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https://issues.apache.org/jira/browse/CB-12085?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Nikita Matrosov resolved CB-12085.
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Resolution: Won't Fix
> FileReader#readAsArrayBuffer reads whole file
> ---------------------------------------------
>
> Key: CB-12085
> URL: https://issues.apache.org/jira/browse/CB-12085
> Project: Apache Cordova
> Issue Type: Bug
> Components: cordova-plugin-file
> Affects Versions: 4.3.0
> Environment: Android
> Reporter: Damian Senn
> Assignee: Nikita Matrosov
> Priority: Critical
> Labels: performance
>
> Reading a File with
> ```js
> let fr = new FileReader
> fr.onload = () => done(fs.result)
> fr.readAsArrayBuffer(blob)
> ```
> Is very slow, I'm assuming this is because it reads the whole file, then
> transfers this via base64 to the JS world, where it is converted to an
> ArrayBuffer. My use-case involves reading some media metadata in JS-World,
> this usually involves reading several bytes (maybe around 100b to 1kb) of 2mb
> to 50mb files.
> I noticed this by profiling via Chrome-DevTools where the most time is being
> spent in the `atob` function in `cordova/base64.toArrayBuffer`.
> So parsing some hundreds of bytes on a 3mb file may take around 3 to 4
> seconds on my Samsung Galaxy S4 and around 1 second on my Samsung Galaxy S6.
> (This is without trying to read the actual metadata from the file).
> My guess is that this also has a very negative impact on memory usage and
> garbage collection.
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