txmap 0.1.0

A concurrent transactional hash map with fine-grained locking and internal mutability
Documentation 
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use crate::{indexer::Indexer, ops::op_trait::OpTrait, result::MISSING_MUTEX_GUARD_ERROR};
use hashbrown::HashMap;
use intmap::IntMap;
use parking_lot::MutexGuard;
use std::hash::Hash;

pub(crate) struct UpdateOp<K, V, P = ()> {
    guards_bitmask: u128,
    key_index: u8,
    key: K,
    #[allow(clippy::type_complexity)]
    transform: Box<dyn Fn(&K, Option<&V>, &P) -> Option<V>>,
}

impl<K, V, P> UpdateOp<K, V, P>
where
    K: Hash + Eq,
{
    pub fn new_with_params<T>(indexer: &Indexer, key: K, transform: T) -> Self
    where
        T: Fn(&K, Option<&V>, &P) -> Option<V> + 'static,
    {
        let key_index = indexer.index(&key);
        Self {
            guards_bitmask: 1 << key_index,
            key_index,
            key,
            transform: Box::new(transform),
        }
    }
    fn mapped_value(
        &self,
        mutex_guards: &IntMap<u8, MutexGuard<'_, HashMap<K, V>>>,
        params: &P,
    ) -> Option<V> {
        let key_guard = mutex_guards.get(self.key_index);
        let key_shard = key_guard.expect(MISSING_MUTEX_GUARD_ERROR);
        let key_value = key_shard.get(&self.key);
        (self.transform)(&self.key, key_value, params)
    }
}

impl<K, V> UpdateOp<K, V, ()>
where
    K: Hash + Eq,
{
    pub fn new<T>(indexer: &Indexer, key: K, transform: T) -> Self
    where
        T: Fn(&K, Option<&V>) -> Option<V> + 'static,
    {
        Self::new_with_params(indexer, key, move |k, v, _| transform(k, v))
    }
}

impl<K, V, P> OpTrait<K, V, P> for UpdateOp<K, V, P>
where
    K: Clone + Hash + Eq,
{
    fn guards_bitmask(&self) -> u128 {
        self.guards_bitmask
    }
    fn apply(&self, mutex_guards: &mut IntMap<u8, MutexGuard<'_, HashMap<K, V>>>, params: &P) {
        let new_value = self.mapped_value(mutex_guards, params);
        let guard = mutex_guards.get_mut(self.key_index);
        let shard = guard.expect(MISSING_MUTEX_GUARD_ERROR);
        match new_value {
            Some(v) => shard.insert(self.key.clone(), v),
            None => shard.remove(&self.key),
        };
    }
}