Re: HowTo for queues - open issues resolved in 3.0.1

[Leon Pollak]

On Sunday June 6 2010, David Sugar wrote:

> I have added new create() methods to the reusable pool templates so it

> can return pre-constructed (initialized) objects. I also found a bug

> internal to queueof lifo method and changed the templates for queueof

> and stackof so that the pool is passed to the constructor rather than in

> the template (linkage requirement issue). Finally, I added an initial

> unit test case, ucommonQueue (test/queue.cpp) which both demonstrates

> the use case and validates at least some basic funcions of the current

> implementation. The unit test case code should be expanded upon to try

> and identify any additional bugs or issues.

David,

I downloaded the SVN head - the problem 1 from the letter below still exists.

I also do not see that file queue.cpp is compiled by the tests.

May be I use incorrect SVN?

svn co svn://svn.sv.gnu.org/commoncpp/trunk/ucommon

Thanks.

>

> On 06/05/2010 03:51 PM, Leon Pollak wrote:

> > On Saturday June 5 2010, David Sugar wrote:

> >> First, the queue core class can use a reusable pool, but this is for

> >> internal management of it's own pointers. The queue is passed an object

> >> to post into it that is derived from "Object", which are reference

> >> counted. Hence, existing on the queue is actually a reference count

> >> instance of a reference counted object. However, if you want a resuable

> >> pool of buffer objects, you would construct an object for your buffer

> >> that is itself derived from ReusableObject (which is derived from

> >> Object), and this is what you would then pass into the queue.

> >>

> >> Hence maybe you would use something like:

> >>

> >> class MyObject : public ReusableObject

> >> {

> >>

> >> public:

> >> char data[100];

> >>

> >> };

> >>

> >> static mempager datapool;

> >>

> >> // we have a pool with a maximum allocation size of 100 objects...

> >> static paged_reuse<MyObject> bufpool(&datapool, 100);

> >>

> >> // and a fixed size stream buffer of referenced objects...

> >> static queueof<MyObject> mycache(&datapool, 10);

> >>

> >> // we have a cache for these 100 objects...

> >>

> >> to post:

> >> // timeout to try

> >> MyObject *x = bufpool.get(100);

> >>

> >> // on error getting a new pool object...

> >> if(!x) ... we could allocate from datapool, throw, whatever...

> >>

> >> // we may also need to add x->retain(), it's been awhile....

> >>

> >> // make sure it survives cache...

> >> String::set(x->data, 100, "something");

> >>

> >> // timeout possible...

> >> if(!mycache.post(x, 100)) ... failed to post ...

> >>

> >> to get an object from the queue:

> >> // with a timeout...

> >> MyObject *x = mycache.lifo(100);

> >>

> >> if(!x) ... we didn't get anything before timer expired...

> >>

> >> printf("data %s\n", x->data);

> >>

> >> // release object back to reuse pool...

> >> bufpool::release(x)

> >

> > Hello David,

> >

> > And again thanks for the example.

> >

> > It seems you were right - no use of the queue/queueof was not tried

> > yet...:-)

> >

> > 1. I tried to compile the example you provided above. There is a problem

> > with the second template parameter of queueof - it cannot be

> > null-pointer according to my search in the internet. See for example

> > http://stackoverflow.com/questions/1418019/casting-pointer-as-template-

> > argument-comeau-msvc-compile-gcc-fails

> >

> > 2. You declared all three objects as 'static', which, besides the

> > problems with compilation also makes them invisible from the outside,

> > no? This forces me to put both threads in the same file, which is not

> > good for me. What was your reason to declare them static?

> >

> > Thanks.

--

            Dr.Leon M.Pollak

                Director

       PLR Information Systems Ltd.

Tel.:+972-98657670  |  POB 8130, H'Aomanut 9,

Fax.:+972-98657621  |  Poleg Industrial Zone,

Mob.:+972-544739246 |  Netanya, 42160, Israel.