feat(code): finish part 3

Signed-off-by: Alex Chi <iskyzh@gmail.com>

mini-lsm-starter/src/lsm_iterator.rs

@@ -1 +1,54 @@
+#![allow(unused_variables)] // TODO(you): remove this lint after implementing this mod
+#![allow(dead_code)] // TODO(you): remove this lint after implementing this mod
+
+use crate::iterators::impls::StorageIterator;
+use anyhow::Result;
+
 pub struct LsmIterator {}
+
+impl StorageIterator for LsmIterator {
+    fn is_valid(&self) -> bool {
+        unimplemented!()
+    }
+
+    fn key(&self) -> &[u8] {
+        unimplemented!()
+    }
+
+    fn value(&self) -> &[u8] {
+        unimplemented!()
+    }
+
+    fn next(&mut self) -> Result<()> {
+        unimplemented!()
+    }
+}
+
+/// A wrapper around existing iterator, will prevent users from calling `next` when the iterator is invalid.
+pub struct FusedIterator<I: StorageIterator> {
+    iter: I,
+}
+
+impl<I: StorageIterator> FusedIterator<I> {
+    pub fn new(iter: I) -> Self {
+        Self { iter }
+    }
+}
+
+impl<I: StorageIterator> StorageIterator for FusedIterator<I> {
+    fn is_valid(&self) -> bool {
+        unimplemented!()
+    }
+
+    fn key(&self) -> &[u8] {
+        unimplemented!()
+    }
+
+    fn value(&self) -> &[u8] {
+        unimplemented!()
+    }
+
+    fn next(&mut self) -> Result<()> {
+        unimplemented!()
+    }
+}

mini-lsm-starter/src/lsm_storage.rs

@@ -1,3 +1,6 @@
+#![allow(unused_variables)] // TODO(you): remove this lint after implementing this mod
+#![allow(dead_code)] // TODO(you): remove this lint after implementing this mod
+
 use std::ops::Bound;
 use std::path::Path;
 use std::sync::Arc;
@@ -6,20 +9,23 @@ use anyhow::Result;
 use arc_swap::ArcSwap;
 use bytes::Bytes;
 
-use crate::lsm_iterator::LsmIterator;
+use crate::lsm_iterator::{FusedIterator, LsmIterator};
 use crate::mem_table::MemTable;
-use crate::table::{SsTable, SsTableIterator};
+use crate::table::SsTable;
 
+#[derive(Clone)]
 pub struct LsmStorageInner {
+    /// MemTables, from oldest to earliest.
     memtables: Vec<Arc<MemTable>>,
-    sstables: Vec<Arc<SsTable>>,
+    /// L0 SsTables, from oldest to earliest.
+    l0_sstables: Vec<Arc<SsTable>>,
 }
 
 impl LsmStorageInner {
     fn create() -> Self {
         Self {
             memtables: vec![Arc::new(MemTable::create())],
-            sstables: vec![],
+            l0_sstables: vec![],
         }
     }
 }
@@ -37,22 +43,7 @@ impl LsmStorage {
     }
 
     pub fn get(&self, key: &[u8]) -> Result<Option<Bytes>> {
-        let snapshot = self.inner.load();
-        for memtable in &snapshot.memtables {
-            if let Some(value) = memtable.get(key)? {
-                if value.is_empty() {
-                    // found tomestone, return key not exists
-                    return Ok(None);
-                }
-                return Ok(Some(value));
-            }
-        }
-        let mut iters = Vec::new();
-        iters.reserve(snapshot.sstables.len());
-        for table in snapshot.sstables.iter().rev() {
-            iters.push(SsTableIterator::create_and_seek_to_key(table.clone(), key)?);
-        }
-        Ok(None)
+        unimplemented!()
     }
 
     pub fn put(&mut self, key: &[u8], value: &[u8]) -> Result<()> {
@@ -69,7 +60,11 @@ impl LsmStorage {
         unimplemented!()
     }
 
-    pub fn scan(&self, _lower: Bound<&[u8]>, _upper: Bound<&[u8]>) -> Result<LsmIterator> {
+    pub fn scan(
+        &self,
+        _lower: Bound<&[u8]>,
+        _upper: Bound<&[u8]>,
+    ) -> Result<FusedIterator<LsmIterator>> {
         unimplemented!()
     }
 }

mini-lsm-starter/src/mem_table.rs

@@ -2,10 +2,12 @@
 #![allow(dead_code)] // TODO(you): remove this lint after implementing this mod
 
 use std::ops::Bound;
+use std::sync::Arc;
 
 use anyhow::Result;
 use bytes::Bytes;
 use crossbeam_skiplist::SkipMap;
+use ouroboros::self_referencing;
 
 use crate::iterators::impls::StorageIterator;
 use crate::table::SsTableBuilder;
@@ -46,17 +48,16 @@ type SkipMapRangeIter<'a> =
     crossbeam_skiplist::map::Range<'a, Bytes, (Bound<Bytes>, Bound<Bytes>), Bytes, Bytes>;
 
 /// An iterator over a range of `SkipMap`.
-pub struct MemTableIterator<'a> {
-    _phantom: std::marker::PhantomData<&'a ()>,
+#[self_referencing]
+pub struct MemTableIterator {
+    map: Arc<SkipMap<Bytes, Bytes>>,
+    #[borrows(map)]
+    #[not_covariant]
+    iter: SkipMapRangeIter<'this>,
+    item: (Bytes, Bytes),
 }
 
-impl<'a> MemTableIterator<'a> {
-    fn new(iter: SkipMapRangeIter<'a>) -> Self {
-        unimplemented!()
-    }
-}
-
-impl StorageIterator for MemTableIterator<'_> {
+impl StorageIterator for MemTableIterator {
     fn value(&self) -> &[u8] {
         unimplemented!()
     }
@@ -74,6 +75,4 @@ impl StorageIterator for MemTableIterator<'_> {
     }
 }
 
-#[cfg(test)]
-#[path = "mem_table_test.rs"]
 mod tests;

mini-lsm-starter/src/mem_table/tests.rs

@@ -0,0 +1 @@
+//! Please copy `mini-lsm/src/mem_table/tests.rs` here so that you can run tests.

mini-lsm-starter/src/mem_table_test.rs

@@ -1 +0,0 @@
-//! Please copy `mini-lsm/src/mem_table_test.rs` here so that you can run tests.