/
ProcessQueue.js
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ProcessQueue.js
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/**
* @author Richard Davey <rich@photonstorm.com>
* @copyright 2020 Photon Storm Ltd.
* @license {@link https://opensource.org/licenses/MIT|MIT License}
*/
var Class = require('../utils/Class');
var EventEmitter = require('eventemitter3');
var Events = require('./events');
/**
* @classdesc
* A Process Queue maintains three internal lists.
*
* The `pending` list is a selection of items which are due to be made 'active' in the next update.
* The `active` list is a selection of items which are considered active and should be updated.
* The `destroy` list is a selection of items that were active and are awaiting being destroyed in the next update.
*
* When new items are added to a Process Queue they are put in the pending list, rather than being added
* immediately the active list. Equally, items that are removed are put into the destroy list, rather than
* being destroyed immediately. This allows the Process Queue to carefully process each item at a specific, fixed
* time, rather than at the time of the request from the API.
*
* @class ProcessQueue
* @extends Phaser.Events.EventEmitter
* @memberof Phaser.Structs
* @constructor
* @since 3.0.0
*
* @generic T
*/
var ProcessQueue = new Class({
Extends: EventEmitter,
initialize:
function ProcessQueue ()
{
EventEmitter.call(this);
/**
* The `pending` list is a selection of items which are due to be made 'active' in the next update.
*
* @genericUse {T[]} - [$type]
*
* @name Phaser.Structs.ProcessQueue#_pending
* @type {Array.<*>}
* @private
* @default []
* @since 3.0.0
*/
this._pending = [];
/**
* The `active` list is a selection of items which are considered active and should be updated.
*
* @genericUse {T[]} - [$type]
*
* @name Phaser.Structs.ProcessQueue#_active
* @type {Array.<*>}
* @private
* @default []
* @since 3.0.0
*/
this._active = [];
/**
* The `destroy` list is a selection of items that were active and are awaiting being destroyed in the next update.
*
* @genericUse {T[]} - [$type]
*
* @name Phaser.Structs.ProcessQueue#_destroy
* @type {Array.<*>}
* @private
* @default []
* @since 3.0.0
*/
this._destroy = [];
/**
* The total number of items awaiting processing.
*
* @name Phaser.Structs.ProcessQueue#_toProcess
* @type {number}
* @private
* @default 0
* @since 3.0.0
*/
this._toProcess = 0;
/**
* If `true` only unique objects will be allowed in the queue.
*
* @name Phaser.Structs.ProcessQueue#checkQueue
* @type {boolean}
* @since 3.50.0
*/
this.checkQueue = false;
},
/**
* Adds a new item to the Process Queue.
*
* The item is added to the pending list and made active in the next update.
*
* @method Phaser.Structs.ProcessQueue#add
* @since 3.0.0
*
* @genericUse {T} - [item]
* @genericUse {Phaser.Structs.ProcessQueue.<T>} - [$return]
*
* @param {*} item - The item to add to the queue.
*
* @return {*} The item that was added.
*/
add: function (item)
{
this._pending.push(item);
this._toProcess++;
return item;
},
/**
* Removes an item from the Process Queue.
*
* The item is added to the pending destroy and fully removed in the next update.
*
* @method Phaser.Structs.ProcessQueue#remove
* @since 3.0.0
*
* @genericUse {T} - [item]
* @genericUse {Phaser.Structs.ProcessQueue.<T>} - [$return]
*
* @param {*} item - The item to be removed from the queue.
*
* @return {*} The item that was removed.
*/
remove: function (item)
{
this._destroy.push(item);
this._toProcess++;
return item;
},
/**
* Removes all active items from this Process Queue.
*
* All the items are marked as 'pending destroy' and fully removed in the next update.
*
* @method Phaser.Structs.ProcessQueue#removeAll
* @since 3.20.0
*
* @return {this} This Process Queue object.
*/
removeAll: function ()
{
var list = this._active;
var destroy = this._destroy;
var i = list.length;
while (i--)
{
destroy.push(list[i]);
this._toProcess++;
}
return this;
},
/**
* Update this queue. First it will process any items awaiting destruction, and remove them.
*
* Then it will check to see if there are any items pending insertion, and move them to an
* active state. Finally, it will return a list of active items for further processing.
*
* @method Phaser.Structs.ProcessQueue#update
* @since 3.0.0
*
* @genericUse {T[]} - [$return]
*
* @return {Array.<*>} A list of active items.
*/
update: function ()
{
if (this._toProcess === 0)
{
// Quick bail
return this._active;
}
var list = this._destroy;
var active = this._active;
var i;
var item;
// Clear the 'destroy' list
for (i = 0; i < list.length; i++)
{
item = list[i];
// Remove from the 'active' array
var idx = active.indexOf(item);
if (idx !== -1)
{
active.splice(idx, 1);
this.emit(Events.PROCESS_QUEUE_REMOVE, item);
}
}
list.length = 0;
// Process the pending addition list
// This stops callbacks and out of sync events from populating the active array mid-way during an update
list = this._pending;
for (i = 0; i < list.length; i++)
{
item = list[i];
if (!this.checkQueue || (this.checkQueue && active.indexOf(item) === -1))
{
active.push(item);
this.emit(Events.PROCESS_QUEUE_ADD, item);
}
}
list.length = 0;
this._toProcess = 0;
// The owner of this queue can now safely do whatever it needs to with the active list
return active;
},
/**
* Returns the current list of active items.
*
* This method returns a reference to the active list array, not a copy of it.
* Therefore, be careful to not modify this array outside of the ProcessQueue.
*
* @method Phaser.Structs.ProcessQueue#getActive
* @since 3.0.0
*
* @genericUse {T[]} - [$return]
*
* @return {Array.<*>} A list of active items.
*/
getActive: function ()
{
return this._active;
},
/**
* The number of entries in the active list.
*
* @name Phaser.Structs.ProcessQueue#length
* @type {number}
* @readonly
* @since 3.20.0
*/
length: {
get: function ()
{
return this._active.length;
}
},
/**
* Immediately destroys this process queue, clearing all of its internal arrays and resetting the process totals.
*
* @method Phaser.Structs.ProcessQueue#destroy
* @since 3.0.0
*/
destroy: function ()
{
this._toProcess = 0;
this._pending = [];
this._active = [];
this._destroy = [];
}
});
module.exports = ProcessQueue;