On 10 Jun 2009, at 22:28, Christopher Jefferson wrote:
On 10 Jun 2009, at 22:08, Thorsten Ottosen wrote:
Christopher Jefferson skrev:
Very interesting. I have been working on a similar, but much more limited, proposal which just does this for vector. I decided I had to implement a new class, because building on top of the 'allocator' framework wasn't sensible, because you waste too much buffer space. For example, I believe your example won't work. I'd be interested to see what you think. Consider your example, in g++ (which I know how it operates internally) boost::monotonic::inline_storage<100*sizeof(Object)> storage; // create local storage on the stack boost::monotonic::vector<Object> deathrow(storage); // create a std::vector that uses this storage foreach (object in world) { if (IsDead(object)) deathrow.push_back(object); // allocation is just advancing a pointer } This will build a vector which will continuously expand, through sizes 1,2,4,8,16,32. At each step, it will allocate a new block of memory and free the old one, making the storage size 1,3,7,15,31,63. When we try to push_back beyond 32 elements, the next allocation will overflow the buffer. Am I missing something?
Maybe
http://www.cs.aau.dk/~nesotto/boost/trunk/libs/auto_buffer/doc/html/ http://www.cs.aau.dk/~nesotto/boost/trunk/boost/auto_buffer/
is what you are looking for?
That doesn't do exactly what I want for two reasons, but most might be fixable.
1) I want run-time variable amounts of space (this does involve some alloca, and probably macro, hackery). 2) I want it to be an error if it is necessary to go to the heap.
For (1) I use a macro something like:
#define GET_ALLOCA_MEM(type, x) box<type>(x, alloca(x * sizeof(type))
Because obviously you can't call alloca inside the auto_buffer constructor.
Replying to myself, passing an external buffer into auto_buffer isn't completely trivial, because you would also have to disable to copy constructor (at least, I can't think of anything else sensible to do). Chris On Thu, Jun 11, 2009 at 6:11 AM, Beman Dawes <bdawes@acm.org> wrote:
There is a pending request for sandbox write access from Christian Schladetsch.
This guy has been exhibiting problem behavior. He has not been following discussion policy and has insulted the motives and competence of various Boosters such as Joel.
I just don't have the time to deal with him, and won't until maybe Monday, so I'm hoping some other moderator could put him on warning that we will ban him if he doesn't follow our discussion policy.
Thanks,
--Beman _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost