[boost] Query of Interest - vlarray

From: David White (dave_at_[hidden])
Date: 2002-04-15 07:13:13

I was wondering if there would be any interest in a class template,
vlarray, which would have functionality similar to a stack-based array,
but which would have its size set at runtime. Essentially it would
provide functionality similar to the Variable Length Arrays (VLAs) now
offered in C. It would have a specialized allocation strategy written
for it, which would provide allocation/deallocation times much faster
than more general containers such as straight heap-based arrays or
vectors.

In order to allow this specialized allocation strategy to be
sufficiently fast, instances of vlarray would only ever be permitted to
be allocated as automatic (stack-based) variables. Thus, since they
would allocate in their constructor, and deallocate in their destructor,
all allocations and deallocations would take place in a
Last-In-First-Out (LIFO) order, and thus the allocation strategy could
be written with this as an assumption. In fact, the allocator would
simply just use a stack-like data structure to allocate and deallocate
from - this being much simpler and faster than strategies that
general-purpose allocators must use.

The interface would be almost identical to boost::array - except that
the size of the array would be a parameter to the constructor instead of
a template parameter, and some more constructors would be added.

Considering the number of requests there are for addition of VLAs into
C++ - or the standardization of the alloca function that some
implementations offer, I feel that vlarray would be of use to many
programmers who want these features because of their speed over normal
heap-based allocation. I would be interested to know if others think
that this idea has merit as an alternative to VLAs/alloca.

Cheers,

David.