TLS socket write + drain

[Joran Dirk Greef]

I have a question regarding how TLS socket write works and am going through the source now too.

The documentation details this behavior as:

"Returns true if the entire data was flushed successfully to the kernel buffer. Returns false if all or part of the data was queued in user memory. 'drain' will be emitted when the buffer is again free. The optional callback parameter will be executed when the data is finally written out - this may not be immediately."

If I pass a 1mb-2mb buffer to write(), does a true return code or executed callback guarantee that I can overwrite parts of that buffer, without changing any data that was passed to the write?

[Ben Noordhuis]

Yes.

[Joran Greef]

Thanks Ben, does a return code of true and the callback being called mean exactly the same thing? Do both give the same guarantee?

The reason I ask is because I am pre-allocating a buffer for a websocket server, and this is overwriting the buffer as soon as write returns true or the callback is fired. I noticed that for large writes it's overwriting data before it gets to the client.

Joran Greef

RONOMON

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[Ben Noordhuis]

On Fri, Jul 19, 2013 at 1:22 PM, Joran Greef <jorandi...@gmail.com> wrote:
> Thanks Ben, does a return code of true and the callback being called mean
> exactly the same thing? Do both give the same guarantee?
>
> The reason I ask is because I am pre-allocating a buffer for a websocket
> server, and this is overwriting the buffer as soon as write returns true or
> the callback is fired. I noticed that for large writes it's overwriting data
> before it gets to the client.
>
> Joran Greef
>
> RONOMON

Yes, they mean the same thing / come with the same guarantees - that
the contents of the buffer has been handed off to the operating
system.