more comments, sync check

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

mini-lsm/src/block/builder.rs

@@ -2,15 +2,18 @@ use bytes::BufMut;
 
 use super::{Block, SIZEOF_U16};
 
-/// Builds a block
+/// Builds a block.
 pub struct BlockBuilder {
+    /// Offsets of each key-value entries.
     offsets: Vec<u16>,
+    /// All key-value pairs in the block.
     data: Vec<u8>,
+    /// The expected block size.
     block_size: usize,
 }
 
 impl BlockBuilder {
-    /// Creates a new block builder
+    /// Creates a new block builder.
     pub fn new(block_size: usize) -> Self {
         Self {
             offsets: Vec::new(),
@@ -23,7 +26,7 @@ impl BlockBuilder {
         self.offsets.len() * SIZEOF_U16 + self.data.len() + SIZEOF_U16
     }
 
-    /// Adds a key-value pair to the block
+    /// 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");
@@ -41,11 +44,12 @@ impl BlockBuilder {
         true
     }
 
+    /// Check if there is no key-value pair in the block.
     pub fn is_empty(&self) -> bool {
         self.offsets.is_empty()
     }
 
-    /// Builds a block
+    /// Finalize the block.
     pub fn build(self) -> Block {
         if self.is_empty() {
             panic!("block should not be empty");

mini-lsm/src/block/iterator.rs

@@ -4,6 +4,7 @@ use bytes::Buf;
 
 use super::Block;
 
+/// Iterates on a block.
 pub struct BlockIterator {
     block: Arc<Block>,
     key: Vec<u8>,
@@ -21,45 +22,44 @@ impl BlockIterator {
         }
     }
 
+    /// Creates a block iterator and seek to the first entry.
     pub fn create_and_seek_to_first(block: Arc<Block>) -> Self {
         let mut iter = Self::new(block);
         iter.seek_to_first();
         iter
     }
 
+    /// Creates a block iterator and seek to the first key that >= `key`.
     pub fn create_and_seek_to_key(block: Arc<Block>, key: &[u8]) -> Self {
         let mut iter = Self::new(block);
         iter.seek_to_key(key);
         iter
     }
 
+    /// Returns the key of the current entry.
     pub fn key(&self) -> &[u8] {
         debug_assert!(!self.key.is_empty(), "invalid iterator");
         &self.key
     }
 
+    /// Returns the value of the current entry.
     pub fn value(&self) -> &[u8] {
         debug_assert!(!self.key.is_empty(), "invalid iterator");
         &self.value
     }
 
+    /// Returns true if the iterator is valid.
     pub fn is_valid(&self) -> bool {
         !self.key.is_empty()
     }
 
+    /// Seeks to the first key in the block.
     pub fn seek_to_first(&mut self) {
         self.seek_to(0);
     }
 
-    pub fn len(&self) -> usize {
-        self.block.offsets.len()
-    }
-
-    pub fn is_empty(&self) -> bool {
-        self.block.offsets.is_empty()
-    }
-
-    pub fn seek_to(&mut self, idx: usize) {
+    /// Seeks to the idx-th key in the block.
+    fn seek_to(&mut self, idx: usize) {
         if idx >= self.block.offsets.len() {
             self.key.clear();
             self.value.clear();
@@ -70,6 +70,7 @@ impl BlockIterator {
         self.idx = idx;
     }
 
+    /// Move to the next key in the block.
     pub fn next(&mut self) {
         self.idx += 1;
         self.seek_to(self.idx);
@@ -89,6 +90,7 @@ impl BlockIterator {
         self.value.extend(value);
     }
 
+    /// Seek to the first key that >= `key`.
     pub fn seek_to_key(&mut self, key: &[u8]) {
         let mut low = 0;
         let mut high = self.block.offsets.len();