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45 lines
1.2 KiB
45 lines
1.2 KiB
/**
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* Array-like data structure that lets you push elements to it, but holds only the last N of them.
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*/
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function CircularArray(maxLength) {
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this.maxLength = maxLength;
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this._data = [];
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this._offset = 0;
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}
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/**
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* @property {Number} - the number of items in the CircularArray.
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*/
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Object.defineProperty(CircularArray.prototype, "length", {
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get: function() { return this._data.length; }
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});
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/**
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* @param {Number} index - An index to fetch, between 0 and length - 1.
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* @returns {Object} The item at the given index.
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*/
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CircularArray.prototype.get = function(index) {
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return this._data[(this._offset + index) % this.maxLength];
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};
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/**
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* @param {Object} item - An item to push onto the end of the CircularArray.
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*/
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CircularArray.prototype.push = function(item) {
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if (this._data.length < this.maxLength) {
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this._data.push(item);
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} else {
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this._data[this._offset] = item;
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this._offset = (this._offset + 1) % this.maxLength;
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}
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};
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/**
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* Returns the entire content of CircularArray as a plain array.
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*/
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CircularArray.prototype.getArray = function() {
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return this._data.slice(this._offset).concat(this._data.slice(0, this._offset));
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};
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module.exports = CircularArray;
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