1 files changed, 270 insertions, 0 deletions
diff --git a/src/db/lmdb_adapter.rs b/src/db/lmdb_adapter.rs
new file mode 100644
index 00000000..caf21517
--- /dev/null
+++ b/src/db/lmdb_adapter.rs
@@ -0,0 +1,270 @@
+use core::marker::PhantomPinned;
+use core::ops::Bound;
+use core::pin::Pin;
+use core::ptr::NonNull;
+
+use std::cell::RefCell;
+use std::collections::HashMap;
+use std::sync::{Arc, RwLock};
+
+use lmdb::{
+	Database, DatabaseFlags, Environment, RoTransaction, RwTransaction, Transaction, WriteFlags,
+};
+
+use crate::{
+	Db, Error, IDb, ITx, ITxFn, IValue, Result, TxError, TxFnResult, TxResult, Value, ValueIter,
+};
+
+pub use lmdb;
+
+// -- err
+
+impl From<lmdb::Error> for Error {
+	fn from(e: lmdb::Error) -> Error {
+		Error(format!("LMDB: {}", e).into())
+	}
+}
+
+impl<T> From<lmdb::Error> for TxError<T> {
+	fn from(e: lmdb::Error) -> TxError<T> {
+		TxError::Db(e.into())
+	}
+}
+
+// -- db
+
+pub struct LmdbDb {
+	db: lmdb::Environment,
+	trees: RwLock<(Vec<lmdb::Database>, HashMap<String, usize>)>,
+}
+
+impl LmdbDb {
+	pub fn init(db: lmdb::Environment) -> Db {
+		let s = Self {
+			db,
+			trees: RwLock::new((Vec::new(), HashMap::new())),
+		};
+		Db(Arc::new(s))
+	}
+
+	fn get_tree(&self, i: usize) -> Result<lmdb::Database> {
+		self.trees
+			.read()
+			.unwrap()
+			.0
+			.get(i)
+			.cloned()
+			.ok_or_else(|| Error("invalid tree id".into()))
+	}
+}
+
+impl IDb for LmdbDb {
+	fn open_tree(&self, name: &str) -> Result<usize> {
+		let mut trees = self.trees.write().unwrap();
+		if let Some(i) = trees.1.get(name) {
+			Ok(*i)
+		} else {
+			let tree = self.db.create_db(Some(name), DatabaseFlags::empty())?;
+			let i = trees.0.len();
+			trees.0.push(tree);
+			trees.1.insert(name.to_string(), i);
+			Ok(i)
+		}
+	}
+
+	fn list_trees(&self) -> Result<Vec<String>> {
+		unimplemented!()
+	}
+
+	// ----
+
+	fn get(&self, tree: usize, key: &[u8]) -> Result<Option<Value<'_>>> {
+		let tree = self.get_tree(tree)?;
+
+		let res = TxAndValue {
+			tx: self.db.begin_ro_txn()?,
+			value: NonNull::dangling(),
+			_pin: PhantomPinned,
+		};
+		let mut boxed = Box::pin(res);
+
+		unsafe {
+			let tx = NonNull::from(&boxed.tx);
+			let val = match tx.as_ref().get(tree, &key) {
+				Err(lmdb::Error::NotFound) => return Ok(None),
+				v => v?,
+			};
+
+			let mut_ref: Pin<&mut TxAndValue<'_>> = Pin::as_mut(&mut boxed);
+			Pin::get_unchecked_mut(mut_ref).value = NonNull::from(&val);
+		}
+
+		Ok(Some(Value(Box::new(TxAndValuePin(boxed)))))
+	}
+
+	fn remove(&self, tree: usize, key: &[u8]) -> Result<bool> {
+		unimplemented!()
+	}
+
+	fn len(&self, tree: usize) -> Result<usize> {
+		unimplemented!()
+	}
+
+	fn insert(&self, tree: usize, key: &[u8], value: &[u8]) -> Result<()> {
+		let tree = self.get_tree(tree)?;
+		let mut tx = self.db.begin_rw_txn()?;
+		tx.put(tree, &key, &value, WriteFlags::empty())?;
+		tx.commit()?;
+		Ok(())
+	}
+
+	fn iter(&self, tree: usize) -> Result<ValueIter<'_>> {
+		unimplemented!()
+	}
+
+	fn iter_rev(&self, tree: usize) -> Result<ValueIter<'_>> {
+		unimplemented!()
+	}
+
+	fn range<'r>(
+		&self,
+		tree: usize,
+		low: Bound<&'r [u8]>,
+		high: Bound<&'r [u8]>,
+	) -> Result<ValueIter<'_>> {
+		unimplemented!()
+	}
+	fn range_rev<'r>(
+		&self,
+		tree: usize,
+		low: Bound<&'r [u8]>,
+		high: Bound<&'r [u8]>,
+	) -> Result<ValueIter<'_>> {
+		unimplemented!()
+	}
+
+	// ----
+
+	fn transaction(&self, f: &dyn ITxFn) -> TxResult<(), ()> {
+		let trees = self.trees.read().unwrap();
+		let mut tx = LmdbTx {
+			trees: &trees.0[..],
+			tx: self.db.begin_rw_txn()?,
+		};
+
+		let res = f.try_on(&mut tx);
+		match res {
+			TxFnResult::Ok => {
+				tx.tx.commit()?;
+				Ok(())
+			}
+			TxFnResult::Abort => {
+				tx.tx.abort();
+				Err(TxError::Abort(()))
+			}
+			TxFnResult::DbErr => {
+				tx.tx.abort();
+				Err(TxError::Db(Error(
+					"(this message will be discarded)".into(),
+				)))
+			}
+		}
+	}
+}
+
+// ----
+
+struct LmdbTx<'a, 'db> {
+	trees: &'db [Database],
+	tx: RwTransaction<'a>,
+}
+
+impl<'a, 'db> LmdbTx<'a, 'db> {
+	fn get_tree(&self, i: usize) -> Result<&Database> {
+		self.trees.get(i).ok_or_else(|| {
+			Error(
+				"invalid tree id (it might have been openned after the transaction started)".into(),
+			)
+		})
+	}
+}
+
+impl<'a, 'db> ITx for LmdbTx<'a, 'db> {
+	fn get(&self, tree: usize, key: &[u8]) -> Result<Option<Value<'_>>> {
+		let tree = self.get_tree(tree)?;
+		match self.tx.get::<'a, _>(*tree, &key) {
+			Err(lmdb::Error::NotFound) => Ok(None),
+			Err(e) => Err(e.into()),
+			Ok(v) => Ok(Some(Value(Box::new(v)))),
+		}
+	}
+	fn len(&self, _tree: usize) -> Result<usize> {
+		unimplemented!(".len() in transaction not supported with LMDB backend")
+	}
+
+	fn insert(&mut self, tree: usize, key: &[u8], value: &[u8]) -> Result<()> {
+		let tree = self.get_tree(tree)?;
+		self.tx.put(*tree, &key, &value, WriteFlags::empty())?;
+		Ok(())
+	}
+	fn remove(&mut self, tree: usize, key: &[u8]) -> Result<bool> {
+		let tree = self.get_tree(tree)?;
+		match self.tx.del::<'a, _>(*tree, &key, None) {
+			Ok(()) => Ok(true),
+			Err(lmdb::Error::NotFound) => Ok(false),
+			Err(e) => Err(e.into()),
+		}
+	}
+
+	fn iter(&self, _tree: usize) -> Result<ValueIter<'_>> {
+		unimplemented!("Iterators in transactions not supported with LMDB backend");
+	}
+	fn iter_rev(&self, _tree: usize) -> Result<ValueIter<'_>> {
+		unimplemented!("Iterators in transactions not supported with LMDB backend");
+	}
+
+	fn range<'r>(
+		&self,
+		_tree: usize,
+		_low: Bound<&'r [u8]>,
+		_high: Bound<&'r [u8]>,
+	) -> Result<ValueIter<'_>> {
+		unimplemented!("Iterators in transactions not supported with LMDB backend");
+	}
+	fn range_rev<'r>(
+		&self,
+		_tree: usize,
+		_low: Bound<&'r [u8]>,
+		_high: Bound<&'r [u8]>,
+	) -> Result<ValueIter<'_>> {
+		unimplemented!("Iterators in transactions not supported with LMDB backend");
+	}
+}
+
+// ----
+
+struct TxAndValue<'a> {
+	tx: RoTransaction<'a>,
+	value: NonNull<&'a [u8]>,
+	_pin: PhantomPinned,
+}
+
+struct TxAndValuePin<'a>(Pin<Box<TxAndValue<'a>>>);
+
+impl<'a> IValue<'a> for TxAndValuePin<'a> {
+	fn take_maybe(&mut self) -> Vec<u8> {
+		self.as_ref().to_vec()
+	}
+}
+
+impl<'a> AsRef<[u8]> for TxAndValuePin<'a> {
+	fn as_ref(&self) -> &[u8] {
+		unsafe { self.0.value.as_ref() }
+	}
+}
+
+impl<'a> std::borrow::Borrow<[u8]> for TxAndValuePin<'a> {
+	fn borrow(&self) -> &[u8] {
+		self.as_ref()
+	}
+}