Also I have tried mutexes and do realize that the global variables are
a big problem. I am just not sure how to get around this. I even tried
using curl_easy_recv in the Multi-threaded example, but it did not
download any data. I think it is because I need to set the socket up and
then use a function of socket_wait, but because socket_wait is an other
function outside the main curl handle and I am expecting problems with
the global variables. If you could let me know if this is worth pursuing
and not a complete waste of my time I am going to try this. I probably
will work on that anyway, unless I hear otherwise.
 Thank you,
  Donald

On Fri, 2010-07-02 at 08:04 -0700, johansen_at_opensolaris.org wrote:
> On Thu, Jul 01, 2010 at 09:47:36PM -0600, Donald Boissonneault wrote:
> > I also tried this, however I think that I need to set the htmlbody in
> > the write_function due to the fact the treads could be overwriting one
> > an other varablies. However I can not for the life of me figure out how
> > to pass it an integer so I know which of the array's to store it in. I
> > will be working on this later tonight and will keep you posted.
>
> A couple of thoughts: if you're new to C programming, it might be better
> to start with a single-threaded program and work from there. The
> 10-at-a-time example uses the Curl_multi interface, which is not
> multi-threaded, but does allow you to perform multiple transfers at
> once. In some performance tests that I ran about a month ago, it was
> fastest to use one multi handle with up to 50 simultaneous requests.
> After that, threading showed a benefit. This was on Solaris, so
> performance may be different elsewhere.
>
> That said, your write-function isn't going to work in a multi-threaded
> environment. The pointer 'memory', is declared globally, but
> manipulated by each thread while it performs the write. I'm surprised
> that this works at all. If you're dead-set on storing this data in an
> array, you'll need to use a mutex to synchronize access to the parts of
> the routine that can be modified by multiple threads at once.
> Personally, I'd store these completed objects in a linked list, but if
> you have to use an array, keep a global counter that points to the next
> free entry. Only allow threads to store the pointer in the array when
> they're holding the lock, and have them increment the counter after
> assigning the pointer. This is a simplified explanation of the
> procedure, but it should be enough to get you started.
>
> You could avoid the need for most of this by using the curl_multi
> interface. It allows you to perform multiple downloads using a single
> thread of control.
>
> -j
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Received on 2010-07-02