implement 2.7

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

mini-lsm/src/table.rs

@@ -6,7 +6,7 @@ use std::fs::File;
 use std::path::Path;
 use std::sync::Arc;
 
-use anyhow::{anyhow, Result};
+use anyhow::{anyhow, bail, Result};
 pub use builder::SsTableBuilder;
 use bytes::{Buf, BufMut};
 pub use iterator::SsTableIterator;
@@ -30,7 +30,7 @@ pub struct BlockMeta {
 impl BlockMeta {
     /// Encode block meta to a buffer.
     pub fn encode_block_meta(block_meta: &[BlockMeta], buf: &mut Vec<u8>) {
-        let mut estimated_size = 0;
+        let mut estimated_size = std::mem::size_of::<u32>();
         for meta in block_meta {
             // The size of offset
             estimated_size += std::mem::size_of::<u32>();
@@ -43,10 +43,12 @@ impl BlockMeta {
             // The size of actual key
             estimated_size += meta.last_key.len();
         }
+        estimated_size += std::mem::size_of::<u32>();
         // Reserve the space to improve performance, especially when the size of incoming data is
         // large
         buf.reserve(estimated_size);
         let original_len = buf.len();
+        buf.put_u32(block_meta.len() as u32);
         for meta in block_meta {
             buf.put_u32(meta.offset as u32);
             buf.put_u16(meta.first_key.len() as u16);
@@ -54,13 +56,16 @@ impl BlockMeta {
             buf.put_u16(meta.last_key.len() as u16);
             buf.put_slice(meta.last_key.raw_ref());
         }
+        buf.put_u32(crc32fast::hash(&buf[original_len + 4..]));
         assert_eq!(estimated_size, buf.len() - original_len);
     }
 
     /// Decode block meta from a buffer.
-    pub fn decode_block_meta(mut buf: impl Buf) -> Vec<BlockMeta> {
+    pub fn decode_block_meta(mut buf: &[u8]) -> Result<Vec<BlockMeta>> {
         let mut block_meta = Vec::new();
-        while buf.has_remaining() {
+        let num = buf.get_u32() as usize;
+        let checksum = crc32fast::hash(&buf[..buf.remaining() - 4]);
+        for _ in 0..num {
             let offset = buf.get_u32() as usize;
             let first_key_len = buf.get_u16() as usize;
             let first_key = KeyBytes::from_bytes(buf.copy_to_bytes(first_key_len));
@@ -72,7 +77,11 @@ impl BlockMeta {
                 last_key,
             });
         }
-        block_meta
+        if buf.get_u32() != checksum {
+            bail!("meta checksum mismatched");
+        }
+
+        Ok(block_meta)
     }
 }
 
@@ -141,7 +150,7 @@ impl SsTable {
         let raw_meta_offset = file.read(bloom_offset - 4, 4)?;
         let block_meta_offset = (&raw_meta_offset[..]).get_u32() as u64;
         let raw_meta = file.read(block_meta_offset, bloom_offset - 4 - block_meta_offset)?;
-        let block_meta = BlockMeta::decode_block_meta(&raw_meta[..]);
+        let block_meta = BlockMeta::decode_block_meta(&raw_meta[..])?;
         Ok(Self {
             file,
             first_key: block_meta.first().unwrap().first_key.clone(),
@@ -180,10 +189,16 @@ impl SsTable {
             .block_meta
             .get(block_idx + 1)
             .map_or(self.block_meta_offset, |x| x.offset);
-        let block_data = self
+        let block_len = offset_end - offset - 4;
+        let block_data_with_chksum: Vec<u8> = self
             .file
             .read(offset as u64, (offset_end - offset) as u64)?;
-        Ok(Arc::new(Block::decode(&block_data[..])))
+        let block_data = &block_data_with_chksum[..block_len];
+        let checksum = (&block_data_with_chksum[block_len..]).get_u32();
+        if checksum != crc32fast::hash(block_data) {
+            bail!("block checksum mismatched");
+        }
+        Ok(Arc::new(Block::decode(block_data)))
     }
 
     /// Read a block from disk, with block cache.