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turn LRUCache into tile-specific TileCache
LRUCache was only being used for tiles and recently we started adding some non-standard behaviour including storing multiple values for a single key. This pr: - replaces `number` key with `OverscaledTileID` so that we can enforce the type and enforce tile id wrapping - moves expiry logic into cache and gets rid of `cacheTimers` in `SourceCache`
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,184 @@ | ||
| // @flow | ||
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| import { OverscaledTileID } from './tile_id'; | ||
| import type Tile from './tile'; | ||
|
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| /** | ||
| * A [least-recently-used cache](http://en.wikipedia.org/wiki/Cache_algorithms) | ||
| * with hash lookup made possible by keeping a list of keys in parallel to | ||
| * an array of dictionary of values | ||
| * | ||
| * @private | ||
| */ | ||
| class TileCache { | ||
| max: number; | ||
| data: {[key: number | string]: Array<{ value: Tile, timeout: ?TimeoutID}>}; | ||
| order: Array<number>; | ||
| onRemove: (element: Tile) => void; | ||
| /** | ||
| * @param {number} max number of permitted values | ||
| * @param {Function} onRemove callback called with items when they expire | ||
| */ | ||
| constructor(max: number, onRemove: (element: Tile) => void) { | ||
| this.max = max; | ||
| this.onRemove = onRemove; | ||
| this.reset(); | ||
| } | ||
|
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| /** | ||
| * Clear the cache | ||
| * | ||
| * @returns {TileCache} this cache | ||
| * @private | ||
| */ | ||
| reset() { | ||
| for (const key in this.data) { | ||
| for (const removedData of this.data[key]) { | ||
| if (removedData.timeout) clearTimeout(removedData.timeout); | ||
| this.onRemove(removedData.value); | ||
| } | ||
| } | ||
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| this.data = {}; | ||
| this.order = []; | ||
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| return this; | ||
| } | ||
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| /** | ||
| * Add a key, value combination to the cache, trimming its size if this pushes | ||
| * it over max length. | ||
| * | ||
| * @param {OverscaledTileID} tileID lookup key for the item | ||
| * @param {*} data any value | ||
| * | ||
| * @returns {TileCache} this cache | ||
| * @private | ||
| */ | ||
| add(tileID: OverscaledTileID, data: Tile, expiryTimeout: number | void) { | ||
| const key = tileID.wrapped().key; | ||
| if (this.data[key] === undefined) { | ||
| this.data[key] = []; | ||
| } | ||
|
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| const dataWrapper = { | ||
| value: data, | ||
| timeout: undefined | ||
| }; | ||
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| if (expiryTimeout !== undefined) { | ||
| dataWrapper.timeout = setTimeout(() => { | ||
| this.remove(tileID, dataWrapper); | ||
| }, expiryTimeout); | ||
| } | ||
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| this.data[key].push(dataWrapper); | ||
| this.order.push(key); | ||
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| if (this.order.length > this.max) { | ||
| const removedData = this._getAndRemoveByKey(this.order[0]); | ||
| if (removedData) this.onRemove(removedData); | ||
| } | ||
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| return this; | ||
| } | ||
|
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| /** | ||
| * Determine whether the value attached to `key` is present | ||
| * | ||
| * @param {OverscaledTileID} tileID the key to be looked-up | ||
| * @returns {boolean} whether the cache has this value | ||
| * @private | ||
| */ | ||
| has(tileID: OverscaledTileID): boolean { | ||
| return tileID.wrapped().key in this.data; | ||
| } | ||
|
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| /** | ||
| * Get the value attached to a specific key and remove data from cache. | ||
| * If the key is not found, returns `null` | ||
| * | ||
| * @param {OverscaledTileID} tileID the key to look up | ||
| * @returns {*} the data, or null if it isn't found | ||
| * @private | ||
| */ | ||
| getAndRemove(tileID: OverscaledTileID): ?Tile { | ||
| if (!this.has(tileID)) { return null; } | ||
| return this._getAndRemoveByKey(tileID.wrapped().key); | ||
| } | ||
|
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| /* | ||
| * Get and remove the value with the specified key. | ||
| */ | ||
| _getAndRemoveByKey(key: number): ?Tile { | ||
| const data = this.data[key].shift(); | ||
| if (data.timeout) clearTimeout(data.timeout); | ||
|
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| if (this.data[key].length === 0) { | ||
| delete this.data[key]; | ||
| } | ||
| this.order.splice(this.order.indexOf(key), 1); | ||
|
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| return data.value; | ||
| } | ||
|
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| /** | ||
| * Get the value attached to a specific key without removing data | ||
| * from the cache. If the key is not found, returns `null` | ||
| * | ||
| * @param {OverscaledTileID} tileID the key to look up | ||
| * @returns {*} the data, or null if it isn't found | ||
| * @private | ||
| */ | ||
| get(tileID: OverscaledTileID): ?Tile { | ||
| if (!this.has(tileID)) { return null; } | ||
|
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| const data = this.data[tileID.wrapped().key][0]; | ||
| return data.value; | ||
| } | ||
|
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| /** | ||
| * Remove a key/value combination from the cache. | ||
| * | ||
| * @param {OverscaledTileID} tileID the key for the pair to delete | ||
| * @param {Tile} value If a value is provided, remove that exact version of the value. | ||
| * @returns {TileCache} this cache | ||
| * @private | ||
| */ | ||
| remove(tileID: OverscaledTileID, value: ?{ value: Tile, timeout: ?TimeoutID}) { | ||
| if (!this.has(tileID)) { return this; } | ||
| const key = tileID.wrapped().key; | ||
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| const dataIndex = value === undefined ? 0 : this.data[key].indexOf(value); | ||
| const data = this.data[key][dataIndex]; | ||
| this.data[key].splice(dataIndex, 1); | ||
| if (data.timeout) clearTimeout(data.timeout); | ||
| if (this.data[key].length === 0) { | ||
| delete this.data[key]; | ||
| } | ||
| this.onRemove(data.value); | ||
| this.order.splice(this.order.indexOf(key), 1); | ||
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| return this; | ||
| } | ||
|
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| /** | ||
| * Change the max size of the cache. | ||
| * | ||
| * @param {number} max the max size of the cache | ||
| * @returns {TileCache} this cache | ||
| * @private | ||
| */ | ||
| setMaxSize(max: number): TileCache { | ||
| this.max = max; | ||
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| while (this.order.length > this.max) { | ||
| const removedData = this._getAndRemoveByKey(this.order[0]); | ||
| if (removedData) this.onRemove(removedData); | ||
| } | ||
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| return this; | ||
| } | ||
| } | ||
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| export default TileCache; |
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