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Posted to issues@cordova.apache.org by "Nikita Matrosov (JIRA)" <ji...@apache.org> on 2017/04/19 12:44:41 UTC
[jira] [Commented] (CB-12085) FileReader#readAsArrayBuffer reads
whole file
[ https://issues.apache.org/jira/browse/CB-12085?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15974563#comment-15974563 ]
Nikita Matrosov commented on CB-12085:
--------------------------------------
[~topaxi], are you still experiencing this issue?
> FileReader#readAsArrayBuffer reads whole file
> ---------------------------------------------
>
> Key: CB-12085
> URL: https://issues.apache.org/jira/browse/CB-12085
> Project: Apache Cordova
> Issue Type: Bug
> Components: 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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