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timers: fix priority queue removeAt

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PR-URL: https://github.com/nodejs/node/pull/24322
Fixes: https://github.com/nodejs/node/issues/24320
Fixes: https://github.com/nodejs/node/issues/24362
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Weijia Wang <starkwang@126.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
This commit is contained in:
Anatoli Papirovski 2018-11-12 08:59:37 -08:00 committed by Rich Trott
parent 7082c61e27
commit 9ca5c525f4
2 changed files with 58 additions and 21 deletions
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49
lib/internal/priority_queue.js
View File

@ -28,25 +28,13 @@ module.exports = class PriorityQueue {
insert(value) { insert(value) {
const heap = this[kHeap]; const heap = this[kHeap];
let pos = ++this[kSize]; const pos = ++this[kSize];
heap[pos] = value;
if (heap.length === pos) if (heap.length === pos)
heap.length *= 2; heap.length *= 2;
const compare = this[kCompare]; this.percolateUp(pos);
const setPosition = this[kSetPosition];
while (pos > 1) {
const parent = heap[pos / 2 | 0];
if (compare(parent, value) <= 0)
break;
heap[pos] = parent;
if (setPosition !== undefined)
setPosition(parent, pos);
pos = pos / 2 | 0;
}
heap[pos] = value;
if (setPosition !== undefined)
setPosition(value, pos);
} }
peek() { peek() {
@ -77,18 +65,37 @@ module.exports = class PriorityQueue {
setPosition(item, pos); setPosition(item, pos);
} }
percolateUp(pos) {
const heap = this[kHeap];
const compare = this[kCompare];
const setPosition = this[kSetPosition];
const item = heap[pos];
while (pos > 1) {
const parent = heap[pos / 2 | 0];
if (compare(parent, item) <= 0)
break;
heap[pos] = parent;
if (setPosition !== undefined)
setPosition(parent, pos);
pos = pos / 2 | 0;
}
heap[pos] = item;
if (setPosition !== undefined)
setPosition(item, pos);
}
removeAt(pos) { removeAt(pos) {
const heap = this[kHeap]; const heap = this[kHeap];
const size = --this[kSize]; const size = --this[kSize];
heap[pos] = heap[size + 1]; heap[pos] = heap[size + 1];
heap[size + 1] = undefined; heap[size + 1] = undefined;
if (size > 0) { if (size > 0 && pos <= size) {
// If not removing the last item, update the shifted item's position. if (pos > 1 && this[kCompare](heap[pos / 2 | 0], heap[pos]) > 0)
if (pos <= size && this[kSetPosition] !== undefined) this.percolateUp(pos);
this[kSetPosition](heap[pos], pos); else
this.percolateDown(pos);
this.percolateDown(1);
} }
} }

30
test/parallel/test-priority-queue.js
View File

@ -131,3 +131,33 @@ const PriorityQueue = require('internal/priority_queue');
assert.strictEqual(queue.shift(), undefined); assert.strictEqual(queue.shift(), undefined);
} }
{
// Checks that removeAt respects binary heap properties
const queue = new PriorityQueue((a, b) => {
return a.value - b.value;
}, (node, pos) => (node.position = pos));
const i3 = { value: 3, position: null };
const i7 = { value: 7, position: null };
const i8 = { value: 8, position: null };
queue.insert({ value: 1, position: null });
queue.insert({ value: 6, position: null });
queue.insert({ value: 2, position: null });
queue.insert(i7);
queue.insert(i8);
queue.insert(i3);
assert.strictEqual(i7.position, 4);
queue.removeAt(4);
// 3 should percolate up to swap with 6 (up)
assert.strictEqual(i3.position, 2);
queue.removeAt(2);
// 8 should swap places with 6 (down)
assert.strictEqual(i8.position, 4);
}