All files / lib/internal priority_queue.js

100% Statements 117/117
97.14% Branches 34/35
100% Functions 8/8
100% Lines 117/117

Press n or j to go to the next uncovered block, b, p or k for the previous block.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 11826x 26x 26x 26x 26x 26x 26x 26x 26x 26x 26x 26x 26x 26x 26x 26x 26x 26x 26x 26x 581x 581x 581x 581x 581x 581x 581x 581x 26x 26x 52411x 52411x 26x 26x 5021x 5021x 5021x 5021x 5021x 5021x 5021x 5021x 5021x 26x 26x 14988x 14988x 26x 26x 8715x 8715x 8715x 8715x 8715x 8715x 8715x 19316x 19316x 19316x 19316x 19316x 19316x 17210x 18252x 17210x 17210x 17210x 8715x 8715x 8715x 8715x 26x 26x 5022x 5022x 5022x 5022x 5022x 5022x 19360x 19360x 19360x 18866x 18866x 18908x 18908x 18908x 5022x 5022x 5022x 5022x 26x 26x 4119x 4119x 4119x 4119x 4119x 4119x 2648x 2648x 2647x 2647x 2648x 4119x 26x 26x 3535x 3535x 3535x 3535x 3535x 3535x 3535x 3535x 3535x 26x  
'use strict';
 
const {
  Array,
  Symbol,
} = primordials;
 
const kCompare = Symbol('compare');
const kHeap = Symbol('heap');
const kSetPosition = Symbol('setPosition');
const kSize = Symbol('size');
 
// The PriorityQueue is a basic implementation of a binary heap that accepts
// a custom sorting function via its constructor. This function is passed
// the two nodes to compare, similar to the native Array#sort. Crucially
// this enables priority queues that are based on a comparison of more than
// just a single criteria.
 
module.exports = class PriorityQueue {
  constructor(comparator, setPosition) {
    if (comparator !== undefined)
      this[kCompare] = comparator;
    if (setPosition !== undefined)
      this[kSetPosition] = setPosition;
 
    this[kHeap] = new Array(64);
    this[kSize] = 0;
  }
 
  [kCompare](a, b) {
    return a - b;
  }
 
  insert(value) {
    const heap = this[kHeap];
    const pos = ++this[kSize];
    heap[pos] = value;
 
    if (heap.length === pos)
      heap.length *= 2;
 
    this.percolateUp(pos);
  }
 
  peek() {
    return this[kHeap][1];
  }
 
  percolateDown(pos) {
    const compare = this[kCompare];
    const setPosition = this[kSetPosition];
    const heap = this[kHeap];
    const size = this[kSize];
    const item = heap[pos];
 
    while (pos * 2 <= size) {
      let childIndex = pos * 2 + 1;
      if (childIndex > size || compare(heap[pos * 2], heap[childIndex]) < 0)
        childIndex = pos * 2;
      const child = heap[childIndex];
      if (compare(item, child) <= 0)
        break;
      if (setPosition !== undefined)
        setPosition(child, pos);
      heap[pos] = child;
      pos = childIndex;
    }
    heap[pos] = item;
    if (setPosition !== undefined)
      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) {
    const heap = this[kHeap];
    const size = --this[kSize];
    heap[pos] = heap[size + 1];
    heap[size + 1] = undefined;
 
    if (size > 0 && pos <= size) {
      if (pos > 1 && this[kCompare](heap[pos / 2 | 0], heap[pos]) > 0)
        this.percolateUp(pos);
      else
        this.percolateDown(pos);
    }
  }
 
  shift() {
    const heap = this[kHeap];
    const value = heap[1];
    if (value === undefined)
      return;
 
    this.removeAt(1);
 
    return value;
  }
};