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refactor: bump hashbrown to v0.15.0, use HashTable api #6

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Nov 4, 2024
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27 changes: 25 additions & 2 deletions Cargo.lock

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2 changes: 1 addition & 1 deletion Cargo.toml
Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,7 @@ categories = ["asynchronous", "concurrency", "data-structures"]

[dependencies]
crossbeam-utils = "0.8.20"
hashbrown = { version = "0.14.5", default-features = false, features = ["raw"] }
hashbrown = { version = "0.15.0" }

[dev-dependencies]
tokio = { version = "1.41.0", features = ["full"] }
2 changes: 1 addition & 1 deletion src/shard.rs
Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,7 @@ mod futures;

use futures::{Read, Write};

pub(crate) type Inner<K, V> = hashbrown::raw::RawTable<(K, V)>;
pub(crate) type Inner<K, V> = hashbrown::HashTable<(K, V)>;
pub(crate) type ShardReader<'a, K, V> = RwLockReadGuard<'a, Inner<K, V>>;
pub(crate) type ShardWriter<'a, K, V> = RwLockWriteGuard<'a, Inner<K, V>>;

Expand Down
38 changes: 17 additions & 21 deletions src/shard_map.rs
Original file line number Diff line number Diff line change
Expand Up @@ -19,21 +19,22 @@
//! });
//! ```
use std::{
hash::{BuildHasher, Hasher, RandomState},
hash::{BuildHasher, RandomState},
sync::{Arc, OnceLock},
};

use crossbeam_utils::CachePadded;
use hashbrown::hash_table::Entry;

use crate::{
mapref::{MapRef, MapRefMut},
shard::Shard,
};

struct Inner<K, V, S = RandomState> {
shift: usize,
shards: Box<[CachePadded<Shard<K, V>>]>,
hasher: S,
shift: usize,
}

impl<K, V, S> std::ops::Deref for Inner<K, V, S> {
Expand Down Expand Up @@ -170,14 +171,6 @@ where
}
}

fn hash_u64(&self, k: &K) -> u64 {
let mut hasher = self.inner.hasher.build_hasher();

k.hash(&mut hasher);

hasher.finish()
}

#[inline]
fn shard_for_hash(&self, hash: usize) -> usize {
// 7 high bits for the HashBrown simd tag
Expand All @@ -186,7 +179,7 @@ where

#[inline]
fn shard(&self, key: &K) -> (&CachePadded<Shard<K, V>>, u64) {
let hash = self.hash_u64(key);
let hash = self.inner.hasher.hash_one(key);

let shard_idx = self.shard_for_hash(hash as usize);

Expand All @@ -213,19 +206,19 @@ where
let (shard, hash) = self.shard(&key);
let mut writer = shard.write().await;

let (old, slot) = match writer.find_or_find_insert_slot(
let (old, slot) = match writer.entry(
hash,
|(k, _)| k == &key,
|(k, _)| self.hash_u64(k),
|(k, _)| self.inner.hasher.hash_one(k),
) {
Ok(bucket) => {
let ((_, old), slot) = unsafe { writer.remove(bucket) };
Entry::Occupied(entry) => {
let ((_, old), slot) = entry.remove();
(Some(old), slot)
}
Err(slot) => (None, slot),
Entry::Vacant(slot) => (None, slot),
};

unsafe { writer.insert_in_slot(hash, slot, (key, value)) };
slot.insert((key, value));

old
}
Expand Down Expand Up @@ -255,7 +248,7 @@ where
let (shard, hash) = self.shard(key);
let reader = shard.read().await;

if let Some((k, v)) = reader.get(hash, |(k, _)| k == key) {
if let Some((k, v)) = reader.find(hash, |(k, _)| k == key) {
let (k, v) = (k as *const K, v as *const V);
// SAFETY: The key and value are guaranteed to be valid for the lifetime of the reader.
unsafe { Some(MapRef::new(reader, &*k, &*v)) }
Expand Down Expand Up @@ -293,7 +286,7 @@ where
let (shard, hash) = self.shard(key);
let mut writer = shard.write().await;

if let Some((k, v)) = writer.get_mut(hash, |(k, _)| k == key) {
if let Some((k, v)) = writer.find_mut(hash, |(k, _)| k == key) {
let (k, v) = (k as *const K, v as *mut V);
// SAFETY: The key and value are guaranteed to be valid for the lifetime of the writer.
unsafe { Some(MapRefMut::new(writer, &*k, &mut *v)) }
Expand Down Expand Up @@ -356,8 +349,11 @@ where
pub async fn remove(&self, key: &K) -> Option<V> {
let (shard, hash) = self.shard(key);

match shard.write().await.remove_entry(hash, |(k, _)| k == key) {
Some((_, v)) => Some(v),
match shard.write().await.find_entry(hash, |(k, _)| k == key) {
Ok(occupied) => {
let ((_, v), _) = occupied.remove();
Some(v)
}
_ => None,
}
}
Expand Down