Steve Block | a7e24c1 | 2009-10-30 11:49:00 +0000 | [diff] [blame] | 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 | */ |
| 39 | function ConsArray() { |
| 40 | this.tail_ = new ConsArray.Cell(null, null); |
| 41 | this.currCell_ = this.tail_; |
| 42 | this.currCellPos_ = 0; |
| 43 | }; |
| 44 | |
| 45 | |
| 46 | /** |
| 47 | * Concatenates another array for iterating. Empty arrays are ignored. |
| 48 | * This operation can be safely performed during ongoing ConsArray |
| 49 | * iteration. |
| 50 | * |
| 51 | * @param {Array} arr Array to concatenate. |
| 52 | */ |
| 53 | ConsArray.prototype.concat = function(arr) { |
| 54 | if (arr.length > 0) { |
| 55 | this.tail_.data = arr; |
| 56 | this.tail_ = this.tail_.next = new ConsArray.Cell(null, null); |
| 57 | } |
| 58 | }; |
| 59 | |
| 60 | |
| 61 | /** |
| 62 | * Whether the end of iteration is reached. |
| 63 | */ |
| 64 | ConsArray.prototype.atEnd = function() { |
| 65 | return this.currCell_ === null || |
| 66 | this.currCell_.data === null || |
| 67 | this.currCellPos_ >= this.currCell_.data.length; |
| 68 | }; |
| 69 | |
| 70 | |
| 71 | /** |
| 72 | * Returns the current item, moves to the next one. |
| 73 | */ |
| 74 | ConsArray.prototype.next = function() { |
| 75 | var result = this.currCell_.data[this.currCellPos_++]; |
| 76 | if (this.currCellPos_ >= this.currCell_.data.length) { |
| 77 | this.currCell_ = this.currCell_.next; |
| 78 | this.currCellPos_ = 0; |
| 79 | } |
| 80 | return result; |
| 81 | }; |
| 82 | |
| 83 | |
| 84 | /** |
| 85 | * A cell object used for constructing a list in ConsArray. |
| 86 | * |
| 87 | * @constructor |
| 88 | */ |
| 89 | ConsArray.Cell = function(data, next) { |
| 90 | this.data = data; |
| 91 | this.next = next; |
| 92 | }; |