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react-native: BundleSegments

Reviewed By: davidaurelio

Differential Revision: D6231309

fbshipit-source-id: 565cbadedc5fd8ab25025b5846c098f24fb15a82
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jeanlauliac authored and facebook-github-bot committed Nov 6, 2017
1 parent 73a01be commit b9f21dc2be14cd51543e6b2d1e63a861e5f433d1
Showing with 54 additions and 0 deletions.
  1. +54 −0 Libraries/Utilities/BundleSegments.js
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/**
* Copyright (c) 2015-present, Facebook, Inc.
* All rights reserved.
*
* This source code is licensed under the BSD-style license found in the
* LICENSE file in the root directory of this source tree. An additional grant
* of patent rights can be found in the PATENTS file in the same directory.
*
* @flow
* @format
* @providesModule BundleSegments
*/
'use strict';
let segmentLoaders = new Map();
/**
* Ensure that a bundle segment is ready for use, for example requiring some of
* its module. We cache load promises so as to avoid calling `fetchBundle` twice
* for the same bundle. We assume that once a segment is fetched/loaded, it is
* never gettting removed during this instance of the JavaScript VM.
*/
async function loadForModule(moduleID: number): Promise<void> {
const {segmentId} = (require: $FlowFixMe).unpackModuleId(moduleID);
if (segmentId === 0) {
return;
}
let segmentLoader = segmentLoaders.get(segmentId);
if (segmentLoader != null) {
return await segmentLoader;
}
// FIXME: `fetchBundle` should be renamed `fetchSegment`.
const {fetchBundle} = global;
if (fetchBundle == null) {
throw new Error(
'When bundle splitting is enabled, the `global.fetchBundle` function ' +
'must be provided to be able to load particular bundle segments.',
);
}
segmentLoader = new Promise((resolve, reject) => {
fetchBundle(segmentId, error => {
if (error != null) {
reject(error);
return;
}
resolve();
});
});
segmentLoaders.set(segmentId, segmentLoader);
return await segmentLoader;
}
module.exports = {loadForModule};

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