Merge branch 'zwq' into jie

CMakeLists.txt

@@ -117,7 +117,10 @@ endif(BUILD_SHARED_LIBS)
 # Must be included before CMAKE_INSTALL_INCLUDEDIR is used.
 include(GNUInstallDirs)
 
-add_library(leveldb)
+add_library(leveldb
+        db/vlog_reader.h
+        db/vlog_writer.h
+        db/vlog_manager.h)
 target_sources(leveldb
   PRIVATE
     "${PROJECT_BINARY_DIR}/${LEVELDB_PORT_CONFIG_DIR}/port_config.h"

db/vlog_manager.h

@@ -0,0 +1,68 @@
+#ifndef LEVELDB_VLOG_MANAGER_H
+#define LEVELDB_VLOG_MANAGER_H
+
+#include <map>
+#include <set>
+#include <cstdint>
+#include "leveldb/env.h"
+
+namespace leveldb {
+namespace vlog {
+
+class VlogWriter;
+class VlogReader;
+
+class VlogInfo {
+    private:
+        /* vlog 当前大小 */
+        size_t size_;
+        /* vlog 当前若插入新 record 的偏移 */
+        size_t head_;
+        /* vlog 当前过期的 record 数量 */
+        uint64_t expired_count_;
+
+        VlogReader* vlog_read_;
+        VlogWriter* vlog_write_;
+
+    public:
+        VlogInfo() : size_(0), head_(0), expired_count_(0) {}
+        ~VlogInfo() = default;
+
+    friend class VlogWriter;
+    friend class VlogReader;
+    friend class VlogManager;
+};
+
+class VlogManager {
+    public:
+        explicit VlogManager(uint64_t expired_threshold);
+        ~VlogManager() = default;
+
+        /* 新建一个 vlog 并编号 */
+        void AddVlog(uint64_t vlog_no);
+        /* 往当前活跃 vlog 插入一条 record */
+        Status AddRecord(const Slice& slice);
+        /* 更新当前活跃 vlog 的头部位置 */
+        Status SetHead(size_t offset);
+        /* 当前活跃 vlog 的写缓冲的数据全部写入磁盘 */
+        Status Sync();
+        /* 从某个 vlog 中获取 value */
+        Status FetchValueFromVlog(Slice record_addr, std::string* value);
+        /* 设置当前活跃 vlog */
+        void SetCurrentVlog(uint64_t vlog_no);
+
+    private:
+        /* 管理所有 vlog 的编号和信息 */
+        std::map<uint64_t, VlogInfo*> vlog_manager_;
+        /* 记录正在 GC 的 vlog 集合 */
+        std::set<uint64_t> gc_vlog_set_;
+        /* 记录触发 GC 的过期阈值 */
+        uint64_t expired_threshold_;
+        /* 记录当前活跃的 vlog 编号 */
+        uint64_t cur_vlog_;
+};
+
+} // namespace vlog
+} // namespace leveldb
+
+#endif  // LEVELDB_VLOG_MANAGER_H

db/vlog_reader.h

@@ -0,0 +1,35 @@
+#ifndef LEVELDB_VLOG_READER_H
+#define LEVELDB_VLOG_READER_H
+
+#include <cstdint>
+#include "leveldb/slice.h"
+#include "leveldb/status.h"
+
+namespace leveldb {
+
+class RandomAccessFile;
+
+namespace vlog {
+
+class VlogInfo;
+class VlogManager;
+
+class VlogReader {
+    public:
+        VlogReader(uint32_t vlog_no);
+        ~VlogReader() = default;
+
+        /* 在 vlog_offset 处往后读取一条 record 的 value */
+        Status Get(uint64_t vlog_offset, std::string* value);
+
+    private:
+        VlogInfo* vlog_info_;
+        RandomAccessFile* vlog_;
+
+    friend class VlogManager;
+};
+
+} // namespace vlog
+} // namespace leveldb
+
+#endif  // LEVELDB_VLOG_READER_H

db/vlog_writer.h

@@ -0,0 +1,39 @@
+#ifndef LEVELDB_VLOG_WRITER_H
+#define LEVELDB_VLOG_WRITER_H
+
+#include <map>
+#include "leveldb/status.h"
+
+namespace leveldb {
+
+class WritableFile;
+
+namespace vlog {
+
+class VlogInfo;
+class VlogManager;
+
+class VlogWriter {
+    public:
+        explicit VlogWriter(WritableFile* vlog);
+        ~VlogWriter();
+
+        /* 往 vlog 的写缓存写入一条 kv 记录 */
+        Status AddRecord(const Slice& slice);
+
+    private:
+        VlogWriter() = default;
+
+        VlogInfo* vlog_info_;
+        WritableFile* vlog_;
+
+        VlogWriter(const VlogWriter&);
+        VlogWriter& operator=(const VlogWriter&);
+
+    friend class VlogManager;
+};
+
+}  // namespace vlog
+}  // namespace leveldb
+
+#endif  // LEVELDB_VLOG_WRITER_H

include/leveldb/options.h

@@ -145,6 +145,12 @@ struct LEVELDB_EXPORT Options {
   // Many applications will benefit from passing the result of
   // NewBloomFilterPolicy() here.
   const FilterPolicy* filter_policy = nullptr;
+
+  // vlog 过期 kv 计数器触发 GC 的阈值
+  int expired_threshold;
+
+  // vlog 文件大小上限
+  int max_vlog_size = 64 * 1024 * 1024;
 };
 
 // Options that control read operations