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reduce amount of math

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This commit is contained in:
Lukas Markeffsky 2023-11-23 10:41:35 +00:00
parent ec95d259e4
commit 500ef67877
1 changed files with 12 additions and 14 deletions
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26
library/alloc/src/collections/vec_deque/drain.rs
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@ -27,8 +27,8 @@ pub struct Drain<
drain_len: usize,
// index into the logical array, not the physical one (always lies in [0..deque.len))
idx: usize,
// number of elements after the drain range
tail_len: usize,
// number of elements remaining after dropping the drain
new_len: usize,
remaining: usize,
// Needed to make Drain covariant over T
_marker: PhantomData<&'a T>,
@ -41,12 +41,12 @@ pub(super) unsafe fn new(
drain_len: usize,
) -> Self {
let orig_len = mem::replace(&mut deque.len, drain_start);
let tail_len = orig_len - drain_start - drain_len;
let new_len = orig_len - drain_len;
Drain {
deque: NonNull::from(deque),
drain_len,
idx: drain_start,
tail_len,
new_len,
remaining: drain_len,
_marker: PhantomData,
}
@ -79,7 +79,7 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_tuple("Drain")
.field(&self.drain_len)
.field(&self.idx)
.field(&self.tail_len)
.field(&self.new_len)
.field(&self.remaining)
.finish()
}
@ -111,18 +111,16 @@ fn drop(&mut self) {
let drain_start = source_deque.len();
let drain_len = self.0.drain_len;
let drain_end = drain_start + drain_len;
let orig_len = self.0.tail_len + drain_end;
let new_len = self.0.new_len;
if T::IS_ZST {
// no need to copy around any memory if T is a ZST
source_deque.len = orig_len - drain_len;
source_deque.len = new_len;
return;
}
let head_len = drain_start;
let tail_len = self.0.tail_len;
let tail_len = new_len - head_len;
match (head_len, tail_len) {
(0, 0) => {
@ -131,10 +129,10 @@ fn drop(&mut self) {
}
(0, _) => {
source_deque.head = source_deque.to_physical_idx(drain_len);
source_deque.len = orig_len - drain_len;
source_deque.len = new_len;
}
(_, 0) => {
source_deque.len = orig_len - drain_len;
source_deque.len = new_len;
}
_ => unsafe {
if head_len <= tail_len {
@ -144,14 +142,14 @@ fn drop(&mut self) {
head_len,
);
source_deque.head = source_deque.to_physical_idx(drain_len);
source_deque.len = orig_len - drain_len;
source_deque.len = new_len;
} else {
source_deque.wrap_copy(
source_deque.to_physical_idx(head_len + drain_len),
source_deque.to_physical_idx(head_len),
tail_len,
);
source_deque.len = orig_len - drain_len;
source_deque.len = new_len;
}
},
}