bump toolchain

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

mini-lsm/src/block/builder.rs

@@ -6,7 +6,7 @@ use super::{Block, SIZEOF_U16};
 pub struct BlockBuilder {
     /// Offsets of each key-value entries.
     offsets: Vec<u16>,
-    /// All key-value pairs in the block.
+    /// All serialized key-value pairs in the block.
     data: Vec<u8>,
     /// The expected block size.
     block_size: usize,
@@ -23,29 +23,33 @@ impl BlockBuilder {
     }
 
     fn estimated_size(&self) -> usize {
-        self.offsets.len() * SIZEOF_U16 + self.data.len() + SIZEOF_U16
+        SIZEOF_U16 /* number of key-value pairs in the block */ +  self.offsets.len() * SIZEOF_U16 /* offsets */ + self.data.len()
+        /* key-value pairs */
     }
 
     /// Adds a key-value pair to the block. Returns false when the block is full.
     #[must_use]
     pub fn add(&mut self, key: &[u8], value: &[u8]) -> bool {
         assert!(!key.is_empty(), "key must not be empty");
-        // The overhead here is `key_len` + `val_len` + `offset`, each is of type `u16`
-        if self.estimated_size() + key.len() + value.len() + SIZEOF_U16 * 3 > self.block_size
+        if self.estimated_size() + key.len() + value.len() + SIZEOF_U16 * 3 /* key_len, value_len and offset */ > self.block_size
             && !self.is_empty()
         {
             return false;
         }
-        // The offsets should be updated at first, to maintain the correct offset
+        // Add the offset of the data into the offset array.
         self.offsets.push(self.data.len() as u16);
+        // Encode key length.
         self.data.put_u16(key.len() as u16);
+        // Encode key content.
         self.data.put(key);
+        // Encode value length.
         self.data.put_u16(value.len() as u16);
+        // Encode value content.
         self.data.put(value);
         true
     }
 
-    /// Check if there is no key-value pair in the block.
+    /// Check if there are no key-value pairs in the block.
     pub fn is_empty(&self) -> bool {
         self.offsets.is_empty()
     }