40 lines
1.4 KiB
JavaScript
40 lines
1.4 KiB
JavaScript
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//@ts-check
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import { fetchContentLength } from "./fetchContentLength.mjs";
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/**
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* Conditional size fetcher, which can be skipped by providing an intial size.
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* This function is only useful when used as part of a larger loading framework, when
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* files loading may or may not have access to size information, and you want a
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* consistent behavior regardless.
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*
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* If `estimatedTotal` is passed, this is a no-op.
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* If `estimatedTotal` is not passed, the created function does a limited `fetch`
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* to attempt to retrieve the file size.
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* Repeated calls to the function will not repeat the fetch request.
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* The function is not guaranteed to succeed, the server has to play along by
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* sending the correct headers.
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* Ideally, `total` is passed instead to avoid this.
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* @see {fetchContentLength} decodeContentLength
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* @param {string} filePath
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* @param {number} estimatedTotal
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* @returns {()=>Promise<number>} a function that always returns the same promise
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*/
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export const makeFileSizeFetcher = (filePath, estimatedTotal = 0) => {
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/**
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* @type {Promise<number> | null}
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*/
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let totalPromise = estimatedTotal ? Promise.resolve(estimatedTotal) : null;
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const fetchSize = () =>
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(totalPromise =
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totalPromise ||
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fetchContentLength(filePath).then(
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(fetchedTotal) => (estimatedTotal = fetchedTotal)
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));
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return fetchSize;
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};
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export default makeFileSizeFetcher;
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