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// Copyright 2009 the V8 project authors. All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following
// disclaimer in the documentation and/or other materials provided
// with the distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived
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//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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/**
* Constructs a ConsArray object. It is used mainly for tree traversal.
* In this use case we have lots of arrays that we need to iterate
* sequentally. The internal Array implementation is horribly slow
* when concatenating on large (10K items) arrays due to memory copying.
* That's why we avoid copying memory and insead build a linked list
* of arrays to iterate through.
*
* @constructor
*/
function ConsArray() {
this.tail_ = new ConsArray.Cell(null, null);
this.currCell_ = this.tail_;
this.currCellPos_ = 0;
};
/**
* Concatenates another array for iterating. Empty arrays are ignored.
* This operation can be safely performed during ongoing ConsArray
* iteration.
*
* @param {Array} arr Array to concatenate.
*/
ConsArray.prototype.concat = function(arr) {
if (arr.length > 0) {
this.tail_.data = arr;
this.tail_ = this.tail_.next = new ConsArray.Cell(null, null);
}
};
/**
* Whether the end of iteration is reached.
*/
ConsArray.prototype.atEnd = function() {
return this.currCell_ === null ||
this.currCell_.data === null ||
this.currCellPos_ >= this.currCell_.data.length;
};
/**
* Returns the current item, moves to the next one.
*/
ConsArray.prototype.next = function() {
var result = this.currCell_.data[this.currCellPos_++];
if (this.currCellPos_ >= this.currCell_.data.length) {
this.currCell_ = this.currCell_.next;
this.currCellPos_ = 0;
}
return result;
};
/**
* A cell object used for constructing a list in ConsArray.
*
* @constructor
*/
ConsArray.Cell = function(data, next) {
this.data = data;
this.next = next;
};