On Mon, Mar 2, 2009 at 4:35 AM, Thorsten Ottosen <thorsten.ottosen@dezide.com> wrote:
Steven Watanabe skrev:
AMDG
Mathias Gaunard wrote:
Thorsten Ottosen wrote:
Basically boost::auto_buffer<T,N> is a C++ version of variable lenght array (from C99).
N is known at compile-time. Thus I do not see how it is related to C99 VLAs at all.
N is not the number of elements in the container. N controls how much stack storage is allocated. The number of elements is dynamic.
Exactly.
The idea is that you know ca in advance the maximum number of elements you need for your temporary array. For example, in a logging library, you might not expect 95% of all lines to be less than 512 chars. Thus you can use
boost::auto_buffer<char,512> buffer;
to avoid heap-allocations in 95% of the cases. This can be a major speed-improvement. For the remaining 5% of the cases, the buffer will be placed on the heap, but the code from the user's persective remains the same.
I think that sounds very useful. I'd be interested in seeing something like that in boost. But it's not anything like C99 VLAs, I wouldn't refer to it as such. -- Cory Nelson