Re: [boost] Review Request: boost.lockfree

Subject: Re: [boost] Review Request: boost.lockfree
From: Tim Blechmann (tim_at_[hidden])
Date: 2009-12-14 09:54:26

hi christopher,

> I have been using this library for the past three weeks and have found
> it incredibly useful. Thank you for your excellent work, Tim!
> 
> I have a pre-review question though. Is it possible to decouple
> container and the predefined wait lists so an user may use his own free
> list type? I have a use case which requires various container instances
> to share only one freelist instance, and I would like to implement this
> via an own free list type.

i reworked the freelist implementations, changing the api to:

template <typename T, bool fixed_size = false,
          typename Alloc = std::allocator<T> >
class internal_freelist;

the fixed_size template argument specifies, if `allocate' may hit the os
memory allocator, when the freelist is empty. if it is set to `true',
all memory needs to be allocated in the constructor, calling the default
constructor is impossible (raises a static assertion failure).

the fifo class has a freelist_t template argument for specifying the
freelist implementation:

template <typename T, typename freelist_t =
          internal_freelist<T, false, std::allocator<T> >
          >
class fifo;

as a helper, a small wrapper class exists for supporting external (or
shared) freelists:

template <typename FreelistType>
class external_freelist;

with this api, you can use a shared freelist like:

typedef fifo<int>::freelist freelist; // freelist type
freelist fl(128);                     // shared
typedef external_freelist<freelist> freelist_wrapper;

// two fifos with, sharing the same freelist:
fifo<int, freelist_wrapper> f1(freelist_wrapper(fl));
fifo<int, freelist_wrapper> f2(freelist_wrapper(fl));

it is also possible to get a handle to the internal freelist of a fifo:

fifo<int> f(64);

typedef fifo<int>::freelist internal_freelist;
typedef external_freelist<internal_freelist> freelist_wrapper;

// use freelist of f for f2
internal_freelist & fl (f.get_freelist());
fifo<int, freelist_wrapper> f2(freelist_wrapper(fl));

the code is available from my git repository [1], branch
topic/freelist_tweaks. christopher (and others), what do you think about
this approach?

thanks, tim

[1] http://tim.klingt.org/git?p=boost_lockfree.git

-- 
tim_at_[hidden]
http://tim.klingt.org
The price an artist pays for doing what he wants is that he has to do
it.
  William S. Burroughs