| 1 | /** |
| 2 | * Copyright (c) Meta Platforms, Inc. and affiliates. |
| 3 | * |
| 4 | * This source code is licensed under the MIT license found in the |
| 5 | * LICENSE file in the root directory of this source tree. |
| 6 | * |
| 7 | * @flow |
| 8 | */ |
| 9 | |
| 10 | import type {Fiber} from './ReactInternalTypes'; |
| 11 | |
| 12 | export type StackCursor<T> = {current: T}; |
| 13 | |
| 14 | const valueStack: Array<any> = []; |
| 15 | |
| 16 | let fiberStack: Array<Fiber | null>; |
| 17 | |
| 18 | if (__DEV__) { |
| 19 | fiberStack = []; |
| 20 | } |
| 21 | |
| 22 | let index = -1; |
| 23 | |
| 24 | function createCursor<T>(defaultValue: T): StackCursor<T> { |
| 25 | return { |
| 26 | current: defaultValue, |
| 27 | }; |
| 28 | } |
| 29 | |
| 30 | function pop<T>(cursor: StackCursor<T>, fiber: Fiber): void { |
| 31 | if (index < 0) { |
| 32 | if (__DEV__) { |
| 33 | console.error('Unexpected pop.'); |
| 34 | } |
| 35 | return; |
| 36 | } |
| 37 | |
| 38 | if (__DEV__) { |
| 39 | if (fiber !== fiberStack[index]) { |
| 40 | console.error('Unexpected Fiber popped.'); |
| 41 | } |
| 42 | } |
| 43 | |
| 44 | cursor.current = valueStack[index]; |
| 45 | |
| 46 | valueStack[index] = null; |
| 47 | |
| 48 | if (__DEV__) { |
| 49 | fiberStack[index] = null; |
| 50 | } |
| 51 | |
| 52 | index--; |
| 53 | } |
| 54 | |
| 55 | function push<T>(cursor: StackCursor<T>, value: T, fiber: Fiber): void { |
| 56 | index++; |
| 57 | |
| 58 | valueStack[index] = cursor.current; |
| 59 | |
| 60 | if (__DEV__) { |
| 61 | fiberStack[index] = fiber; |
| 62 | } |
| 63 | |
| 64 | cursor.current = value; |
| 65 | } |
| 66 | export {createCursor, pop, push}; |