1// Copyright 2009 the V8 project authors. All rights reserved. 2// Redistribution and use in source and binary forms, with or without 3// modification, are permitted provided that the following conditions are 4// met: 5// 6// * Redistributions of source code must retain the above copyright 7// notice, this list of conditions and the following disclaimer. 8// * Redistributions in binary form must reproduce the above 9// copyright notice, this list of conditions and the following 10// disclaimer in the documentation and/or other materials provided 11// with the distribution. 12// * Neither the name of Google Inc. nor the names of its 13// contributors may be used to endorse or promote products derived 14// from this software without specific prior written permission. 15// 16// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 17// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 18// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 19// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 20// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 21// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 22// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 26// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 28 29/** 30 * Constructs a ConsArray object. It is used mainly for tree traversal. 31 * In this use case we have lots of arrays that we need to iterate 32 * sequentally. The internal Array implementation is horribly slow 33 * when concatenating on large (10K items) arrays due to memory copying. 34 * That's why we avoid copying memory and insead build a linked list 35 * of arrays to iterate through. 36 * 37 * @constructor 38 */ 39export class ConsArray { 40 constructor() { 41 this.tail_ = new ConsArrayCell(null, null); 42 this.currCell_ = this.tail_; 43 this.currCellPos_ = 0; 44 } 45 /** 46 * Concatenates another array for iterating. Empty arrays are ignored. 47 * This operation can be safely performed during ongoing ConsArray 48 * iteration. 49 * 50 * @param {Array} arr Array to concatenate. 51 */ 52 concat(arr) { 53 if (arr.length > 0) { 54 this.tail_.data = arr; 55 this.tail_ = this.tail_.next = new ConsArrayCell(null, null); 56 } 57 } 58 59 /** 60 * Whether the end of iteration is reached. 61 */ 62 atEnd() { 63 return this.currCell_ === null || 64 this.currCell_.data === null || 65 this.currCellPos_ >= this.currCell_.data.length; 66 } 67 68 /** 69 * Returns the current item, moves to the next one. 70 */ 71 next() { 72 const result = this.currCell_.data[this.currCellPos_++]; 73 if (this.currCellPos_ >= this.currCell_.data.length) { 74 this.currCell_ = this.currCell_.next; 75 this.currCellPos_ = 0; 76 } 77 return result; 78 } 79} 80 81 82/** 83 * A cell object used for constructing a list in ConsArray. 84 * 85 * @constructor 86 */ 87class ConsArrayCell { 88 constructor(data, next) { 89 this.data = data; 90 this.next = next; 91 } 92} 93