Re:A Database Without Dynamic Memory Allocation
by aidenn0 on Thursday October 13, 2022 @03:22PM
(#33195344)
Yeah, a stack of free indexes is good. In the rare case of "lots of indexes, but little (extra) memory" a bitmap can be good because it's 1 bit per index rather than ⌈log2(N)⌉ bits per index and has a constant factor speed up equal to the word-size of the architecture.
The approach I've seen for larger fixed-sized tables is a free list: when the table is allocated, also initialize an array of the slot numbers, with an associated length index. To allocate, pop the last slot # off the array and decrement the length index. To free, push the slot # onto the end of the array and increment the length index. Checking for a free slot is then just testing for length index > 0.