Move salsa fork in-tree

crates/salsa/src/storage.rs

@@ -0,0 +1,59 @@
+use crate::{plumbing::DatabaseStorageTypes, Runtime};
+use triomphe::Arc;
+
+/// Stores the cached results and dependency information for all the queries
+/// defined on your salsa database. Also embeds a [`Runtime`] which is used to
+/// manage query execution. Every database must include a `storage:
+/// Storage<Self>` field.
+pub struct Storage<DB: DatabaseStorageTypes> {
+    query_store: Arc<DB::DatabaseStorage>,
+    runtime: Runtime,
+}
+
+impl<DB: DatabaseStorageTypes> Default for Storage<DB> {
+    fn default() -> Self {
+        Self {
+            query_store: Default::default(),
+            runtime: Default::default(),
+        }
+    }
+}
+
+impl<DB: DatabaseStorageTypes> Storage<DB> {
+    /// Gives access to the underlying salsa runtime.
+    pub fn salsa_runtime(&self) -> &Runtime {
+        &self.runtime
+    }
+
+    /// Gives access to the underlying salsa runtime.
+    pub fn salsa_runtime_mut(&mut self) -> &mut Runtime {
+        &mut self.runtime
+    }
+
+    /// Access the query storage tables. Not meant to be used directly by end
+    /// users.
+    pub fn query_store(&self) -> &DB::DatabaseStorage {
+        &self.query_store
+    }
+
+    /// Access the query storage tables. Not meant to be used directly by end
+    /// users.
+    pub fn query_store_mut(&mut self) -> (&DB::DatabaseStorage, &mut Runtime) {
+        (&self.query_store, &mut self.runtime)
+    }
+
+    /// Returns a "snapshotted" storage, suitable for use in a forked database.
+    /// This snapshot hold a read-lock on the global state, which means that any
+    /// attempt to `set` an input will block until the forked runtime is
+    /// dropped. See `ParallelDatabase::snapshot` for more information.
+    ///
+    /// **Warning.** This second handle is intended to be used from a separate
+    /// thread. Using two database handles from the **same thread** can lead to
+    /// deadlock.
+    pub fn snapshot(&self) -> Self {
+        Storage {
+            query_store: self.query_store.clone(),
+            runtime: self.runtime.snapshot(),
+        }
+    }
+}