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Re: Data API: what is agreed, what is open

From: Stefan Hakansson LK <stefan.lk.hakansson@ericsson.com>
Date: Tue, 14 Feb 2012 19:00:22 +0100
Message-ID: <4F3AA136.2000308@ericsson.com>
To: public-webrtc@w3.org
On 02/13/2012 07:54 PM, Timothy B. Terriberry wrote:
> Stefan Hakansson LK wrote:
>>>> * The API should initially enable sending and receiving DOMString,
>>>> Blob and ArrayBuffer data
>>>
>>> Like to know more but suspect I won't care
>>
>> This is basically the data types that you can send/receive with
>> WebSockets, so it is an alignment.
>
> I was curious how WebSockets distinguishes these things on the wire, so
> I did some digging. The WebSockets protocol
> (http://www.rfc-editor.org/rfc/rfc6455.txt) has a 4-bit "opcode" field
> that lets it specify "binary" or "text" data messages and can signal
> various control messages ("close", "ping", "pong", etc.).
>
> But it doesn't distinguish between "Blob" and "ArrayBuffer". Instead,
> the WebSocket API (http://dev.w3.org/html5/websockets/) has a
> user-settable "binaryType" attribute, which can be set to the string
> "blob" or "arraybuffer", and whatever incoming binary messages arrive
> will be delivered as an object of that type. Incoming text messges are
> delivered as DOMStrings (they have to be distinguished from binary,
> because of the need to convert the on-the-wire UTF8 to and from whatever
> JS-land is expecting). On the sending side, DOMStrings go out as "text"
> and both Blobs and ArrayBuffers go out as "binary".
>
> Also, despite protocol support for 16 exabyte messages, they are limited
> to 16 MB by default.
>
Tim, thanks for looking this up. This was valuable input.

//Stefan
Received on Tuesday, 14 February 2012 18:00:50 UTC

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