lib: priority_queue pre-grow array and avoid holey reads

Author: gurgunday

lib/internal/priority_queue.js

@@ -26,11 +26,12 @@ module.exports = class PriorityQueue {
   insert(value) {
     const heap = this.#heap;
     const pos = ++this.#size;
-    heap[pos] = value;
 
-    if (heap.length === pos)
+    if (pos === heap.length)
       heap.length *= 2;
 
+    heap[pos] = value;
+
     this.percolateUp(pos);
   }
 
@@ -45,6 +46,7 @@ module.exports = class PriorityQueue {
   percolateDown(pos) {
     const compare = this.#compare;
     const setPosition = this.#setPosition;
+    const hasSetPosition = setPosition !== undefined;
     const heap = this.#heap;
     const size = this.#size;
     const hsize = size >> 1;
@@ -62,22 +64,23 @@ module.exports = class PriorityQueue {
 
       if (compare(item, childItem) <= 0) break;
 
-      if (setPosition !== undefined)
+      if (hasSetPosition)
         setPosition(childItem, pos);
 
       heap[pos] = childItem;
       pos = child;
     }
 
     heap[pos] = item;
-    if (setPosition !== undefined)
+    if (hasSetPosition)
       setPosition(item, pos);
   }
 
   percolateUp(pos) {
     const heap = this.#heap;
     const compare = this.#compare;
     const setPosition = this.#setPosition;
+    const hasSetPosition = setPosition !== undefined;
     const item = heap[pos];
 
     while (pos > 1) {
@@ -86,13 +89,13 @@ module.exports = class PriorityQueue {
       if (compare(parentItem, item) <= 0)
         break;
       heap[pos] = parentItem;
-      if (setPosition !== undefined)
+      if (hasSetPosition)
         setPosition(parentItem, pos);
       pos = parent;
     }
 
     heap[pos] = item;
-    if (setPosition !== undefined)
+    if (hasSetPosition)
       setPosition(item, pos);
   }
 
@@ -112,10 +115,10 @@ module.exports = class PriorityQueue {
   }
 
   shift() {
+    if (this.#size === 0)
+      return;
     const heap = this.#heap;
     const value = heap[1];
-    if (value === undefined)
-      return;
 
     this.removeAt(1);