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|
use std::{borrow::Borrow, collections::HashMap, hash::Hash};
use anyhow::{bail, Error};
pub mod binding;
pub enum TreeCacheNode<K, V> {
Leaf(V),
Branch(usize, HashMap<K, TreeCacheNode<K, V>>),
}
impl<K, V> TreeCacheNode<K, V> {
pub fn new_branch() -> Self {
TreeCacheNode::Branch(0, Default::default())
}
fn len(&self) -> usize {
match self {
TreeCacheNode::Leaf(_) => 1,
TreeCacheNode::Branch(size, _) => *size,
}
}
}
impl<'a, K: Eq + Hash + 'a, V> TreeCacheNode<K, V> {
pub fn set(
&mut self,
mut key: impl Iterator<Item = K>,
value: V,
) -> Result<(usize, usize), Error> {
if let Some(k) = key.next() {
match self {
TreeCacheNode::Leaf(_) => bail!("Given key is too long"),
TreeCacheNode::Branch(size, map) => {
let node = map.entry(k).or_insert_with(TreeCacheNode::new_branch);
let (added, removed) = node.set(key, value)?;
*size += added;
*size -= removed;
Ok((added, removed))
}
}
} else {
let added = if let TreeCacheNode::Branch(_, map) = self {
(1, map.len())
} else {
(0, 0)
};
*self = TreeCacheNode::Leaf(value);
Ok(added)
}
}
pub fn pop<Q>(
&mut self,
current_key: Q,
mut next_keys: impl Iterator<Item = Q>,
) -> Result<Option<TreeCacheNode<K, V>>, Error>
where
Q: Borrow<K>,
Q: Hash + Eq + 'a,
{
if let Some(next_key) = next_keys.next() {
match self {
TreeCacheNode::Leaf(_) => bail!("Given key is too long"),
TreeCacheNode::Branch(size, map) => {
let node = if let Some(node) = map.get_mut(current_key.borrow()) {
node
} else {
return Ok(None);
};
if let Some(popped) = node.pop(next_key, next_keys)? {
*size -= node.len();
Ok(Some(popped))
} else {
Ok(None)
}
}
}
} else {
match self {
TreeCacheNode::Leaf(_) => bail!("Given key is too long"),
TreeCacheNode::Branch(size, map) => {
if let Some(node) = map.remove(current_key.borrow()) {
*size -= node.len();
Ok(Some(node))
} else {
Ok(None)
}
}
}
}
}
pub fn items(&'a self) -> impl Iterator<Item = (Vec<&K>, &V)> {
// To avoid a lot of mallocs we guess the length of the key. Ideally
// we'd know this.
let capacity_guesstimate = 10;
let mut stack = vec![(Vec::with_capacity(capacity_guesstimate), self)];
std::iter::from_fn(move || {
while let Some((prefix, node)) = stack.pop() {
match node {
TreeCacheNode::Leaf(value) => return Some((prefix, value)),
TreeCacheNode::Branch(_, map) => {
stack.extend(map.iter().map(|(k, v)| {
let mut new_prefix = Vec::with_capacity(capacity_guesstimate);
new_prefix.extend_from_slice(&prefix);
new_prefix.push(k);
(new_prefix, v)
}));
}
}
}
None
})
}
pub fn values(&'a self) -> impl Iterator<Item = &V> {
let mut stack = vec![self];
std::iter::from_fn(move || {
while let Some(node) = stack.pop() {
match node {
TreeCacheNode::Leaf(value) => return Some(value),
TreeCacheNode::Branch(_, map) => {
stack.extend(map.iter().map(|(_k, v)| v));
}
}
}
None
})
}
}
impl<'a, K: Clone + Eq + Hash + 'a, V> TreeCacheNode<K, V> {
pub fn into_items(self) -> impl Iterator<Item = (Vec<K>, V)> {
let mut stack = vec![(Vec::new(), self)];
std::iter::from_fn(move || {
while let Some((prefix, node)) = stack.pop() {
match node {
TreeCacheNode::Leaf(value) => return Some((prefix, value)),
TreeCacheNode::Branch(_, map) => {
stack.extend(map.into_iter().map(|(k, v)| {
let mut prefix = prefix.clone();
prefix.push(k);
(prefix, v)
}));
}
}
}
None
})
}
}
impl<K, V> Default for TreeCacheNode<K, V> {
fn default() -> Self {
TreeCacheNode::new_branch()
}
}
pub struct TreeCache<K, V> {
root: TreeCacheNode<K, V>,
}
impl<K, V> TreeCache<K, V> {
pub fn new() -> Self {
TreeCache {
root: TreeCacheNode::new_branch(),
}
}
}
impl<'a, K: Eq + Hash + 'a, V> TreeCache<K, V> {
pub fn set(&mut self, key: impl IntoIterator<Item = K>, value: V) -> Result<(), Error> {
self.root.set(key.into_iter(), value)?;
Ok(())
}
pub fn get_node<Q>(
&self,
key: impl IntoIterator<Item = Q>,
) -> Result<Option<&TreeCacheNode<K, V>>, Error>
where
Q: Borrow<K>,
Q: Hash + Eq + 'a,
{
let mut node = &self.root;
for k in key {
match node {
TreeCacheNode::Leaf(_) => bail!("Given key is too long"),
TreeCacheNode::Branch(_, map) => {
node = if let Some(node) = map.get(k.borrow()) {
node
} else {
return Ok(None);
};
}
}
}
Ok(Some(node))
}
pub fn get<Q>(&self, key: impl IntoIterator<Item = Q>) -> Result<Option<&V>, Error>
where
Q: Borrow<K>,
Q: Hash + Eq + 'a,
{
if let Some(node) = self.get_node(key)? {
match node {
TreeCacheNode::Leaf(value) => Ok(Some(value)),
TreeCacheNode::Branch(_, _) => bail!("Given key is too short"),
}
} else {
Ok(None)
}
}
pub fn pop_node<Q>(
&mut self,
key: impl IntoIterator<Item = Q>,
) -> Result<Option<TreeCacheNode<K, V>>, Error>
where
Q: Borrow<K>,
Q: Hash + Eq + 'a,
{
let mut key_iter = key.into_iter();
let k = if let Some(k) = key_iter.next() {
k
} else {
let node = std::mem::replace(&mut self.root, TreeCacheNode::new_branch());
return Ok(Some(node));
};
self.root.pop(k, key_iter)
}
pub fn pop(&mut self, key: &[K]) -> Result<Option<V>, Error> {
if let Some(node) = self.pop_node(key)? {
match node {
TreeCacheNode::Leaf(value) => Ok(Some(value)),
TreeCacheNode::Branch(_, _) => bail!("Given key is too short"),
}
} else {
Ok(None)
}
}
pub fn clear(&mut self) {
self.root = TreeCacheNode::new_branch();
}
pub fn len(&self) -> usize {
match self.root {
TreeCacheNode::Leaf(_) => 1,
TreeCacheNode::Branch(size, _) => size,
}
}
pub fn values(&self) -> impl Iterator<Item = &V> {
let mut stack = vec![&self.root];
std::iter::from_fn(move || {
while let Some(node) = stack.pop() {
match node {
TreeCacheNode::Leaf(value) => return Some(value),
TreeCacheNode::Branch(_, map) => {
stack.extend(map.values());
}
}
}
None
})
}
pub fn items(&self) -> impl Iterator<Item = (Vec<&K>, &V)> {
self.root.items()
}
}
impl<K, V> Default for TreeCache<K, V> {
fn default() -> Self {
TreeCache::new()
}
}
#[cfg(test)]
mod test {
use std::collections::BTreeSet;
use super::*;
#[test]
fn get_set() -> Result<(), Error> {
let mut cache = TreeCache::new();
cache.set(vec!["a", "b"], "c")?;
assert_eq!(cache.get(&["a", "b"])?, Some(&"c"));
let node = cache.get_node(&["a"])?.unwrap();
match node {
TreeCacheNode::Leaf(_) => bail!("expected branch"),
TreeCacheNode::Branch(_, map) => {
assert_eq!(map.len(), 1);
assert!(map.contains_key("b"));
}
}
Ok(())
}
#[test]
fn length() -> Result<(), Error> {
let mut cache = TreeCache::new();
cache.set(vec!["a", "b"], "c")?;
assert_eq!(cache.len(), 1);
cache.set(vec!["a", "b"], "d")?;
assert_eq!(cache.len(), 1);
cache.set(vec!["e", "f"], "g")?;
assert_eq!(cache.len(), 2);
cache.set(vec!["e", "h"], "i")?;
assert_eq!(cache.len(), 3);
cache.set(vec!["e"], "i")?;
assert_eq!(cache.len(), 2);
cache.pop_node(&["a"])?;
assert_eq!(cache.len(), 1);
Ok(())
}
#[test]
fn clear() -> Result<(), Error> {
let mut cache = TreeCache::new();
cache.set(vec!["a", "b"], "c")?;
assert_eq!(cache.len(), 1);
cache.clear();
assert_eq!(cache.len(), 0);
assert_eq!(cache.get(&["a", "b"])?, None);
Ok(())
}
#[test]
fn pop() -> Result<(), Error> {
let mut cache = TreeCache::new();
cache.set(vec!["a", "b"], "c")?;
assert_eq!(cache.pop(&["a", "b"])?, Some("c"));
assert_eq!(cache.pop(&["a", "b"])?, None);
Ok(())
}
#[test]
fn values() -> Result<(), Error> {
let mut cache = TreeCache::new();
cache.set(vec!["a", "b"], "c")?;
let expected = ["c"].iter().collect();
assert_eq!(cache.values().collect::<BTreeSet<_>>(), expected);
cache.set(vec!["d", "e"], "f")?;
let expected = ["c", "f"].iter().collect();
assert_eq!(cache.values().collect::<BTreeSet<_>>(), expected);
Ok(())
}
#[test]
fn items() -> Result<(), Error> {
let mut cache = TreeCache::new();
cache.set(vec!["a", "b"], "c")?;
cache.set(vec!["d", "e"], "f")?;
let expected = [(vec![&"a", &"b"], &"c"), (vec![&"d", &"e"], &"f")]
.into_iter()
.collect();
assert_eq!(cache.items().collect::<BTreeSet<_>>(), expected);
Ok(())
}
}
|
