[boost] Interest check: container with preallocated buffer

Boost.Array offers constant size container with preallocated buffer, Boost.Optional provides from zero to one element. There are no STL container with preallocated buffer and it seems custom allocator does not help to do this with existing containers. Does any container exist to offer functionality like Boost.Array but allowing to store from 0 to N elements? Is there any interest in such container? PS. It's similar to fixed_string but as a generic container. -- Dmitry