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* resolves #72 introduce a recovery queue * remove suite * ensure that no error is thrown * default maxSize 1024 and remove arbitrary setTimeout * add documentation * copy editing and emit a warning when recovery failed * fix typo in comment * events consistency and update CLI * improve doc * copy editing * fix for node 14
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,98 @@ | ||
| 'use strict' | ||
|
|
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| const { emitWarning } = require('process') | ||
|
|
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| /** | ||
| * @typedef {object} QueueOptions | ||
| * @prop {number} [maxSize] Positive integer to track the sizes of items added to the cache, and automatically evict items in order to stay below this size. Default: `Infinity` | ||
| * @prop {(any) => number?} [sizeCalculation] Function used to calculate the size of stored items. Default: `item => item.length`. | ||
| */ | ||
|
|
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| /** | ||
| * A linear data structure of a FIFO (First In - First Out) type. | ||
| * | ||
| * Inspired by: | ||
| * - https://vhudyma-blog.eu/implement-queue-in-javascript/ | ||
| * - https://github.com/isaacs/node-lru-cache | ||
| */ | ||
| module.exports = class Queue { | ||
| /** | ||
| * @param {QueueOptions} opts | ||
| */ | ||
| constructor (opts) { | ||
| // The actual queue | ||
| this.items = {} | ||
| // The index of the head item | ||
| this.head = 0 | ||
| // The index of the tail item | ||
| this.tail = 0 | ||
| this.calculatedSize = 0 | ||
| this.sizes = {} | ||
| this.opts = { | ||
| maxSize: Infinity, | ||
| sizeCalculation: (item) => item.length, | ||
| ...opts | ||
| } | ||
| } | ||
|
|
||
| enqueue (item) { | ||
| const index = this.tail | ||
| const size = this.opts.sizeCalculation(item) | ||
| if (size > this.opts.maxSize) { | ||
| emitWarning(`unable to enqueue item because item size ${size} is greater than maxSize ${this.opts.maxSize}`) | ||
| return | ||
| } | ||
| this.sizes[index] = size | ||
| const maxSize = this.opts.maxSize - size | ||
| while (this.calculatedSize > maxSize) { | ||
| this.evict() | ||
| } | ||
| this.calculatedSize += size | ||
| // Add an item on the current tail index | ||
| this.items[index] = item | ||
| // Increase the index of the tail item | ||
| // So the next items are added at the end | ||
| this.tail++ | ||
| } | ||
|
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| evict () { | ||
| // If the queue is empty | ||
| if (this.tail === this.head) { | ||
| return undefined | ||
| } | ||
| const index = this.head | ||
| this.calculatedSize -= this.sizes[index] | ||
| delete this.sizes[index] | ||
| this.dequeue() | ||
| } | ||
|
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||
| dequeue () { | ||
| const item = this.peek() | ||
| if (item === undefined) { | ||
| return item | ||
| } | ||
| // Delete it | ||
| delete this.items[this.head] | ||
| // Increase the head index | ||
| this.head++ | ||
| // Return the item | ||
| return item | ||
| } | ||
|
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||
| peek () { | ||
| // If the queue is empty, return "undefined" | ||
| if (this.tail === this.head) { | ||
| return undefined | ||
| } | ||
| // Pick an item | ||
| return this.items[this.head] | ||
| } | ||
|
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||
| size () { | ||
| return Object.keys(this.items).length | ||
| } | ||
|
|
||
| isEmpty () { | ||
| return this.size() === 0 | ||
| } | ||
| } |
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