2

I'm writing a custom object pool because I couldn't find any that meet the specific requirements of my application. The object pool itself follows a simple model of "fetch a pre-allocated object from list if exists, otherwise create a new one and add to list of pre-allocated objects". So far so good: locking in case of multi-threading, RAII on returned object construction/destruction, and it has been templated so that I can specify any object type to "pool".

Now I'm at my final task. I want to be able to allow the client to specify a custom function to use which constructs a new object to be returned when requested, instead of the default constructor new _obj(). Reasoning so that a non-default constructor can be used which perhaps someone may want to pre-bind some arguments and use that bounded constructor as the allocation method. A simplified example of usage:

class obj {
  obj(int x) { ... }
};

void foo() {
  object_pool<obj> pool(bind(&obj::obj, 1))
  obj *o = pool.acquire()  // obj pool will construct as "new obj(1)"
}

I've been looking into allocator, which seems more appropriate for low-level memory-related performance than object construction. I've also considered boost::bind with boost::function or functor's, which seems more inherently appropriate to the problem I'm trying to solve.

I'm sure this has been done before - so, what's the typical approach?

jwalk
  • 1,120
  • 11
  • 27
  • Most STL containers allow custom allocator classes to be passed as a template parameter (and this class is expected to have a certain set of functions, namely to allocate memory for the container). You can probably apply this idea for your problem and have the second template parameter in `object_pool` be a class that has a function `create()` which returns a constructed object of type `T`, and have `object_pool::acquire` use this class in the case of creating the object. – Jengerer Apr 04 '13 at 14:14
  • @Jengerer so you're suggesting to create a new class interface which deals with handling custom object construction and returns one through `create()` interface call? this would seem like overkill for the case of using non-default constructor with bound values. is there not a more standard way something like this can be achieved? – jwalk Apr 04 '13 at 14:32
  • I don't know if there's a "standard" way for most problems in C++. ;) Keep in mind the STL class-binding solution was done when there was no default support for function bindings as you're using in your example, so there's nothing to say that your solution isn't perfectly fine (as long as it actually works). I was just pointing out one way I've seen something like this done. – Jengerer Apr 04 '13 at 14:54
  • Well I would think your solution will definitely be useful for accepting construction methods even more specialized than just variable bindings, but for now I'm only concerned with the latter. Thanks for the suggestion! – jwalk Apr 04 '13 at 17:43

0 Answers0