[whatwg] WebSocket bufferedAmount includes overhead or not

Jonas Sicking jonas at sicking.cc
Tue Mar 30 07:22:07 PDT 2010

On Tue, Mar 30, 2010 at 1:51 AM, Niklas Beischer <no at opera.com> wrote:
> On Tue, 30 Mar 2010 09:19:33 +0300, Jonas Sicking <jonas at sicking.cc> wrote:
>> On Wed, Mar 24, 2010 at 2:33 PM, Ian Hickson <ian at hixie.ch> wrote:
>>> On Tue, 23 Mar 2010, Anne van Kesteren wrote:
>>>> We (Opera) would prefer this too. I.e. to not impose details of the
>>>> protocol on the API.
>>> If we're exposing nothing from the protocol, does that mean we shouldn't
>>> be exposing that the string converts to UTF-8 either?
>> While exposing the fact that strings are sent as UTF-8 does say
>> something about the protocol, I think it's still much more protocol
>> independent than including the message headers. The string has to be
>> serialized in some way, and it seems unlikely that any newly developed
>> protocol in the foreseeable future would use anything other than UTF-8
>> as serialization.
> True, but if bufferedAmount does not byte for byte (or character for
> character) match what is fed to the API, what does a few bytes
> representing the current overhead matter? IIRC EcmaScript uses UTF-16,
> which means that serialization will in most cases make the number of
> actually buffered bytes differ from the number of bytes in the original
> message buffer.

EcmaScript doesn't do any serialization so I'm not sure what you mean here?

> And just because we currently use UTF-8 for
> serialization doesn't mean that will always be the case. Thus API users
> cannot rely on performing their own conversion to UTF-8 just to find out
> exactly how many characters in their message have been sent.

My point was that using anything but UTF-8 is unlikely. So the
opposite of what you're saying here.

> The fact remains that, unless we want to force implementors of the
> protocol to match each byte sent over the network with a specific
> character in the original message handed to the API, bufferedAmount cannot
> represent something unaffected by the protocol. And if we allow
> bufferedAmount to be affected by the protocol, why not let it be decided
> by the implementation whether or not to include protocol overhead?

Making it implementation dependent is likely to lead to website
incompatibilities. Such as:

ws = new WebSocket(...);
ws.onopen = function() {
  if (ws.bufferedAmount > X) {

If this is implementation dependent then the above could reliably call
doStuff in one implementation, but reliably not another.

/ Jonas

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