miden_crypto/utils/kv_map.rs
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use alloc::{
boxed::Box,
collections::{BTreeMap, BTreeSet},
};
use core::cell::RefCell;
// KEY-VALUE MAP TRAIT
// ================================================================================================
/// A trait that defines the interface for a key-value map.
pub trait KvMap<K: Ord + Clone, V: Clone>:
Extend<(K, V)> + FromIterator<(K, V)> + IntoIterator<Item = (K, V)>
{
fn get(&self, key: &K) -> Option<&V>;
fn contains_key(&self, key: &K) -> bool;
fn len(&self) -> usize;
fn is_empty(&self) -> bool {
self.len() == 0
}
fn insert(&mut self, key: K, value: V) -> Option<V>;
fn remove(&mut self, key: &K) -> Option<V>;
fn iter(&self) -> Box<dyn Iterator<Item = (&K, &V)> + '_>;
}
// BTREE MAP `KvMap` IMPLEMENTATION
// ================================================================================================
impl<K: Ord + Clone, V: Clone> KvMap<K, V> for BTreeMap<K, V> {
fn get(&self, key: &K) -> Option<&V> {
self.get(key)
}
fn contains_key(&self, key: &K) -> bool {
self.contains_key(key)
}
fn len(&self) -> usize {
self.len()
}
fn insert(&mut self, key: K, value: V) -> Option<V> {
self.insert(key, value)
}
fn remove(&mut self, key: &K) -> Option<V> {
self.remove(key)
}
fn iter(&self) -> Box<dyn Iterator<Item = (&K, &V)> + '_> {
Box::new(self.iter())
}
}
// RECORDING MAP
// ================================================================================================
/// A [RecordingMap] that records read requests to the underlying key-value map.
///
/// The data recorder is used to generate a proof for read requests.
///
/// The [RecordingMap] is composed of three parts:
/// - `data`: which contains the current set of key-value pairs in the map.
/// - `updates`: which tracks keys for which values have been changed since the map was
/// instantiated. updates include both insertions, removals and updates of values under existing
/// keys.
/// - `trace`: which contains the key-value pairs from the original data which have been accesses
/// since the map was instantiated.
#[derive(Debug, Default, Clone, Eq, PartialEq)]
pub struct RecordingMap<K, V> {
data: BTreeMap<K, V>,
updates: BTreeSet<K>,
trace: RefCell<BTreeMap<K, V>>,
}
impl<K: Ord + Clone, V: Clone> RecordingMap<K, V> {
// CONSTRUCTOR
// --------------------------------------------------------------------------------------------
/// Returns a new [RecordingMap] instance initialized with the provided key-value pairs.
/// ([BTreeMap]).
pub fn new(init: impl IntoIterator<Item = (K, V)>) -> Self {
RecordingMap {
data: init.into_iter().collect(),
updates: BTreeSet::new(),
trace: RefCell::new(BTreeMap::new()),
}
}
// PUBLIC ACCESSORS
// --------------------------------------------------------------------------------------------
pub fn inner(&self) -> &BTreeMap<K, V> {
&self.data
}
// FINALIZER
// --------------------------------------------------------------------------------------------
/// Consumes the [RecordingMap] and returns a ([BTreeMap], [BTreeMap]) tuple. The first
/// element of the tuple is a map that represents the state of the map at the time `.finalize()`
/// is called. The second element contains the key-value pairs from the initial data set that
/// were read during recording.
pub fn finalize(self) -> (BTreeMap<K, V>, BTreeMap<K, V>) {
(self.data, self.trace.take())
}
// TEST HELPERS
// --------------------------------------------------------------------------------------------
#[cfg(test)]
pub fn trace_len(&self) -> usize {
self.trace.borrow().len()
}
#[cfg(test)]
pub fn updates_len(&self) -> usize {
self.updates.len()
}
}
impl<K: Ord + Clone, V: Clone> KvMap<K, V> for RecordingMap<K, V> {
// PUBLIC ACCESSORS
// --------------------------------------------------------------------------------------------
/// Returns a reference to the value associated with the given key if the value exists.
///
/// If the key is part of the initial data set, the key access is recorded.
fn get(&self, key: &K) -> Option<&V> {
self.data.get(key).inspect(|&value| {
if !self.updates.contains(key) {
self.trace.borrow_mut().insert(key.clone(), value.clone());
}
})
}
/// Returns a boolean to indicate whether the given key exists in the data set.
///
/// If the key is part of the initial data set, the key access is recorded.
fn contains_key(&self, key: &K) -> bool {
self.get(key).is_some()
}
/// Returns the number of key-value pairs in the data set.
fn len(&self) -> usize {
self.data.len()
}
// MUTATORS
// --------------------------------------------------------------------------------------------
/// Inserts a key-value pair into the data set.
///
/// If the key already exists in the data set, the value is updated and the old value is
/// returned.
fn insert(&mut self, key: K, value: V) -> Option<V> {
let new_update = self.updates.insert(key.clone());
self.data.insert(key.clone(), value).inspect(|old_value| {
if new_update {
self.trace.borrow_mut().insert(key, old_value.clone());
}
})
}
/// Removes a key-value pair from the data set.
///
/// If the key exists in the data set, the old value is returned.
fn remove(&mut self, key: &K) -> Option<V> {
self.data.remove(key).inspect(|old_value| {
let new_update = self.updates.insert(key.clone());
if new_update {
self.trace.borrow_mut().insert(key.clone(), old_value.clone());
}
})
}
// ITERATION
// --------------------------------------------------------------------------------------------
/// Returns an iterator over the key-value pairs in the data set.
fn iter(&self) -> Box<dyn Iterator<Item = (&K, &V)> + '_> {
Box::new(self.data.iter())
}
}
impl<K: Clone + Ord, V: Clone> Extend<(K, V)> for RecordingMap<K, V> {
fn extend<T: IntoIterator<Item = (K, V)>>(&mut self, iter: T) {
iter.into_iter().for_each(move |(k, v)| {
self.insert(k, v);
});
}
}
impl<K: Clone + Ord, V: Clone> FromIterator<(K, V)> for RecordingMap<K, V> {
fn from_iter<T: IntoIterator<Item = (K, V)>>(iter: T) -> Self {
Self::new(iter)
}
}
impl<K: Clone + Ord, V: Clone> IntoIterator for RecordingMap<K, V> {
type Item = (K, V);
type IntoIter = alloc::collections::btree_map::IntoIter<K, V>;
fn into_iter(self) -> Self::IntoIter {
self.data.into_iter()
}
}
// TESTS
// ================================================================================================
#[cfg(test)]
mod tests {
use super::*;
const ITEMS: [(u64, u64); 5] = [(0, 0), (1, 1), (2, 2), (3, 3), (4, 4)];
#[test]
fn test_get_item() {
// instantiate a recording map
let map = RecordingMap::new(ITEMS.to_vec());
// get a few items
let get_items = [0, 1, 2];
for key in get_items.iter() {
map.get(key);
}
// convert the map into a proof
let (_, proof) = map.finalize();
// check that the proof contains the expected values
for (key, value) in ITEMS.iter() {
match get_items.contains(key) {
true => assert_eq!(proof.get(key), Some(value)),
false => assert_eq!(proof.get(key), None),
}
}
}
#[test]
fn test_contains_key() {
// instantiate a recording map
let map = RecordingMap::new(ITEMS.to_vec());
// check if the map contains a few items
let get_items = [0, 1, 2];
for key in get_items.iter() {
map.contains_key(key);
}
// convert the map into a proof
let (_, proof) = map.finalize();
// check that the proof contains the expected values
for (key, _) in ITEMS.iter() {
match get_items.contains(key) {
true => assert!(proof.contains_key(key)),
false => assert!(!proof.contains_key(key)),
}
}
}
#[test]
fn test_len() {
// instantiate a recording map
let mut map = RecordingMap::new(ITEMS.to_vec());
// length of the map should be equal to the number of items
assert_eq!(map.len(), ITEMS.len());
// inserting entry with key that already exists should not change the length, but it does
// add entries to the trace and update sets
map.insert(4, 5);
assert_eq!(map.len(), ITEMS.len());
assert_eq!(map.trace_len(), 1);
assert_eq!(map.updates_len(), 1);
// inserting entry with new key should increase the length; it should also record the key
// as an updated key, but the trace length does not change since old values were not touched
map.insert(5, 5);
assert_eq!(map.len(), ITEMS.len() + 1);
assert_eq!(map.trace_len(), 1);
assert_eq!(map.updates_len(), 2);
// get some items so that they are saved in the trace; this should record original items
// in the trace, but should not affect the set of updates
let get_items = [0, 1, 2];
for key in get_items.iter() {
map.contains_key(key);
}
assert_eq!(map.trace_len(), 4);
assert_eq!(map.updates_len(), 2);
// read the same items again, this should not have any effect on either length, trace, or
// the set of updates
let get_items = [0, 1, 2];
for key in get_items.iter() {
map.contains_key(key);
}
assert_eq!(map.trace_len(), 4);
assert_eq!(map.updates_len(), 2);
// read a newly inserted item; this should not affect either length, trace, or the set of
// updates
let _val = map.get(&5).unwrap();
assert_eq!(map.trace_len(), 4);
assert_eq!(map.updates_len(), 2);
// update a newly inserted item; this should not affect either length, trace, or the set
// of updates
map.insert(5, 11);
assert_eq!(map.trace_len(), 4);
assert_eq!(map.updates_len(), 2);
// Note: The length reported by the proof will be different to the length originally
// reported by the map.
let (_, proof) = map.finalize();
// length of the proof should be equal to get_items + 1. The extra item is the original
// value at key = 4u64
assert_eq!(proof.len(), get_items.len() + 1);
}
#[test]
fn test_iter() {
let mut map = RecordingMap::new(ITEMS.to_vec());
assert!(map.iter().all(|(x, y)| ITEMS.contains(&(*x, *y))));
// when inserting entry with key that already exists the iterator should return the new value
let new_value = 5;
map.insert(4, new_value);
assert_eq!(map.iter().count(), ITEMS.len());
assert!(map.iter().all(|(x, y)| if x == &4 {
y == &new_value
} else {
ITEMS.contains(&(*x, *y))
}));
}
#[test]
fn test_is_empty() {
// instantiate an empty recording map
let empty_map: RecordingMap<u64, u64> = RecordingMap::default();
assert!(empty_map.is_empty());
// instantiate a non-empty recording map
let map = RecordingMap::new(ITEMS.to_vec());
assert!(!map.is_empty());
}
#[test]
fn test_remove() {
let mut map = RecordingMap::new(ITEMS.to_vec());
// remove an item that exists
let key = 0;
let value = map.remove(&key).unwrap();
assert_eq!(value, ITEMS[0].1);
assert_eq!(map.len(), ITEMS.len() - 1);
assert_eq!(map.trace_len(), 1);
assert_eq!(map.updates_len(), 1);
// add the item back and then remove it again
let key = 0;
let value = 0;
map.insert(key, value);
let value = map.remove(&key).unwrap();
assert_eq!(value, 0);
assert_eq!(map.len(), ITEMS.len() - 1);
assert_eq!(map.trace_len(), 1);
assert_eq!(map.updates_len(), 1);
// remove an item that does not exist
let key = 100;
let value = map.remove(&key);
assert_eq!(value, None);
assert_eq!(map.len(), ITEMS.len() - 1);
assert_eq!(map.trace_len(), 1);
assert_eq!(map.updates_len(), 1);
// insert a new item and then remove it
let key = 100;
let value = 100;
map.insert(key, value);
let value = map.remove(&key).unwrap();
assert_eq!(value, 100);
assert_eq!(map.len(), ITEMS.len() - 1);
assert_eq!(map.trace_len(), 1);
assert_eq!(map.updates_len(), 2);
// convert the map into a proof
let (_, proof) = map.finalize();
// check that the proof contains the expected values
for (key, value) in ITEMS.iter() {
match key {
0 => assert_eq!(proof.get(key), Some(value)),
_ => assert_eq!(proof.get(key), None),
}
}
}
}