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93 lines
3.1 KiB
JavaScript
93 lines
3.1 KiB
JavaScript
// Copyright 2009 the V8 project authors. All rights reserved.
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following
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// disclaimer in the documentation and/or other materials provided
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// with the distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived
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// from this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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/**
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* Constructs a ConsArray object. It is used mainly for tree traversal.
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* In this use case we have lots of arrays that we need to iterate
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* sequentally. The internal Array implementation is horribly slow
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* when concatenating on large (10K items) arrays due to memory copying.
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* That's why we avoid copying memory and insead build a linked list
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* of arrays to iterate through.
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*
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* @constructor
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*/
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function ConsArray() {
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this.tail_ = new ConsArray.Cell(null, null);
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this.currCell_ = this.tail_;
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this.currCellPos_ = 0;
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};
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/**
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* Concatenates another array for iterating. Empty arrays are ignored.
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* This operation can be safely performed during ongoing ConsArray
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* iteration.
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*
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* @param {Array} arr Array to concatenate.
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*/
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ConsArray.prototype.concat = function(arr) {
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if (arr.length > 0) {
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this.tail_.data = arr;
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this.tail_ = this.tail_.next = new ConsArray.Cell(null, null);
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}
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};
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/**
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* Whether the end of iteration is reached.
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*/
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ConsArray.prototype.atEnd = function() {
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return this.currCell_ === null ||
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this.currCell_.data === null ||
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this.currCellPos_ >= this.currCell_.data.length;
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};
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/**
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* Returns the current item, moves to the next one.
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*/
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ConsArray.prototype.next = function() {
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var result = this.currCell_.data[this.currCellPos_++];
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if (this.currCellPos_ >= this.currCell_.data.length) {
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this.currCell_ = this.currCell_.next;
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this.currCellPos_ = 0;
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}
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return result;
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};
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/**
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* A cell object used for constructing a list in ConsArray.
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*
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* @constructor
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*/
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ConsArray.Cell = function(data, next) {
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this.data = data;
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this.next = next;
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};
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