Re: [Libevent-users] How can I write exact length of a evbuffer?

[Nick Mathewson <nickm@xxxxxxxxxxxxx>]

On Sat, Apr 14, 2012 at 4:15 AM, Dawen Rie <dawenhing@xxxxxxx> wrote:
> Hello everybody. I am a new user of libevent. I can't find the correct API
> to do my work.
> I had found the API:
>
> int bufferevent_write_buffer(struct bufferevent *bufev, struct evbuffer
> *buf);
> It will send all data of evbuffer. But I just want to send a special
> length not all.
>
> And API:
> int bufferevent_write(struct bufferevent *bufev, const void *data, size_t
> size);
>
>
> It require me copy out the data from evbuffer, I think it's inefficiency.
>
> So, is there andy API like:
> int bufferevent_write_buffer(struct bufferevent *bufev, struct evbuffer
> *buf, size_t size);
>
> It just send size of data in but?

Hi!

What you want to be looking at first is bufferevent_get_output().  It
returns an output evbuffer that you can add data to manually.  The
bufferevent_write() and bufferevent_write_buffer() functions are thin
wrappers around bufferevent_get_output() and one of the evbuffer_*
functions.

So now the question becomes, "how can I add move (but not all) of the
data from one evbuffer to another?"

For that, see evbuffer_remove_buffer().

For more information, you might want to read the (perpetually
work-in-progress) reference manual at
http://www.wangafu.net/~nickm/libevent-book/

yrs,
-- 
Nick
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