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chore: align MPSC queue with standard head/tail naming #124

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chore: align MPSC queue with standard head/tail naming #124

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32 changes: 16 additions & 16 deletions src/queue_mpsc.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -39,37 +39,37 @@ pub fn Intrusive(comptime T: type) type {
/// of producers.
pub fn push(self: *Self, v: *T) void {
@atomicStore(?*T, &v.next, null, .unordered);
const prev = @atomicRmw(*T, &self.head, .Xchg, v, .acq_rel);
const prev = @atomicRmw(*T, &self.tail, .Xchg, v, .acq_rel);
@atomicStore(?*T, &prev.next, v, .release);
}

/// Pop the first in element from the queue. This must be called
/// by only a single consumer at any given time.
pub fn pop(self: *Self) ?*T {
var tail = @atomicLoad(*T, &self.tail, .unordered);
var next_ = @atomicLoad(?*T, &tail.next, .acquire);
if (tail == &self.stub) {
var head = @atomicLoad(*T, &self.head, .unordered);
var next_ = @atomicLoad(?*T, &head.next, .acquire);
if (head == &self.stub) {
const next = next_ orelse return null;
@atomicStore(*T, &self.tail, next, .unordered);
tail = next;
next_ = @atomicLoad(?*T, &tail.next, .acquire);
@atomicStore(*T, &self.head, next, .unordered);
head = next;
next_ = @atomicLoad(?*T, &head.next, .acquire);
}

if (next_) |next| {
@atomicStore(*T, &self.tail, next, .release);
tail.next = null;
return tail;
@atomicStore(*T, &self.head, next, .release);
head.next = null;
return head;
}

const head = @atomicLoad(*T, &self.head, .unordered);
if (tail != head) return null;
const tail = @atomicLoad(*T, &self.tail, .unordered);
if (head != tail) return null;
self.push(&self.stub);

next_ = @atomicLoad(?*T, &tail.next, .acquire);
next_ = @atomicLoad(?*T, &head.next, .acquire);
if (next_) |next| {
@atomicStore(*T, &self.tail, next, .unordered);
tail.next = null;
return tail;
@atomicStore(*T, &self.head, next, .unordered);
head.next = null;
return head;
}

return null;
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