Reading bytes from a JavaScript blob received by WebSocket

Question

I have a WebSocket that receives binary messages and I want iterate over the bytes.

I came up with the following conversion function...

// Convert the buffer to a byte array.
function convert(data, cb) {
    // Initialize a new instance of the FileReader class.
    var fileReader = new FileReader();
    // Called when the read operation is successfully completed.
    fileReader.onload = function () {
        // Invoke the callback.
        cb(new Uint8Array(this.result));
    };
    // Starts reading the contents of the specified blob.
    fileReader.readAsArrayBuffer(data);
}

This does work, but the performance is terrible. Is there a better way to allow reading bytes?

What is the browser you are using?

karthick
– karthick

2013-08-01 09:42:19 +00:00
Commented Aug 1, 2013 at 9:42 — karthick
– karthick, Commented Aug 1, 2013 at 9:42
Google Chrome is the browser I am using.

Deathspike
– Deathspike

2013-08-01 09:52:16 +00:00
Commented Aug 1, 2013 at 9:52 — Deathspike
– Deathspike, Commented Aug 1, 2013 at 9:52

mre · Accepted Answer · 2016-01-29 11:20:15Z

24

Have you considered:

socket.binaryType = 'arraybuffer';

The function becomes:

function convert(data) {
     return new Uint8Array(data);
}

Which will not actually have to do any work because it's just a view on the buffer.

edited Jan 29, 2016 at 11:20

mre

71 silver badge4 bronze badges

answered Aug 1, 2013 at 14:13

Esailija

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1 Comment

Deathspike Over a year ago

Massive improvement in terms of maintainability AND performance. Great!

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