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rewrite to use parking lot rw-locks and make everything threadsafe

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This commit is contained in:
Niko Matsakis 2018-09-28 14:02:39 -04:00
parent 086005dc52
commit 302a89fea5
3 changed files with 16 additions and 16 deletions
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1
Cargo.toml
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@ -11,3 +11,4 @@ readme = "README.md"
[dependencies]
derive-new = "0.5.5"
rustc-hash = "1.0"
parking_lot = "0.6.4"

2
src/lib.rs
View file

@ -48,7 +48,7 @@ pub trait BaseQueryContext: Sized {
pub trait Query<QC: BaseQueryContext>: Debug + Default + Sized + 'static {
type Key: Clone + Debug + Hash + Eq + Send;
type Value: Clone + Debug + Hash + Eq + Send;
type Storage: QueryStorageOps<QC, Self> + Send;
type Storage: QueryStorageOps<QC, Self> + Send + Sync;
fn execute(query: &QC, key: Self::Key) -> Self::Value;
}

23
src/storage.rs
View file

@ -3,6 +3,7 @@ use crate::CycleDetected;
use crate::Query;
use crate::QueryStorageOps;
use crate::QueryTable;
use parking_lot::{RwLock, RwLockUpgradableReadGuard};
use rustc_hash::FxHashMap;
use std::any::Any;
use std::cell::RefCell;
@ -21,7 +22,7 @@ where
Q: Query<QC>,
QC: BaseQueryContext,
{
map: RefCell<FxHashMap<Q::Key, QueryState<Q::Value>>>,
map: RwLock<FxHashMap<Q::Key, QueryState<Q::Value>>>,
}
/// Defines the "current state" of query's memoized results.
@ -42,7 +43,7 @@ where
{
fn default() -> Self {
MemoizedStorage {
map: RefCell::new(FxHashMap::default()),
map: RwLock::new(FxHashMap::default()),
}
}
}
@ -59,18 +60,16 @@ where
descriptor: impl FnOnce() -> QC::QueryDescriptor,
) -> Result<Q::Value, CycleDetected> {
{
let mut map = self.map.borrow_mut();
match map.entry(key.clone()) {
Entry::Occupied(entry) => {
return match entry.get() {
let map_read = self.map.upgradable_read();
if let Some(value) = map_read.get(key) {
return match value {
QueryState::InProgress => Err(CycleDetected),
QueryState::Memoized(value) => Ok(value.clone()),
};
}
Entry::Vacant(entry) => {
entry.insert(QueryState::InProgress);
}
}
let mut map_write = RwLockUpgradableReadGuard::upgrade(map_read);
map_write.insert(key.clone(), QueryState::InProgress);
}
// If we get here, the query is in progress, and we are the
@ -79,8 +78,8 @@ where
let value = query.execute_query_implementation::<Q>(descriptor, key);
{
let mut map = self.map.borrow_mut();
let old_value = map.insert(key.clone(), QueryState::Memoized(value.clone()));
let mut map_write = self.map.write();
let old_value = map_write.insert(key.clone(), QueryState::Memoized(value.clone()));
assert!(
match old_value {
Some(QueryState::InProgress) => true,