write_bytes(self.as_mut_ptr(), value, self.len());
}
} else {
for item in self.iter_mut() {
*item = value;
}
}
}
}