This allocator is very simple. It is simply a bump allocator from a fixed size buffer. It cannot free or resize, and will return null when it has used all memory in the buffer given to it.

This kind of allocator is useful for temporary string building or similar circumstances, where you know that the needed memory size will not be exceeded, but you don't what to deal with potential slowness of a general heap allocator. By using this allocator, you can continue to use the same code that does allocations like normal, but can get the speed increase of a simple allocation strategy.