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Add unsafe comments

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This commit is contained in:
Jeong YunWon
2022-05-18 10:37:51 +09:00
parent 52cce3f048
commit 25a6629742
1 changed files with 23 additions and 6 deletions
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29
vm/src/dictdatatype.rs
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@@ -45,6 +45,8 @@ impl IndexEntry {
const FREE: Self = Self(-1);
const DUMMY: Self = Self(-2);
/// # Safety
/// idx must not be one of FREE or DUMMY
unsafe fn from_index_unchecked(idx: usize) -> Self {
debug_assert!((idx as isize) >= 0);
Self(idx as i64)
@@ -164,7 +166,9 @@ impl<T> DictInner<T> {
loop {
let index_index = idxs.next();
unsafe {
// index is always valid here
// Safety: index is always valid here
// index_index is generated by idxs
// entry_idx is saved one
let idx = self.indices.get_unchecked_mut(index_index);
if *idx == IndexEntry::FREE {
*idx = IndexEntry::from_index_unchecked(entry_idx);
@@ -196,7 +200,11 @@ impl<T> DictInner<T> {
};
let entry_index = self.entries.len();
self.entries.push(Some(entry));
self.indices[index] = unsafe { IndexEntry::from_index_unchecked(entry_index) };
self.indices[index] = unsafe {
// SAFETY: entry_index is self.entries.len(). it never can
// grow to `usize-2` because hash tables cannot full its index
IndexEntry::from_index_unchecked(entry_index)
};
self.used += 1;
if let IndexEntry::FREE = index_entry {
self.filled += 1;
@@ -540,7 +548,10 @@ impl<T: Clone> Dict<T> {
});
loop {
let index_index = idxs.next();
let index_entry = *unsafe { inner.indices.get_unchecked(index_index) };
let index_entry = *unsafe {
// Safety: index_index is generated
inner.indices.get_unchecked(index_index)
};
match index_entry {
IndexEntry::DUMMY => {
if free_slot.is_none() {
@@ -556,7 +567,7 @@ impl<T: Clone> Dict<T> {
}
idx => {
let entry = unsafe {
// DUMMY and FREE are already handled above.
// Safety: DUMMY and FREE are already handled above.
// i is always valid and entry always exists.
let i = idx.index().unwrap_unchecked();
inner.entries.get_unchecked(i).as_ref().unwrap_unchecked()
@@ -619,7 +630,10 @@ impl<T: Clone> Dict<T> {
// The dict was changed since we did lookup. Let's try again.
_ => return Ok(ControlFlow::Continue(())),
}
*unsafe { inner.indices.get_unchecked_mut(index_index) } = IndexEntry::DUMMY;
*unsafe {
// index_index is result of lookup
inner.indices.get_unchecked_mut(index_index)
} = IndexEntry::DUMMY;
inner.used -= 1;
let removed = slot.take();
Ok(ControlFlow::Break(removed))
@@ -647,7 +661,10 @@ impl<T: Clone> Dict<T> {
}
};
inner.used -= 1;
*unsafe { inner.indices.get_unchecked_mut(entry.index) } = IndexEntry::DUMMY;
*unsafe {
// entry.index always refers valid index
inner.indices.get_unchecked_mut(entry.index)
} = IndexEntry::DUMMY;
Some((entry.key, entry.value))
}