82 lines
1.8 KiB
TypeScript
82 lines
1.8 KiB
TypeScript
interface Lengthwise {
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length: number
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}
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export class RingBuffer<T extends Lengthwise> {
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private capacity: number
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private maxItems: number
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private usage: number = 0
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private items: Array<T> = []
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private start: number = 0
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private end: number = 0
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constructor(capacity: number, maxItems = Infinity, ringBuffer?: RingBuffer<T>) {
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this.capacity = capacity
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this.maxItems = maxItems
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if (ringBuffer) {
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this.items = ringBuffer.toArray()
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this.end = this.items.length
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this.usage = ringBuffer.usage
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}
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}
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private enforceCapacityConstraints(addedItemSize: number) {
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const remainingSize = this.capacity - (this.usage + addedItemSize)
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if (remainingSize < 0) {
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this.freeSomeSpace(Math.abs(remainingSize))
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}
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while (this.end - this.start >= this.maxItems) {
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this.dropFirst()
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}
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}
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private freeSpace(): number {
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return this.capacity - this.usage
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}
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private isEmpty(): boolean {
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return this.usage === 0
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}
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private freeSomeSpace(requiredSpace: number) {
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while (this.freeSpace() < requiredSpace && !this.isEmpty()) {
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this.dropFirst()
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}
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}
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private dropFirst() {
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const firstItem = this.items[this.start]
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delete this.items[this.start]
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this.start += 1
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const freedSpace = firstItem.length
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this.usage -= freedSpace
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}
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public setCapacity(items: number, bytes: number) {
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this.maxItems = items
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this.capacity = bytes
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}
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public clone(): RingBuffer<T> {
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return new RingBuffer(this.capacity, this.maxItems, this)
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}
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public toArray() {
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return this.items.slice(this.start, this.end)
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}
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public count() {
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return this.end - this.start
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}
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public add(item: T) {
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const size = item.length
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this.enforceCapacityConstraints(size)
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this.usage += size
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this.items[this.end] = item
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this.end += 1
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}
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}
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