add wal and manifest

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

mini-lsm/src/mem_table.rs

@@ -1,4 +1,6 @@
 use std::ops::Bound;
+use std::path::Path;
+use std::sync::atomic::AtomicBool;
 use std::sync::Arc;
 
 use anyhow::Result;
@@ -9,10 +11,13 @@ use ouroboros::self_referencing;
 
 use crate::iterators::StorageIterator;
 use crate::table::SsTableBuilder;
+use crate::wal::Wal;
 
 /// A basic mem-table based on crossbeam-skiplist
 pub struct MemTable {
     map: Arc<SkipMap<Bytes, Bytes>>,
+    wal: Option<Wal>,
+    id: usize,
 }
 
 pub(crate) fn map_bound(bound: Bound<&[u8]>) -> Bound<Bytes> {
@@ -25,21 +30,47 @@ pub(crate) fn map_bound(bound: Bound<&[u8]>) -> Bound<Bytes> {
 
 impl MemTable {
     /// Create a new mem-table.
-    pub fn create() -> Self {
+    pub fn create(id: usize) -> Self {
         Self {
+            id,
             map: Arc::new(SkipMap::new()),
+            wal: None,
         }
     }
 
+    /// Create a new mem-table with WAL
+    pub fn create_with_wal(id: usize, path: impl AsRef<Path>) -> Result<Self> {
+        Ok(Self {
+            id,
+            map: Arc::new(SkipMap::new()),
+            wal: Some(Wal::create(path.as_ref())?),
+        })
+    }
+
+    pub fn recover_from_wal(id: usize, path: impl AsRef<Path>) -> Result<Self> {
+        unimplemented!()
+    }
+
     /// Get a value by key.
     pub fn get(&self, key: &[u8]) -> Option<Bytes> {
         self.map.get(key).map(|e| e.value().clone())
     }
 
     /// Put a key-value pair into the mem-table.
-    pub fn put(&self, key: &[u8], value: &[u8]) {
+    pub fn put(&self, key: &[u8], value: &[u8]) -> Result<()> {
         self.map
             .insert(Bytes::copy_from_slice(key), Bytes::copy_from_slice(value));
+        if let Some(ref wal) = self.wal {
+            wal.put(key, value)?;
+        }
+        Ok(())
+    }
+
+    pub fn sync_wal(&self) -> Result<()> {
+        if let Some(ref wal) = self.wal {
+            wal.sync()?;
+        }
+        Ok(())
     }
 
     /// Get an iterator over a range of keys.
@@ -63,6 +94,10 @@ impl MemTable {
         }
         Ok(())
     }
+
+    pub fn id(&self) -> usize {
+        self.id
+    }
 }
 
 type SkipMapRangeIter<'a> =