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SVG.Queue = SVG.invent({
create: function () {
this._first = null
this._last = null
},
extend: {
push: function (value) {
// An item stores an id and the provided value
var item = value.next ? value : { value: value, next: null, prev: null }
// Deal with the queue being empty or populated
if (this._last) {
item.prev = this._last
this._last.next = item
this._last = item
} else {
this._last = item
this._first = item
}
// Update the length and return the current item
return item
},
shift: function () {
// Check if we have a value
var remove = this._first
if (!remove) return null
// If we do, remove it and relink things
this._first = remove.next
if (this._first) this._first.prev = null
this._last = this._first ? this._last : null
return remove.value
},
// Shows us the first item in the list
first: function () {
return this._first && this._first.value
},
// Shows us the last item in the list
last: function () {
return this._last && this._last.value
},
// Removes the item that was returned from the push
remove: function (item) {
// Relink the previous item
if (item.prev) item.prev.next = item.next
if (item.next) item.next.prev = item.prev
if (item === this._last) this._last = item.prev
if (item === this._first) this._first = item.next
// Invalidate item
item.prev = null
item.next = null
}
}
})
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