Feat/table multiple implementations (#28)

* style: module classification

* refactor(ss_table): methods for abstracting SSTables

* feat(table): implement Table abstraction, improve SkipTable's Iter and remove IoType::Mem type

* feat(config): Level 0 memory implementation is configurable (disabled by default)

* style: loader directory transfer

src/kernel/io/mod.rs

@@ -1,15 +1,9 @@
 pub(crate) mod buf;
 pub(crate) mod direct;
-mod mem;
 
 use crate::kernel::io::buf::{BufIoReader, BufIoWriter};
 use crate::kernel::io::direct::{DirectIoReader, DirectIoWriter};
-use crate::kernel::io::mem::{MemIoReader, MemIoWriter};
 use crate::kernel::Result;
-use crate::KernelError;
-use bytes::BytesMut;
-use parking_lot::Mutex;
-use std::collections::HashMap;
 use std::fs;
 use std::io::{Read, Seek, Write};
 use std::path::{Path, PathBuf};
@@ -40,14 +34,12 @@ impl FileExtension {
 pub struct IoFactory {
     dir_path: Arc<PathBuf>,
     extension: Arc<FileExtension>,
-    mem_files: Mutex<HashMap<i64, MemIoWriter>>,
 }
 
 #[derive(PartialEq, Copy, Clone, Debug)]
 pub enum IoType {
     Buf,
     Direct,
-    Mem,
 }
 
 impl IoFactory {
@@ -59,15 +51,6 @@ impl IoFactory {
         Ok(match io_type {
             IoType::Buf => Box::new(BufIoReader::new(dir_path, gen, extension)?),
             IoType::Direct => Box::new(DirectIoReader::new(dir_path, gen, extension)?),
-            IoType::Mem => {
-                let bytes = self
-                    .mem_files
-                    .lock()
-                    .get(&gen)
-                    .ok_or(KernelError::FileNotFound)?
-                    .bytes();
-                Box::new(MemIoReader::new(gen, bytes))
-            }
         })
     }
 
@@ -79,7 +62,6 @@ impl IoFactory {
         Ok(match io_type {
             IoType::Buf => Box::new(BufIoWriter::new(dir_path, gen, extension)?),
             IoType::Direct => Box::new(DirectIoWriter::new(dir_path, gen, extension)?),
-            IoType::Mem => Box::new(self.load_mem_file(gen)),
         })
     }
 
@@ -88,46 +70,28 @@ impl IoFactory {
         &self.dir_path
     }
 
-    fn load_mem_file(&self, gen: i64) -> MemIoWriter {
-        self.mem_files
-            .lock()
-            .entry(gen)
-            .or_insert_with(|| MemIoWriter::new(BytesMut::new()))
-            .clone()
-    }
-
     #[inline]
     pub fn new(dir_path: impl Into<PathBuf>, extension: FileExtension) -> Result<Self> {
         let path_buf = dir_path.into();
         // 创建文件夹（如果他们缺失）
         fs::create_dir_all(&path_buf)?;
         let dir_path = Arc::new(path_buf);
         let extension = Arc::new(extension);
-        let mem_files = Mutex::new(HashMap::new());
 
         Ok(Self {
             dir_path,
             extension,
-            mem_files,
         })
     }
 
     #[inline]
     pub fn clean(&self, gen: i64) -> Result<()> {
-        if self.mem_files.lock().remove(&gen).is_some() {
-            return Ok(());
-        }
-
         fs::remove_file(self.extension.path_with_gen(&self.dir_path, gen))?;
         Ok(())
     }
 
     #[inline]
     pub fn exists(&self, gen: i64) -> Result<bool> {
-        if self.mem_files.lock().contains_key(&gen) {
-            return Ok(true);
-        }
-
         let path = self.extension.path_with_gen(&self.dir_path, gen);
         Ok(fs::try_exists(path)?)
     }