cesiumDemo/Source/Core/ManagedArray.js

import Check from './Check.js';
import defaultValue from './defaultValue.js';
import defineProperties from './defineProperties.js';

    /**
     * A wrapper around arrays so that the internal length of the array can be manually managed.
     *
     * @alias ManagedArray
     * @constructor
     * @private
     *
     * @param {Number} [length=0] The initial length of the array.
     */
    function ManagedArray(length) {
        length = defaultValue(length, 0);
        this._array = new Array(length);
        this._length = length;
    }

    defineProperties(ManagedArray.prototype, {
        /**
         * Gets or sets the length of the array.
         * If the set length is greater than the length of the internal array, the internal array is resized.
         *
         * @memberof ManagedArray.prototype
         * @type Number
         */
        length : {
            get : function() {
                return this._length;
            },
            set : function(length) {
                this._length = length;
                if (length > this._array.length) {
                    this._array.length = length;
                }
            }
        },

        /**
         * Gets the internal array.
         *
         * @memberof ManagedArray.prototype
         * @type Array
         * @readonly
         */
        values : {
            get : function() {
                return this._array;
            }
        }
    });

    /**
     * Gets the element at an index.
     *
     * @param {Number} index The index to get.
     */
    ManagedArray.prototype.get = function(index) {
        //>>includeStart('debug', pragmas.debug);
        Check.typeOf.number.lessThan('index', index, this._array.length);
        //>>includeEnd('debug');

        return this._array[index];
    };

    /**
     * Sets the element at an index. Resizes the array if index is greater than the length of the array.
     *
     * @param {Number} index The index to set.
     * @param {*} element The element to set at index.
     */
    ManagedArray.prototype.set = function(index, element) {
        //>>includeStart('debug', pragmas.debug);
        Check.typeOf.number('index', index);
        //>>includeEnd('debug');

        if (index >= this.length) {
            this.length = index + 1;
        }
        this._array[index] = element;
    };

    /**
     * Returns the last element in the array without modifying the array.
     *
     * @returns {*} The last element in the array.
     */
    ManagedArray.prototype.peek = function() {
        return this._array[this._length - 1];
    };

    /**
     * Push an element into the array.
     *
     * @param {*} element The element to push.
     */
    ManagedArray.prototype.push = function(element) {
        var index = this.length++;
        this._array[index] = element;
    };

    /**
     * Pop an element from the array.
     *
     * @returns {*} The last element in the array.
     */
    ManagedArray.prototype.pop = function() {
        return this._array[--this.length];
    };

    /**
     * Resize the internal array if length > _array.length.
     *
     * @param {Number} length The length.
     */
    ManagedArray.prototype.reserve = function(length) {
        //>>includeStart('debug', pragmas.debug);
        Check.typeOf.number.greaterThanOrEquals('length', length, 0);
        //>>includeEnd('debug');

        if (length > this._array.length) {
            this._array.length = length;
        }
    };

    /**
     * Resize the array.
     *
     * @param {Number} length The length.
     */
    ManagedArray.prototype.resize = function(length) {
        //>>includeStart('debug', pragmas.debug);
        Check.typeOf.number.greaterThanOrEquals('length', length, 0);
        //>>includeEnd('debug');

        this.length = length;
    };

    /**
     * Trim the internal array to the specified length. Defaults to the current length.
     *
     * @param {Number} [length] The length.
     */
    ManagedArray.prototype.trim = function(length) {
        length = defaultValue(length, this.length);
        this._array.length = length;
    };
export default ManagedArray;