Re: [asio-users] using external library

[Alejandro S. <al...@gm...>]

 Hi ! I'm a novice with ASIO but i can tell you that, internally, ASIO
uses different methods to "know" when some data has arrived. One of
them is asyncronous notifications (Windows IOCP, for example); meaning
that you make the call to read on the socket providing some buffer,
and, some time later, the library receives a notification that some
data has arrived on the buffers.

 So, when the notification has arrived you dont need to call the
"read" operation on the socket because you already have the data on
the buffers you gave some time back. That's how it works an
asyncronous read and that's why ASIO gives you the data on the
callback.

 I belive ASIO also emulates asyncronous notifications using non-async
methods (with different Reactors: poll, select, etc), but that's an
implementation issue and gives the library the "uniform" interface
wich makes the library so nice =)

Perhaps this link will be more helpful to you (heavy reading):
http://www.kegel.com/c10k.html

Cheers,
Alejandro.


On 10/31/06, Mahesh Bhat <mah...@gm...> wrote:
> Hi Chris,
>
>
> I see that with the interfaces provided I can provide callbacks to handle
> read using async_read etc.
> My problem is that I am using a library which gives you a socket descriptor
> but its read function is private.
> It is not even in the header file that I see. What the library expects is
> that you invoke its public function whenever the socket has any data on it.
> It uses its own buffers. But asio does not provide an interface to just
> invoke a callback when the socket becomes readable( or does it ?). asio does
> the read and then passes the buffer to the handle_read of the client class.
> How can I get around this ?
> In short can I get asio to invoke a callback when the socket becomes
> readable and not do the actual read.
>
> Thanks in advance
>
> Mahesh.
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