bmset
BitmapSet - compact stack-allocated ordered set for small numbers.
It provides a similar API to standard BTreeSet, but can store u8 only, and is more efficient for this use-case.
Defining features:
- Compact
- Performant
- No allocations
- No dependencies
no_stdu8only- Dumb (stupidly simple implementation)
Usage
use bmset::BitmapSet;
let set1: BitmapSet<10> = (0..45).collect();
let set2: BitmapSet<10> = (42..80).collect();
let mut set3 = set1.intersection(&set2);
set3.insert(73);
set3.remove(44);
assert_eq!(set3, [42, 43, 73].iter().collect());
let mut set4 = BitmapSet::<10>::new();
set4.insert(42);
// set4.insert(85); // PANIC: max value for 10-bytes set is 79
assert!(set4.is_subset(&set3));Details
It occupies from 1 to 32 bytes (defined explicitly by const generic), and can store a maximum value of up to a total number of bits (non-inclusive, i.e. 255 for 32 bytes).
It is ridiculously simple: just a sequence of bits, each representing a presence of its index in the set. This means that all set operations are very efficient and boil down to bitwise operations on the bitmaps, having time complexity of O(1) (independent of the number of values in the set, though proportional to the max set size):
- Insert/remove/check value - set/clear/check a bit by its index
- Union - bitwise OR
- Intersection - bitwise AND
- Complement - bitwise NOT
- Difference - bitwise AND with complement
- Subset/superset check - equality check with intersection/union
See benchmarks and run them (cargo bench) for performance comparison with BTreeSet.