If you pre-allocate a large enough buffer, you can keep a pointer to mark the boundary between the part where you have already stored data and the part still em

If you pre-allocate a large enough buffer, you can keep a pointer to mark the boundary between the part where you have already stored data and the part still empty. Then re-implement malloc() to just move such pointer. Of course you must check for running out of allocated memory, etc. This simple approach assumes that you seldom delete entries, because it never reclaims the room occupied by deleted entries.