Buffer size policy when using std.experimental.allocator.

[QAston via Digitalmars-d]

Hi.

I have the following code:
/++
A queue like buffer that's first filled up with insertBack, then 
depopulated using removeFront() until it's empty.
+/
struct TransducerBuffer (T, Allocator)
{
     private Allocator _allocator;
     private T[] _array;
     void insertBack(auto ref T newElem) {
// the interesing part
     }

     T removeFront() {
     }

     size_t length() {
     }

     void clear() {
     }
}

The buffer will allocate elements one by one (total amount is not 
known beforehand).

My question is:
Should I just use expandArray(_allocator, _array, 1 newElem) and 
count on the allocator to provide sensible allocation size 
policy, or should I do the policy myself by for example 
requesting expandArray(_allocator, _array, 2*lastAllocationSize 
newElem)?