Add basic Skymap methods
Sayan Nandan
3 years ago
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/*
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* Created on Mon Aug 09 2021
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*
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* This file is a part of Skytable
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* Skytable (formerly known as TerrabaseDB or Skybase) is a free and open-source
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* NoSQL database written by Sayan Nandan ("the Author") with the
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* vision to provide flexibility in data modelling without compromising
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* on performance, queryability or scalability.
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*
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* Copyright (c) 2021, Sayan Nandan <ohsayan@outlook.com>
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Affero General Public License for more details.
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*
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* You should have received a copy of the GNU Affero General Public License
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* along with this program. If not, see <https://www.gnu.org/licenses/>.
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*
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*/
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@ -0,0 +1,238 @@
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/*
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* Created on Mon Aug 09 2021
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*
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* This file is a part of Skytable
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* Skytable (formerly known as TerrabaseDB or Skybase) is a free and open-source
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* NoSQL database written by Sayan Nandan ("the Author") with the
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* vision to provide flexibility in data modelling without compromising
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* on performance, queryability or scalability.
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*
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* Copyright (c) 2021, Sayan Nandan <ohsayan@outlook.com>
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Affero General Public License for more details.
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*
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* You should have received a copy of the GNU Affero General Public License
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* along with this program. If not, see <https://www.gnu.org/licenses/>.
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*
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*/
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#![allow(dead_code)] // TODO(@ohsayan): Remove this lint once we're done
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#![allow(clippy::manual_map)] // avoid LLVM bloat
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use core::borrow::Borrow;
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use core::hash::BuildHasher;
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use core::hash::Hash;
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use core::hash::Hasher;
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use core::mem;
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use parking_lot::RwLock;
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use parking_lot::RwLockReadGuard;
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use parking_lot::RwLockWriteGuard;
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use std::collections::hash_map::RandomState;
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type LowMap<K, V> = hashbrown::raw::RawTable<(K, V)>;
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type ShardSlice<K, V> = [RwLock<LowMap<K, V>>];
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type SRlock<'a, K, V> = RwLockReadGuard<'a, hashbrown::raw::RawTable<(K, V)>>;
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type SWlock<'a, K, V> = RwLockWriteGuard<'a, hashbrown::raw::RawTable<(K, V)>>;
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const BITS_IN_USIZE: usize = mem::size_of::<usize>() * 8;
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const DEFAULT_CAP: usize = 128;
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fn make_hash<K, Q, S>(hash_builder: &S, val: &Q) -> u64
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where
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K: Borrow<Q>,
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Q: Hash + ?Sized,
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S: BuildHasher,
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{
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let mut state = hash_builder.build_hasher();
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val.hash(&mut state);
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state.finish()
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}
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fn make_insert_hash<K, S>(hash_builder: &S, val: &K) -> u64
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where
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K: Hash,
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S: BuildHasher,
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{
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let mut state = hash_builder.build_hasher();
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val.hash(&mut state);
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state.finish()
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}
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fn make_hasher<K, Q, V, S>(hash_builder: &S) -> impl Fn(&(Q, V)) -> u64 + '_
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where
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K: Borrow<Q>,
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Q: Hash,
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S: BuildHasher,
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{
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move |val| make_hash::<K, Q, S>(hash_builder, &val.0)
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}
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fn ceq<Q, K, V>(k: &Q) -> impl Fn(&(K, V)) -> bool + '_
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where
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K: Borrow<Q>,
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Q: ?Sized + Eq,
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{
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move |x| k.eq(x.0.borrow())
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}
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fn get_shard_count() -> usize {
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(num_cpus::get() * 4).next_power_of_two()
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}
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const fn cttz(amount: usize) -> usize {
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amount.trailing_zeros() as usize
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}
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pub struct Skymap<K, V, S = RandomState> {
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shards: Box<ShardSlice<K, V>>,
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hasher: S,
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shift: usize,
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}
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impl<K, V> Default for Skymap<K, V, RandomState> {
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fn default() -> Self {
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Self::with_hasher(RandomState::default())
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}
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}
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// basic impls
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impl<K, V, S> Skymap<K, V, S>
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where
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S: BuildHasher + Default,
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{
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pub fn new() -> Self {
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Self::with_hasher(S::default())
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}
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pub fn with_capacity(cap: usize) -> Self {
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Self::with_capacity_and_hasher(cap, S::default())
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}
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pub fn with_capacity_and_hasher(mut cap: usize, hasher: S) -> Self {
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let shard_count = get_shard_count();
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let shift = BITS_IN_USIZE - cttz(shard_count);
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if cap != 0 {
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cap = (cap + (shard_count - 1)) & !(shard_count - 1);
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}
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let cap_per_shard = cap / shard_count;
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Self {
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shards: (0..shard_count)
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.map(|_| RwLock::new(LowMap::with_capacity(cap_per_shard)))
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.collect(),
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hasher,
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shift,
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}
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}
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pub fn with_hasher(hasher: S) -> Self {
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Self::with_capacity_and_hasher(DEFAULT_CAP, hasher)
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}
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}
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// const impls
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impl<K, V, S> Skymap<K, V, S> {
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const fn shards(&self) -> &ShardSlice<K, V> {
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&self.shards
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}
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const fn determine_shard(&self, hash: usize) -> usize {
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(hash << 7) >> self.shift
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}
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const fn h(&self) -> &S {
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&self.hasher
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}
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}
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// insert/get/remove impls
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impl<K, V, S> Skymap<K, V, S>
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where
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K: Eq + Hash,
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S: BuildHasher + Clone,
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{
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pub fn insert(&self, k: K, v: V) -> Option<V> {
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let hash = make_insert_hash::<K, S>(&self.hasher, &k);
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let idx = self.determine_shard(hash as usize);
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unsafe {
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// begin critical section
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let mut lowtable = self.get_wshard_unchecked(idx);
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if let Some((_, item)) = lowtable.get_mut(hash, ceq(&k)) {
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Some(mem::replace(item, v))
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} else {
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lowtable.insert(hash, (k, v), make_hasher::<K, _, V, S>(self.h()));
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None
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}
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// end critical section
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}
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}
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pub fn remove<Q>(&self, k: &Q) -> Option<(K, V)>
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where
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K: Borrow<Q>,
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Q: Hash + Eq + ?Sized,
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{
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let hash = make_hash::<K, Q, S>(self.h(), k);
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let idx = self.determine_shard(hash as usize);
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unsafe {
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// begin critical section
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let mut lowtable = self.get_wshard_unchecked(idx);
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match lowtable.remove_entry(hash, ceq(k)) {
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Some(kv) => Some(kv),
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None => None,
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}
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// end critical section
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}
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}
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pub fn remove_if<Q>(&self, k: &Q, f: impl Fn(&(K, V)) -> bool) -> Option<(K, V)>
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where
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K: Borrow<Q>,
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Q: Hash + Eq + ?Sized,
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{
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let hash = make_hash::<K, Q, S>(self.h(), k);
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let idx = self.determine_shard(hash as usize);
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unsafe {
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// begin critical section
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let mut lowtable = self.get_wshard_unchecked(idx);
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match lowtable.find(hash, ceq(k)) {
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Some(bucket) => {
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if f(bucket.as_ref()) {
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Some(lowtable.remove(bucket))
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} else {
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None
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}
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}
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None => None,
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}
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// end critical section
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}
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}
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}
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// inner impls
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impl<K, V, S> Skymap<K, V, S> {
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unsafe fn get_rshard_unchecked(&self, shard: usize) -> SRlock<K, V> {
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self.shards.get_unchecked(shard).read()
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}
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unsafe fn get_wshard_unchecked(&self, shard: usize) -> SWlock<K, V> {
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self.shards.get_unchecked(shard).write()
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}
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}
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#[test]
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fn test_insert_remove() {
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let map = Skymap::default();
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map.insert("hello", "world");
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assert_eq!(map.remove("hello").unwrap().1, "world");
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}
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#[test]
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fn test_remove_if() {
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let map = Skymap::default();
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map.insert("hello", "world");
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assert!(map
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.remove_if("hello", |(_k, v)| { (*v).eq("notworld") })
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.is_none());
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}
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