Rust library useful for storing structs that needs to be accessed through various different indexes of the fields of the struct. Inspired by C++/Boost Multi-index Containers but redesigned for a more idiomatic Rust API.
Current implementation supports: * Hashed indexes using FxHashMap from rustc-hash. * Sorted indexes using BTreeMap from std::collections. * Unique and non-unique indexes. * Unindexed fields. * Iterators for each indexed field. * Iterators for the underlying backing storage.
panic.This crate provides a derive macro MultiIndexMap, which when applied to the struct representing an element will generate a map to store and access these elements.
Annotations are used to specify which fields to index. Currently hashed_unique, hashed_non_unique, ordered_unique, and ordered_non_unique are supported.
The element must implement Clone.
```rust use multiindexmap::MultiIndexMap;
struct Order { #[multiindex(hashedunique)] orderid: u32, #[multiindex(orderedunique)] timestamp: u64, #[multiindex(hashednonunique)] trader_name: String, filled: bool, volume: u64, }
fn main() { let order1 = Order { orderid: 1, timestamp: 1656145181, tradername: "JohnDoe".into(), filled: false, volume: 100, };
let order2 = Order {
order_id: 2,
timestamp: 1656145182,
trader_name: "JohnDoe".into(),
filled: false,
volume: 100,
};
let mut map = MultiIndexOrderMap::default();
map.insert(order1);
map.insert(order2);
let orders = map.get_by_trader_name(&"JohnDoe".to_string());
assert_eq!(orders.len(), 2);
println!("Found 2 orders for JohnDoe: [{orders:?}]");
let order1_ref = map.get_by_order_id(&1).unwrap();
assert_eq!(order1_ref.timestamp, 1656145181);
let order2_ref = map
.modify_by_order_id(&2, |o| {
o.timestamp = 1656145183;
o.order_id = 42;
})
.unwrap();
assert_eq!(order2_ref.timestamp, 1656145183);
assert_eq!(order2_ref.order_id, 42);
assert_eq!(order2_ref.trader_name, "JohnDoe".to_string());
let order2_ref = map.update_by_order_id(&2, |filled: &mut bool, volume: &mut u64| {
*filled = true;
*volume = 0;
});
assert_eq!(order2_ref.filled, true);
assert_eq!(order2_ref.volume, 0);
let orders = map.get_by_trader_name(&"JohnDoe".to_string());
assert_eq!(orders.len(), 2);
println!("Found 2 orders for JohnDoe: [{orders:?}]");
let orders = map.remove_by_trader_name(&"JohnDoe".to_string());
for (_idx, order) in map.iter() {
assert_eq!(order.trader_name, "JohnDoe");
}
assert_eq!(orders.len(), 2);
// See examples and tests directories for more in depth usage.
} ```
The above example will generate the following MultiIndexMap and associated Iterators.
The Orders are stored in a Slab, in contiguous memory, which allows for fast lookup and quick iteration.
A lookup table is created for each indexed field, which maps the index key to a index in the Slab.
The exact type used for these depends on the annotations.
For hashed_unique and hashed_non_unique a FxHashMap is used, for ordered_unique and ordered_non_unique a BTreeMap is used.
* When inserting an element, we add it to the backing store, then add elements to each lookup table pointing to the index in the backing store.
* When retrieving elements for a given key, we lookup the key in the lookup table, then retrieve the item at that index in the backing store.
* When removing an element for a given key, we do the same, but we then must also remove keys from all the other lookup tables before returning the element.
* When iterating over an index, we use the default iterators for the lookup table, then simply retrieve the element at the given index in the backing store.
* When updating un-indexed fields, we lookup the element(s) through the given key, then apply the closure to modify just the unindexed fields in-place.
We then return a reference to the modified element(s).
If the key doesn't match, the closure won't be applied, and Option::None will be returned.
* When modifying indexed fields of an element, we do the same process, but the closure takes a mutable reference to the whole element.
Any fields, indexed and un-indexed can be modified.
We must then update all the lookup tables to account for any changes to indexed fields, so this is slower than an un-indexed update.
```rust
struct MultiIndexOrderMap {
store: slab::Slab
struct MultiIndexOrderMapOrderIdIter<'a> { ... }
struct MultiIndexOrderMapTimestampIter<'a> { ... }
struct MultiIndexOrderMapTraderNameIter<'a> { ... }
impl MultiIndexOrderMap { fn insert(&mut self, elem: Order);
fn len(&self) -> usize;
fn is_empty(&self) -> bool;
fn clear(&mut self);
fn get_by_order_id(&self, key: &u32) -> Option<&Order>;
fn get_by_timestamp(&self, key: &u64) -> Option<&Order>;
fn get_by_trader_name(&self, key: &String) -> Vec<&Order>;
fn update_by_order_id(&mut self, key: &u32, f: impl FnOnce(&mut bool, &mut u64)) -> Option<&Order>;
fn update_by_timestamp(&mut self, key: &u64, f: impl FnOnce(&mut bool, &mut u64)) -> Option<&Order>;
fn update_by_trader_name(&mut self, key: &String, f: impl FnOnce(&mut bool, &mut u64)) -> Vec<&Order>;
fn modify_by_order_id(&mut self, key: &u32, f: impl FnOnce(&mut Order)) -> Option<&Order>;
fn modify_by_timestamp(&mut self, key: &u64, f: impl FnOnce(&mut Order)) -> Option<&Order>;
fn modify_by_trader_name(&mut self, key: &String, f: impl Fn(&mut Order)) -> Vec<&Order>;
fn remove_by_order_id(&mut self, key: &u32) -> Option<Order>;
fn remove_by_timestamp(&mut self, key: &u64) -> Option<Order>;
fn remove_by_trader_name(&mut self, key: &String) -> Vec<Order>;
fn iter(&self) -> slab::Iter<Order>;
unsafe fn iter_mut(&mut self) -> slab::IterMut<Order>;
fn iter_by_order_id(&self) -> MultiIndexOrderMapOrderIdIter;
fn iter_by_timestamp(&self) -> MultiIndexOrderMapTimestampIter;
fn iter_by_trader_name(&self) -> MultiIndexOrderMapTraderNameIter;
} ```
See Cargo.toml for information on each dependency.