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Make custom hashers actually usable #18

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Oct 31, 2023
Merged

Make custom hashers actually usable #18

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76 changes: 72 additions & 4 deletions src/lfu/tinylfu.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -27,12 +27,12 @@ pub struct TinyLFUBuilder<K, KH = DefaultKeyHasher<K>> {
marker: PhantomData<K>,
}

impl<K: Hash + Eq> Default for TinyLFUBuilder<K> {
impl<K: Hash + Eq, KH: KeyHasher<K> + Default> Default for TinyLFUBuilder<K, KH> {
fn default() -> Self {
Self {
samples: 0,
size: 0,
key_hasher: Some(DefaultKeyHasher::default()),
key_hasher: Some(KH::default()),
false_positive_ratio: Some(DEFAULT_FALSE_POSITIVE_RATIO),
marker: Default::default(),
}
Expand All @@ -47,6 +47,17 @@ impl<K: Hash + Eq> TinyLFUBuilder<K> {
}

impl<K: Hash + Eq, KH: KeyHasher<K>> TinyLFUBuilder<K, KH> {
/// The constructor of TinyLFUBuilder
pub fn with_hasher(key_hasher: KH) -> Self {
Self {
samples: 0,
size: 0,
key_hasher: Some(key_hasher),
false_positive_ratio: Some(DEFAULT_FALSE_POSITIVE_RATIO),
marker: Default::default(),
}
}

/// Set the samples of TinyLFU
pub fn set_samples(self, samples: usize) -> Self {
Self {
Expand Down Expand Up @@ -387,8 +398,65 @@ impl<K: Hash + Eq, KH: KeyHasher<K>> TinyLFU<K, KH> {
}

#[cfg(test)]
mod test {
use crate::lfu::tinylfu::TinyLFU;
pub(crate) mod test {
use core::hash::Hasher;

use crate::lfu::{tinylfu::TinyLFU, KeyHasher};

use super::TinyLFUBuilder;

#[derive(Default)]
pub(crate) struct PassthroughU64Hasher(u64);
impl core::hash::Hasher for PassthroughU64Hasher {
fn finish(&self) -> u64 {
self.0
}

fn write(&mut self, _bytes: &[u8]) {
panic!("Can only write u64");
}

fn write_u64(&mut self, i: u64) {
self.0 = i;
}
}

#[derive(Default)]
pub(crate) struct PassthroughU64KeyHasher {}

impl KeyHasher<u64> for PassthroughU64KeyHasher {
fn hash_key<Q>(&self, key: &Q) -> u64
where
u64: core::borrow::Borrow<Q>,
Q: core::hash::Hash + Eq + ?Sized,
{
let mut state = PassthroughU64Hasher::default();
key.hash(&mut state);
state.finish()
}
}

#[test]
fn test_custom_hasher() {
let mut l: TinyLFU<u64, PassthroughU64KeyHasher> = TinyLFUBuilder::default()
.set_size(4)
.set_samples(4)
.finalize()
.unwrap();
assert_eq!(l.hash_key(&0), 0);
assert_eq!(l.hash_key(&10), 10);

l.increment(&1);
l.increment(&1);
l.increment(&1);

assert!(l.doorkeeper.contains(1));
assert_eq!(l.ctr.estimate(1), 2);

l.increment(&1);
assert!(!l.doorkeeper.contains(1));
assert_eq!(l.ctr.estimate(1), 1);
}

#[test]
fn test_increment() {
Expand Down
187 changes: 167 additions & 20 deletions src/lfu/wtinylfu.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -36,24 +36,38 @@ pub struct WTinyLFUCacheBuilder<
marker: PhantomData<K>,
}

impl<K: Hash + Eq> Default for WTinyLFUCacheBuilder<K> {
impl<
K: Hash + Eq,
KH: KeyHasher<K> + Default,
FH: BuildHasher + Default,
RH: BuildHasher + Default,
WH: BuildHasher + Default,
> Default for WTinyLFUCacheBuilder<K, KH, FH, RH, WH>
{
fn default() -> Self {
Self {
samples: 0,
window_cache_size: 0,
main_cache_protected_size: 0,
main_cache_probationary_size: 0,
window_cache_hasher: Some(DefaultHashBuilder::default()),
main_cache_protected_hasher: Some(DefaultHashBuilder::default()),
main_cache_probationary_hasher: Some(DefaultHashBuilder::default()),
key_hasher: Some(DefaultKeyHasher::default()),
window_cache_hasher: Some(WH::default()),
main_cache_protected_hasher: Some(FH::default()),
main_cache_probationary_hasher: Some(RH::default()),
key_hasher: Some(KH::default()),
false_positive_ratio: Some(DEFAULT_FALSE_POSITIVE_RATIO),
marker: Default::default(),
}
}
}

impl<K: Hash + Eq> WTinyLFUCacheBuilder<K> {
impl<
K: Hash + Eq,
KH: KeyHasher<K> + Default,
FH: BuildHasher + Default,
RH: BuildHasher + Default,
WH: BuildHasher + Default,
> WTinyLFUCacheBuilder<K, KH, FH, RH, WH>
{
/// The constructor of WTinyLFUCacheBuilder
pub fn new(
window_cache_size: usize,
Expand All @@ -72,6 +86,27 @@ impl<K: Hash + Eq> WTinyLFUCacheBuilder<K> {
impl<K: Hash + Eq, KH: KeyHasher<K>, FH: BuildHasher, RH: BuildHasher, WH: BuildHasher>
WTinyLFUCacheBuilder<K, KH, FH, RH, WH>
{
/// Construct a WTinyLFUCacheBuilder using the custom hashers.
pub fn with_hashers(
key_hasher: KH,
protected_hasher: FH,
probationary_hasher: RH,
window_hasher: WH,
) -> Self {
Self {
samples: 0,
window_cache_size: 0,
main_cache_protected_size: 0,
main_cache_probationary_size: 0,
window_cache_hasher: Some(window_hasher),
main_cache_protected_hasher: Some(protected_hasher),
main_cache_probationary_hasher: Some(probationary_hasher),
key_hasher: Some(key_hasher),
false_positive_ratio: Some(DEFAULT_FALSE_POSITIVE_RATIO),
marker: Default::default(),
}
}

/// Set the samples of TinyLFU
pub fn set_samples(self, samples: usize) -> Self {
Self {
Expand Down Expand Up @@ -400,6 +435,19 @@ impl<K: Hash + Eq, V> WTinyLFUCache<K, V, DefaultKeyHasher<K>> {
)
.finalize()
}
}

impl<K: Hash + Eq, V, KH: KeyHasher<K>, FH: BuildHasher, RH: BuildHasher, WH: BuildHasher>
WTinyLFUCache<K, V, KH, FH, RH, WH>
{
/// Creates a WTinyLFUCache according to [`WTinyLFUCacheBuilder`]
///
/// [`WTinyLFUCacheBuilder`]: struct.WTinyLFUCacheBuilder.html
pub fn from_builder(
builder: WTinyLFUCacheBuilder<K, KH, FH, RH, WH>,
) -> Result<Self, WTinyLFUError> {
builder.finalize()
}

/// Returns a [`WTinyLFUCacheBuilder`] with default configurations.
///
Expand Down Expand Up @@ -429,19 +477,6 @@ impl<K: Hash + Eq, V> WTinyLFUCache<K, V, DefaultKeyHasher<K>> {
}
}

impl<K: Hash + Eq, V, KH: KeyHasher<K>, FH: BuildHasher, RH: BuildHasher, WH: BuildHasher>
WTinyLFUCache<K, V, KH, FH, RH, WH>
{
/// Creates a WTinyLFUCache according to [`WTinyLFUCacheBuilder`]
///
/// [`WTinyLFUCacheBuilder`]: struct.WTinyLFUCacheBuilder.html
pub fn from_builder(
builder: WTinyLFUCacheBuilder<K, KH, FH, RH, WH>,
) -> Result<Self, WTinyLFUError> {
builder.finalize()
}
}

impl<K: Hash + Eq, V, KH: KeyHasher<K>, FH: BuildHasher, RH: BuildHasher, WH: BuildHasher>
Cache<K, V> for WTinyLFUCache<K, V, KH, FH, RH, WH>
{
Expand Down Expand Up @@ -654,8 +689,120 @@ impl<K: Hash + Eq, V, KH: KeyHasher<K>, FH: BuildHasher, RH: BuildHasher, WH: Bu

#[cfg(test)]
mod test {
use core::hash::BuildHasher;

use crate::lfu::tinylfu::test::{PassthroughU64Hasher, PassthroughU64KeyHasher};
use crate::lfu::WTinyLFUCache;
use crate::{Cache, PutResult};
use crate::{Cache, PutResult, WTinyLFUCacheBuilder};

#[derive(Default)]
struct PassthroughBuilderU64Hasher {}

impl BuildHasher for PassthroughBuilderU64Hasher {
type Hasher = PassthroughU64Hasher;

fn build_hasher(&self) -> Self::Hasher {
Default::default()
}
}

#[test]
#[cfg_attr(miri, ignore)]
fn test_wtinylfu_custom_hasher() {
let mut cache: WTinyLFUCache<
u64,
u32,
PassthroughU64KeyHasher,
PassthroughBuilderU64Hasher,
PassthroughBuilderU64Hasher,
PassthroughBuilderU64Hasher,
> = WTinyLFUCacheBuilder::default()
.set_window_cache_size(1)
.set_protected_cache_size(2)
.set_probationary_cache_size(2)
.set_samples(5)
.finalize()
.unwrap();
assert_eq!(cache.cap(), 5);
assert_eq!(cache.window_cache_cap(), 1);
assert_eq!(cache.main_cache_cap(), 4);

assert_eq!(cache.put(1, 1), PutResult::Put);
assert!(cache.contains(&1));
assert_eq!(cache.put(2, 2), PutResult::Put);
assert!(cache.contains(&2));
assert_eq!(cache.put(3, 3), PutResult::Put);
assert!(cache.contains(&3));

// current state
// window cache: (MRU) [3] (LRU)
// probationary cache: (MRU) [2, 1] (LRU)
// protected cache: (MRU) [] (LRU)
assert_eq!(cache.window_cache_len(), 1);
assert_eq!(cache.main_cache_len(), 2);

assert_eq!(cache.put(2, 22), PutResult::Update(2));
assert_eq!(cache.put(1, 11), PutResult::Update(1));

// current state
// window cache: (MRU) [3] (LRU)
// probationary cache: (MRU) [] (LRU)
// protected cache: (MRU) [1, 2] (LRU)
assert_eq!(cache.slru.peek_lru_from_protected(), Some((&2, &22)));
assert_eq!(cache.slru.peek_mru_from_protected(), Some((&1, &11)));
assert_eq!(cache.window_cache_len(), 1);
assert_eq!(cache.slru.protected_len(), 2);
assert_eq!(cache.slru.probationary_len(), 0);

assert_eq!(cache.put(3, 33), PutResult::Update(3));

// current state
// window cache: (MRU) [2] (LRU)
// probationary cache: (MRU) [] (LRU)
// protected cache: (MRU) [3, 1] (LRU)
assert_eq!(cache.lru.peek_lru(), Some((&2, &22)));
assert_eq!(cache.slru.peek_lru_from_protected(), Some((&1, &11)));
assert_eq!(cache.slru.peek_mru_from_protected(), Some((&3, &33)));
assert_eq!(cache.window_cache_len(), 1);
assert_eq!(cache.slru.protected_len(), 2);
assert_eq!(cache.slru.probationary_len(), 0);

assert_eq!(cache.put(4, 4), PutResult::Put);
assert_eq!(cache.put(5, 5), PutResult::Put);

// current state
// window cache: (MRU) [5] (LRU)
// probationary cache: (MRU) [4, 2] (LRU)
// protected cache: (MRU) [3, 1] (LRU)
assert_eq!(cache.lru.peek_lru(), Some((&5, &5)));
assert_eq!(cache.slru.peek_lru_from_probationary(), Some((&2, &22)));
assert_eq!(cache.slru.peek_mru_from_probationary(), Some((&4, &4)));
assert_eq!(cache.lru.len(), 1);
assert_eq!(cache.slru.protected_len(), 2);
assert_eq!(cache.slru.probationary_len(), 2);

assert_eq!(cache.get(&4), Some(&4));
assert_eq!(cache.get_mut(&5), Some(&mut 5));

// current state
// window cache: (MRU) [5] (LRU)
// probationary cache: (MRU) [1, 2] (LRU)
// protected cache: (MRU) [4, 3] (LRU)
assert_eq!(cache.lru.peek_lru(), Some((&5, &5)));
assert_eq!(cache.slru.peek_lru_from_probationary(), Some((&2, &22)));
assert_eq!(cache.slru.peek_mru_from_probationary(), Some((&1, &11)));
assert_eq!(cache.slru.peek_lru_from_protected(), Some((&3, &33)));
assert_eq!(cache.slru.peek_mru_from_protected(), Some((&4, &4)));
assert_eq!(cache.lru.len(), 1);
assert_eq!(cache.slru.protected_len(), 2);
assert_eq!(cache.slru.probationary_len(), 2);

assert_eq!(cache.peek(&3), Some(&33));
assert_eq!(cache.peek_mut(&2), Some(&mut 22));

assert_eq!(cache.remove(&3), Some(33));
assert_eq!(cache.remove(&2), Some(22));
}

#[test]
#[cfg_attr(miri, ignore)]
Expand Down
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