90 lines
2.4 KiB
JavaScript
90 lines
2.4 KiB
JavaScript
import {constants} from 'micromark-util-symbol'
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/**
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* Like `Array#splice`, but smarter for giant arrays.
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*
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* `Array#splice` takes all items to be inserted as individual argument which
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* causes a stack overflow in V8 when trying to insert 100k items for instance.
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*
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* Otherwise, this does not return the removed items, and takes `items` as an
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* array instead of rest parameters.
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*
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* @template {unknown} T
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* Item type.
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* @param {Array<T>} list
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* List to operate on.
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* @param {number} start
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* Index to remove/insert at (can be negative).
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* @param {number} remove
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* Number of items to remove.
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* @param {Array<T>} items
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* Items to inject into `list`.
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* @returns {undefined}
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* Nothing.
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*/
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export function splice(list, start, remove, items) {
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const end = list.length
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let chunkStart = 0
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/** @type {Array<unknown>} */
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let parameters
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// Make start between zero and `end` (included).
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if (start < 0) {
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start = -start > end ? 0 : end + start
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} else {
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start = start > end ? end : start
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}
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remove = remove > 0 ? remove : 0
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// No need to chunk the items if there’s only a couple (10k) items.
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if (items.length < constants.v8MaxSafeChunkSize) {
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parameters = Array.from(items)
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parameters.unshift(start, remove)
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// @ts-expect-error Hush, it’s fine.
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list.splice(...parameters)
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} else {
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// Delete `remove` items starting from `start`
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if (remove) list.splice(start, remove)
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// Insert the items in chunks to not cause stack overflows.
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while (chunkStart < items.length) {
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parameters = items.slice(
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chunkStart,
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chunkStart + constants.v8MaxSafeChunkSize
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)
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parameters.unshift(start, 0)
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// @ts-expect-error Hush, it’s fine.
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list.splice(...parameters)
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chunkStart += constants.v8MaxSafeChunkSize
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start += constants.v8MaxSafeChunkSize
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}
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}
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}
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/**
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* Append `items` (an array) at the end of `list` (another array).
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* When `list` was empty, returns `items` instead.
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*
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* This prevents a potentially expensive operation when `list` is empty,
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* and adds items in batches to prevent V8 from hanging.
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*
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* @template {unknown} T
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* Item type.
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* @param {Array<T>} list
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* List to operate on.
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* @param {Array<T>} items
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* Items to add to `list`.
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* @returns {Array<T>}
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* Either `list` or `items`.
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*/
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export function push(list, items) {
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if (list.length > 0) {
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splice(list, list.length, 0, items)
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return list
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}
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return items
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}
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