Tidy store crate, add comments

beacon_node/store/src/memory_store.rs

@@ -0,0 +1,63 @@
+use super::{Error, Store};
+use parking_lot::RwLock;
+use std::collections::HashMap;
+
+type DBHashMap = HashMap<Vec<u8>, Vec<u8>>;
+
+/// A thread-safe `HashMap` wrapper.
+pub struct MemoryStore {
+    db: RwLock<DBHashMap>,
+}
+
+impl MemoryStore {
+    /// Create a new, empty database.
+    pub fn open() -> Self {
+        Self {
+            db: RwLock::new(HashMap::new()),
+        }
+    }
+
+    fn get_key_for_col(col: &str, key: &[u8]) -> Vec<u8> {
+        let mut col = col.as_bytes().to_vec();
+        col.append(&mut key.to_vec());
+        col
+    }
+}
+
+impl Store for MemoryStore {
+    /// Get the value of some key from the database. Returns `None` if the key does not exist.
+    fn get_bytes(&self, col: &str, key: &[u8]) -> Result<Option<Vec<u8>>, Error> {
+        let column_key = MemoryStore::get_key_for_col(col, key);
+
+        Ok(self
+            .db
+            .read()
+            .get(&column_key)
+            .and_then(|val| Some(val.clone())))
+    }
+
+    /// Puts a key in the database.
+    fn put_bytes(&self, col: &str, key: &[u8], val: &[u8]) -> Result<(), Error> {
+        let column_key = MemoryStore::get_key_for_col(col, key);
+
+        self.db.write().insert(column_key, val.to_vec());
+
+        Ok(())
+    }
+
+    /// Return true if some key exists in some column.
+    fn key_exists(&self, col: &str, key: &[u8]) -> Result<bool, Error> {
+        let column_key = MemoryStore::get_key_for_col(col, key);
+
+        Ok(self.db.read().contains_key(&column_key))
+    }
+
+    /// Delete some key from the database.
+    fn key_delete(&self, col: &str, key: &[u8]) -> Result<(), Error> {
+        let column_key = MemoryStore::get_key_for_col(col, key);
+
+        self.db.write().remove(&column_key);
+
+        Ok(())
+    }
+}