rocketmq-store 0.8.0

// Copyright 2023 The RocketMQ Rust Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use std::hash::BuildHasher;
use std::hash::Hash;
use std::sync::Arc;

use hashbrown::DefaultHashBuilder;
use tokio::sync::Mutex;
use tokio::sync::MutexGuard;

const MAXIMUM_CAPACITY: usize = 1 << 6;

#[derive(Clone)]
pub struct TopicQueueLock {
    mask: usize,
    locks: Arc<Vec<Mutex<()>>>,
    hasher_builder: DefaultHashBuilder,
}

impl Default for TopicQueueLock {
    fn default() -> Self {
        Self::new()
    }
}

impl TopicQueueLock {
    pub fn new() -> Self {
        Self::with_size(32)
    }

    pub fn with_size(size: usize) -> Self {
        let capacity = size.next_power_of_two();
        let locks = (0..capacity).map(|_| Mutex::new(())).collect::<Vec<_>>();
        Self {
            mask: capacity - 1,
            locks: Arc::new(locks),
            hasher_builder: DefaultHashBuilder::default(),
        }
    }

    #[inline(always)]
    pub async fn lock<'a, K>(&'a self, key: &K) -> MutexGuard<'a, ()>
    where
        K: Hash + ?Sized,
    {
        let index = self.index_for_key(key);
        self.locks[index].lock().await
    }

    #[inline(always)]
    fn index_for_key<K: Hash + ?Sized>(&self, key: &K) -> usize {
        (self.hasher_builder.hash_one(key) as usize) & self.mask
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn creates_correct_number_of_locks() {
        let lock = TopicQueueLock::with_size(32);
        assert_eq!(lock.locks.len(), 32);
    }

    #[test]
    fn handles_zero_capacity_gracefully() {
        let lock = TopicQueueLock::with_size(0);
        assert_eq!(lock.locks.len(), 1);
    }
}