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wood1986
bd12e41188
Summary:
```js
async () => {
let blobs = [];
for (let i = 0; i < 4; i++) {
const res = await fetch();
blobs = [...blobs, await res.blob()]
}
const blob = new Blob(blobs); // <<<<<<<<<<<<<<< a
return await new Promise((resolve, reject) => {
const fileReader = new FileReader();
fileReader.onload = async () => {
await RNFS.writeFile(destPath, (fileReader.result as string).split(',')[1], 'base64');
resolve(destPath);
};
fileReader.onabort = () => {
reject('');
};
fileReader.onerror = (event) => {
reject('');
};
fileReader.readAsDataURL(blob); // <<<<<<<<<<<<<<< b
});
}
```
Sometime `fileReader.readAsDataURL` is unable to get blob from the dictionary after `new Blob(blobs)` and then reject with `Unable to resolve data for blob: blobId` in iOS or `The specified blob is invalid` in android. Because line `a` and `b` can be run in different thread. `new Blob([])` is in progress and `fileReader.readAsDataURL` accesses the blob dictionary ahead of the blob creation.
The expected behaviour is it should finish new Blob([]) first and then readAsDataURL(blob)
To fix that, there should be a lock inside the method `createFromParts`. For iOS, It needs to be a recursive_mutex to allow same thread to acquire lock
## Changelog
<!-- Help reviewers and the release process by writing your own changelog entry. For an example, see:
https://github.com/facebook/react-native/wiki/Changelog
-->
[iOS] [Fixed] - fix the race condition when calling readAsDataURL after new Blob(blobs)
Pull Request resolved: https://github.com/facebook/react-native/pull/34096
Reviewed By: cipolleschi
Differential Revision: D37514981
Pulled By: javache
fbshipit-source-id: 4bf84ece99871276ecaa5aa1849b9145ff44dbf4