miden_crypto/merkle/smt/full/leaf.rs
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use alloc::{string::ToString, vec::Vec};
use core::cmp::Ordering;
use super::{Felt, LeafIndex, Rpo256, RpoDigest, SmtLeafError, Word, EMPTY_WORD, SMT_DEPTH};
use crate::utils::{ByteReader, ByteWriter, Deserializable, DeserializationError, Serializable};
#[derive(Clone, Debug, PartialEq, Eq)]
#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
pub enum SmtLeaf {
Empty(LeafIndex<SMT_DEPTH>),
Single((RpoDigest, Word)),
Multiple(Vec<(RpoDigest, Word)>),
}
impl SmtLeaf {
// CONSTRUCTORS
// ---------------------------------------------------------------------------------------------
/// Returns a new leaf with the specified entries
///
/// # Errors
/// - Returns an error if 2 keys in `entries` map to a different leaf index
/// - Returns an error if 1 or more keys in `entries` map to a leaf index different from
/// `leaf_index`
pub fn new(
entries: Vec<(RpoDigest, Word)>,
leaf_index: LeafIndex<SMT_DEPTH>,
) -> Result<Self, SmtLeafError> {
match entries.len() {
0 => Ok(Self::new_empty(leaf_index)),
1 => {
let (key, value) = entries[0];
if LeafIndex::<SMT_DEPTH>::from(key) != leaf_index {
return Err(SmtLeafError::SingleKeyInconsistentWithLeafIndex {
key,
leaf_index,
});
}
Ok(Self::new_single(key, value))
},
_ => {
let leaf = Self::new_multiple(entries)?;
// `new_multiple()` checked that all keys map to the same leaf index. We still need
// to ensure that that leaf index is `leaf_index`.
if leaf.index() != leaf_index {
Err(SmtLeafError::MultipleKeysInconsistentWithLeafIndex {
leaf_index_from_keys: leaf.index(),
leaf_index_supplied: leaf_index,
})
} else {
Ok(leaf)
}
},
}
}
/// Returns a new empty leaf with the specified leaf index
pub fn new_empty(leaf_index: LeafIndex<SMT_DEPTH>) -> Self {
Self::Empty(leaf_index)
}
/// Returns a new single leaf with the specified entry. The leaf index is derived from the
/// entry's key.
pub fn new_single(key: RpoDigest, value: Word) -> Self {
Self::Single((key, value))
}
/// Returns a new single leaf with the specified entry. The leaf index is derived from the
/// entries' keys.
///
/// # Errors
/// - Returns an error if 2 keys in `entries` map to a different leaf index
pub fn new_multiple(entries: Vec<(RpoDigest, Word)>) -> Result<Self, SmtLeafError> {
if entries.len() < 2 {
return Err(SmtLeafError::InvalidNumEntriesForMultiple(entries.len()));
}
// Check that all keys map to the same leaf index
{
let mut keys = entries.iter().map(|(key, _)| key);
let first_key = *keys.next().expect("ensured at least 2 entries");
let first_leaf_index: LeafIndex<SMT_DEPTH> = first_key.into();
for &next_key in keys {
let next_leaf_index: LeafIndex<SMT_DEPTH> = next_key.into();
if next_leaf_index != first_leaf_index {
return Err(SmtLeafError::InconsistentKeys {
entries,
key_1: first_key,
key_2: next_key,
});
}
}
}
Ok(Self::Multiple(entries))
}
// PUBLIC ACCESSORS
// ---------------------------------------------------------------------------------------------
/// Returns true if the leaf is empty
pub fn is_empty(&self) -> bool {
matches!(self, Self::Empty(_))
}
/// Returns the leaf's index in the [`super::Smt`]
pub fn index(&self) -> LeafIndex<SMT_DEPTH> {
match self {
SmtLeaf::Empty(leaf_index) => *leaf_index,
SmtLeaf::Single((key, _)) => key.into(),
SmtLeaf::Multiple(entries) => {
// Note: All keys are guaranteed to have the same leaf index
let (first_key, _) = entries[0];
first_key.into()
},
}
}
/// Returns the number of entries stored in the leaf
pub fn num_entries(&self) -> u64 {
match self {
SmtLeaf::Empty(_) => 0,
SmtLeaf::Single(_) => 1,
SmtLeaf::Multiple(entries) => {
entries.len().try_into().expect("shouldn't have more than 2^64 entries")
},
}
}
/// Computes the hash of the leaf
pub fn hash(&self) -> RpoDigest {
match self {
SmtLeaf::Empty(_) => EMPTY_WORD.into(),
SmtLeaf::Single((key, value)) => Rpo256::merge(&[*key, value.into()]),
SmtLeaf::Multiple(kvs) => {
let elements: Vec<Felt> = kvs.iter().copied().flat_map(kv_to_elements).collect();
Rpo256::hash_elements(&elements)
},
}
}
// ITERATORS
// ---------------------------------------------------------------------------------------------
/// Returns the key-value pairs in the leaf
pub fn entries(&self) -> Vec<&(RpoDigest, Word)> {
match self {
SmtLeaf::Empty(_) => Vec::new(),
SmtLeaf::Single(kv_pair) => vec![kv_pair],
SmtLeaf::Multiple(kv_pairs) => kv_pairs.iter().collect(),
}
}
// CONVERSIONS
// ---------------------------------------------------------------------------------------------
/// Converts a leaf to a list of field elements
pub fn to_elements(&self) -> Vec<Felt> {
self.clone().into_elements()
}
/// Converts a leaf to a list of field elements
pub fn into_elements(self) -> Vec<Felt> {
self.into_entries().into_iter().flat_map(kv_to_elements).collect()
}
/// Converts a leaf the key-value pairs in the leaf
pub fn into_entries(self) -> Vec<(RpoDigest, Word)> {
match self {
SmtLeaf::Empty(_) => Vec::new(),
SmtLeaf::Single(kv_pair) => vec![kv_pair],
SmtLeaf::Multiple(kv_pairs) => kv_pairs,
}
}
// HELPERS
// ---------------------------------------------------------------------------------------------
/// Returns the value associated with `key` in the leaf, or `None` if `key` maps to another
/// leaf.
pub(super) fn get_value(&self, key: &RpoDigest) -> Option<Word> {
// Ensure that `key` maps to this leaf
if self.index() != key.into() {
return None;
}
match self {
SmtLeaf::Empty(_) => Some(EMPTY_WORD),
SmtLeaf::Single((key_in_leaf, value_in_leaf)) => {
if key == key_in_leaf {
Some(*value_in_leaf)
} else {
Some(EMPTY_WORD)
}
},
SmtLeaf::Multiple(kv_pairs) => {
for (key_in_leaf, value_in_leaf) in kv_pairs {
if key == key_in_leaf {
return Some(*value_in_leaf);
}
}
Some(EMPTY_WORD)
},
}
}
/// Inserts key-value pair into the leaf; returns the previous value associated with `key`, if
/// any.
///
/// The caller needs to ensure that `key` has the same leaf index as all other keys in the leaf
pub(super) fn insert(&mut self, key: RpoDigest, value: Word) -> Option<Word> {
match self {
SmtLeaf::Empty(_) => {
*self = SmtLeaf::new_single(key, value);
None
},
SmtLeaf::Single(kv_pair) => {
if kv_pair.0 == key {
// the key is already in this leaf. Update the value and return the previous
// value
let old_value = kv_pair.1;
kv_pair.1 = value;
Some(old_value)
} else {
// Another entry is present in this leaf. Transform the entry into a list
// entry, and make sure the key-value pairs are sorted by key
let mut pairs = vec![*kv_pair, (key, value)];
pairs.sort_by(|(key_1, _), (key_2, _)| cmp_keys(*key_1, *key_2));
*self = SmtLeaf::Multiple(pairs);
None
}
},
SmtLeaf::Multiple(kv_pairs) => {
match kv_pairs.binary_search_by(|kv_pair| cmp_keys(kv_pair.0, key)) {
Ok(pos) => {
let old_value = kv_pairs[pos].1;
kv_pairs[pos].1 = value;
Some(old_value)
},
Err(pos) => {
kv_pairs.insert(pos, (key, value));
None
},
}
},
}
}
/// Removes key-value pair from the leaf stored at key; returns the previous value associated
/// with `key`, if any. Also returns an `is_empty` flag, indicating whether the leaf became
/// empty, and must be removed from the data structure it is contained in.
pub(super) fn remove(&mut self, key: RpoDigest) -> (Option<Word>, bool) {
match self {
SmtLeaf::Empty(_) => (None, false),
SmtLeaf::Single((key_at_leaf, value_at_leaf)) => {
if *key_at_leaf == key {
// our key was indeed stored in the leaf, so we return the value that was stored
// in it, and indicate that the leaf should be removed
let old_value = *value_at_leaf;
// Note: this is not strictly needed, since the caller is expected to drop this
// `SmtLeaf` object.
*self = SmtLeaf::new_empty(key.into());
(Some(old_value), true)
} else {
// another key is stored at leaf; nothing to update
(None, false)
}
},
SmtLeaf::Multiple(kv_pairs) => {
match kv_pairs.binary_search_by(|kv_pair| cmp_keys(kv_pair.0, key)) {
Ok(pos) => {
let old_value = kv_pairs[pos].1;
kv_pairs.remove(pos);
debug_assert!(!kv_pairs.is_empty());
if kv_pairs.len() == 1 {
// convert the leaf into `Single`
*self = SmtLeaf::Single(kv_pairs[0]);
}
(Some(old_value), false)
},
Err(_) => {
// other keys are stored at leaf; nothing to update
(None, false)
},
}
},
}
}
}
impl Serializable for SmtLeaf {
fn write_into<W: ByteWriter>(&self, target: &mut W) {
// Write: num entries
self.num_entries().write_into(target);
// Write: leaf index
let leaf_index: u64 = self.index().value();
leaf_index.write_into(target);
// Write: entries
for (key, value) in self.entries() {
key.write_into(target);
value.write_into(target);
}
}
}
impl Deserializable for SmtLeaf {
fn read_from<R: ByteReader>(source: &mut R) -> Result<Self, DeserializationError> {
// Read: num entries
let num_entries = source.read_u64()?;
// Read: leaf index
let leaf_index: LeafIndex<SMT_DEPTH> = {
let value = source.read_u64()?;
LeafIndex::new_max_depth(value)
};
// Read: entries
let mut entries: Vec<(RpoDigest, Word)> = Vec::new();
for _ in 0..num_entries {
let key: RpoDigest = source.read()?;
let value: Word = source.read()?;
entries.push((key, value));
}
Self::new(entries, leaf_index)
.map_err(|err| DeserializationError::InvalidValue(err.to_string()))
}
}
// HELPER FUNCTIONS
// ================================================================================================
/// Converts a key-value tuple to an iterator of `Felt`s
pub(crate) fn kv_to_elements((key, value): (RpoDigest, Word)) -> impl Iterator<Item = Felt> {
let key_elements = key.into_iter();
let value_elements = value.into_iter();
key_elements.chain(value_elements)
}
/// Compares two keys, compared element-by-element using their integer representations starting with
/// the most significant element.
pub(crate) fn cmp_keys(key_1: RpoDigest, key_2: RpoDigest) -> Ordering {
for (v1, v2) in key_1.iter().zip(key_2.iter()).rev() {
let v1 = v1.as_int();
let v2 = v2.as_int();
if v1 != v2 {
return v1.cmp(&v2);
}
}
Ordering::Equal
}