use rocksdb::{Options, DB}; use std::cmp::Ordering; use std::iter::FromIterator; /// This function is for ensuring test of backwards compatibility pub fn rocks_old_compare(one: &[u8], two: &[u8]) -> Ordering { one.cmp(two) } /// create database add some values, and iterate over these pub fn write_to_db_with_comparator( compare_fn: Box Ordering>, ) -> Vec { let mut result_vec = Vec::new(); let path = "_path_for_rocksdb_storage"; { let mut db_opts = Options::default(); db_opts.create_missing_column_families(true); db_opts.create_if_missing(true); db_opts.set_comparator("cname", compare_fn); let db = DB::open(&db_opts, path).unwrap(); db.put(b"a-key", b"a-value").unwrap(); db.put(b"b-key", b"b-value").unwrap(); let mut iter = db.raw_iterator(); iter.seek_to_first(); while iter.valid() { let key = iter.key().unwrap(); // maybe not best way to copy? let key_str = key.iter().map(|b| *b as char).collect::>(); result_vec.push(String::from_iter(key_str)); iter.next(); } } let _ = DB::destroy(&Options::default(), path); result_vec } #[test] /// First verify that using a function as a comparator works as expected /// This should verify backwards compatablity /// Then run a test with a clojure where an x-variable is passed /// Keep in mind that this variable must be moved to the clojure /// Then run a test with a reverse sorting clojure and make sure the order is reverted fn test_comparator() { let local_compare = move |one: &[u8], two: &[u8]| one.cmp(two); let x = 0; let local_compare_reverse = move |one: &[u8], two: &[u8]| { println!( "Use the x value from the closure scope to do something smart: {:?}", x ); match one.cmp(two) { Ordering::Less => Ordering::Greater, Ordering::Equal => Ordering::Equal, Ordering::Greater => Ordering::Less, } }; let old_res = write_to_db_with_comparator(Box::new(rocks_old_compare)); println!("Keys in normal sort order, no closure: {:?}", old_res); assert_eq!(vec!["a-key", "b-key"], old_res); let res_closure = write_to_db_with_comparator(Box::new(local_compare)); println!("Keys in normal sort order, closure: {:?}", res_closure); assert_eq!(res_closure, old_res); let res_closure_reverse = write_to_db_with_comparator(Box::new(local_compare_reverse)); println!( "Keys in reverse sort order, closure: {:?}", res_closure_reverse ); assert_eq!(vec!["b-key", "a-key"], res_closure_reverse); }