Hi Nick,
Thanks a lot for your reply.
One more doubt about bufferevent.
As in socket networking programming, Sometimes It may require more than one
read/recv in server side for a single write by a client, depending upon
server socket's read buffer availability. Similarly here our read callback
may get call more than one for a single write by a client depending upon
server socket's read buffer availability. Specially If you are going to deal
with big chunk of data. Am i correct here?
Thanks
Deepak
On Tue, May 31, 2011 at 10:33 AM, Nick Mathewson <ni...@freehaven.net>wrote:
> On Mon, May 30, 2011 at 5:03 AM, deepak jain <deepakjain...@gmail.com>
> wrote:
> > Hello,
> > I am a new user of libevent and new to asynchronous I/O , so the
> question
> > may seem quite naive.
> > I am building an application based on libevent on linux using epoll
> backend.
> > Sometime clients of my application can write a huge data to my
> application
> > say 100K bytes.
> > I am using buffer_read_buffer() api for reading data from clients. In
> that
> > case, would always only one call of buffer_read_buffer be sufficient
> > or buffer_read_buffer() will get call multiple time until i did not get
> > whole 100K bytes.
>
> You can read any amount of data from the bufferevent, from one byte up
> to all the bytes that are waiting.
>
> The is one catch here: the read callback that you provide for the
> bufferevent will be called when new data arrives, and only when new
> data arrives. So if there is 50K waiting on the buffer, and your
> callback handles 30K and then returns, Libevent won't invoke your
> callback again until some more data is read. So if you want to handle
> all the data as it arrives, a callback like this will work fine:
>
> void readcb(struct bufferevent *bev, void *ctx) {
> char bytes[1024];
> size_t n;
> while ((n = bufferevent_read(bev, bytes, 1024)) {
> process(bytes, n);
> }
> }
>
> but a callback like this will potentially leave data around until more
> data arrives:
>
> void readcb(struct bufferevent *bev, void *ctx) {
> char bytes[1024];
> size_t n = bufferevent_read(bev, bytes, 1024);
> if (n) process(bytes, n);
> }
>
> Also, you might want to look through the interface a little. If you
> need more finegrained control over reading and draining data, have a
> look at the evbuffer interface, and use the evbuffer commands on the
> input buffer returned by bufferevent_get_input().
>
> Hoping this helps,
> --
> Nick
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