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 11820x 20x 20x 20x 20x 20x 20x 20x 20x 20x 20x 20x 20x 20x 20x 20x 20x 20x 20x 20x 587x 587x 587x 587x 587x 587x 587x 587x 20x 20x 52411x 52411x 20x 20x 5444x 5444x 5444x 5444x 5444x 5444x 5444x 5444x 5444x 20x 20x 12173x 12173x 20x 20x 7316x 7316x 7316x 7316x 7316x 7316x 7316x 19569x 19569x 19569x 19569x 19569x 19569x 17296x 18338x 17296x 17296x 17296x 7316x 7316x 7316x 7316x 20x 20x 5445x 5445x 5445x 5445x 5445x 5445x 19776x 19776x 19776x 19207x 19207x 19249x 19249x 19249x 5445x 5445x 5445x 5445x 20x 20x 4142x 4142x 4142x 4142x 4142x 4142x 2682x 2682x 2681x 2681x 2682x 4142x 20x 20x 3561x 3561x 3561x 3561x 3561x 3561x 3561x 3561x 3561x 20x  
'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;
  }
};