kopia lustrzana https://github.com/Tldraw/Tldraw
147 wiersze
2.9 KiB
TypeScript
147 wiersze
2.9 KiB
TypeScript
// The maximum size for an array in an ArraySet
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export const ARRAY_SIZE_THRESHOLD = 8
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/**
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* An ArraySet operates as an array until it reaches a certain size, after which a Set is used
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* instead. In either case, the same methods are used to get, set, remove, and visit the items.
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* @internal
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*/
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export class ArraySet<T> {
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private arraySize = 0
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private array: (T | undefined)[] | null = Array(ARRAY_SIZE_THRESHOLD)
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private set: Set<T> | null = null
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/**
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* Get whether this ArraySet has any elements.
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*
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* @returns True if this ArraySet has any elements, false otherwise.
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*/
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get isEmpty() {
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if (this.array) {
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return this.arraySize === 0
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}
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if (this.set) {
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return this.set.size === 0
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}
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throw new Error('no set or array')
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}
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/**
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* Add an item to the ArraySet if it is not already present.
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*
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* @param elem - The element to add.
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*/
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add(elem: T) {
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if (this.array) {
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const idx = this.array.indexOf(elem)
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// Return false if the element is already in the array.
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if (idx !== -1) {
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return false
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}
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if (this.arraySize < ARRAY_SIZE_THRESHOLD) {
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// If the array is below the size threshold, push items into the array.
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// Insert the element into the array's next available slot.
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this.array[this.arraySize] = elem
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this.arraySize++
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return true
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} else {
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// If the array is full, convert it to a set and remove the array.
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this.set = new Set(this.array as any)
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this.array = null
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this.set.add(elem)
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return true
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}
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}
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if (this.set) {
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// Return false if the element is already in the set.
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if (this.set.has(elem)) {
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return false
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}
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this.set.add(elem)
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return true
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}
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throw new Error('no set or array')
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}
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/**
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* Remove an item from the ArraySet if it is present.
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*
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* @param elem - The element to remove
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*/
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remove(elem: T) {
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if (this.array) {
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const idx = this.array.indexOf(elem)
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// If the item is not in the array, return false.
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if (idx === -1) {
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return false
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}
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this.array[idx] = undefined
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this.arraySize--
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if (idx !== this.arraySize) {
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// If the item is not the last item in the array, move the last item into the
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// removed item's slot.
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this.array[idx] = this.array[this.arraySize]
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this.array[this.arraySize] = undefined
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}
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return true
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}
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if (this.set) {
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// If the item is not in the set, return false.
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if (!this.set.has(elem)) {
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return false
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}
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this.set.delete(elem)
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return true
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}
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throw new Error('no set or array')
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}
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/**
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* Run a callback for each element in the ArraySet.
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*
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* @param visitor - The callback to run for each element.
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*/
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visit(visitor: (item: T) => void) {
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if (this.array) {
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for (let i = 0; i < this.arraySize; i++) {
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const elem = this.array[i]
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if (typeof elem !== 'undefined') {
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visitor(elem)
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}
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}
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return
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}
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if (this.set) {
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this.set.forEach(visitor)
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return
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}
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throw new Error('no set or array')
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}
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}
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