From fd8d5c37f73d93a0cdfd8ab08f7447b0f6d3ce3e Mon Sep 17 00:00:00 2001
From: Alex Auvolat <alex@adnab.me>
Date: Thu, 2 Jun 2022 14:59:26 +0200
Subject: First iteration of a generic DB layer

---
 src/db/sled_adapter.rs | 132 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 132 insertions(+)
 create mode 100644 src/db/sled_adapter.rs

(limited to 'src/db/sled_adapter.rs')

diff --git a/src/db/sled_adapter.rs b/src/db/sled_adapter.rs
new file mode 100644
index 00000000..617b4844
--- /dev/null
+++ b/src/db/sled_adapter.rs
@@ -0,0 +1,132 @@
+use std::collections::HashMap;
+use std::sync::{Arc, RwLock};
+
+use arc_swap::ArcSwapOption;
+
+use sled::transaction::{
+	ConflictableTransactionError, TransactionError, Transactional, TransactionalTree, UnabortableTransactionError
+};
+
+use crate::{Error, IDb, ITx, ITxFn, Result, TxError, TxFnResult, TxResult, Value, Db};
+
+impl From<sled::Error> for Error {
+	fn from(e: sled::Error) -> Error {
+		Error(format!("{}", e).into())
+	}
+}
+
+pub struct SledDb {
+	db: sled::Db,
+	trees: RwLock<(Vec<sled::Tree>, HashMap<String, usize>)>,
+}
+
+impl SledDb {
+	pub fn new(db: sled::Db) -> Db {
+		let s = Self {
+			db,
+			trees: RwLock::new((Vec::new(), HashMap::new())),
+		};
+		Db(Arc::new(s))
+	}
+
+	fn get_tree(&self, i: usize) -> Result<sled::Tree> {
+		self.trees
+			.read()
+			.unwrap()
+			.0
+			.get(i)
+			.cloned()
+			.ok_or(Error("invalid tree id".into()))
+	}
+}
+
+impl IDb for SledDb {
+	fn 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.open_tree(name)?;
+			let i = trees.0.len();
+			trees.0.push(tree);
+			trees.1.insert(name.to_string(), i);
+			Ok(i)
+		}
+	}
+
+	fn get<'a>(&'a self, tree: usize, key: &[u8]) -> Result<Option<Value<'a>>> {
+		let tree = self.get_tree(tree)?;
+		Ok(tree.get(key)?.map(|v| v.to_vec().into()))
+	}
+	fn put(&self, tree: usize, key: &[u8], value: &[u8]) -> Result<()> {
+		let tree = self.get_tree(tree)?;
+		tree.insert(key, value)?;
+		Ok(())
+	}
+
+	fn transaction(&self, f: &dyn ITxFn) -> TxResult<(), ()> {
+		let trees = self.trees.read().unwrap();
+		let res = trees.0.transaction(|txtrees| {
+			let tx = SledTx {
+				trees: txtrees,
+				err: ArcSwapOption::new(None),
+			};
+			match f.try_on(&tx) {
+				TxFnResult::Ok => {
+					assert!(tx.err.into_inner().is_none());
+					Ok(())
+				}
+				TxFnResult::Abort => Err(ConflictableTransactionError::Abort(())),
+				TxFnResult::Err => {
+					let err_arc = tx
+						.err
+						.into_inner()
+						.expect("Transaction did not store error");
+					let err = Arc::try_unwrap(err_arc).ok().expect("Many refs");
+					Err(err.into())
+				}
+			}
+		});
+		match res {
+			Ok(()) => Ok(()),
+			Err(TransactionError::Abort(())) => Err(TxError::Abort(())),
+			Err(TransactionError::Storage(s)) => Err(TxError::Db(s.into())),
+		}
+	}
+}
+
+// ----
+
+struct SledTx<'a> {
+	trees: &'a [TransactionalTree],
+	err: ArcSwapOption<UnabortableTransactionError>,
+}
+
+impl<'a> SledTx<'a> {
+	fn save_error<R>(&self, v: std::result::Result<R, UnabortableTransactionError>) -> Result<R> {
+		match v {
+			Ok(x) => Ok(x),
+			Err(e) => {
+				let txt = format!("{}", e);
+				self.err.store(Some(Arc::new(e)));
+				Err(Error(txt.into()))
+			}
+		}
+	}
+}
+
+impl<'a> ITx<'a> for SledTx<'a> {
+	fn get(&self, tree: usize, key: &[u8]) -> Result<Option<Value<'a>>> {
+		let tree = self.trees.get(tree)
+			.ok_or(Error("invalid tree id".into()))?;
+		let tmp = self.save_error(tree.get(key))?;
+		Ok(tmp.map(|v| v.to_vec().into()))
+	}
+
+	fn put(&self, tree: usize, key: &[u8], value: &[u8]) -> Result<()> {
+		let tree = self.trees.get(tree)
+			.ok_or(Error("invalid tree id".into()))?;
+		self.save_error(tree.insert(key, value))?;
+		Ok(())
+	}
+}
-- 
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